Portable A/C Unit

[BytorJr]

Anybody have any experience with these. Good brands? Will they work as supplemental cooling?

My home office is on the hot side of the house. Crappy contractor home (as most are where I live) and the office is at the end of the ductwork. Truth be told they should have had one extra vent in the room as the heat load is more due to more windows. Bedrooms are 73/74, office & kitchen 79-80. I've dicked around with the vents and lessened airflow into bedrooms but to no avail. Toying with buying a portable unit which, when I bite the bullet and buy a new HVAC central unit may do duty in the garage - not sure how that's going to rig up; but the mini-split for garage was ridiculous. Again, contractor home.....think there would be a spare breaker slot? So, it'd require an additional panel.

Thanks.

 

[oneshot86]

There's a couple guys here that are super pros.
Is there an external wall to cut a hole and put a small hotel styled AC and heat?

 

[Greg Langelius *]

Our VFW uses them in the canteen kitchen when it's hot and there's a big dinner going on.

They work well enough.

Add a slave breaker box; but don't up the main breaker capacity. Better to pop the main than burn down the digs. Main power drops would otherwise need to be resized, and mine are underground.

Mylar foam window shades; at your hardware store. Or.

Don't put up Mylar mirror foil; the birds will attack, and can break your windows.

No need to ask how I know.

....And here's another idear...

...Or..., go 21th century...:

Smart Vents. Flair Puck. Eco-bee Smart Sensor.

 

[MtnCreek]

@DarnYankeeUSMC
@FS1

 

[woodsmoke]

If you have a window in the room, I’d grab a small window ac from Walmart for $99 and be happy.

 

[Greg Langelius *]

If his windows are like mine, they are big sliders.

 

[BytorJr]

Our VFW uses them in the canteen kitchen when it's hot and there's a big dinner going on.

They work well enough.

Add a slave breaker box; but don't up the main breaker capacity. Better to pop the main than burn down the digs. Main power drops would otherwise need to be resized, and mine are underground.

Mylar foam window shades; at your hardware store. Or.

Don't put up Mylar mirror foil; the birds will attack, and can break your windows.

No need to ask how I know.

....And here's another idear... Smart Vents. Flair Puck. Eco-bee Smart Sensor.

I have an eco-bee smart sensor. Otherwise it'd be more like 85. . Never heard of the other two.

So you're saying the load of the portable needs a separate breaker? I wasn't aware they would pull that many amps.

I need to pony up and have a new HVAC, but to be honest, I don't particularly like this house and continually toy with dumping it.
-------------------------------
I toyed with the window unit; but since it wouldn't dual purpose I shelved it. I like the idea of moving the portable to the garage at times and cutting a hole in a 1x6 or something and shutting door on the board to seal the gap. For those days when detailing and brake work, etc are to be done.

 

[packratt]

I've been having to mess with these a lot lately. 3-400000sqft building whose hvac system is on its last legs. Trying to cool some offices and the computer room that aren't on the temp chiller.

The biggest challenge you are going to have is venting the hot exhaust to the outside of the house. Take your hand and hold it over the condenser of your unit, outside. The problem I've got is I dont have any outside openings to vent to and the walls go all the way up with no openings out of the room. The space I've got is too small to dissipate the heat.

If you can get the exhaust out of the building it is equal to a window unit.

If you have a sliding window, you could cut a piece of plywood 12 by the height of the window with a hole for the pipe. Open window insert panel and close against panel when you need to use the unit. Remove panel so you can secure the house.

 

[packratt]

Iirc the 14000btu units I've are 15amp. Depending on how much junk you have on the circuit you shouldn't need a dedicated circuit.

 

[pmclaine]

Never really found the couple we had to be near to the output of a window unit.

 

[BytorJr]

Thanks guys!!! Yeah, the thing I like about portable is to be able to actually secure the window much better than otherwise. I'm cheap; but the fact I'll eventually move this to the garage means it's not a total loss.

 

[FS1]

I agree that a small window unit would be the best option. Portable would likely work also but are a bigger pita for semi permanent use.

You may also want to check your air filter, if neglected it becomes quite an air choker. Check your return air temp against the supply air temp of you main unit. The difference should be between 16-20 degrees. anything else suggests a possible air flow problem. The real problem may be an easier fix than adding a unit.

