Furnace Fan will not Stop

cmr_3168

I was installing a new thermostat. I had to run a 7 conductor wire so that I could have a common. My system is a Amana Distinctions Heat Pump with a gas back-up (aux). When I put the new stat on (Debonair 400) it would not leave the off mode. I could not get it to go to heat or cool. I got concerned so I went to hook the old stat back up. When I removed the new stat, the fan on the furnace kicked on with nothing connected. I immediately hooked up the old stat and it will not shut off. The unit is not responding to the stat. I removed the fan wire at the control panel (G) for the thermostat and the furnace - nothing happened. The unit will not heat or cool either. The only way to stop the furnace is at the breaker (I do not have a switch at the unit).

What could be the problem?

cmr_3168

The reason I changed the stat is because the original stat was a HoneywellFocusPro 5000. It seemed like a great stat except you can not change the "deadband" on the stat. If I set the temp to 68 degrees heating mode, it would cycle on and off every 5 minutes. My house never got to 67 degrees. The internal setpoit was like a 1/2degree.

My bills are skyrocketing with the constat starting and stopping of the unit. I am used to the thermostat calling for heat when it drops 2 degrees. There is no setting in this stat to change this. Any thoughts?

JJDH

Did you try disconnecting all the low voltage wires from the furnace? From my understanding the deadband is the difference between heat and cool when the stat is in the auto changeover mode. Doesnt sound like the stat. Sounds more like a high limit problem. They dont make 7 wire.

cmr_3168

I did not disconnect all the low voltage wires. I wired the system the same way it was wired before. I am concerned I may have shorted out a transformer or relay.

When I say "dead band" I mean the range before the unit kicks on. This thermostat has like a less than 1/2 degree accuracy and I want one that I can adjust for optimal performance of my house.

JJDH

Try disconnecting all the wires from the furnace first. Start the process of elimination, lets determine if the furnace is doing this, or a bad low voltage wire. Is your new stat wire 18awg?

cmr_3168

It is 18 guage wire. I will check when I get home tonight to disconnect the wires. I have disconnected the fan wire from the thermostat side and the furnace side of a "controller" on the unit. When I disconnected the fan wire, the fan still ran and I do not have any thermostat on the unit controlling it now.

JJDH

Start with disconnecting them. Then it will be easier to help from there.... Always turn line voltage off when servicing, or installing a stat.

cmr_3168

I got the fan to stop. The low voltage fuse on the control panel had failed. I replaced the fuse and now the fan has stopped and is operating properly. This does not help with the unit continually cycling, but I have heat again!

Nathan

Please post on DIYChatroom.com.

Thanks.