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Posted by Todd on January 20, 2004 at 04:48:04:
In Reply to: Re: Usual boiler overtemp posted by Harold hydronicnetwork.net on January 19, 2004 at 09:53:00:
First of all, thank you for the reply. I appreciate it. Secondly, a clarification or two is in order.
: It is 'usual' for a boiler to reach its high limit when only one zone is open because when one zone is open only half the radiation is available to get rid of the full amount of heat the burner is putting into the water. The boiler does not reduce its input to match the radiation.
I haven't read my original post, but I my intent was to be clear about that fact that BOTH of my zones are operating. One is operating normally. That is, the zone valve is controlled by the associated thermostat. The other zone valve is set so that it is ALWAYS open. Only one thermostat controls the heater at present, therefore, whenever the one remaining thermostat calls for heat, all available zones are operating. Consequently every heating pipe in the house is dissipating heat. The problem that you describe (heat input greater than output) is exactly what I am concerned about. My problem is that, since as mentioned about all available means to extract heat from the system are already being used, I'm not sure how to increase heat output nor do I know whether or not it's possible to decrease heat input. I am a homeowner with a reasonable degree of smarts, not a heating expert.
:This problem was solved 40 years ago by recommending an outdoor reset control or two-stage thermostats. However; it takes time for word to get around to the trades.
Where can I get more information on this?
: The high limit is a safety device that should NEVER actuate until there is a problem.
This is EXACTLY why I posted the question on this forum. It was apparent to me that this situation is not one that should be allowed to continue. My problem is that I have had several heating "experts" attempt to fix my heating system (not for this problem, but others) and have nothing but bad luck. I know that good people are out there, I'm just not sure how to find them.
:Reducing the radiation to 1/2 that required to eliminate the heat put into the boiler is a deliberate breach of safety. If you are going to continue to allow this primitive control method, at least install an additional manual reset high limit so there is something to kill the fire when the first high limit wears out. That is REQUIRED on a commercial boiler.
If I understand you correctly, you would prefer that the problem not be solved by the addition of a manual reset, but by a better, more proper solution. I would definitely agree with that. Any information that you can provide in order to help me accomplish that would be greatly appreciated.
Once again, I appreciate your help. Unfortunately, you have confirmed my concerns about operation of my heating system.
Thanks,
Todd