 

[W54/XM-388]

I'm actually looking for something similar to the OP but to have as a backup incase my AC goes out in the middle of summer or their is an extended power outage in the middle of summer. Something that can be wheeled into place or set it place and run off a wall socket or a 1500w generator via an extension cord to outside if need be.

Something big enough to keep about 350 sq ft cool in 110 degree high humidity weather.

 

[Greg Langelius *]

Your request triggered a bunch of research on my own. Your a/c unit could draw 10 or more amps, a 10k BTU would want a 15 amp breaker to be safe, a 20 to be sure. I firmly believe on running as much breaker as the wire gauge can accommodate. Depending on your existing breaker capacity and and cumulative existing load, you may not need to do anything. Assuming 120v and 10A, wattage comes to 1200W, and so on. 20 amp requires 12ga wire.

I am thinking about my workshop, a separate space within my garage. I'm considering this unit, or something like it. I want a rating for 450sq ft. No-name brand units can fail soon. I'm willing to pay for a good one; I may have to consider dropping a grand for this project to do it right the first time.

We just went through a 100-110 degree week, and in extremes, 115-120 degrees is possible here in 'way down SE AZ. Our central Heat-AA/C unit is a very adequate rated Trane and runs like one. But the garage and shop is an add-on with no enviro.

Greg

 

[FS1]

5-

I'm actually looking for something similar to the OP but to have as a backup incase my AC goes out in the middle of summer or their is an extended power outage in the middle of summer. Something that can be wheeled into place or set it place and run off a wall socket or a 1500w generator via an extension cord to outside if need be.

Something big en free ough to keep about 350 sq ft cool in 110 degree high humidity weather.

8-10k BTU window unit

 

[FS1]

Your request triggered a bunch of research on my own. Your a/c unit could draw 10 or more amps, a 10k BTU would want a 15 amp breaker to be safe, a 20 to be sure.

I am thinking about my workshop, a separate space within my garage. I'm considering this unit, or something like it. Non-name brand units can fail soon. I'm willing to pay for a good one; I may have to consider dropping a grand for this project; do it right the first time.

Greg

For a garage 15-18 k BTU mini split inverter unit. The inverter will adjust to the load.

 

[Eli17L]

Window units are cheaper to buy and run.
I have had maybe 8 of the portables over the years and they were just ok dies and lasted about a year but last year I picked up this SereneLife unit and I get complaints from staff about the cold. It blows at 34 degrees and it exhausts the condensate out the window so there is no tank to empty.

 

[Greg Langelius *]

What is this term 'Inverter' of which you speak? Got it... MY shop is under the one roof, but has a separating wall with a doorway which can have a hung door added. Can you recommend a solid one for 10,000-12,000 BTU?

 

[FS1]

Mitsubishi, Samsung and Carriers all good quality. More importantly good parts and support. Get the heat pump near same cost and they have heat too.

Dirt cheap units are a crap shoot but many will suffice.

 

[Dragonscout25]

I actually bought a Dyson fan. Weird little shit, plugs in to the wall and can cool and heat room air...https://www.dyson.com/purifiers/dyson-pure-hot-cool-hp04-white-silver.html cost a little more , but it can oscillate, filter the air has a remote. Got mine on sale for about $300 four years ago. Still cooling me in my recliner as we speak. They have several different models and you can see where you can get a deal....YMMV

 

[Greg Langelius *]

Much thanks FS1. Still in the what if stage; it's great to have good advice right about now. Wife is insisting portable, under $800. sigh...

Greg

 

[Tims]

Anybody have any experience with these. Good brands? Will they work as supplemental cooling?

My home office is on the hot side of the house. Crappy contractor home (as most are where I live) and the office is at the end of the ductwork. Truth be told they should have had one extra vent in the room as the heat load is more due to more windows. Bedrooms are 73/74, office & kitchen 79-80. I've dicked around with the vents and lessened airflow into bedrooms but to no avail. Toying with buying a portable unit which, when I bite the bullet and buy a new HVAC central unit may do duty in the garage - not sure how that's going to rig up; but the mini-split for garage was ridiculous. Again, contractor home.....think there would be a spare breaker slot? So, it'd require an additional panel.

