I have an old Magic Chef gas furnace in my garage. Gas is connected, but wiring for fan and thermostat are a question. 55K BTU, 12 amp blower. Need to know what wires to connect to thermostat. Also, there are three wires exiting furnace. I know which ones power the 110v blower, but there is a third (white) wire of smaller gauge. Don't know what this one is for. Can you help?

Does the furnane have a model number

Model # G66-55D2C2-6

does the furnane have a model number

Yes, Model G66-55D2C2-6

Magic Chef was bought out by Maytag in 1986 so that is a old unit. Sorry but I do not have a manual for that unit. Post pictures and we will see if we can figure it out.

Thanks for your help. I have pics posted at this URL: http://www5.snapfish.com/thumbnailshare/AlbumID=3513055014/

Not too sure that worked. Try this if you will. Snapfish: Registration:FD:Lite (http://www5.snapfish.com/thumbnailshare/AlbumID=3513055014/)

Sorry I do not have a snap fish account. Go to advanced and hit the paper clip then post here.

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Again, thanks for looking at this for me. One pic shows the three wires exiting the unit. The close up of the transformer shows two pair of wires, yellow/blue, red/green.

First you better have a look inside the 4X4 handy box the fan center is mounted on. Usually white wires go to the neutral line of the 120 volts and the black goes to the hot side of 120 volts. There also should be a screw or ground point inside or on that 4X4 box for a ground. The GROUND is the most important wire since if it is not properly attached the shock in case of a fault can KILL YOU. So take the fan center off the box and investigate the situation and at that time trace both white wires down and get me a picture of the inside of the box so we can find the ground point. Also you will be using a box connector and all wiring splices will be made IN THAT BOX so the job is done properly.

While you have it apart you need to find the manufacturer and the model number of the fan center (the transformer and relay combo is called a fan center). This way I will find a wiring diagram for you of your fan center.

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I think we're looking at what you are describing. Of the 3 wires exiting the fan box, the larger gauge black & white wires are coming from the fan motor. The smaller gauge white wire is coming from the transformer.

On the left side of the 4X4 box is the screw (hex head) for the ground from the 120 volt line.
Looks like the two white wires go together and then go to the white neutral wire from the 120 volt power.

Then the black wire goes to the black power wire from the 120 volt line.

All connections wire nut and go in the box. You will need a romex connector to attach the feed wire from the power source to the 4X4 box. The feed wire goes into the box connector then the box connector is attached to the 4X4 box. This allows all the power wires to be neat and within code.

Thanks again! I'll follow your instructions. Referring back to the pics I sent earlier, does it make a difference which of the colored wires I will connect to my thermostat cable? Or should I just pick a pair? No AC involved here.

Use Red=R or RH and White=W. Those are for heat to bring the furnace on.

I have two pair: red/blue, yellow/green. No white.

From my previous post

While you have it apart you need to find the manufacturer and the model number of the fan center (the transformer and relay combo is called a fan center). This way I will find a wiring diagram for you of your fan center.

Post the above requested info so I can find the correct fan center.

Exact model and Brand

Sorry, overlooked that in your previous post.

FAN CENTER: ESSEX 175-232101-10

Are we talking about the low voltage thermostat wiring?

Essex NLA but here is a W/R diagram for there fan center.
Color code should be the same. You will only use the R=RED and W=White wire from the thermostat since the furnace will be heat only.

You should already have the 120 volt power hooked up.

http://www.white-rodgers.com/wrdhom/pdfs/06_Cat_pages/Cat_06_pg0104.pdf

Yes, low voltage thermostat wiring remains my question. I have two pair: red/green, yellow/black. No white. I have the 120v wired and ready. Will I need to have a "heat only" thermostat?

I have two pair: red/green, yellow/black

Are these wires coming from the thermostat?

The normal heat colors are W=white and R=Red

Green is for the activation of the blower for A/C use

Yellow is for outside A/C unit activation.

These wires are coming from the front of the transformer as you can see from the picture. I'm assuming that is where I should make my connections to the cable going to the thermostat. Is that correct? Sorry this is taking so much of your time.

Actually the thermostat wires go under the screws that are labeled R and W on the face of the transformer. I have no idea what the other wires are for unless they were somehow removed from the transformer. It is impossible for me to figure out with the wrong color wires.

That answers my question! I can see the R & W on the transformer. Thanks for all of you help and patience!!

NO problem and be careful if this is in a garage since it is supposed to be mounted 18 inches off the floor to prevent vapor flash from the gas in the cars/lawnmowers and the furnace has to have protection posts if set in front of a car where the car can hit it. This is the building/mechanical code for garage install. Sorry but I just remembered that. You can probably get by if the combustion chamber is 18 inches off the ground but the posts are a must. You would be surprised what I have seen on inspections.

This furnace is being used to heat my shop and workout rooms. No cars. I have constructed a standard that elevates the appliance 22" from the floor so all is well. Thanks for the info. I'm finished!

You got it working. GREAT.

Does the furnane have a model number

Yes eg6a100d-11

Robertshaw wiring unit is a 780-715-u