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tndiyguy 08-02-2012 07:51 PM

EVAP coil install questions
I had a new evap coil installed today on my 4 ton unit and I had a few questions for the resident pros in this forum!

Prior to recharging the technician used a "vacuum tank/cylinder" to evacuate the system. Is this standard practice in the field? I am used to using a vacuum pump on auto a/c systems and pulling a vacuum for 45+ minutes, and am wondering if this technique is widely used.

The tech used low-side pressure reading to charge system...not by refrigerant weight. Again, not what I'm used to seeing. He said a low pressure reading of 75psi is what he is "shooting for" to get a complete charge. Is this standard practice?

During the initial visit I was told the condensation drain (or is it called an evaporator drain?) had to be upgraded to meet current code. Being the handyman I wanted to do it myself before they returned for the install. I was told I couldn't because of the "licensed installer" requirement. Is this true in TN? $210 for 4 feet of PVC, a few fittings, and 10 minutes labor seemed a little steep.

Thanks for y'all helping educate a do-it-yourselfer!

turnermech 08-02-2012 08:29 PM

If you got a price on a new evaporator installed my question is why did it not include the drain work if not up to code? If I miss something I should not have I don't charge for it if it is part of the job. Just my opinion but drain line is part of evap install.

It would generaly be best to charge by wieght not pressure when possible. Most systems can be pumped down into its self thus saving the refrigerant. a vaccum pump should be used to pull the system down after lines are open. I would guess simialr to what you use in auto a/c's. it is also best to measure the vaccum in microns with a micron gauge.

tndiyguy 08-02-2012 08:51 PM

Thanks for the quick reply!
The drain line was part of the initial quote. The Home Warranty Company covers the evap but not drain upgrade, disposal fee, permits... I was trying to avoid the drain upgrade fee which I thought was a little steep.

carmon 08-02-2012 08:57 PM

you had a less than experienced tec do the work for you.... 75 lbs suction .,...really ..... what was the superheat ..or sub cooling:eek::eek::eek::eek:

turnermech 08-02-2012 08:59 PM

Home warranty company. That would make me think contractor is padding the little pay with overcharging for uncovered repair. I have no idea if that is the case but it is what comes to mind. I do know the home warranty company try to pay the contractors as little as possible. I have worked for several of them when they can't find anyone in my area willing to work for peanuts then they complain about the bill. Which is always fair.

Missouri Bound 08-02-2012 09:03 PM

It's very steep. Did you tell the installer that it was a home warranty job?
Did the warranty company send the installer? These are the kind of things that give the hvac trade a bad name.

ben's plumbing 08-02-2012 09:54 PM

used to work for home warranty company.....they will hose you every time if they can.....they only pay for so much....homeowner pays the rest...they dispatch companys that work for you know why I quit...:yes: there crooks

tndiyguy 08-02-2012 10:24 PM

Same company truck came for initial visit by technician, follow up visit by salesman, and 3 days later, the installer. Salesman called Home Warranty Company from my kitchen to verify what was covered by my policy and what I had to pay. I understand that they have to make a buck, but I was trying to keep my costs down too.

I am concerned about the technical details. Was my system serviced properly? Were shortcuts taken? How and when will I be able to see any problems as a result?

It's been 5 hours and the temp has come down from 80 to 78. It's been broken for a week. 100 degrees outside the last few days. Upstairs unit working nominally . Hope it can get a little cooler in here!

turnermech 08-02-2012 11:01 PM

By morning temp should be at set point. if not you have problems. once the extreem load is removed from the home it should function as normal. If not call them back.

beenthere 08-03-2012 04:21 AM

The tech used very poor procedures.

raylo32 08-03-2012 06:39 AM

So this "vacuum tank cylinder" is a tank that he drew a vacuum on in the truck or shop then just connected up to your system and opened the valve to pull an instant vacuum? I never heard of this method. I guess it could work but its sounds very iffy to get a good vacuum unless the tank was very large and had a very good vacuum. Sure saved him some time, I bet.

Charging by low pressure reading regardless of the conditions and system parameters? Whew... I am a DIY and even I know to start with the specified weight then adjust by superheat and subcooling as appropriate for the type of system.

scottmcd9999 08-03-2012 06:48 AM

Just to pile on: I agree with the other techs, the company did a poor job.

You cannot accurately charge a system using only lowside pressure readings.

There's no substitute for a proper evacuation, and if they used a "vacuum tank" (which is, I believe, a tank that is in a vacuum and is connected to the system and opened) then you should insist they return and do the job right. HVAC systems need to be evacuated to 500 microns or less (and also checked for moisture/noncondensables during the process). They didn't do that, which could mean that you have moisture (read: acid formation) in the system.

Note too that if the drain upgrade was due to a CODE issue, then it would stand to reason that the company would have pulled a permit for the work, and would have called the local code inspector out to review the work. If that didn't happen, I'd call them back and ask them why they performed code work without the requisite inspection - and also ask to see the permit they pulled. You could also ask for references to the code section that requires the drain upgrade.

Finally: I've worked for some of the warranty companies when times got tough. Always remember that they are an insurance company, not a warranty service - so treat your interaction with them the same way you would any insurance claim.

tndiyguy 08-03-2012 03:56 PM

Day 2 update...
Scott, you are correct. I called the "Company" and they scheduled the inspection for next week. I wonder how many homeowners would call requesting the inspection. No call = no inspection = profit in their pocket.

Got home from work just now and did a quick inspection:
Unit has been running since install completed yesterday. Outside low pressure line is coated with 1"+ ice!! hi pressure line at the evap coil is room temp. Very little air flow from registers. Assume evap is iced up too. Couldn't see inside unit for evap ice but given what i have outside...

Turned unit off and waiting for tech to come back today at 5pm. Boy is he in for a surprise!!!

beenthere 08-03-2012 04:03 PM

Turn the fan switch on the thermostat to ON. So it thaws by the time the teh gets there. So he doesn't have to thaw it. or tell you he'll be back when it is thawed.

turnermech 08-03-2012 04:05 PM


Originally Posted by beenthere (Post 980714)
Turn the fan switch on the thermostat to ON. So it thaws by the time the teh gets there. So he doesn't have to thaw it. or tell you he'll be back when it is thawed.

I would tend to agree but you may want them to see the ice. Sounds like they are not the best at what they do.

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