High limit is tripping. Cleaned filter and evaporator coil. I have all registers open. The high limit was touching the heat exchanger. I bought some sheet metal and made a gasket so that the HL woul not touch the heat exchanger.
I suspect the previous home owner might have changed the high limt explaining the clearnce problem. The range is 135-175 DegF and set at the 175 DegF mark.
Can someone confirm this range is correct. I have not been able to find this information on the net.
Thanks for your help.:)
Did the control board have diag LED?
Can you post pic of the high limit that you have?
Yes I do have the diagnostics. Flashing 4 times - High Limt open.
Here is a pic.
I think that is right. Needs to be set at 175. I'm not 100% sure I can call in monday to confirm. If you would like please post model and serial numbers.
This comfortmaker is an inner city which is alittle before I started selling comfortmaker. Comfortmaker is now made by International Cooling Porducts.
Thanks a lot for helping.
Was the filter of evap coil dirty?
Do you have a thermometer with a 5 or 6 in probe that will go up to 200 deg?
Do you know which is your return air and supply air ducts?
If so take the thermometer and make a hole in the 3 ft from the furnace return opening and 3 ft from the furnace supply discharge big enough for the probe to be inserted.
Measure each then substract the return from the supply. The difference should be about 45-50 deg
Example if return is 50 deg and supply is 100 deg then there is a 50 deg temp rise of 50 deg Delta T
I just want to make sure that you don't really have a high limit issue.
Filter and evaporator coil were caked. The filter is cleanable it got it clean. I used a vacume cleaner with the soft brush attachment to clean the coil. Its hard to tell if I got everything because I can only see the coil at an angle.
I tried the temperature test.
Reading 70 DegF return air at the filter.
Reading 130 DegF leaving the unit (after evap coil)
The high limit tripped again when the supplty temp was 130 DegF.
Because the existing high limit was touching the heat exchanger there were phisical marks on the switch. It still opens high and closes low but I think my next step is to replace it with a new one. I have seen them for about $25. That is why I need to confirm the range is correct.
The temperature test makes it look like the switch is way off or the evaporator coil is still very dirty in between the fins.
I took a second look at the limit. That is a universal limit and not the one it should have. Below is what you should have. There isn't any pic but I think it is a camstat limit. I will check Monday.
Also, the temp rise is a little high for me. When I set up a furnace I set them up at 45-55. There is a sticker inside the furnace that has temp and gas specs. I think on this furnace temp min and max are 35 to 65.
If you need I can get you a price on this part or depending on your location I may be able to tell you where you can get it cheaper.
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Price $166.01 Available Yes-In Stock Additional info FAN LIMIT CONTROL STAT
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Wow I thought I was looking at a $25 part.
I live in Sterling VA 20165
There is a Grainger supply house close and they cary stuff like this. There is also an Aireco HVAC supply house near me.
How did you figure out what part number I need, I had no luck.
I went to my dealer site. The age of your furnace wasn't there but I did some looking st some comparable furnaces. Because something about the limit judt didnt look right.
Then I google'd "comfortmaker furnace parts"
I looked at several sites and camstat kept coming up. The problem that needs to be answered are;
1. Determine right limit
2. Determine lenght of limit. ie. 6", 8", 9" and so on
With the wires on the limit you have this has me a little stumped. usually there are 2 or 4. you might look at the wiring schematic on your furnace. There seems to be some aftermarket engineering.
It look something like this
Range voltage from 24 Volt - 120,240 Volt.
WIRING CONNECTIONS: (C) COMMON, (NC) NORMALLY CLOSED, (NO) NORMALLY OPEN
Temperature Range:120-250 F
Differential Range: 20-40 F
I may be off base but what you have is not right.
ICP or International Cooling Products is basically Carrier
ICP also makes Comfortmaker, Tempstar, Aricoair
So if in your area you can find one of the above they will be able to get this part.
Just on the other side of the high limit is the center heat exchanger. The existing limit is only about 1/2" depth and it was touching the heat exchanger metal. My high limit is a snap disc type. It is the size of about a quarter-1/2" depth.
Nothing longer would work.
The wiring matches the factory diagram. The limit switch really only has two terminals. There are three wires because one side of the switch has a double blade connector which gets 24v from main controller and one branch goes to the blower DP switch. The other end of the limit switch goes back to the main controller.
I agree with plumber. I don't know of any manufacture that used a snap disc type limit (like the one pictured) for the conbustion chamber. I have used them on floor furnaces Not a forced air furnace
Called in this morning and the limit you need is part # 1320361 my cost is $20.
If you can find a Tempstar, Aricoair, Heil or Comfortmaker dealer and give them that part number they should be able to help you.
This limit is for 230 deg +/- 20
Hope this helps
You are the man!
That explains my tripping. There is a spec on the unit which shows the 230 DegF but I thought that was some kind of manufacturing rating.
I will look for the part locally.
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