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  #1  
Old 06-17-2005, 04:20 PM
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DIY Home-Residential HVAC (A/C) Anyone?

I have been wanting to start this thread for a while since we have some very smart people on this forum, I think we can venture into the DIY residential hvac area also.

I am enjoying learning about auto a/c so much that I want to learn about Residential a/c (central air-R22).

The hvac-talk forum techs are very rude and do not want anybody that is not liscensed and in the busness full time. But I have watched many a trainee moron that has come to my house scratch thier heads, throw parts at the problem, ect....

I have been studying about the subcool, latent heat, supercool, ect... i know how to disconnect the power and take covers off, clean condenser, evaorator, evap drains ect....I even bought some condenser coil cleaner which i am going to use soon. I have R22 gauges and access to 30lb r22 freon.

My unit is a 2 ton Armstrong R22 unit, on the label it says high side 300psi and low side 150 psi, I wonder if this is max? anyone know of a high/low side pressure temp chart for r22?

my tips so far:

Use pleated return filters for better flow, last longer (3-pack $4 at Lowes) change often.

Keep condenser and evaporator fins clean and straight. use your air compressor blow gun or leaf blower.

Make sure evap drain is not clogged and draining.

I did change a bad blower motor once, a squirell cage on a A O Smith $80 motor, looked like a big Benz blower motor!(the tech had the polarity wrong and it spun the wrong way, no flow at the vents, took him two trips to figure this out and switch the wires)

Let's keep this topic going!

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1993 Mercedes Benz 300D 2.5 205K (ex wife's)
1984 Mercedes Benz 300SD 320K (SOLD)
2004 Mercedes Benz C240 75K
1995 GMC Sierra 2WD 5.7L 188K
1983 Mercedes Benz 300SD 239K (SOLD)
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  #2  
Old 06-17-2005, 04:36 PM
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First ... be careful with that compressor blow gun... sure has the potential for bending fins....

Second... Do you have a good HVAC manual ? If not check out the local Community College and get the manual they require for poeple in training there... usually a thousand pages plus or minus... but has all the charts and warnings... and theory also...
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  #3  
Old 06-17-2005, 06:04 PM
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It's all pretty straightforward stuff...commonsense basic electricity and mechanicals. Clean coils are a must...nothing piled around the condenser. If you're needing to add refrigerant, then you have a leak that should/must be fixed because these are hermetic (sealed systems). Another important thing to be aware of is the condition of the ducting in your attic. Leaks there will cost you big $$$ and are tough to detect without a visual inspection..unless you feel cold air coming out from around a wall outlet or switchplate.

Leathermang and I know all about thermostats and incorrect wiring diagrams, don't we Greg?
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  #4  
Old 06-17-2005, 06:06 PM
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Quote:
Originally Posted by James L
I did change a bad blower motor once, a squirell cage on a A O Smith $80 motor, looked like a big Benz blower motor!(the tech had the polarity wrong and it spun the wrong way, no flow at the vents, took him two trips to figure this out and switch the wires)
He did something else, there's no polarity on AC motors like that. The blower wheel was on backwards or something.
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Last edited by R Leo; 06-17-2005 at 06:16 PM.
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  #5  
Old 06-17-2005, 06:15 PM
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One more thing...

When you pull those covers on the condenser, lube the fan motor out there too. Some motors will have little aluminium or rubber plugs that can be removed to access oil galleries for the motor bearings. Squirt some turbine oil in those when you PM that condenser, it will increase the MTBF on the motor by at least 1000%.

I know this for a fact because in another life, I used to pull a/c service on the systems at 12 different apartment complexes totalling over 550 units. One summer, we were losing on average one condenser fan per day. The next spring, we did PM on all the systems before hot weather. THe service included oiling the inside and outside motors, blowing out the condensate drain and putting a chlorine tablet in the pan. We sat and played a LOT of cards that summer.
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  #6  
Old 06-17-2005, 06:48 PM
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Most newer motors are serviceless=(

THe old time rule for R-22 a/c units was 200 psi plus the outdoor temp(a/c mode summertime). So, 300 psi would be at 100F. Ussually there is a chart, but it depends on the age of the unit. I had a unit which leaked slowly and I'd top it up a few times a year. The leak got worse and the unit died and then I installed a new one.


Michael
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  #7  
Old 06-19-2005, 03:39 PM
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You can't properly charge a system based on pressure alone. Charge a system with an expansion valve by subcool and a system with an orifice by superheat.

Hello, from Holiday Motor Lodge, Pearisburg, VA. We are about halfway through our hike.
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  #8  
Old 06-19-2005, 04:08 PM
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Quote:
Originally Posted by R Leo
, blowing out the condensate drain and putting a chlorine tablet in the pan. We sat and played a LOT of cards that summer.

Great trick I will have to do that. I have 3 systems and 1 drain that always gets clogged and the overflow pan starts to drip, usually during the hot summer and we all know how wonderful it is in the Attic in Texas.

I have a bottle of Drano and then some mold and mildew remover that I will poor int he drain. then the chlorine tablet will go in the tray.
Now I assume you install the chlorine tablet inside the evaporator unit and not the overflow pan, or do you do both?

