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Old 10-02-2011, 10:19 PM   #1
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Yet more DIY HVAC progress


Hello!

Little by little, getting my first condenser installed, on the foreclosure house with the removed HVAC. As you may recall, one entire system was removed, and the other one still has the furnace in the attic. I opted to
install the condenser on that one first.

Last week, I opened up the wall, cut off the mangled lineset ends, brazed on new ends ( flowing nitrogen ), brazed up the new condenser with a suction line filter. Today, I pressure tested the system to 81PSI ( I was almost out of nitrogen ), and then started vacuuming it. Wow, that takes a long time! By 4:00 this afternoon, it was down to 950 microns ( and still falling ) but we had to go.

While the pump vacuumed, I went to identify wires to install a thermostat - the Forces of Evil had removed those, too. By messing with clip leads, I identified the following wires:

* Red - 24VAC (R)
* Green - call for Fan (G)
* Yellow - call for AC (Y)
* White - call for heat (W)
* Blue - don't know what this was. The voltmeter showed 17VAC between this one and the R. I was hoping to find a "common" to
supply my thermostat, but would expect that to read 24VAC. Anybody
have a clue as to what this one was? The actual furnace is a Payne of unknown model( vintage 2008 ). It's in the attic, and at this time, I don't have a ladder long enough to get up there. Well, I could probably get up, but I don't think I'd be able to get down again .

- JerryK

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Old 10-02-2011, 10:32 PM   #2
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You're blue is your common. 17 volts is a little low, btw. Might want to change the transformer if by chance it's too low to control anything come time to turn it all on.

Post some pics.

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Old 10-02-2011, 10:47 PM   #3
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You're also going to have a set of wires, usually with only two or three, stat wires from the furnace to the condenser. Most of the time, not that color actually matters, it will be a red and a white to the condenser. Don't confuse that condenser red with the red that travels down to the stat or your condenser will never shut off.

The r terminal on the control board is your constant hot.

The two wires to the condenser will terminate (land on) the y and the common terminal at the control board in the furnace.

At the condenser itself it doesn not matter which wire from the control board (of the red and white) connects to which low control wire provided in the condenser. It doens't matter at either end, actually, just so long as the condenser wires land on Y and C in furnace.

Good job tackling this yourself, btw. You'r doing it right although I'd re-up onthe nitrogen, pull a short vacuum, then add 3-5 psi nitrogen and let sit for ten minutes. Pull another short vacuum, add 5 psig nitrogen and let sit for ten minutes. One more time after that, short vacuum and a few pounds of nitrogen and let sit for ten minutes.

Then I'd shoot it up to around 250 psig and let sit for 15-20 minutes at 250 psig. Nitrogen pressure test will show leaks better than a vacuum or microns.

Than I'd vacuum down to 500 microns and let it go. DO NOT FORGET TO PURGE YOUR GAUGES AS YOU FILL THE SYSTEM. Pretty much this means, with the hoses slightly screwd onto their correct ports and with refrigerant connected to middle hose of gauges, slightly open up the refrigerant cylinder. Then slightly open the gauges so refrigerant comes out of both the high and low side hoses which should be slightly screwed onto the service ports of the condenser. As refrigerant is coming out is when you tighten the hoses fully onto the condenser.

You just pulled a vacuum, why put air into the lines?
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Old 10-02-2011, 10:50 PM   #4
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Quote:
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You're blue is your common. 17 volts is a little low, btw.
*** Indeed. The strange thing is, the other leads measure over 24VAC
to the (R) wire. Now that I think of it, I bet the blue lead is
disconnected up at the furnace, and my highly sensitive Fluke voltmeter is just reading leakage.

- JerryK
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Old 10-02-2011, 10:59 PM   #5
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Quote:
Originally Posted by jerryk1234 View Post
*** Indeed. The strange thing is, the other leads measure over 24VAC
to the (R) wire. Now that I think of it, I bet the blue lead is
disconnected up at the furnace, and my highly sensitive Fluke voltmeter is just reading leakage.

