I have installed new rooftop unit- electrical heating & cooling- few weeks ago. When I run the cooling everything goes fine (blower and composer) but if I run the heating; heat element will fire up but the blower will not work unless I put the fan on ON position not AUTO position, so, please, I need to know is it the T-stat or the unit itself. Thank you

It could be almost anything on the NO NAME BRAND-NO EXACT MODEL NUMBER unit.

Since there are about 2,327 different ones it is really hard to tell. Sorry.

OK, my bad:) it is Carrier, model: 50SD, sigle-package Electrical Cooling/Heating Units.

It has 2 separate unites; AC unit and Heating unit with separate control leads. 1st control lead includes: Brown for common, Red for power, Yellow for cooling and Green for fan blower. 2nd control leads includes: Brown for common, White for stage one heating and violet for stage 2 heating.

I connected the Browns together( Brown wire in cooling control with Brown wire in heating control, then I connected Red wire in Unite to R terminal in T-stat, Green wire in unite to G terminal in T-stat, Yellow wire in unit to Y terminal In T-state, White wire in unite to W1 in


T-stat and Violet wire in unit to W2 in T-stat.

The problem I have; if the T-stat in Auto and run the heat, the Blower will NOT run but if I change the Blower to on it will work just fine.
I do not get to same problem if I run cooling even the blower in Auto position, every thing run fine.

I checked all connections, I changed the T-stat to new and deferent T-stat; I still get the same problem. Please if you can help please do so. Sparky

Not sure on that unit but you need to find out if the unit controls the fan in heating. If not you need to set your t-stat to turn fan on when a call for heat. Depends on your t stat how you set that. You need to set the t-stat for electric heat

Check the thermostat for a switch or selection jumper with positions for "gas" or "electric". Set it to "Electric".

I do not have this option, Do you have any brand and model suitable to work with this unit

Quote:

---

Originally Posted by onle a sparky

I do not have this option, Do you have any brand and model suitable to work with this unit

---

Most quality stats will be compatible with electric or gas. Did you look at the circuit board of the stat for the selector switch? It will NOT be on the exterior of the stat.

Quote:

---

Originally Posted by onle a sparky

I do not have this option, Do you have any brand and model suitable to work with this unit

---

Are you sure? It could be on the back of the thermostat or sub-base. Check the installation instructions if available.

I'm not sure, it's late to go back now but I'll go 1st in the morning, you guys saved my ###, thank you very, very much. I'll late you know tomorrow. Thanks

Quote:

---

Originally Posted by onle a sparky

I'm not sure, it's late to go back now but I'll go 1st in the morning, you guys saved my ###, thank you very, very much. I'll late you know tomorrow. thanks

---

One note from your install instructions.

NOTE: Do not use any type of power-stealing thermostat. Unit
control problems may result.

Also

1. Place room thermostat SYSTEM switch in OFF position.
Observe that blower motor starts when FAN switch is placed
in ON position and shuts down after 30 second fan time delay

expires when FAN switch is placed in AUTO position.

NOTE: To enable fan ON activation the thermostat you use must have a R to G connection built into the thermostat or thermostat subbase.

Also check status and wiring of TDR (time delay relay). If you need to change blower speeds to maintain unit specs the TDR is where you do it. Usually the fan speed selected at the factory works well.

Here is complete install instructions for that Carrier. I have placed a sub-channel call into one of my engineering friend at Carrier. Now they are building them with no relay for speed selection between heat and cool. How cheap can they get. LOL

http://www.xpedio.carrier.com/idc/gr...t/50sd-1si.pdf

BTW The two brown wires that are twisted together would be for the C terminal on the thermostat if it had a C terminal. It is the common leg or the 24 volt control circuit.