Twinned Carrier Issue

**Hvacbyday** · 08-15-2008, 09:43 PM

Ive got two Carrier Furnaces Model 58tx155---11120 twinned together and having an issue with the blower relay on the primary unit chattering. The only thing that gets it to stop is pulling the wire that connects the two units. Both work perfectly fine individually but when connected together I have the afore mentioned issue . Figuring it was the primary units control board I replaced it but the problem is still there.Spent most of the day today getting beat up by this problem today an help would be appreciated. Thanks

**iamcanadiandave** · 08-15-2008, 10:54 PM

Are they twinned using a factory kit or are they twinned using field installed isolation relays?

**jay688** · 08-16-2008, 08:00 AM

i had the same problem,,you have to make sure the 115 volt line feeding
the furnace is pulled off the same leg or side of the power panel to the house or space,,( that means two seperate feeds off the same bus of the panel) you cannot have one 115 volt line coming in and split it for both furnaces,,it wont work.also make sure equipment grounds are installed.

later jay

**Hvacbyday** · 08-16-2008, 12:41 PM

Was thinking along those lines but wasn't sure if it made a difference. The school recently had a major electrical upgrade all new main switch gear and panel, ect. Originally was single phase but now its 3 phase. The units are twinned using isolation relays.

**jay688** · 08-16-2008, 12:47 PM

pull the cover off the panel and make sure your coming off the same buss or leg
that will remedy the problem

**jayhawker** · 08-16-2008, 02:03 PM

http://www.johnsoncontrols.com/publi..._controls.html

I have used these twinning kits and never had any trouble

**jay688** · 08-16-2008, 02:38 PM

johnson controls is the way to go if you can afford it,,
$600.00 here,,,but the twinning features in most of the white rodgers boards
will work as long as they are wired from the same bus of the panel and are identically the same