- JerryK
I'd go ahead and shut off the main power to the furnace. Not that it's an expensive or hard part to find or replace but you don't want to blow a fuse (or transformer for that matter) in the event that a possible loose wire shorts on something. It's just another small headache you don't need.

If you have more than 24 volts you'll be good. Usually we see around 24 to 28 low voltage, sometimes even higher.
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Old 10-02-2011, 11:07 PM   #6
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You're also going to have a set of wires, usually with only two or three, stat wires from the furnace to the condenser.
*** Not an issue. Those wires were still there, just chopped off. I restored them with a piece of HVAC control cable ( with too many wires, but just used two of them ). It was obvious where they went - two dangling wires in a little box in the condenser that went to the coil of its contactor. I soldered the connections inside the wall - I do NOT want to get any intermittents there.

Quote:
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Good job tackling this yourself, btw. You'r doing it right although I'd re-up onthe nitrogen,
*** How about argon? I have a 60CF jug of argon that's almost full.



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DO NOT FORGET TO PURGE YOUR GAUGES AS YOU FILL THE SYSTEM.
*** thanks for the reminder, Doc. It's an easy detail to forget.

- JerryK
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Old 10-02-2011, 11:16 PM   #7
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I can't say about Argon, I've never heard of anyone using it and not sure of it's characteristics. Maybe someone else would know..?
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Old 10-03-2011, 06:40 AM   #8
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I can't say about Argon, I've never heard of anyone using it and not sure of it's characteristics. Maybe someone else would know..?
*** It's an inert gas, like Nitrogen. It's more expensive than Nitrogen.


Name: Nitrogen
Symbol: N
Atomic Number: 7
Atomic Mass: 14.00674 amu
Melting Point: -209.9 C (63.250008 K, -345.81998 F)
Boiling Point: -195.8 C (77.35 K, -320.44 F)
Number of Protons/Electrons: 7
Number of Neutrons: 7
Classification: Non-metal
Crystal Structure: Hexagonal
Density @ 293 K: 1.2506 g/cm3
Color: colorless

Name: Argon
Symbol: Ar
Atomic Number: 18
Atomic Mass: 39.948 amu
Melting Point: -189.3 C (83.85 K, -308.74 F)
Boiling Point: -186.0 C (87.15 K, -302.8 F)
Number of Protons/Electrons: 18
Number of Neutrons: 22
Classification: Noble Gas
Crystal Structure: Cubic
Density @ 293 K: 1.784 g/cm3
Color: Colorless Gas

So Argon is a heavier and larger atom than Nitrogen. Either one of them is small compared to a molecule of R22, which has



* one chlorine atom, (35)

* two fluorines, (38)

* one carbon (12)

* and one hydrogen (1)
total atomic mass: 86


But I suspect that the main reason nitro is used for HVAC is cost. It's got to be one of the cheaper gases. I have the argon because I use it for TIG welding.


- JerryK
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Old 10-03-2011, 06:55 AM   #9
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I'll be picking up an extension ladder this morning to get a closer look at that furnace in the attic. Coincidentally, the welding store is right next to the Home Depot, so I can get my nitro refilled. Depending on what they have, I might eschew the usual exchange deal, and make them refill my own tank, because it's a really nice one.

It was an Ebay deal, came in a fitted case with regulator and hose. Only problem was, the hose came with a set of really strange ends that have nothing to do with HVAC or any technology that I'm familiar with. But when you unscrew the strange ends, you are left with a female NPT fitting at the end of the hose.

I bought a tire inflator end with a locking clip at the welding shop ( luckily, fairly cheap ). No go, HVAC Schraders are larger in outer diameter than the car kind.

But the other day, I had an idea. I got an old, very simple, hose inflator end out of the junk. Unscrewed the brass business end off it, stuck it in my little metal lathe and enlarged its inside diameter. Worked absolutely fine, although I have to push it on the fitting while inflating the system for pressure test. Just like filling a tire.

- JerryK

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