Help with Reznor/tstat wiring!

[thammel]

I have a Reznor UDAS that's almost done. Tstat is Honeywell Vision pro 8320U (saved from prior hvac system).

I have a 24 v transformer.
Reiznor is single stage and Reznor takes G, W and R wires. G - fan, w - gas valve?, R - ?

Now, how to wire the tstat?

Per the tsat manual for a heat only system:
Rc - power
R - (Rc and R joined by jumper)
W - heat relay
C - 24vac common


So do I wire from the 24 v transformer to the c and R terminals on the tsat?

Then do I run an R wire to the reznor?

I know the G and W wires run from tsat to Reznor. Reznor manual does not make clear what the R controls. Perhaps I don't need a separate transformer, as the circuit diagram does show a 24 v transformer on the reznor. Doe this supply 24 v to the tsat?

I also see a Reznor note about setting the tsat heat anticipator to 0.6 amps. I see nothing in the tstat manual about heat anticipator; the closest I see is that the electrical ratings of the terminals are:

W - heating, 0.02 to 1.0 amps
W2 - heating - 0.02 to 0.6 amps

Can anyone help with these questions?

Thanks,
Tom

 

[nehog]

The heater should have the 24 volt transformer built in, and I get the impression you wanted to add another, not necessary...

Your heater should have a Y, G, W, R and C. Thermostat should have similar terminals. (At least the manual I am looking at does.)

Edit: (Finish reply, Nehog, finish the reply!)

Just wire like terminal to like terminal. For the heat anticipator, the default should work OK, but it is controlled by software in a computerized thermostat, there's a setting when you configure the thermostat. For my system I didn't change it, and I'm happy with the result.

 

[sms1974]

you really only need to run wires from the R and W on the heater to the R/RC and W on the thermostat. the G terminals can be connected if you want to be able to turn the fan on by its self. this is dependent on the thermostat using batteries, if it does not use batteries you will also need to connect a wire between the C on the heater and the C on the thermostat...

industry standard wiring is

R is 24 volt power
C is 24 volt common
W is heat
G is fan
Y is cooling contactor

 

[thammel]

Thanks nehog....yes, 24 v transformer built in - you're right, I don't need an external one. Should work fine! Thanks for your reply!
Tom

 

[sms1974]

just saw your using a vision pro, you will need the C connected between the heater and thermostat...

 

[thammel]

The back of the reznor doesn't have a C terminal. Only G, W1, R and W2. W2 is not connected anywhere internally so I could wire C to that and use that. C is the common side of the 24v transformer so I could do that.

So my next perplexity is the external temp sensor I wired up to the tstat. From all my checks, it should be reading ok but I just get two dashes at the external temp location. I wonder if I need 24 volts to the tstat to see a reading? With just batteries everything else seems to be reading ok. I did check the external sensor resistance and it's in line with expected values.

Tom

 

[sms1974]

You will have to have a 24volt power and common for the outdoor sensor to work.

If you dig into the unit you should be able to find the secondary or 24volt leads that come off the transformer.

 

[nehog]

I'm going to suggest you check to see if the common wire is in fact connected to the unit's ground (chassis) and that would make it an easy thing to handle. Take a meter and measure the voltage between the power wire (R) and the chassis, if you get about 24 volts, then that is it!