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BillyHvac
BillyHvac, Journeyman HVAC Tech
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, Goodman Furnace install manual: If an air

Customer Question

Customer: ***** *****-
JA: Thanks. Can you give me any more details about your issue?
Customer: Goodman Furnace install manual : If an air conditioning coil is installed with furnace a common drain may be used. An open tee must be installed in the drain line near the coil to relieve positive air pressure from the coils plenum. This is necessary to prohibit interference with the function of the furnace drain trap. Question is: What do the mean by "open tee" and where do I cut it in? Also, existing drains are not trapped both drain and overflow. Should I trap them and how would that affect where I place "open tee" ?
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Submitted: 11 months ago.
Category: HVAC
Expert:  BillyHvac replied 11 months ago.

Hello,

The only trap you need is already in the furnace.

What this means is you come outthe ac coil with 3/4 pvc..

when you turn it down towards floor, you use a tee instead of a 90 degree elbow. This leaves the top part of tee pointing up with no cap.

Then as the pipe runs down vertically you can run the furnace drain directly into the same pipe with a tee.

If you need I can draw something up for you

Blly

Expert:  BillyHvac replied 11 months ago.

see if this helps

Customer: replied 11 months ago.
Well, you are not the person I posed the question to and my understanding was that I would not be charged until I indicated I was satisfied so we are off to a rocky start.
Let me try to again. I know the furnace is already trapped as provided by the mfg, it can hang off the side or bottom in horizontal installation (which mine is). The two drains coming off the coil are not trapped. I want them to be. After installing the traps where would I make the connection ( without creating a double trap)? The drawing you provide would relieve the pressure but looks like it provides a 3/4 inch hole to the outside which traps are supposed to close off also looks like there would be a chance of some condensate running into the mfg trap and possibly causing problems there. Also I wished to be certain that there is no chance of the acidic furnace condensate causing problems with the coil. I have seen pictures of the damage to copper and aluminum from this. And if you choose send diagrams or pictures I would prefer horizontal.
Expert:  BillyHvac replied 11 months ago.

I understand what you want to do...but we do not want to trap the condensate lines. That is why the manual specifically states to use open tee. The water would overflow pan before it could reach the top of tee anyway.

It is common for the furnace to be trapped but not the ac coil when on the positive side of pressure...we only trap on commercial units if drain is on negative side.

The deposit you saw go through is returned at any time you wish...I can send to customer service right now for you.

As far as installing the way you describe, I would opt out since it is not the normal installation I am accustomed to installing or teaching.

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