well mclain model cgi-3-pin series 1

NEtech

Hello

I have the above mentioned boiler. First I noticed I had no heat diagnosed flame roll out then found heat exchanger was very clogged. Could not figure out how to remove top portion completely couldnt remove heat exchanger cover. Ive heard not all have access. Anyways unit was short cycling very quickly so i cleared as much soot from the bottom with a as possible from both access ports in the front and the back. Resealed with high temp silicone checked for co all good

my unit contiunes to short cycle. it turns on for maybe 30 seconds to a minute. then turns off for maybe 5s the fires back up. This is what need opinons on. Ive never seen a boiler short cycle like this. Not sure if its like a furnace where it stops and relights if its a bad flame sensor.

why is my boiler short cycling? 24v consistent in circuit

JUGHNE

From the sounds of lack of cleaning, I would guess you have a dirty flame sensor and could also be cycling on high limit.

EBEBRATT-Ed

There is always access to clean a boiler one way or the other. I would suggest having it serviced. Its time.

EdTheHeaterMan

To make a short story long:

I agree with Ed above.

In order to get to the heat exchanger and really clean all the carbon from the boiler sections you first remove the front door and you will have access to the gas valve and other controls.
Once you have access to the controls take a picture of the way the wires are connected to the controls. You will want to remove all the burners at this point. The next step is to remove the top cover of the heater. That will require removing some screws and two side covers. The panels are number 3, 4, and 6. Some of the wires and controls may need to be removed, so take pictures of where the wires are connected.

Once those panels are removed the collector box (number 8) will be visible. That is no doubt filled with soot, you will need to remove that box to get access to the top of the heat exchanger. The collector box is made of a thicker steel and has gaskets or high temperature silicone that will be damaged when removing it. You may also need to remove the fan motor assembly (number 10) to clean the fan blades.





Do not disassemble the boiler section block itself. (Parts 1, 2, and 3). They must stay together. With the collector box removed, you can now remove the baffles (number 7) from between the sections. With the sections now clear of obstacles you can run a boiler cleaning brush between the sections on a diagonal in line with the cast iron pins. All the soot will fall to the bottom of the burner box. You will want to use an optional soot bag on your shop vac to remove the soot from the burner box. like this. https://www.homedepot.com/p/RIDGID-High-Efficiency-Wet-Dry-Vac-Dry-Pick-up-Only-Dust-Bags-for-3-to-4-5-Gal-and-HD06001-RIDGID-Shop-Vacuums-Size-C-2-Pack-VF3501/100520395Or you may just throw the shop vac away after you get it full of soot. Be careful of the ceramic fiber insulation on the sides of the burner box. That is very fragile and can fall apart easily.


Once you have all the soot removed and all the parts cleaned, you may now start to reassemble the heater. The first step is to put the baffles back first before you do anything else. If I may be redundant here, Put the baffles in now that everything is clean. Before you go to the next step… put the babbles in now. The worst feeling is when you have cleaned everything and put it all back together with a new sealer and have wiped off your fingerprints and the heater looks almost brand new the you look on the floor to see the baffles still sitting there. (Don't ask how I know this)


The next step is to check if the baffles are in between the sections before you put the collector box in place. With the collector box on the floor, take a tube of RTV high temperature silicone and run a bead all the way around the cast iron boiler where the collector box meets the boiler. Once the silicone is there , check to see if you forgot the baffles, if you didn’t forget the baffles, you can place the flue collector box in place and attach the hold down fasteners making sure the silicone makes a tight seal around the box. Add more silicone as needed to make the seal air tight. Then using the silicone as a new gasket put the fan box on the side of the boiler and the side (number 3) exterior panel. Finish replacing all the parts in the reverse order that you removed them until the boiler is assembled.


Check the wiring, check the burner alignment, check for gas leaks, check for water leaks. Then you can test fire the burner. But do not operate the burner for more than a few minutes. You will want to get a professional to check for proper combustion with the proper combustion analyzer in order to determine why the boiler sooted up in the first place.


I believe you will be hard pressed to find a professional HVAC guy to do this job unless he also works on oil heat. This is not a usual maintenance call for most burner repair men that work on gas heat only. They prefer to have the competitor do this job.

NEtech

EBEBRATT-Ed said:

There is always access to clean a boiler one way or the other. I would suggest having it serviced. Its time.

Yes I agree. I am a technician by trade. I would like to perform the cleaning myself if possible. Ive done it on others but as I said this one is more difficult getting apart.

NEtech

EdTheHeaterMan said:

To make a short story long:

I agree with Ed above.

In order to get to the heat exchanger and really clean all the carbon from the boiler sections you first remove the front door and you will have access to the gas valve and other controls.


I believe you will be hard pressed to find a professional HVAC guy to do this job unless he also works on oil heat. This is not a usual maintenance call for most burner repair men that work on gas heat only. They prefer to have the competitor do this job.

thanks so much. I got it mostly disassembled didnt realize I needed to remove the side panels. this info and breakdown is very useful. One more question I could not find the high limit switch at all?

NEtech

Also yes I reapplied hi heat silicone and tested for CO. I will need to dissamble again on the weekend thanks for all the help

EdTheHeaterMan

Inside the front door, usually on the upper left... that is where it is on just about every WM "CG" type boiler, CG, CGa, CGi, CG-t. all the way back to the beginning.

NEtech

Hey guys thanks for the tips and resources. I completed the repair. Unit now running fine no longer overheating. Im pretty experienced with boilers I am a tech in new england I just wasnt sure how to get mines apart. Thanks again.

NEtech

can only be so many things guy

EdTheHeaterMan

I just want to check with you on one important isssue…..

Did you remember to put the baffles back in?