Boiler gets "stuck"

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tallmon

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So, once in a while in the wintertime when we are using the heat, the boiler seems to get stuck off occasionally.
The system is an oil fired water furnace that produces domestic hot water and for the baseboard heat.

We'll notice that sometimes in the morning it seems a little cold or that the shower isn't as warm as it should be. When I go to check it out the water temperature says around 170 (the low setting), the furnace is not burning, and the circulator is off, even though heat is being called for. I switch the power switch on/off/on and sometimes that kicks it back on. Sometimes I'll cycle the power and then gently tap the outside of the control box to get it going.

By getting going I mean it'll fire up and circulator kicks in.

Does this sound like a bad control box or bad settings?

It's set to 190, 167, and a diff of 20.
 

Dana

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A boiler heats water, a furnace moves hot air- they're not the same thing.

If tapping on the thing makes a difference it's not the settings. A loose wiring connection, dirty/worn relay or aquastat contacts, or a weak relay coil could have such a symptom. When you say "control box" are you talking about a zone relay or zone controller, or are you talking about an aquastat mounted on the boiler?
 

tallmon

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A boiler heats water, a furnace moves hot air- they're not the same thing.

If tapping on the thing makes a difference it's not the settings. A loose wiring connection, dirty/worn relay or aquastat contacts, or a weak relay coil could have such a symptom. When you say "control box" are you talking about a zone relay or zone controller, or are you talking about an aquastat mounted on the boiler?

I'm talking about the aquastat.
 

Dana

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His questions are:

Does it have an embedded hot water heating coil for your domestic hot water?

Does it have a indirect fired tank for domestic hot water operated as a separate zone?
 

Jadnashua

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Without knowing how your control system is wired, it may be normal. A few things to keep in mind...in the morning, the incoming cold water is probably about as cold as it will get all day, so the coil must heat it up further to make it useful, and while doing that, it may be setup to limit running the main circulator to keep as much heat in the boiler to heat your water for showers better. That is a limitation of coil (embedded, or tankless systems). A tank can work better as long as it is sized properly since it can provide maximum volume at whatever temperature it is set to until it is diluted nearly to the end; then, it has all day to recoup verses trying to make it all at once as the water passes by. Many of the embedded coil systems just aren't designed for large volumes of hot water. Is it only one, or multiple showers going on at once? Are they the only user of hot water at the time?
 

Tom Sawyer

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The circulator has nothing to do with making hot water. Depending on where the aquastat well is located, it may just be hot water stacking in the boiler.
 
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