What are some possible reasons my gas-fired Weil-McLain boiler has blown its rollout fuse?

I recently had a hot water heater installed in the same chimney, and I'm hoping the new HWH isn't interfering with the venting of the boiler.

Are there some simple straight forward methods of checking the air flow past the burner tubes, temperature at the RO fuse, etc.

Thanks!

Sorry to say it but sounds like the water heater venting may be causing your problem. If the roll out switch is tripping then something is effecting the drafting of the boiler and I would look at the water heater.

By the way, if it were a HOT water heater then it wouldn't need to be heated lol. Sorry, just a pet peeve of mine.

Youe best bet on this is to call for a ON SITE inspection and get to the bottom of the problem right away. The hot water heater could be causing this problem or there could be a restriction in the chimney.

You can check for the restriction yourself by placing a light in the bottom of the chimny area by turn off the appliances that use the chimney and getting on the roof and looking down OR sometimes you can use a mirror and look up the chimney.

The size of the chimney might be to small to service both appliances or a down draft condition can also cause this problem.

You are playing with CO and this can kill you if not vented properly to the outside. What ever you do get it checked and corrected right away.

Thanks to both of you.

Yes, I'll do all that and get to the bottom of it. In any event, I won't run without a working fuse in place, and I also have CO detectors working just to make sure.

Mark: I agree, and I've gone around with that for as long as I can remember. I guess people will always say "hot water heater", and maybe abbreviate it to just "HW", but never WH.

About the only justification I can think of to say hot water heater, is that one could instead be talking about a "water heater" that, say, warms up some kind of circulating water so it won't freeze -- but it's not designed to make "hot water".

On target, and interesting.

Detailed, thoughtful and considerate.

Problem was a rusted horizontal support for the back end of the burner tubes. The right side let go and the right hand two or three tubes had their back ends on the ground!

Probably resulted from dampness from the unfinished basement floor. I think it might also be caused by poor venting, however this began long before the WH was installed.

This boiler is only 2 or 3 years old. The almost identical one it replaced ran fine for well over 15 years and virtually nothing in the basement has changed.

The plumber/installer will be here within the next couple of days to evaluate. It may be time for a Weil-Mclain rep to have a look too.

Any further ideas would be welcome, such as how to insulate it from the floor. How about raising the whole thing 4-6 inches? I assume that would require pouring a cement pad, since these babies are darn heavy.

Thanks!
Larry

It is possible the boiler is condensing from to low of a return water temperature. This will allow the condensate to cause rusting in the burner area. Been there done that many years ago on a boiler we did not install. Have the contractor check the return water temp.

Last February I had the same problem, would replace the rollout fuse, and it might last a few hours to maybe over night then would blow again. Heater had been in service for about 3 years with NO such problem.
Ventilation was OK, intake air was OK, every thing seem to be in working order.

Last February 2008, I had the same problem, would replace the rollout fuse, and it might last a few minutes to maybe a few hours then would blow again. Heater had been in service for about 3 years with NO previous such problem.
1) Exaust Ventilation was OK
2) Intake air was OK
3) I cleaned the 5 or 6 burner tubes of dust & rust
4) I removed the top of furnace and cleaned the air intake box
Nothing I did solved the problem, and I went through about a half dozen fuses (had no choice it was -20 F outside)
Then I noticed that the rectangle cover plate that goes on just above the burner tubes, and located below the Thermal roll-out fuse actually had a screw at either end to hold it firm in place (they had always been just a little loose for easy removal of this cover) and I tightened these down tight. This solved my problem. This small "draft" was causing a roll out on the burner and burning out the fuse.
I hope this information might help others with this same problem.

Thanks for all your help. Mfg agreed boiler was defective - perhaps a small leak - and replaced it at no charge. I did pay for moving, electrical and plumbing though. Mounted new one on 4" patio blocks.

If there's a good part, it's that I've learned an awful lot about boilers and their peripheral controls. I'll treat this new one like it was a vintage car.