UT-3000 / Dual Fuel w/ 2-Stage Furnace

[Mr. T]

UT-3000, 3 zones, Dual-Fuel Amana ComfortNet 2-stage HP and 2-stage gas furnace. Communicating stat on Z1, Honeywell Prestige on Z2 & Z3 configured for heatpump mode.

OAS SP is 32, W2 threshold is 85%

When the outside temp is below 32 and a single zone calls for heat (always Z2 or Z3, as Z1 is in a non-used part of the house), the furnace immediately goes to high-stage fire (Furnace LED's say "HI 18"). The zone board shows W2/E and 60% demand for heat, with only one zone calling.

The documentation says (bottom of page 10) that hi-stage fire is controlled by the W2 Threshold -- I'm far below that 85% threshold, yet the furnace is still going to high fire.

I would expect the furnace to start out in low-stage fire and ramp up when the W2 threshold is crossed but that's not happening.

Any ideas what's going on?

[Erik W.]

What code version of the UT-3000 do you have and what is the demand you have set for your legacy thermostats?

Erik Wnoroski
EWC Controls, Inc.
385 State Route 33
Englishtown, NJ 07726
800-446-3110 ext 483

[Mr. T]

My board is v1.16 (installed new last July) and the legacy demand is set to 75%

When the HP stats are calling for heat, the individual zones show 37%, which seems correct since the stat thinks its controlling a 2-stage heat pump. But still, with only one zone calling for heat (at 37%), the system demand shows 60% and I get high fire.

[Mr. T]

The plot thickens.

Today, I came home and found 2 zones calling for heat, the OAS shows 41 degrees and the system was running in hi fire and showed 62% system demand.

And that's with the OAS SP at 30 degrees.

So clearly, something's not right.

I power cycled and did a full reset of the UT-3000 to restore factory defaults, then went through and configured for HP stats and power cycled again just for good measure.

The system eventually came back online and (properly) started the HP in low stage. I'll wait till tonight when the temp drops below the OAS SP and see what happens.

Is this a known bug in the system with v1.16?

[Mr. T]

Outside temp finally dropped enough for the gas backup to kick in, went right to 60% system demand with 2 zones calling at 37%.

[bdev]

I have a similar dual fuel system with the same problem. The 2-stage furnace always runs in high stage.

[Paul Z.]

Have a few more question, call the office 1-800-446-3110.