Residential Carrier Puron Unit

[lacajun]

If this isn't the right place for this, let me know and I'll move it.

In 2009, the home unit needed about a 3# charge. In 2011, it needed another 1.5# charge. This week, it needed a 3+# charge of 410A.

Each time and times in between, the accessible parts of the system have been leak checked with a sniffer. No one has found a leak. Do any of you know of leak problems with Carrier's central units? Is there an additive that will seal leaks?

It's beyond warranty by two years so that's probably not an option. Not sure about how to correct this and looking for ideas.

Pamela K. Quillin, P.E.
Quillin Engineering, LLC

 

[MintJulep]

That's a big ass leak.

If the tech can't find it he's lazy or incompetent.

 

[lacajun]

MintJulep, 4 different techs have searched.

Pamela K. Quillin, P.E.
Quillin Engineering, LLC

 

[berkshire]

Pamela,
The forum403 is a better place, but the people who have the answers have found you, so you might as well leave it here.
A couple of things, one, the tech may be over charging the unit, if he does, it will get worse instead of better.
two, The leak may be where the serviceman is charging the unit ( schrader valve improper seating) and may be occuring after he has left.
I would recomend that you have the unit evacuated, weigh the removed charge,then have it charged with dry nitrogen to max allowable pressure, then check every brazed joint and flare nut fitting with a soap and water solution. Also check your line set to make sure nobody nicked it with a nail or screw during construction.
Any competent Tech should do this without being asked.
B.E.
And by the way I have 608 universal licence.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[IRstuff]

Perhaps, there's nothing wrong at all:

http://toad.net/~jsmeenen/charge.html

Was there a problem with the A/C before the techs were called?

TTFN
faq731-376

 

[MintJulep]

the accessible parts of the system have been leak checked with a sniffer.

Which suggests that the leak is in an "inaccessible" part of the system - which goes back to lazy techs.

There is no "bars leak" equivalent for refrigerant

There are dyes that fluoresce under black light that might help locate the leak.

 

[rmw]

Pamela,

I enjoyed the same process for 4-5-6 years. This year it requred re-charging earlier than normal - much earlier; usually it made the whole season on my spring spruce up. The technician found a leak in the evaporator coil at on eof the places where one of the tube passes was soldered in. That wasn't an "accessible" area. The Tech had to remove part of the air handler cowling to get to it.

One new evaporator coil later and quite a bit lighter wallet later, and the unit cools like it hasn't in a while.

I furnished the R-22 for the job since I had plenty from before. I also had to furnish a set of gages to check their gages. Mine are older and read more accurately than their new toys. The AC Service Co owner is a personal friend and he was amused at watching his techs with someone looking over their shoulders coaching them on how to do it right - me.

They did detect a leak at the suction side service valve that required that the service valve be backseated solidly in order not to leak. Try your soap test there.

Good luck,

rmw

 

[berkshire]

RMW,
"They did detect a leak at the suction side service valve that required that the service valve be backseated solidly in order not to leak. Try your soap test there."
You just hit one of my favorites. The tech rarely finds that one, because he has his gauges on there while he is looking for leaks.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[DRWeig]

Agree with all the above suggestions, especially the probability of the service valve issue. One customer who now has over 100 rooftop units on a large mall placed brightly colored balloons over every service valve so that a tech could simply ride his bike around the roof during his daily "roof rounds" and check them all at a glance.

Many that leaked were repaired by adding teflon tape to the service valve threads and replacing the plastic cap with a brass one. That stop-gap method eliminates the need to take the unit out of service during the day and the unavoidable loss of refrigerant during changing of the service-valve core. It seems to work. Units with sealed valve caps have not been found with inflated or missing balloons.

Good on ya,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

 

[lacajun]

The unit cooled the air to 62F so its failure wasn't a big surprise. They've all looked around the valves for leaks and found nothing. Each time new caps have been put on the valves.

When I get time, I'll look for a leak with soapy water. They put pipe dope on the threads. If I find anything, you'll know. Thanks for the help!

Pamela K. Quillin, P.E.
Quillin Engineering, LLC

 

[berkshire]

Pam,
The soapy water will not find a leak very well on the low side with the unit running unless it is a large leak.
you need the higher pressure of the nitrogen charge to push bubbles out of a small leak. You will be ok on the high side though.
If your service guy has not found it yet, it is going to be where he has not looked. Where does your line set go? Is it up in the attic, or buried in the walls?
I am presuming you have looked in the obvious places, like stone dings from the lawn mower in the condensor coil. and all of the Brazed/soldered joints on the compressor receiver.The evaporator and condensor coils.
One of the hardest leaks to find, is a nail or a screw in the return line, especialy if it is screwed in tight and not disturbed.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[rmw]

Gee, my low side runs ~70 psig when running and ~120 psig when not running. I think the soap ought to work OK. My leak was on the low side and it managed to leak sufficiently well enough on the low side to cause me to have to add Freon every year for about 4 years until I got it fixed.

rmw

 

[berkshire]

Rmw,
You may be right, I forgot Pam was running 410A. The system pressures are much higher than your R22 unit.
Her system will be running somewhere around 400 psi on the high side and 130 on the low side when running.
I test at 500 psi with nitrogen. I use soapy water and an electronic ultrasonic stethoscope when hunting these things. Also I do not think there is any rule against just topping up a 410A system.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[lacajun]

B.E., I've looked for the obvious stuff and so has my brother, a really good Jack-of-all-trades kinda' guy. The techs have looked and a friend looked recently, too. Everything if fairly accessible outside and in the basement, which is unfinished. The backside of the coil in the plenum hasn't been checked. Thanks again for the help! You guys are some of the best!

Pamela K. Quillin, P.E.
Quillin Engineering, LLC

 

[berkshire]

Ok Pamela,
Being Mr. obvious you know where you have got to look then.
Good luck,
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor