HAI Omistat RC-100B Blank Display

[dabincharlotte]

Hi All,

This was probably not the day to switch out thermostats with it being so cold...

I installed two HAI Omistat RC-100B today, and one seems to work perfectly, the other is only showing a green LED and a bit of a blue back light, but nothing else on the display. They are wired from the two furnaces the same way, and if I swap them around, the problem stays put - i.e. the furnace \ wiring seems to be the issue - not the thermostat. I have checked and triple-checked the wiring, even to the point that since I have enough slack in the thermostat wire that I cut it back and reconnect it thinking maybe there was a break in the wire. But it did no good.

The previous thermostat I was using was working fine - as was the furnace.

I have two Waterfurnace brand geothermal heat pumps. There is a Red (1), Green (2), Orange (3), Blue (5), Yellow (6), and White (7) wire coming out of the furnace. The number in parenthesis is the terminal i am connected to on the Omnistat.

(I don't know what the wires are attached to on the Furnace - i don't have a wiring guide or installation manual for the furnaces.)

Is there something incredibly obvious that i might be missing here? Is there something I can try - i.e. are there voltages on some of the wires? can I jumper wires to make sure the furnace or fan goes on? If not, is there a place to go to find out more about how to troubleshoot?


Thanks in advance - Jim

 

[ano]

Hi All,

This was probably not the day to switch out thermostats with it being so cold...

I installed two HAI Omistat RC-100B today, and one seems to work perfectly, the other is only showing a green LED and a bit of a blue back light, but nothing else on the display. They are wired from the two furnaces the same way, and if I swap them around, the problem stays put - i.e. the furnace \ wiring seems to be the issue - not the thermostat. I have checked and triple-checked the wiring, even to the point that since I have enough slack in the thermostat wire that I cut it back and reconnect it thinking maybe there was a break in the wire. But it did no good.

The previous thermostat I was using was working fine - as was the furnace.

I have two Waterfurnace brand geothermal heat pumps. There is a Red (1), Green (2), Orange (3), Blue (5), Yellow (6), and White (7) wire coming out of the furnace. The number in parenthesis is the terminal i am connected to on the Omnistat.

(I don't know what the wires are attached to on the Furnace - i don't have a wiring guide or installation manual for the furnaces.)

Is there something incredibly obvious that i might be missing here? Is there something I can try - i.e. are there voltages on some of the wires? can I jumper wires to make sure the furnace or fan goes on? If not, is there a place to go to find out more about how to troubleshoot?


Thanks in advance - Jim

Its likely your furnace doesn't supply enough current to light the display. Try removing the backlight jumper to see if that fixes it. If so, there are some options to get backlighting.

 

[sda]

This was probably not the day to switch out thermostats with it being so cold...

hindsight.

(I don't know what the wires are attached to on the Furnace - i don't have a wiring guide or installation manual for the furnaces.)

Is there something incredibly obvious that i might be missing here? Is there something I can try - i.e. are there voltages on some of the wires? can I jumper wires to make sure the furnace or fan goes on? If not, is there a place to go to find out more about how to troubleshoot?

Another possibility is that the wires aren't what you think they are.

Thermostat control wires colors are semi-standard, and there's no guarantee the two units were wired the same. When changing thermostats you should label each wire with its position on the original thermostat and not rely on color.

Here's a couple of web pages that explain terminals and wiring conventions
http://highperformancehvac.com/thermostat-wiring-colors.html
http://wiki.xtronics.com/index.php/Thermos...nals_and_wiring

You should get 24vac between the R (power) and C (common) terminals. But not all installs will have common brought to the thermostat.

On a typical HVAC unit (not sure about heat pumps) jump R (power) to G (fan) to turn on the fan. But unless you know for sure which wires are which I caution you against randomly connecting wires together.

You may have to open up the unit, find the control board, and verify what wire colors are being used.

 

[sic0048]

Another possibility is that the wires aren't what you think they are.

Thermostat control wires colors are semi-standard, and there's no guarantee the two units were wired the same. When changing thermostats you should label each wire with its position on the original thermostat and not rely on color.

Here's a couple of web pages that explain terminals and wiring conventions
http://highperformancehvac.com/thermostat-wiring-colors.html
http://wiki.xtronics.com/index.php/Thermos...nals_and_wiring

You should get 24vac between the R (power) and C (common) terminals. But not all installs will have common brought to the thermostat.

On a typical HVAC unit (not sure about heat pumps) jump R (power) to G (fan) to turn on the fan. But unless you know for sure which wires are which I caution you against randomly connecting wires together.

You may have to open up the unit, find the control board, and verify what wire colors are being used.

That is probably the best 1st step. Make sure the wiring for the two thermostats is the same at the control board. If it is, then I think disconnecting the backlight is another good step to take.

I also swtiched out a thermostat recently (Monday). I had disconnected the old unit and was in the process of reconnecting the new unit when it hit me....."If I have a problem, or cannot finish this, I'm screwed!" Not a very good thought at the time. Luckily, my switchover was relatively painless. The only minor delay I had was trying to find the 24v Common feed since my old system only sent the 24v + to the thermostat. I eventually found a ground point that worked, but I was sweating it out for about 5 minutes until I found it.