James if you got the 609 license now consider getting your 608 Universal license. This will allow you to buy and work on your house R22, etc system.

I just got the study book for the 608 Universal license for Fathers day.

Dave
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  #9  
Old 06-19-2005, 04:19 PM
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White Vinegar would probably do just as good a job...
And I worry about chlorine touching galvanized metal... which often the overflow pan is...
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  #10  
Old 06-19-2005, 11:37 PM
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I got the 608 universal license. It was some work but it didn't cost much money. I took the test at a Johnstone dealer. I studied the material for about three weeks. YMMV, I do well on tests.

Develop good rapport with a dealer to get the prices on future purchases.

You will get more useful knowledge from the textbook approach than from certification.

I bought a couple used recovery machines for $50 each.
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  #11  
Old 06-20-2005, 03:41 PM
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thanks for all the good info and keep it comming!

the hvac guys in my area charge a minumum of $70 for a 1/2 hour visit.
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1993 Mercedes Benz 300D 2.5 205K (ex wife's)
1984 Mercedes Benz 300SD 320K (SOLD)
2004 Mercedes Benz C240 75K
1995 GMC Sierra 2WD 5.7L 188K
1983 Mercedes Benz 300SD 239K (SOLD)
1987 BMW 325i 220K (SOLD FOR SALVAGE)

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  #12  
Old 06-20-2005, 05:12 PM
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Had to repair the 17 year old Goodman heat-pump at Mom's Virginia Beach house after Hurricane Isabel. Condenser fan died. Not sure if this was hurricane related or just coincidence. Anyway, the wire splice inside the motor burned up and took out the defrost timer circuit board. The motor relay was still working but looked pretty fried so I replaced it along with the motor capacitor. The motor, capacitor and relay were generic parts so I was able to get new ones without too much diffculty. Unfortunately, Goodman is not a popular brand in Tidewater Virginia so finding the defrost board was a challenge, involving finding a number to call Goodman in Houston for help in finding a Virginia parts vendor, then getting a vendor to actually sell the part to me. One vendor refused to sell, or even give me a price, because I'm not a licensed HVAC contractor! Eventually found a vendor in Norfolk that did (reluctantly) agree to sell me the defrost board.
Total parts cost was $190. (I figure at least triple that to have a tech come out to fix it, if they didn't try to sell me a new heatpump first)

Since the repairs, it's worked perfectly heating and cooling last year and so far, this summer, it's still working fine.

Happy Motoring, Mark
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  #13  
Old 07-13-2005, 05:11 PM
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I recently had to do a repair on a roof AC on an RV. The unit quit blowing cold air. I checked the electrics and determined that the compressor was running. I had to add service ports to determine pressures. I prefer Robinair line taps and installed them on vertical runs of line to minimize the amount of oil loss. I measured zero pressure in the system. I hooked up the R22 bottle to check the line taps and see if they were actually working, they were. I found a small amount of oil on the outside of the lines and on closer inspection and removal of insulating foam found where two lines had been touching and eroded each other. Soap bubbles confirmed a leak at that point. I cleaned and soldered the leak. I pressurized the system slightly to check my patch with bubbles and found no leak. I pulled a vacuum and recharged the system. While the vacuum pump was running I cleaned the condenser coils. I did not have access to adequate temperature gauges or charging information so I had to "wing it". I charged the system until the whole surface of the evaporator was producing condensation. The system has been performing well for a couple weeks since the repair.

This is the short story and there are many other considerations that went into this simple repair.

06/15/2006 - System is still working great and is very appreciated.
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Last edited by TwitchKitty; 06-16-2006 at 12:49 AM.
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  #14  
Old 07-13-2005, 05:32 PM
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Quote:
Originally Posted by James L
The hvac-talk forum techs are very rude and do not want anybody that is not liscensed and in the busness full time.
Oh man ain't that the truth! That's why I asked my questions here too. Ther is *NOTHING* like going on a DIY forum and hearing, "Hire a pro" -- yeah, no thanks.

I needed a coil changed in my home unit. The coil is $191 (Goodman), plus charging. The "pro" wanted $1400 to do the job. Yeah, ok. took about 3 hours for me to do it, and I'm not a pro.

Sorry, but some people just don't warrant what they ask.

Pete
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  #15  
Old 07-13-2005, 05:41 PM
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good job pete! the hvac industry is a big mark up business, the techs are not really that experienced that i have seen, sort of "in training". i was quoted $2500 for a 2 ton gas pac (Trane and Carrier - regular seer) if i needed no ductwork. my armstrong cheap pot metal heat exchanger has rust holes in it and will not let the gas pilot light because of a vacuum fault code on the fenwall igniter. i bought a radiator heater and just use the a/c because that part of the unit still works.

what you mean by coil (condenser)?

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1993 Mercedes Benz 300D 2.5 205K (ex wife's)
1984 Mercedes Benz 300SD 320K (SOLD)
2004 Mercedes Benz C240 75K
1995 GMC Sierra 2WD 5.7L 188K
1983 Mercedes Benz 300SD 239K (SOLD)
1987 BMW 325i 220K (SOLD FOR SALVAGE)

609 Certification
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