Harman PB105 Problem

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Chrisr04626

New Member
Feb 5, 2024
6
Maine
I just started having an issue, the pellet boiler is running and getting up to temp according to the guage on top, but the oil boiler its connected with temp is not going up. It used to match or close to it with the pellet boiler temp. And theres very little to no heat coming from my baseboard. If i turn pellet boiler off and just use my oil boiler it works fine. SO whats causing this to not heat with using the PB?
 
It sounds like a problem with circulation, not the boiler, which really runs independently of what the circ pump might be doing. For some reason it seems like the pump isn't circulating unless the oil boiler is running (I'd bet the pellet boiler is getting up to max temp whether the oil boiler is running or not).
 
Generally when I run the pellet boiler I disconnect the oil boiler as I don't want that kicking on too. The pellet boiler gets up to max temp then shuts off then fires back up when it gets below the set point. Like it's supposed to It's just the heat doesn't appear to get circulated to the baseboards. Even though pipes coming from pellet boiler are hot.
 
The thermostat controlling my system actually triggers the circulation pump and the oil boiler at the same time -- but we have an aquastat wired into the boiler circuit that is clamped on the piping. The aquastat keeps the circuit open unless the aquastat senses a temperature below a certain point.

Is it possible that you shut off the circulation pump the same time you shut down the boiler? Obviously if the pump isn't running the baseboards won't get hot.
 
I would change you wiring setup...
The reason for having a backup system is for it to come on when your primary system is down. Especially if you are away, so your house does not freeze up
 
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I would change you wiring setup...
The reason for having a backup system is for it to come on when your primary system is down. Especially if you are away, so your house does not freeze up
That's the way my boilers are set up, with the aquastat. From the original post, it seems clear that the circulation pump(s) run when the oil boiler fires but don't run when the oil burner is off. Fixing that issue should solve the problem.
 
if i leave my oil boiler plugged in when the pellet boiler is going the pellet boiler gets up to temp still but the oil boiler dont heat and turns on when it falls below the temp, so both are running and the pellets are just wasting. SOmething in the system appears to have stopped working for this to be happening
 
Generally when I run the pellet boiler I disconnect the oil boiler as I don't want that kicking on too. The pellet boiler gets up to max temp then shuts off then fires back up when it gets below the set point. Like it's supposed to It's just the heat doesn't appear to get circulated to the baseboards. Even though pipes coming from pellet boiler are hot.
This right here is what makes me say you should change your wiring.
Is this how you have always run the system?
The term" generally" is it referring to stranded operating procedure or just since you have been having issues
 
yes this has always how ive used it. if i leave the oil boiler plugged in it acts as a back up, but now the heat doesnt seem to be transferring from the pellet boiler to the oil boiler as the pellet boiler gets up to max 180 i set it for while the oil boiler will be down to 140
 
Yea i would do something about your controls/wiring
The only time my back up oil boiler comes into play is when the wood side temps drop below around 100F.
Until that time the oil boiler just sits there cold and has no interface with the wood side, once the wood side drops the aqua state powers up the oil boiler and it goes to work till the wood side temp builds over 100F
When the oil boiler runs it is controlled by the high limit setting. When i go on a holiday during heating season the oil boiler does all the work. When i get back i start the wood boiler and once the storage is back above 100 F the oil boiler goes back to sleep.
The only thing i do is close a valve on my heat ex changer so the oil dosn't heat the storage with ghost flows as i usually don't burn the day before i leave just to make sure the oil side is happy.
 
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