Thanks.

I have a similar situation. Back room on the house is the hottest. I bought the Whynter 14,000 BTU from amazon. It works off a standard wall socket. I've had it about 2 years . Not sure how big the room you need to cool is. The room I use it in is about 12x12. Summers here can be in the low 100's here. It is a little noisy though.

I also had an LG for the same room at one time. It died after 1 year. I wouldn't go LG.

 

[W54/XM-388]

Mitsubishi, Samsung and Carriers all good quality. More importantly good parts and support. Get the heat pump near same cost and they have heat too.

Dirt cheap units are a crap shoot but many will suffice.

Do you they make heat pump units that come all ready to go and you can take the compressor part in and out of the window for storage & don't require professional installation?

I was thinking about just the AC unit, but if it has a heat pump, that would also pull double duty for heating the house if the power goes off or the AC unit takes a dump in the middle of the winter.

 

[P-Squared]

A couple of things to consider. I don't know what exactly a 'contractor' home is, however I'm assuming it's a tract home. Generally speaking they tend to over-size the units compared to when you actually do a heat load calculations. We down-size about 40% of the units we replace. We don't do much new home construction, we are mainly a residential retrofit operation with some small commercial and about 3 new construction projects a year. Overall we do just under 700 projects a year. We're not huge, but we're not small either.

Two things that will definitely help you are to get 1) a blower door test. This test will let you know how sealed your house is. You need to know if your AC is just leaking out through who knows what, and 2) have them do a duct blast. That will tell you if you have leakage in the duct work. According to the EPA, over 50% of homes have at least 30% leakage (or more), that means YOU are doing your best to solve global warming (and heating) by dumping all you conditioned air into non-conditioned (outside) space.

Once you know if you have leaks, do an inspection of the duct work. It is quite possible the flex duct to the back office is kinked, smashed, or just not connected. You really (really, really, really) need to do a heat load calculation called a Manual J. That will determine how much cooling and heating you really need. DO NOT be surprised if your current unit is too big, it wouldn't surprise us.

I'd stay away from portables or window units, or something called a PTAC (think motel 6) if you can. Go with a mini-split if you can.

I'm about to embark on installing a multi-port mini-split in my 3 bay garage. I'm going to run ceiling cassettes so everything is flush and doesn't distract you from my reloading bench in the 'Man-Cave'.

Good luck, make sure and get those tests and calculations done so you know where the problems are before you just treat the symptoms.

Pete

 

[BytorJr]

For a garage 15-18 k BTU mini split inverter unit. The inverter will adjust to the load.

I got quoted 5K for one...wasn't even a Mitsubishi. Simple as hell install too. Panel and meter on garage side of house. Main HVAC right there. No reason they couldn't fish lines through with ease. Hang in garage and be done. I'm shocked how proud these folks are of their labor rates.

 

[BytorJr]

A couple of things to consider. I don't know what exactly a 'contractor' home is, however I'm assuming it's a tract home. Generally speaking they tend to over-size the units compared to when you actually do a heat load calculations. We down-size about 40% of the units we replace. We don't do much new home construction, we are mainly a residential retrofit operation with some small commercial and about 3 new construction projects a year. Overall we do just under 700 projects a year. We're not huge, but we're not small either.

Two things that will definitely help you are to get 1) a blower door test. This test will let you know how sealed your house is. You need to know if your AC is just leaking out through who knows what, and 2) have them do a duct blast. That will tell you if you have leakage in the duct work. According to the EPA, over 50% of homes have at least 30% leakage (or more), that means YOU are doing your best to solve global warming (and heating) by dumping all you conditioned air into non-conditioned (outside) space.

Once you know if you have leaks, do an inspection of the duct work. It is quite possible the flex duct to the back office is kinked, smashed, or just not connected. You really (really, really, really) need to do a heat load calculation called a Manual J. That will determine how much cooling and heating you really need. DO NOT be surprised if your current unit is too big, it wouldn't surprise us.

I'd stay away from portables or window units, or something called a PTAC (think motel 6) if you can. Go with a mini-split if you can.

I'm about to embark on installing a multi-port mini-split in my 3 bay garage. I'm going to run ceiling cassettes so everything is flush and doesn't distract you from my reloading bench in the 'Man-Cave'.

