Weil McLain Eco 155 gas boiler constantly cycling problem

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np369

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Hi,

I have a one year old Weil McLain Eco 155 gas boiler. It is constantly cycling through prepurge, ignition, heating (lasting about 10 secs), postpurge, prepurge, ignition..... every time it starts fire, it lasts only about 10 secs, and the flame signal is below 100, and then it shuts off the fire, restarts the cycle again.

We did exchange almost all parts (we have an identical unit next to it), and all parts seem function well.

At one point we took almost everything apart and put back, it worked for a while, but it returned to same behavior again. Since it constantly cycles through, I can smell incomplete burning gas smell from external exhaustion pipe.

Any advice would be very much appreciated.
 

np369

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Thanks, I did change the sensor with the unit next to it, same thing. Will try adjust the position. thx.
 

DonL

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Thanks, I did change the sensor with the unit next to it, same thing. Will try adjust the position. thx.

Position may do it.

Do you have a power Vent ?

Please do report back. That unit is to new to have problems. I think.


Good Luck.
 

np369

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Actually there isn't much to adjust the position of the sensor. Same sensor works on one but not the other. Now I have a second unit having same issue after remove and reinstall the sensor. Third one still works fine with either sensor. :(
 

Tom Sawyer

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I would think the intelligent thing to do would be to call a technician that has the proper test equipment so that you don't waste time changing parts that don't need changing. I can narrow your problem down to three possibilities but all three require a trained professional to deal with.
 

np369

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Thanks, I am actually working with a technician, who isn't able to figure this out... Maybe I need a different one. Would you mind to share your three possibilities?
 

DonL

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Thanks, I am actually working with a technician, who isn't able to figure this out... Maybe I need a different one. Would you mind to share your three possibilities?


If your technician can not understand the link to the service manual, then he should not be working on it.

The manual tells how to get to the diagnosis codes.


Messing with Gas is not like changing a blown fuse, or resetting a breaker.


Be safe.
 
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Keitho991

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I had the same problem myself & I guess the wrong burner gasket has been installed at the factory on some Eco 155 models.
The tech support people say the burner gasket needs to be replaced with a different gasket, supplied by Weil-McLain.
For a temporary fix, you can go to "Contractor Menu", "Boiler Setting", "Boiler Model" and choose the "110" model.
The Eco 110 model & the 155 model have different "flame signal shutdown" valves / settings.
This temporarily solved my problem but the tech people say the correct gasket for the 155 must still be installed.
Hope this saves somebody the headaches I occurred.

Read more: http://www.doityourself.com/forum/b...constantly-cycling-problem.html#ixzz3RaAAOErs
 
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