Burnham oil fired boiler and no hot water

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Maylar

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I have a Burnham oil fired boiler with a 40 gallon external tank. I've been in this house about 1-1/2 years and since this last weekend I'm not getting hot water.

The circulator runs continuously unless I turn the tank's thermostat way down. The pipe between the boiler and the tank (with the circulator motor) is not hot, even though the boiler temp says 150 F. Eventually the burner will fire and by the time it shuts off the water pipe between boiler and water tank is nice and hot as it should be. But it doesn't stay hot long enough to bring the water heater up to temperature, and the circulator keeps running.

The control boxes (aquistat and a separate one for the hot water) were replaced earlier this year during the heating season.

So, it seems that the boiler just isn't supplying hot water to the tank. My question is, should the water heater initiate the burner control or is that done strictly by the boiler itself?

And, what can be wrong here?

Thanks.
 

Dana

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Usually the controls are set up to not fire the boiler until the boiler reaches it's low-limit.

If the boiler is 150F and the pipes are't hot when the pump is running the pump may have a broken impeller, spinning without moving any water. An obstruction ( or cl0sed valve) on that path would have a similar symptom.
 

Dana

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That makes sense, except why would the pipes get hot when the burner is running?

If the average temp at the pipe being convection cooled by room air is normally ~50F colder than the boiler's temp it'll only be at human body temp when the boiler is 150F.

The high limit temperature on the boiler is probably something like 180-200F, so at the end of a burn everything is at least 30F hotter. A 130F metal pipe is too hot to hold onto for very long without burning.

Is the return water pipe also hot at the end of a burn? If the pump were pumping 180F water into it the return water from the heat exchanger in the water heater would be over 150F.

Ultimately it's the pump that delivers the hot water to the water heater, not the boiler. The boiler is just the heat source. If the heat source is hot, and the water in the tank isn't getting hot, it's either that the pump isn't really pumping, or something is blocking the flow.
 

Maylar

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Turned out to be simple - there was air in the system and the pump wasn't moving water through the pipe. The service tech knew instantly by listening to the noise the pump was making. He bled the air out and all is well.

Thanks for the help.
 

Dana

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I should have thought of that, but it's a rare for a system to develop a vapor lock like that unless the system has been opened up recently, say to replace or add a radiator or something. Most systems have air capturing devices and vents to prevent that sort of thing. The fact that it went 1.5 years and still occurred implies there may be some (probably minor) errors in the system design/implementation.
 
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