Good luck, make sure and get those tests and calculations done so you know where the problems are before you just treat the symptoms.

Pete

This is just for temporary until I get the funds for a good new system or do what I want to do and build my own. I grew up more or less in the business (but that's been 30 years ago since I left home), family ran HVAC business for 50+ years, and I've done analysis on this house and it's 0.5 tons too small. It'd be fine if I were up in Iowa, but not here in SE. One guy of the two that gave estimates, spotted it immediately - the most professional of the two. The other guy did all this magic BS on his phone and got a GPS out and all that shit, took measurements of windows and all that. His # came up with same as contractor.

And yes, it's a tract home and it's absolutely crap design. Everything is CHEAP. About the only thing mech/elec I can see that was decent was the Square D panel; but it's not a QO load center which is what I'm accustomed to - yes, even for home. Despite one of biggest builders in 'Bama it's not laid out by an architect. It's obvious. Lighting in ceiling not placed in center of stuff because there is a joist in the center of the room, etc, etc. So disturbing to have sold my father's house after he died for about this house's value...school districts matter!!! Tree fell into Dad's house....BROKE tree!!! If a tree hit this house....it'd collapse.

Duct is connected, I can feel it and airflow roughly same as all others. It's that this is the only room that gets direct afternoon sunlight into the room. I think when/if I get a new unit I'm having another vent installed. Also the nook is off the kitchen which obviously has more heat load.

If I build a house it's going to have a minisplit system throughout. 24 seer is amazing from Mitsubishi. Retrofitting existing house is just too freaking expensive.

 

[Sean the Nailer]

If you (or anyone) does do the mylar on the windows, be sure to put up a few pieces of tape on the windows (on the outside) just to show birds that there really is something there and it isn't a 'tunnel' to fly through.

Especially the mirrored style of mylar. That is what we have. And YES, it actually does help a heck of a lot to keep the room/house cooler. Hugely, actually. But there are drawbacks. Few pieces of tape for birds, and you can't have any indoor plants. (unless you do grow-lights and stuff) because the mylar keeps all the 'growth light' out of the house.

It works, no doubt about it. Adding insulation to the outside of the house ALSO helps a huge amount. (we did that too) Using a programmable thermostat ALSO helps. Keeps even'er temperatures, as well as lowers the bills.

I'm just sayin'...

 

[hermosabeach]

So a Window sill model is the best option. The toshiba at depot are good enough. I have had great longevity with Sanyo.

the window units can benefit from a leaf Blower and using the air to blow dust and debris out of them as needed.

The ones on the rollers are not efficient. The portable ones... The heat of the unit is in the case. The 12k btu units provide about 7500 btu of cooling as the entire heat device is in the case in the room. The window AC has the hot side outside.

so the portable ones consume 45% more power for the cooling vs he windowsill models.

If you have the Title 24 Double pane windows- the ones that cut down on UV, Tinting can ruin the coating and void the warranty. The metallic costing inside the windows can overheat if tinted....

 

[Waorani]

Aren't you in AL? I've got a small window unit you can have if you want to make the drive to Opelika. Old but probably less than 100hrs use.

 

[BytorJr]

Aren't you in AL? I've got a small window unit you can have if you want to make the drive to Opelika. Old but probably less than 100hrs use.

Thanks for the offer. I’m liking the Mylar approach.

Yes we have folks that have it and they do kill birds. So I’m aware of the Bird window killers.

I don’t grow plants (I seem to keep killing my outdoor gardenias screw indoor plants). and would probably only do the Mylar on the back side where the sun is worst and maybe my one East facing window.

My ecobee says it saves me money. So I’ll take for its word. Lol. I should buy a whole unit but gotta finish other projects first. If I could find a good contractor it’d help. Too hot now to force people in attic. Just need to get through August. Can cruise then till cold weather.

