Coleman EB15B Blower Speed

[trailrider]

I have a Coleman EB15B electric furnace with the Deluxe Blend Air II. The furnace comes on with the high blower speed. It used to use a slower blower speed with the furnace. I installed a digital thermostat this summer. Honeywell model RTH110B. I don't think that has anything to do with it as it just tells the furnace to send heat or the AC to send cooling. Also there is some kind of relay beside a wall switch in the bathroom that clicks when the AC turns on. Now it clicks when the furnace comes on with the faster blower speed. So where should I start to troubleshoot it? The wiring diagrams are kind of faded so I am having a bit of trouble trying to understand how it works. Is the blower relay the only thing that determines blower speed?
Also, I just noticed the blower speed goes back down to the slow speed about the last 20 seconds of operation. Thanks.

[trailrider]

Any one? Thanks.

[trailrider]

Still need help, thanks.

[trailrider]

Back from vacation yet?

[Robert]

Hi,

Yes the fan relay sends signal to correct speed wire for each mode. Have no idea what the relay and switch is in your bathroom.


For heat cycle, test the wire from fan relay terminal 6 for 120vac at all times during heat cycle.


Thanks,
Robert

[trailrider]

I have 120v at top left terminal, 120v at top right terminal-black wire,wiring diagram "cooling speed", 120v at middle left terminal, 215v at middle right terminal-red wire, wiring diagram "heating speed" when furnace is running. After thermostat is satisfied, the fan slows down and runs for another 20 seconds. At this time the voltage on the top right terminal is 31v and the middle right terminal is 120v.

[Robert]

Hi,

Be sure your meter is set correctly and working correctly. Then with t-stat set to heat-auto-95* or highest setting to give call for heat, your fan relay should read this:

Bottom gray and black = 0vac across them, 0vac from gray and black each to ground

Middle gray and orange = 0vac across them, 120vac from gray to ground and 120vac from orange to ground

Top yellow and black =240vac across them, 120vac from yellow and black each to ground



Thanks,
Robert

[trailrider]

My original numbers are from each terminal to ground. I tested across the terminals and I get 24v across the bottom two, 90v across the middle two and 0v across the top two. Then for the last 20 seconds after the thermostat is satisfied and the blower speed slows down the readings are: 0v across the bottom two, 0v across the middle two and 88v across the top two. And I tested the top two terminals with no furnace operation and they read 244v. Thanks.

[Robert]

Hi,

Either your t-stat is bad or you have an intermittant short. You should never have any voltage across bottom 1 and 3 terminals while in heating mode.


It is sending power during heat mode which causes blower motor to run in high speed which is the cooling speed.

Then when it stops sending power to the bottom terminals, it goes back to normal low speed which is heating speed.

Need to find where the 24vac is coming from during time it is in heat mode and there is 24vac across bottom terminals.


Thanks,
Robert

[flcruising]

Hopefully Robert won't mind my input...

When I installed our digital t-stat, there was a jumper on the back side that selected 'Gas/Elec' heating type. Can't remember which was which, but one made the blower operate on 'cooling' speed, and the other made it follow the lower speed like I wanted. This one is a 'Rite-Temp', and I had to call them to figure out what was going on with it. They directed me to changing the jumper (I believe it is set to gas), which fixed my issue.

[trailrider]

Thanks Aaron, I just switched the jumper and it's working like it's supposed to. But it's backwards. The instructions say set the jumper to HE if you have an electric furnace, which is the way I had it set when I installed it. I switched it to HG which is for gas or fuel oil furnace and now it works perfect. I guess the difference is the instructions say " When the thermostat is placed in heat mode, the fan is controlled by the furnace fan control circuitry". This is when the jumper is in HG position.

[flcruising]

That's how mine behaved. When set to electric, the thermostat somehow made the blower run on MedHi (my a/c blower speed), once I changed the jumper to 'Gas', it ran on MedLo (the heat speed) as connected on the blower relay.