Monitor 40 overheating

[RWS]

Thanks for all the useful information!

I have a Monitor 40 that appears to be shutting down due to overheating. Rather than a clean blue flame all around, I'm seeing long yellow/orange flares, mostly along one side of the flame ring. After a few minutes, the top and front of the unit becomes unusually hot and a minute or two later the heater turns off. The ventilation fan is unobstructed and appears to be working normally, there are no unusual sounds during startup (e.g. noisy bearings) and the initial combustion process appears to advance normally.

Any ideas?

Thanks,
Rick

[Bryand]

Sounds as if you have a warped burner ring also could be a burner cloth but sound like the burner ring. You are more than likely getting soot on the flame detector which is shutting the heater down. Clean the flame detector you can do that without removing it. However you will have to take the access door off the burner. Inspect the distance between the flame detector and the burner ring. The flame detector should be almost equal distance between the burner ring and the burner pot. If the ring is warped it could be that the flame detector is touching the burner rings as things heat up. If so and you can't get one right now you might be able to remove the ring and turn it so you have clearance between it and the flame detector.

[Bryand]

Also while you are in there check the baffle in the upper right hand corner of the burner chamber to ensure it is not coming loose. It is only spot welded and will eventually fall inside the pot and could burn a hole in the burner chamber it's self if it does not fall on the flame detector. If it is loose you can remove it and throw it away and you will never know it is gone.

[HayZee518]

you can also remove the air inlet hose off the blower of the heater. the heater will now suck inside air to the combustion pot. yellow flames usually means insufficient air to the pot, restricted holes around the inner sleeve of the burner pot, a warped burner ring or the burner mat has become unglued off the bottom and is curling upward.

[RWS]

Thanks. What about the unit becoming significantly hotter than normal with the accompanying burning odor? It reminds me of the glowing-red chimney pipe that results from a woodstove fire flaming too high.

We've had problems with it shutting down intermittently when the outside temperature is near the set temperature, usually just after successfully reigniting, but not on colder days when it has to work harder (four or more bars). I suspect this may be the flame rod failing to detect the low flame. I tried cleaning the flame rod, but it didn't correct the problem. When this occurs, we get two bars, successful reignition, and after a couple of minutes, flashing 8 bars.

With this new problem, the thermostat never reaches the set temperature. The heater burns at high, the thermostat increases by a few degrees, the heater gets hot, the circulation fan starts and a few minutes later, the flame cuts out and status lights turn off. The lights don't start flashing until a couple of minutes later (unlike the previous problem where they started flashing immediately).

I will try the above suggestions. Is it possible to remove or examine the burner pot/mat/head and flame ring without removing the chamber (i.e. through the front door)? How far should the flame rod be from the flame ring?

Thanks,
Rick

[HayZee518]

you can remove the viewer window but don't break the flimsy gasket. the flamerod should be centered between the burner ring and the side of the pot. with the window off you can examine the burner ring. see if it is warped. the burner mat is on the bottom of the pot. I doubt you can see it from that window. check out ebay. they have gasket overhaul kits [new gaskets] plus there's some other things you may enjoy. what would cause an overheat is the blower fan not coming on when it is supposed to. this is all relevant to the microprocessor. I'm not sure you can adjust the cut in time. hawkins111 used to be a monitor dealer. he is in bethel alaska and is part of this forum. ask him.

[RWS]

Thanks for responding so quickly.

I have fiberglass gasket material that was left over from when I had the heater rebuilt several years ago (by the infamous Al Luce, no less), so I'll replace it if it's damaged. The blower is coming on when expected. It's a few minutes later when the flame cuts out and a couple more minutes before the status lights start flashing. High flames won't cause overheating?

I'll ask hawkins111.

Thanks again for your help.

Rick

[FordMan59]

I had a similar problem a couple weeks ago with my 422. It would start the heat cycle, the circulation motor would come on and within a couple minutes the heater would shut down with all the indicator lights flashing. I took the flame rod lose wiggled it around a little bit and put the screws back in and it started running right. I suspect it was some carbon built up between the flame rod and the burner ring, shorting out the flame rod causing it to go into lockout mode.

[HayZee518]

a couple of other things I was thinking of is the exhaust tube clogged with soot. this would account for any back pressure and retention of heat. the other thing would be the temperature the circulator fan kicks in at. these are standard klixon motor overloads and are rated at a temperature. you need one that is normally open - closes on heat rise.

[Bryand]

There is no way to adust when the fan comes on or goes off. I know you said the fan had no obstructions. Does it have any dust build up on the blades. I have had them that had alot of dust on the blades and cut down on the air circulation and shut them down. However it takes alot of dust to do that. Or has the fan blade been take off. I have seen them put back on and the screw not back in the set position and the fan blade not turn as fast as it should. If the heater goes as far as kicking on high you might want to check your fuel line going into the burner to see if it is clogged but that will not cause it to get hot but will shut down. If these are not a issue. I tend to agree with Hawkins that you may have a clog in the exaust somewhere.

[hawkins111]

old Monitor 40

When you have a high yellow flame the stove can get very hot. Because the stove is a Monitor 40 you are dealing with a unit that has been around a long time. With that in mind you need to start thinking about what you are willing to pay or put up with in the way of a fix. The combustion chamber needs to be overhauled. You may need to deal with the solenoid damper and “O” ring. Before any money is spent I would check the fuel flow. If the flow is out of spec and can not be corrected with the very small adjustment allowed on the controller, the stove needs to be scraped. You can have the main board and the indicator panel fixed at Mathis, however, they do not work on the fuel pump control circuit. If you do scrap the unit, think about what you are trying to heat. You may only need a 20K BTU unit instead of a 40K unit. The smaller units require many times less maintenance and burn half as much fuel. Another thing to think about is the cost of a new flue pipe as part of the overhaul. Monitor pipes are very thin and should be looked at regularly.

Tom