 

[kenny1773]

I have a similar problem, my office in the front of the house that catches all the afternoon sun. I built and installed screens with 80 solar shade on the front of my house in every window

I bought some aluminum stock and some corners to build the frames

https://www.amazon.com/Prime-Line-Products-MP14038-Aluminum-Screen/dp/B01LGAVBHS/ref=sr_1_1_sspa?dchild=1&keywords=windows+screen+frame&qid=1595133024&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzMDdUUllDV0FPVUFYJmVuY3J5cHRlZElkPUEwOTEzNjM0MllFV0RIMlNMRlg0OSZlbmNyeXB0ZWRBZElkPUEwOTAxOTA2SU5UMkxaSjFFMFRIJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

screen material

Bulk Solar Screen Fabric - Phifer Suntex Solar Screen Material

Priced by the linear foot. Bulk 80% Phifer Suntex solar screen fabric material is perfect for those large jobs where you'll be re-screening several frames or screening in a patio or sun room. 72" wide roll. Choose your length and color.

solarscreenoutlet.com

It did help a good bit, but wasn't a silver bullet. I might try those mylar foam window shades to see

 

[DellaDog]

I tried and returned *every* portable AC unit at both Lowes and Home Depot for my garage, they all did very little to cool a Texas garage. I also installed and returned several window units that just didn’t keep up. Finally spent the $$ on a Frigidaire window AC/Heater that now adequately cools in the summer (over 100 outside, mid 70s inside) and keeps it warm in the winter.

Had to run a 30 amp plug (for the heater), but definitely worth it.

Don't bother with a portable unit for real cooling.

 

[2aBaC̶a̶]

Your request triggered a bunch of research on my own. Your a/c unit could draw 10 or more amps, a 10k BTU would want a 15 amp breaker to be safe, a 20 to be sure. I firmly believe on running as much breaker as the wire gauge can accommodate. Depending on your existing breaker capacity and and cumulative existing load, you may not need to do anything. Assuming 120v and 10A, wattage comes to 1200W, and so on. 20 amp requires 12ga wire.

I am thinking about my workshop, a separate space within my garage. I'm considering this unit, or something like it. I want a rating for 450sq ft. No-name brand units can fail soon. I'm willing to pay for a good one; I may have to consider dropping a grand for this project to do it right the first time.

We just went through a 100-110 degree week, and in extremes, 115-120 degrees is possible here in 'way down SE AZ. Our central Heat-AA/C unit is a very adequate rated Trane and runs like one. But the garage and shop is an add-on with no enviro.

Greg

Do you realize that requires a somewhat professional to install. Its not plug and play.

 

[2aBaC̶a̶]

Anybody have any experience with these. Good brands? Will they work as supplemental cooling?

My home office is on the hot side of the house. Crappy contractor home (as most are where I live) and the office is at the end of the ductwork. Truth be told they should have had one extra vent in the room as the heat load is more due to more windows. Bedrooms are 73/74, office & kitchen 79-80. I've dicked around with the vents and lessened airflow into bedrooms but to no avail. Toying with buying a portable unit which, when I bite the bullet and buy a new HVAC central unit may do duty in the garage - not sure how that's going to rig up; but the mini-split for garage was ridiculous. Again, contractor home.....think there would be a spare breaker slot? So, it'd require an additional panel.

Thanks.

How big is the room?

Portable AC and window units work well for small rooms. And even better when the room is insulated. Many houses were built for heat only and therefore have undersized ductwork. Cooling requires more airflow to work efficiently.

I would opt for a standard plug in window unit if it was possible. The build a nice panel to cover the space above it. For a Portable AC you still have to vent the hot air and also keep an eye on the condensate drain reservoir.

If the sun on your wall or window generates a lot of heat you might consider mitigating it with some shade. Ive stapled some of that garden shade cloth to the eve and let it hang, that was before the tree grew out.

 

[BytorJr]

Do you realize that requires a somewhat professional to install. Its not plug and play.

Just curious to what the average install costs. Because the two estimates I had were within 1500 of what it'd take to replace whole house unit. Because I too had wanted a mini-split for my garage. But 5500 for a 2 ton Lennox (COSTCO/not-a-deal) for the install was not going to happen and that was before the electrical work. And it would take a run about 14 feet max for the lines.

 

[scharfschutze762]

Picked up a De Longhi portable from Costco across the street from the loews that wouldnt replace the 60 day old GE window unit that took a shit. Its a very very good unit and better than the LG portable that I also have in another room.
this one

https://www.costco.com/de'longhi-pinguino-700-sq-ft-4-in-1-all-season-use%3a-air-conditioner%2c-heater%2c-dehumidifier%2c-fan-with-wifi-remote-access.product.100521008.html

 

[Greg Langelius *]

Pete; as a former GI Electrician USMC Utilities Engineer, and also as a computer site manager, I've always sided with excess capacity. If you don't need it now, you will eventually.

