WBRU80K boiler cycling issue

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Nanker

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I have a Westinghouse WBRUNG80K fire tube boiler that has worked great the past 6 years or so. I have (2) zones (main floor and bsmt). The bsmt zone has only (2) radiators and the main floor has (5) radiators.

I put a wood stove in this year as an auxiliary heat source and have really enjoyed the addition. However, now that I am able to keep the main floor heated primarily with the wood stove during waking hours (~16 hours / day) I have discovered (2) related issues.

The first issue is that because we keep the temp in the bsmt quite low, ~60F requiring the boiler target tempt set for ~107F, ice was building up on the exhaust pipe outside, eventually causing an ER:29 error code: APS (air pressure sensor) Open.

So by increasing the boiler's target temperature to increase the exhaust temperature to minimize/resolve ice build up issue, I created a new issue where the boiler is cycling on and off with much greater frequency just keeping the bsmt heated when the wood stove is in use.

I am guessing that the (2) radiators in the bsmt are not a big enough load for the boiler's output, and so the return water temperature is too high and so causing the boiler to keep cycling its burn time off and on.

Before the addition of the wood stove, I pretty much had the boiler numbers dialed in with respect to outdoor temps so that the boiler just ran at a steady/continuous low target temp, which was ideal. I would now like to try and find that happy medium again, taking the wood stove into account, using the bsmt zone as the boiler's primary load for the bulk of any given day.

I am thinking I need to change the boiler's C:lt CH Return Temperature parameter to try and reduce the boiler's current set point between its b:tt CH Target Temperature and the C:lt CH Return Temperature to try and minimize the boiler's tendency to cycle off and on because the bsmt zone is not big enough to absorb enough heat for the return temperature to go below the current value.

So, first I would like it if someone with a little more know-how can confirm this possible solution to my current boiler woes. Second, if this does seem like a likely possible solution, I am hoping someone can tell me how to change that parameter, as the C:lt CH Return Temperature parameter does not seem to be one that is obvious to change.
 

fitter30

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Need a piping diagram how the system is piped with the wood boiler tied in. Don't think our model number is correct there's on u.
 
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Dana

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This may be a lot of worry for nothing.

What type of radiation (and how much of it) is on the basement zone?

How many cycles per hour?

How long is each burn cycle?

If it's <5 burns/hour &/or >150 seconds per burn fuggedaboudit- set the boiler temp to whatever keeps the exhaust vent from icing up and declare victory.
 

Dana

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While good & correct advice no amount of slope is sufficient to keep the vent from icing up when operating near or at minimum fire in condensing mode in a climate as cool as International Falls MN.

Vent icing is a common problem for condensing equipment (even 1 speed condensing furnaces) in the Canadian midwest (just over the border from Int'l Falls.)
 

fitter30

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While good & correct advice no amount of slope is sufficient to keep the vent from icing up when operating near or at minimum fire in condensing mode in a climate as cool as International Falls MN.

Vent icing is a common problem for condensing equipment (even 1 speed condensing furnaces) in the Canadian midwest (just over the border from Int'l Falls.)
Worked in -40 wind chill not true -40 if i did I'd drive to palm trees. Wonder if self regulating heat trace with 2" thick or better fiberglass insulation wrapped in aluminum.
 

Dana

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Worked in -40 wind chill not true -40 if i did I'd drive to palm trees. Wonder if self regulating heat trace with 2" thick or better fiberglass insulation wrapped in aluminum.

Wind chill is only about the heat loss from exposed human skin- it has zero effect on the physics of the water in the exhaust gases condensing & freezing in the flue. The absolute temperature is what matters here.

Heat tape does indeed help mitigate against flue frost-up on those -40 (true temp, not wind chill) days.
 
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