Power vent issue with Carrier furnace

[jojogeorgina]

58CVA090-1-16
This dual stage system is working fine and is installed under the house. The existing power vent (PV) was used with the new Carrier Infinity system. The furnace has its own exhaust and the PV works with it and the PV is wired into the furnace circuit board.

Every time the furnace cuts on, the PV runs for 30 seconds and cuts out. When the furnace runs in the second stage, the PV runs constantly, which is fine. Why is the PV running for 30 seconds in the low stage when it isn't necessary? The installing company has very poor service. I told them to call Carrier and ask about the wiring but they have not thus far. Anyone have a similar issue?

[INTECHBILL]

The cycling you are mentioning is possible for additional heat build up.. Although the installation contractor should offer service in a prompt and professional manner. Some equipment we installed over 20 years ago and today we still offer good service to our clients, no matter what it takes .

[beshvac]

It could be energized during the startup sequence, hard to determine without knowing how its wired. It's rare to have an infinity hooked up to a power venter.

[jhallinstaller]

if the pv is wired to the common it is going to run as long as the board is getting a call. 30 sec.or less is about right.

[jojogeorgina]

It could be energized during the startup sequence, hard to determine without knowing how its wired. It's rare to have an infinity hooked up to a power venter.

They told me there is a high and low connection on the furnace circuit boards, and the PV wiring was attached to the high. But it still comes on for 30 sec when it turns on.

Are you saying that they are OK to disconnect the PV and let the furnace handle pushing out the exhaust 40 feet or so out the vent? Is this OK in the second stage also?

[hvacrmedic]

They told me there is a high and low connection on the furnace circuit boards, and the PV wiring was attached to the high. But it still comes on for 30 sec when it turns on.

Are you saying that they are OK to disconnect the PV and let the furnace handle pushing out the exhaust 40 feet or so out the vent? Is this OK in the second stage also?

Most likely the power venter is wired/installed incorrectly. Your furnace will not run with a positive draft pressure very long. A draft safegaurd switch will lock out the furnace if a negative pressure isn't estabished in the flue within a minute or two after a call for either low or high stage burners.

[beenthere]

Yep. Its not installed right for a furnace. That furnace isn't approved for side wall venting without the PV running no matter what stage its in.

[jojogeorgina]

Yep. Its not installed right for a furnace. That furnace isn't approved for side wall venting without the PV running no matter what stage its in.

According to the contractor (and I don't really trust them) Carrier said that the power venter is not necessary on this furnace, and that the furnace would exhaust itself through the vent pipe!

[beenthere]

Then why did they leave the PV on at all?

[hvacrmedic]

According to the contractor (and I don't really trust them) Carrier said that the power venter is not necessary on this furnace, and that the furnace would exhaust itself through the vent pipe!

Whether a power venter is required or not depends upon the installation. Venting instructions are detailed in the installation and service manual that came with the furnace. You might urge your installing contractor to actually read those instructions.

Your contractor seems to be working under the mistaken impression that the furnace's venter motor pushes the flue gases out under positive pressure. That's incorrect. The flue must run in a negative pressure on this furnace, or the furnace will not operate. If the vent pipe cannot be run straight up, or nearly straight up, with a minimum 7 ft total rise, then a power venter may be required. For sidewall venting the power venter is required, period. A barometric damper must also be installed when a power venter is used with this furnace. If your contractor has questions he can always call Carrier tech support. The call is free.

[jojogeorgina]

Then why did they leave the PV on at all?

The PV was there from the old system. I told them that even though Carrier said it was not necessary, that I would feel better having a PV. I suppose there is no way that I could speak to Carrier to find out the "true" facts?

[beenthere]

In the install instructions it says.

SIDEWALL VENTING
This furnace is not approved for direct sidewall horizontal venting.
In the U.S.: Per section 10.3.4 of the NFGC, any listed mechanical
venter may be used, when approved by the authority having
jurisdiction.
In Canada: Per section 7.24.2 of the NSCNGPIC, any listed
mechanical venter may be used, when approved by the authority
having jurisdiction.
Select the listed mechanical venter to match the Btuh input of the
furnace being vented. Follow all manufacturer’s installation requirements
for venting and termination included with the listed
mechanical venter.


In other words. The power venter must work no matter if the furnace is in first or second stage.

[BURL-REF]

If the outdoor PV isnt running, you should not be able to get any actions of the furnace. You need service now.