IT capacity engineer, "You gotta getta biggah Box, boy..."

We always had to balance the efficiency against the reliability; running at full (not peak ) capacity. With some excess capacity, we could take a breather, but computer capacity needs are always growing.

FWIW, I once had an Osborne Executive portable PC assigned to me; hardly a laptop.

But I'm also open to discussion on that.

Are there difficulties with excess capacity, and what would they be?

sharfshutz; will a 10A breaker suffice for the DeLonghi? (I refer to the 700 sq ft model)

Very curious;

Greg

 

[Stevo86]

Did someone say portable AC unit? This should do the trick for you

 

[2aBaC̶a̶]

Just curious to what the average install costs. Because the two estimates I had were within 1500 of what it'd take to replace whole house unit. Because I too had wanted a mini-split for my garage. But 5500 for a 2 ton Lennox (COSTCO/not-a-deal) for the install was not going to happen and that was before the electrical work. And it would take a run about 14 feet max for the lines.

Install cost can be all over the place, usually a couple grand. Each cooling solution is different depending on what's existing and your needs and wants. Not sure there is an average. I do commercial HVAC by trade and residential on the side.

The lack of air to the back room sounds like a airflow issue. So either undersized ductwork, restriction like a clogged evap coil, or undersized fan.

If you upsized the house unit, could you also run ductwork to the garage?

 

[armorpl8chikn]

Properly installed and vented, they work good.

Louder than a fargin D8 cat.

 

[BoilerUP]

I use a Hisense 300sq ft portable floor AC unit from Lowe's in my boys' bedroom, which is on the second story of our house and positioned where it gets full evening sun. Need it basically mid-May thru mid-Sept; set it to 72 during the day and down to 68 an hour before bed. Works GREAT, plenty of white noise, only downside is the exhaust vent doesn't look asthetically pleasing from outside but its on the back of our house so who cares.

Already had the unit from when the central air failed at our hold house over Memorial Day weekend 2018 and it took 9 days to be replaced...a hell of a lot cheaper than having a second central air unit installed in our current home (which probably will happen in a year or two).

 

[Rthur]

Bought this:

https://www.amazon.com/gp/product/B01DLPUWHQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

My shop is 16 x 16 x 10
Could hang meat in it if left on kill at 100/90% conditions.
Shop is well insulated.

R

 

[BytorJr]

Install cost can be all over the place, usually a couple grand. Each cooling solution is different depending on what's existing and your needs and wants. Not sure there is an average. I do commercial HVAC by trade and residential on the side.

The lack of air to the back room sounds like a airflow issue. So either undersized ductwork, restriction like a clogged evap coil, or undersized fan.

If you upsized the house unit, could you also run ductwork to the garage?

I think it's an undersized duct myself. Everything or not enough vents.

No, there are ordinances/code against running duct to garage due to the potential VOC/Carbon Monoxide entry to the rest of the house. A friend of mine did the mini-split to her garage down in FL and it ran her like 1K for the unit and 1K for install. Tops, there is 10 hours labor there. Literally the unit could sit almost next to the other unit or right by the main panel. Either core drill though the brick, insert PVC pipe, seal, put lines in - call electrician and get hooked up to a wee bit of alternating current. The only lines to be run are strictly from the outside of the house up to the roof line (straight up), that's it.

 

[Dirty D]

A couple of things to consider. I don't know what exactly a 'contractor' home is, however I'm assuming it's a tract home. Generally speaking they tend to over-size the units compared to when you actually do a heat load calculations. We down-size about 40% of the units we replace. We don't do much new home construction, we are mainly a residential retrofit operation with some small commercial and about 3 new construction projects a year. Overall we do just under 700 projects a year. We're not huge, but we're not small either.

