Hydronic Design for Solid Fuel Boiler

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keegs
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Post by keegs » Fri. Dec. 27, 2019 10:01 pm

So I've been noodling around lately with hydronic design for a New Yorker WC 90 solid fuel boiler system.

The 800 sq ft house in zone 6-7 requires a heat source of approx 50k btu/ h. I'm getting this number from three different online calculators.

The first floor is one room. Because of kitchen cabinetry and appliances etc.... I want to utilize hydronic underfloor radiant using 1/2" PEX in the first floor joist bays. Also on the first floor. I can run approx 25' of 3/4" copper fin tube baseboard along exterior walls giving me an additional heating capacity of approx. 13k btu/h.

During construction while the walls were open I ran a 1/2" PEX loop up to the 2nd floor bathroom floor joist bays and to baseboard locations in each of the two 2nd floor bedrooms.

I thought to utilize this first floor baseboard as a dump zone w/default open zone valve but I don't think it will adequately radiate and reduce the boiler water temp during a power outage, especially given the use of PEX in the balance of the system.

I think this would be a relatively simple design to execute using a gas or oil fired heat source (minus the resiliency of solid fuel). But I do have the Chubby.

I know some of you guys do this kind of thing often enough and maybe could point out something I may have overlooked.... so your thoughts please.

 
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Rob R.
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Post by Rob R. » Tue. Jan. 07, 2020 6:04 am

Your dump zone will be used to scrub off some heat when the boiler gets too warm during long periods of little/no demand, or when it overshoots the setpoint after a long burn. 25' of baseboard that is normally at room temperature will work fine for this purpose.

Good idea on the radiant in the kitchen - it will feel great.

 
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freetown fred
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Post by freetown fred » Tue. Jan. 07, 2020 6:07 am

morninn Rob!!!!!!!!!!!!!!!!!!!!!!!!!!!! :)


 
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keegs
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Post by keegs » Tue. Jan. 07, 2020 12:30 pm

Rob R. wrote:
Tue. Jan. 07, 2020 6:04 am
Your dump zone will be used to scrub off some heat when the boiler gets too warm during long periods of little/no demand, or when it overshoots the setpoint after a long burn. 25' of baseboard that is normally at room temperature will work fine for this purpose.

Good idea on the radiant in the kitchen - it will feel great.
Rob R... proper sizing of the boiler would seem to me to be one of the major elements of the design. With Slant Fin's heat loss calculator and more general sizing rules based on climate zone, the house requires about a 50k BTU heat source. I don't want to spend $2k on a small (new) DS boiler. It's pretty hard to find a used boiler that small. The New Yorker WC 90 (90k BTU/h) is among the smallest and produces almost double the heat output that I need. And so to your point about periods of no demand, will I have the windows open all the time in order to keep the PRV on the WC 90 from blowing hot water on the basement floor :?:

I thought about a large cast iron radiator in the basement which might not be a bad idea. Just not sure where the margins are with this boiler capacity thing.

 
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Rob R.
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Post by Rob R. » Tue. Jan. 07, 2020 12:48 pm

I think the WC90 will be fine for you. A big CI radiator in the basement would be a great choice for a dump zone.

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