wood boiler over heating

[mjjones_1]

Hello, I've a hot water oil boiler running with an NY wood boiler next to it. the oil boiler seems to be running fine.When I fired up the wood boiler this year after about an hour the pressure relief value opens.the wood boiler sounds like its low on water.I'm not sure how one boiler's fine and not the other? also they share an expansion tank that seems to be empty,How much is full ?, the tank has vales on the bottom of the tank at both ends. what the proper way to fill and bleed the system?

(In previous years sometimes our cold water at the sink would get really hot. go figure)

Thank You mike

 

[MrEd]

Don't know the answer to your questions for sure, but about 5 years ago I had the same problem where all of a sudden all of my cold water faucets were getting hot water (steaming hot water) instead of cold. Even the garden hoses. (It did make the toilets nice and toasty to sit on too!).

As it turns out a piece of debris has logged itself in either a backflow valve or check valve of some sort so as the pressure built up in the system it was allowed to flow backwards into the cold domestic water piping). Not sure if this would explain all of your issues, but it might be part of the problem.

 

[webbie]

Could be a lot of things. Most expansion tanks have a way of being drained - you close off the valve on the way to it (with boilers off), drain it, then open the valve.

One thing to look for is whether the PR is blowing steam or water. If water, it is possible that your system pressure is too high (should be 10-15 PSI) - which could mean that your cold water make-up valve is defective or set wrong.

If it is building up steam or water that is too hot - that could be a control, piping or circ issue. It is difficult to troubleshoot accurately from afar, but this should give you some idea. You should become very familiar with how the entire thing works - including controls, overheat protection, etc. -