Low Temperature Thermostat

[Hydroman22]

I just purchased the Honeywell low temp thermostat (CT50K) for my Reznor UDAP 100 natural gas hanging heater. The thermostat is heat only with 2 wire connect. My heater has what appears to be three wires going to the wire panel (R, G and W1) at the back. Can I still use this thermostat? Thanks

 

[mfd1992]

Yes, assuming that it is a low voltage (24 volt) thermostat. You will only need to use 2-conductor wire from the heater to the thermostat. Traditionally, 2-conductor wire has red and white wires within the protective covering. Just hook the red wire to the R terminal on the t-stat and the furnace and the white wire to the W terminal on the t-stat and the furnace. Hope this helps you out.

 

[Hydroman22]

That's what I tried still didn't want to light. The power draft fan kicks on but the igniter doesn't click and it doesn't light. Maybe need to bleed my 125 ft of gas line? Whats the best way to do that?

 

[billp603]

G is for ground, that would need to be grounded for the igniter to work, not connected to thermostat

 

[RCStocker]

Most furnaces have a low voltage at the furnace and all you need to do is run 2 wires but you don't have the voltage at the furnace so you will need to look up your furnace on line and see what kind of stat. you need. 2 wires without any voltge will not work.

Was there a small voltage regulater installed hear the heater? If ther is you have it hooked up wrong. Withour seeing your set up I can't tell you how to hook it up.

 

[koditten]

That's what I tried still didn't want to light. The power draft fan kicks on but the igniter doesn't click and it doesn't light. Maybe need to bleed my 125 ft of gas line? Whats the best way to do that?

You are going to have to crack the union as close to the furnace as possible. I know people are going to come un-nutted, but you are going to have to smell the gas coming out of the union. Tighten it up and soap check.

You have about the same distance I had, I had to bleed mine for a while before I could get the pilot to light.

KO

 

[dave67fd]

G is for ground, that would need to be grounded for the igniter to work, not connected to thermostat

Wrong. "G" is for optional fan control. Connect between "W1" and "R". Jumper directly at the heater to eliminate any thermostat issue.

If the igniter doesn't fire but the combustion air blower runs you may have a problem with the combustion air pressure switch. Regardless, consult your manual as i believe you have on-board diagnostic LED's that should help you out. Typically once the combustion blower starts the pressure switch gives the igniter the comand to light.

If you don't here the igniter trying to light it's not a gas flow problem.

 

[Hydroman22]

OK, I jumped the R and W1 and it powers the vent, short 3' run horizontal out side wall but no noise from igniter. The LED flashes Green fast,

manual indicates:

Control Status - Green LED Codes
Steady ON .......Normal Operation, No call for heat
Fast Flash ........Normal Operation, Call for heat
1 Flash .............System Lockout, Failed to detect or sustain flame
2 Flashes .........Pressure Switch Did Not Close within 30 Seconds of Venter
motor
3 Flashes .........High Limit or Flame Rollout Switch Open
4 Flashes .........Pressure switch is closed before venter motor is energized
Steady OFF .....Blown Fuse, No Power, or Defective Board
Flame Status - Yellow LED Code

1) Call for Heat - The thermostat calls for heat by energizing the “W” terminal. The control checks to see that the limit switch is closed and the pressure switch is open. If the limit switch is open, the control responds as defined in the “Abnormal Heat Cycle, Limit Switch Operation”. If the pressure switch is closed, the control will do four flashes on the green LED and wait indefinitely for the pressure switch to open. If the pressure switch is open, the control proceeds to prepurge.

The code doesen't suggest pressure switch? Thanks

 

[nehog]

G is for ground, that would need to be grounded for the igniter to work, not connected to thermostat

Not sure where you got that bit of (miss) information...

Terminal
Designation         Wire Color  Function Description
       [B]Rh               Red           24 Volt Hot for Heating[/B] 
       Rc               Red           24 Volt Hot for Cooling 
       Y1               Yellow        First Stage Cooling     
       Y2               Blue          Second Stage Cooling           
       [B]G                Green/Gray Energizes Indoor Fan[/B]     
       [B]W1               White         Energizes First Stage Heat [/B]
       W2               Black          Energizes Second Stage Heat 
       O                Orange        Heat Pump Reversing Valve
                                          (Energized In Cooling)       
       B                Brown         Heat Pump Reversing Valve
                                           (Energized In Heating)     
       C               Brown**       24 Volt Neutral 
                                           (Common) leg

Green allows you to run the fan without heat (for air movement) while W1 and R turn on heat (the fan will automatically come on when the heat is ready. You can safely ignore the G wire/terminal if you don't want fan only operation.

 

[dave67fd]

Reconnect your thermostat the correct way, shut off ac power and then turn on again while watching your code LED's to watch the sequence.

Give us as much info on the heater as well as detailed desc. on how it was installed. Is this unit brand new and first time trying to fire? Did you install and run the vent?
Do you have a warranty on the heater?

 

[Hydroman22]

Unit is 3 yrs old. Reznor UDAP 100 was installed for one winter at a local commercial building but was removed because it was undersized (building was uninsulated). It sat for about 1.5 yrs before I got it. So I assume I have no warranty. Gas co. swapped out regulator at the house to up my line pressure to 2 psi. Gas was run to the unit from the house ~150 ft of 1/2" line and all connected by local heating co. They installed a new 0.5 psi regulator in front of the heater and connected the heater (not sure if they bled the line) and wanted another $350 to run the chimney out the side wall. I opted to do the 3 ft run out the side wall myself and get it going. Have 3 ft 4" B-vent with a 1/4 down slope per ft.

I reconnected the Tstat today and powered it up, the powervent started it tends to run very slow for about 30 seconds (its cold here ~ 15 F) until the fan warms up then seems to run well and I can feel the exhaust on the outlet of the chimmney. On subsequent startups the powervent fan starts and gets up to speed much quicker. If I let the powervent run it goes ~ 4 minutes then shuts down then will restart. Green LED will flash fast throughout. After a couple of 4 min cycles it will powerdown and do one flash on the green LED = System Lockout, Failed to detect or sustain flame. If I unhook the tube to the pressure switch coming off the powervent it doesn't seem to matter. I can feel a very slight positive pressure coming from the tube. I pulled the powervent fan and pressure switch tube off and cleaned everything up. I wasn't dirty, just a little bit of dust. Any suggestions, should I bleed the line?

 

[domain]

seems it does not detect sufficient inducer/power vent flow and will not fire without proper exhaust...

 

[Hydroman22]

domain you may be correct. Now after 3 of the 4 minute cycles of the power vent it will flash green LED 2 times = Pressure Switch Did Not Close within 30 Seconds of Venter motor. The tube from the power vent fan is connected to the (-) side of the pressure switch. I assume that is correct as that is how it was? Pulled the switch off but it is sealed plastic, no way to open it. Probably just a diaphragm?

 

[dave67fd]

I would thoroughly inspect the blower fan, tube and pressure switch for debris. You could also test the pressure switch with a ohm meter while inducing a +/- pressure on the switch. I'm sure Reznor has replacements available if needed.

 

[Hydroman22]

Will do! Thanks guys for the great insight and tips...!