Max Caddy circuit board problem

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Jason762

Member
Feb 14, 2006
64
Newtown, CT
OK here is my situation. I purchased a Honeywell wireless thermostat so I can have the oil burner thermostat on my second floor. This is a 24v thermostat and I attempted to wire it into my Max caddy control panel. I got the 24v from the upper left connection which powered up the new thermostat without a problem. But when I ran the "W" wire to call for heat I connected it to the lower right port on the circuit board where my old thermostat was wired in and when I called for heat it fired up and ran. The problem is when I called for the heat to shut down the oil burner continued to run. When I turned off the thermostat the burned continued to run. When I unwired the new thermostat and rewired the old one back in it continued to run. When I removed all thermostat wires it continued to run. I tried shutting the unit down multiple times but when I turned power back on you can hear the relay click and the oil burned fires back up. What does it sound like happened and how can I fix it?
 
OK here is my situation. I purchased a Honeywell wireless thermostat so I can have the oil burner thermostat on my second floor. This is a 24v thermostat and I attempted to wire it into my Max caddy control panel. I got the 24v from the upper left connection which powered up the new thermostat without a problem. But when I ran the "W" wire to call for heat I connected it to the lower right port on the circuit board where my old thermostat was wired in and when I called for heat it fired up and ran. The problem is when I called for the heat to shut down the oil burner continued to run. When I turned off the thermostat the burned continued to run. When I unwired the new thermostat and rewired the old one back in it continued to run. When I removed all thermostat wires it continued to run. I tried shutting the unit down multiple times but when I turned power back on you can hear the relay click and the oil burned fires back up. What does it sound like happened and how can I fix it?
the oil burner is in the max caddy right? So you tried to wire two thermostats to the same unit?
 
wp_ss_20150409_0001.png wp_ss_20150409_0002.png Here is how it should be wired and the diagram.
 
The thermostat requires a hot, a common and a wire hooked up to the "W" to call for heat. Where should these wires have been attached on the circuit board and could I have blown the circuit board by doing it wrong?
if that thermostat can use optional batteries you better off to just use the batteries and not use the common wire. If it doesn't use optional batteries than you will need a transformer to power it. Watch this video.
 
If the wood thermostat uses batteries it will be hooked up to wood mech, if it uses 24v common it will be hooked up to wood 24VaC. The oil burner will be hooked up to either user mech is battery or user 24VaC if 24v. I honestly don't know if you hurry the circuit board.
 
RH and W will go to User 24v. How are you powering the thermostat common wire?
 
Yeah I connected the R and C to the left side of the board at the 24V port. I ran the W wire to the top slot on the User T-stat mech. What should I have done differently?
 
c goes to left side of board 24VaC
r and w to right side of board to user 24VaC
 
it doesn't matter if r is on top or bottom as long as both are on user 24VaC
 
Just so we make sure we have it right, where is your r and w for your wood thermostat hooked up?
 
When I removed all thermostat wires it continued to run. I tried shutting the unit down multiple times but when I turned power back on you can hear the relay click and the oil burned fires back up. What does it sound like happened and how can I fix it?
At first I thought maybe the relay just stuck on you, but since you say you can hear it click when the furnace is powered up, the relay is not just stuck. If all the thermostat wires that you installed are now removed, and it is still running as soon as you power up, sounds like the control board has been damaged. May be repairable by someone that is familiar with electronics/boards?
 
R and W is hooked into the Wood T-stat Mech. Yeah it looks like I wired it wrong and must have damaged the board. Guess that's gonna be a costly mistake.
 
R and W is hooked into the Wood T-stat Mech. Yeah it looks like I wired it wrong and must have damaged the board. Guess that's gonna be a costly mistake.
Did you try it again now? Is there any fuses on that board? Because could of possibly blown one.
 
I currently have no thermostat wires on the oil hooked up at all and the unit is still calling for heat, I don't think hooking the thermostat back up is going to fix it. There are two fuses and neither is blown.
 
You should unplug the unit. Hook the thermostat wires up correctly and plug it back in and try it once.
 
I currently have no thermostat wires on the oil hooked up at all and the unit is still calling for heat, I don't think hooking the thermostat back up is going to fix it. There are two fuses and neither is blown.
I hooked up my thermostat wrong when I was installing my ac unit and blew one on the unit. After much research I now know where the wires go.
 
How long did you have the power to the furnace off? Some electronics take a minute or two to completely power down. After re-reading your OP, I guess I don't see what you did that would have fried anything. I really wonder if you don't have a bad control board.
 
Ok the thermostat will only power up if I connect the R and C to the hot and common 24 on the left side of the board. If I do it as you said, it doesn't turn on
 
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I think what I did that may have fried the board was I applied the W wire to the User T-stat port not the User T-Stat 24V port. I think I sent 24 volts where it shouldn't have gone.
 
When I hook the thermostat up with the C and R ports to the 24 volt connection on the left side of the board and the W up to the User T-stat 24V hookup on the right side of the board the thermostat calls for heat and shits down properly. The only problem is the oil burner does not respond to these requests and continues to run non-stop.
 
On the left side where the 24v is do you have the common in top or bottom? Take the r off there because it doesn't go there. Try each of the top and bottom with the common it if doesn't power the thermostat then hook it into one and put a jumper wire from one to the other.
 
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