Two things that will definitely help you are to get 1) a blower door test. This test will let you know how sealed your house is. You need to know if your AC is just leaking out through who knows what, and 2) have them do a duct blast. That will tell you if you have leakage in the duct work. According to the EPA, over 50% of homes have at least 30% leakage (or more), that means YOU are doing your best to solve global warming (and heating) by dumping all you conditioned air into non-conditioned (outside) space.

Once you know if you have leaks, do an inspection of the duct work. It is quite possible the flex duct to the back office is kinked, smashed, or just not connected. You really (really, really, really) need to do a heat load calculation called a Manual J. That will determine how much cooling and heating you really need. DO NOT be surprised if your current unit is too big, it wouldn't surprise us.

I'd stay away from portables or window units, or something called a PTAC (think motel 6) if you can. Go with a mini-split if you can.

I'm about to embark on installing a multi-port mini-split in my 3 bay garage. I'm going to run ceiling cassettes so everything is flush and doesn't distract you from my reloading bench in the 'Man-Cave'.

Good luck, make sure and get those tests and calculations done so you know where the problems are before you just treat the symptoms.

Pete

Very good advice here, pretty much mirrors what I see on the daily here in PHX doing 99% retrofits.

 

[P-Squared]

Pete; as a former GI Electrician USMC Utilities Engineer, and also as a computer site manager, I've always sided with excess capacity. If you don't need it now, you will eventually.

IT capacity engineer, "You gotta getta biggah Box, boy..."

We always had to balance the efficiency against the reliability; running at full (not peak ) capacity. With some excess capacity, we could take a breather, but computer capacity needs are always growing.

FWIW, I once had an Osborne Executive portable PC assigned to me; hardly a laptop.

But I'm also open to discussion on that.

Are there difficulties with excess capacity, and what would they be?

sharfshutz; will a 10A breaker suffice for the DeLonghi? (I refer to the 700 sq ft model)

Very curious;

Greg

Hey @Greg Langelius * ,

I just saw your post.

Before I got involved with HVAC, I figured bigger was better. That was before I received my education by the folks at the company I work for. If we're talking traditional 1 and 2 stage systems, bigger can often times lead to 'short cycling'. That means the unit comes on to satisfy the thermostat and then it shuts off. If the unit is oversized, it comes on for a brief time because it's dumping lots of BTUs and then shuts off. This is hell on the compressor. Think of it this way, your daily driver is a fuel funny car. You have 10K horsepower. The light turns green and you only have one or two speeds. You absolutely destroy everyone else to get to the next light, then you shut it down. How long is that engine going to last?

You can mitigate some of that by going to an inverter system because the compressor is going to ramp up or down to what it needs to satisfy the need. As long as you don't go crazy and put in 5 tons where you only need 1 ton, the inverter takes car of it. Most inverters can ramp down to about 20% of rated capacity. Capacity is another reason you have to do heat load calculations. Let's suppose you and I have the exact same size man-caves, 60,000 sq ft (in my dreams). First off, yours is at least 1,500 feet higher from where I live. You are going to need a smaller unit (probably) because you will have different average temperatures. Maybe mine faces due south and has lots of single pane windows, I'll need even more BTU capacity. I really cringe when folks only look at sq ft. It might work, it might be too big, it might be too small, who knows.

I'm in the process of installing a system in my garage. I was out looking at the templates for the ceiling cassettes just a few minutes ago. I'm putting in a 30,000 BTU outdoor unit and I have 36,000 BTUs of ceiling cassettes. That would be a design issue except for the fact that two of the cassettes will seldom be used. Their TXV will be shut down and only the one around my bench will be fired up. I could keep the other two set to about 80 so the entire garage keeps cooler than the outside and then my bay only has to come down from 80 instead of 105 or so.

The fun part of my project is trying to squeeze the cassettes between 24" centers. They are 21.5 plus the thickness of the insulation, plus the hanging hardware, minus how far off the framers set those trusses, etc, etc, etc.

You and the wife should come down when I get this done. We're just a short southern jaunt from when you head into the VA.

Pete

 

[Stevo86]

Hey @Greg Langelius * ,

I just saw your post.

