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airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8164
Experience:  Furnace, A/C and heat pump specialist.
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I have a Trane evaporator positive pressure system.

Customer Question

I have a Trane evaporator positive pressure system. Secondary was not hooked up and caught in a inspection. Had my HVAC guy out to drop a secondary into the pan below. When he removed the plug condensate runs out. He removed the trap on primary and same problem. He elevated the slope of the secondary a little, same problem. He vented the primary, same problem. He is stumped at this point, and so am I. The positive pressure seems to push the water out both ports.
JA: Are you an HVAC professional?
Customer: No, home owner with stumped HVAC pro.
JA: Do you plan on doing the work yourself?
Customer: Not sure at this point. PVC is pretty easy if I knew the solution
JA: Anything else we should know to help you best?
Customer: I have a second almost identical system that has secondary drain with no problem
Submitted: 9 months ago.
Category: HVAC
Expert:  airheatman replied 9 months ago.

OK what is the model on the unit? Is this a gas furnace and coil installation or an electric air handler?

Customer: replied 9 months ago.
Trane 4CXC sitting on a gas furnace
Expert:  airheatman replied 9 months ago.

Thanks for this information. And sounds like it is in upflow position correct?

Expert:  airheatman replied 9 months ago.

ake a look at the drawing below and tell me if he has at least a 4" from center of drain outlet to center of bottom of trap and then at least 2" back up as shown below.

Many installers are using a store bought tee that has a very slight trap

Customer: replied 9 months ago.
I am not sure, and now has removed the trap saying that it is not needed on positive pressure. I am sure how the trap on the primary would affect the secondary other than to place more pressure on the secondary. Currently the primary is vented with no trap which equalize the pressure between the two
Expert:  airheatman replied 9 months ago.

OK I feel most likely the problem is that your inspector does not understand the equipment manufacturer's guidelines.

You should have the main drain with both a trap and a cap installed.

You should not need the secondary drain when this coil is installed in a vertical (upflow)position.

This secondary connection must be plugged when installed in upflow position. See link below.You may need to show this to the inspector and have installer re install the trap and tee with cap as shown in first picture.

Expert:  airheatman replied 9 months ago.

I am also providing you with a link to the manufacturers installation manual so you can show it to both installer and inspector.

If you have further questions, please let me know.

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