HVAC TECHs- question for y'all

[Milf Dots]

Question for full time HVAC techs...

Is it reasonable to believe that a cooling only system allegedly 3 lbs low (told it needs 8 lbs total for optimum cooling) of 410a in a 3.5 ton, 10Kw system- could cool to 76 deg F, in south Florida in July, in temps in the 90s with the expected humidity?

A relative relayed the above to me. I personally don't believe that his system could cool that well if it were 3 lbs low, which is about 38 percent of the total gas charge.

He used a new contractor and no one was present at the condenser coil to observe the tech.


Thanks in advance.

 

[Milf Dots]

To add: In the average residential A/C installation, is there any way to bleed refrigerant from inside the house, or is it usually only at the evap coil's service valve(s)?
Thnx

 

[Milf Dots]

One more thing- has anyone seen a way to lock the actual service valves/ports at the evap coil? Or should he just build a cage around it with lock?

 

[2aBaC̶a̶]

its possible. a typical system in optimal condition can do up to 30°F of cooling. the lower the refrigerant level gets the less it cools. The question is how does he know its 3lbs short? did he recover all the refrigerant in the system and weigh it or is he guessing its probably about 3lbs? thats the only way to know for sure. you can diagnose low charge, but not know exactly how low until you either recover it or add it until the correct pressure/temperature relationship is achieved.

 

[2aBaC̶a̶]

Typically service valves are only outside at the condenser and you can get locking shreader caps.

Pack of (2) C&D Valve # CD2290-1/4" Locking Safety Caps with Core & Cap Tool CD3813

 

[jg6.5]

Generally an AC can keep up with a 20 degree temperature differential between outside and conditioned space, contingent upon a properly charged system, reasonably clean coils (inside and out), insulated ductwork, and a reasonably insulated and sealed building envelope. You can beat that with super efficient building insulation and building design (among other things), but in general that's the rule as it's always been explained to me.

Given this, asking to get to 76* inside with 90* OA temps would be a stretch with a system that is, by all accounts regardless of who's story you're buying, low on refrigerant.

All of the service valves for refrigeration are always on the outdoor coil, I've personally never seen any indoors.

As for locking the service valves, do you not trust your service providers in the area or are you worried about junkies bleeding off Freon to get high?

 

[missed]

for a 3.5 ton the factory charge should be about 8 lbs. lineset and seer rating this can vary some.

Yeah it could still cool #3 low, its going to be working its ass off as there is reduced heat removal capacity with less refrigerant. Being able to cool to 76 degrees in 90 degree humidity is also going to depend on the house and how much actual load is on the unit.

Typically there are only service valves/ports at the condenser unit outside. I have never put service valves inside.

Yes there are locking service valves available. Being 410a this is not as much of an issue, when R-22 was over $1000 for #30 that was the rage was to steal refrigerant. That and the dopeheads liked huffing it. I would be more worried about the tweakers trying to steal the coils if there copper.

Like said above they would have to recover and weigh, or they just added #3 and got the subcooling back to where it is supposed to be. (should be 8-10 degrees) Checking subcooling is the best way to determine charge if you do not pull and weigh. I do not worry about weight in the system, I want the proper subcooling. Lineset, seer, interior coil sizing can all affect that. If the condenser has a variable speed drive and a electronic expansion valve inside it can also deal with being low on charge. Even with a thermal expansion valve and single speed it can still make a 30 degree delta, they have to get real low to be loosing noticeable capacity or freezing up

 

[Milf Dots]

Apparently it's a not uncommon problem in south Florida for techs to bleed systems a bit so they can make the profit of adding refrigerant- probably because so many homes are 2nd/3rd homes and aren't occupied often.

 

[DarnYankeeUSMC]

You don't have to drain the system to know how low it was.
You weigh the refrigerant can before charging it to the required subcool or superheat. Then you weigh the can again. The difference is what you added to the system. It's not rocket science.
I highly doubt that a 410A system that is almost 40% low cooled at all. Especially in a humid area.
Now the real grit. Just because it cooled last July doesn't mean it didn't leak between then and now. If it was low then they should have done a leak check and resolved the problem. If it leaked 3lbs in eight months it should be easy to find.

 

[Milf Dots]

You don't have to drain the system to know how low it was.
You weigh the refrigerant can before charging it to the required subcool or superheat. Then you weigh the can again. The difference is what you added to the system. It's not rocket science.
I highly doubt that a 410A system that is almost 40% low cooled at all. Especially in a humid area.
Now the real grit. Just because it cooled last July doesn't mean it didn't leak between then and now. If it was low then they should have done a leak check and resolved the problem. If it leaked 3lbs in eight months it should be easy to find.

He had them come out for a maintenance about 2-3 months after their July stay in their Florida house- so it was allegedly a loss of 3 lbs in 2-3 months.

A red flag- he said they didn't even call to give a summary and get the okay to add the 3 lbs of refrigerant- they just did it, but right after that they called to ask him if he wanted leak stop added- for $195- to which he declined. LOL

He said the A/C unit is about 9 years old. Home has the insulation of a 30 year old house. Insulated duct work.

 

[DarnYankeeUSMC]

Leak stop is a gimmick.
Sounds like it's time for a new company to get called in. Best thing to do is call one of the local HVAC parts suppliers. Ask for the manager and then ask who he would recommend.

He had them come out for a maintenance about 2-3 months after their July stay in their Florida house- so it was allegedly a loss of 3 lbs in 2-3 months.

A red flag- he said they didn't even call to give a summary and get the okay to add the 3 lbs of refrigerant- they just did it, but right after that they called to ask him if he wanted leak stop added- for $195- to which he declined. LOL

He said the A/C unit is about 9 years old. Home has the insulation of a 30 year old house. Insulated duct work.

 

[NoDopes]

One problem that is probably universal is the cheap install companies often won't run nitrogen when brazing which puts soot into lines which then creates acid. It will eat the lines and coils from the inside. I had a unit that needed coils in only 7 years because it was leaking so bad. I want to get my EPA 608 cert just so I can do my own work/buy legally. Daughters system was installed by 3 illegal immigrants and the cert guy only showed up at end of day to collect check.

 

[missed]

One problem that is probably universal is the cheap install companies often won't run nitrogen when brazing which puts soot into lines which then creates acid. It will eat the lines and coils from the inside. I had a unit that needed coils in only 7 years because it was leaking so bad. I want to get my EPA 608 cert just so I can do my own work/buy legally. Daughters system was installed by 3 illegal immigrants and the cert guy only showed up at end of day to collect check.

Yep lack of purge gas creates problems. Many will not pressure check with N2 after. Just braze it up and stick the vacuum pump on it, run the pump for a couple smokes and open the service valves. You know how many times I've blown a brand new coil and line set down and gotten metal shavings out of a brand new system.....

Another way around it is to buy package units that you can get with no license. Looks like the direction things are going with refrigerant is back to flammable refrigerants, when this happens I'll be swapping to a package unit.