Before I got involved with HVAC, I figured bigger was better. That was before I received my education by the folks at the company I work for. If we're talking traditional 1 and 2 stage systems, bigger can often times lead to 'short cycling'. That means the unit comes on to satisfy the thermostat and then it shuts off. If the unit is oversized, it comes on for a brief time because it's dumping lots of BTUs and then shuts off. This is hell on the compressor. Think of it this way, your daily driver is a fuel funny car. You have 10K horsepower. The light turns green and you only have one or two speeds. You absolutely destroy everyone else to get to the next light, then you shut it down. How long is that engine going to last?

You can mitigate some of that by going to an inverter system because the compressor is going to ramp up or down to what it needs to satisfy the need. As long as you don't go crazy and put in 5 tons where you only need 1 ton, the inverter takes car of it. Most inverters can ramp down to about 20% of rated capacity. Capacity is another reason you have to do heat load calculations. Let's suppose you and I have the exact same size man-caves, 60,000 sq ft (in my dreams). First off, yours is at least 1,500 feet higher from where I live. You are going to need a smaller unit (probably) because you will have different average temperatures. Maybe mine faces due south and has lots of single pane windows, I'll need even more BTU capacity. I really cringe when folks only look at sq ft. It might work, it might be too big, it might be too small, who knows.

I'm in the process of installing a system in my garage. I was out looking at the templates for the ceiling cassettes just a few minutes ago. I'm putting in a 30,000 BTU outdoor unit and I have 36,000 BTUs of ceiling cassettes. That would be a design issue except for the fact that two of the cassettes will seldom be used. Their TXV will be shut down and only the one around my bench will be fired up. I could keep the other two set to about 80 so the entire garage keeps cooler than the outside and then my bay only has to come down from 80 instead of 105 or so.

The fun part of my project is trying to squeeze the cassettes between 24" centers. They are 21.5 plus the thickness of the insulation, plus the hanging hardware, minus how far off the framers set those trusses, etc, etc, etc.

You and the wife should come down when I get this done. We're just a short southern jaunt from when you head into the VA.

Pete

Mitsubishi/Trane makes a Cassette that will fit in a 16” center truss now. We used a few not to long ago and man was it nice not having to cut and reframe everything.

 

[Icallem]

I use a Hisense 300sq ft portable floor AC unit from Lowe's in my boys' bedroom, which is on the second story of our house and positioned where it gets full evening sun. Need it basically mid-May thru mid-Sept; set it to 72 during the day and down to 68 an hour before bed. Works GREAT, plenty of white noise, only downside is the exhaust vent doesn't look asthetically pleasing from outside but its on the back of our house so who cares.

Already had the unit from when the central air failed at our hold house over Memorial Day weekend 2018 and it took 9 days to be replaced...a hell of a lot cheaper than having a second central air unit installed in our current home (which probably will happen in a year or two).

I bought this same unit yesterday for my reloading room. Looks like it is going to work great. For something as a supplement I think is is a good investment.

 

[BytorJr]

Mitsubishi/Trane makes a Cassette that will fit in a 16” center truss now. We used a few not to long ago and man was it nice not having to cut and reframe everything.

That would be for my "new" house if I build. But yes, retrofitting with the cassette is prohibitive in cost (to me). Depends on what you're renovating I guess.

 

[scharfschutze762]

Pete; as a former GI Electrician USMC Utilities Engineer, and also as a computer site manager, I've always sided with excess capacity. If you don't need it now, you will eventually.

IT capacity engineer, "You gotta getta biggah Box, boy..."

We always had to balance the efficiency against the reliability; running at full (not peak ) capacity. With some excess capacity, we could take a breather, but computer capacity needs are always growing.

FWIW, I once had an Osborne Executive portable PC assigned to me; hardly a laptop.

But I'm also open to discussion on that.

Are there difficulties with excess capacity, and what would they be?

sharfshutz; will a 10A breaker suffice for the DeLonghi? (I refer to the 700 sq ft model)

Very curious;

Greg

Greg,

Im not sure about the 10A as I just checked the box and it said 15A.
But I have a big TV and ceiling fans/lights another small window unit in the office on the same breaker and never tripped.

My power goes out quite often and the troy built 7k watt genny runs 3 ACs and 2 fridges along with TVs and wifi so these A/Cs cant be drawing that much power.
96 deg today and this De Longhi AC kicks ass and so quiet.

 

[Greg Langelius *]

Outside vent covers.

Dampers keep the heat/cold, rain, and bugs at bay.