Determining Needed Baseboard Radiation

LTStorm07 wrote: ↑

Mon. Jan. 10, 2022 5:49 pm

Just a thought I had, but what about a through wall vent or two located between rooms?

Hey that's good thinking!

Lee, a lot of kitchens have a “toe-kick” heater installed under a cabinet. They work well, but they also make some noise.

Do you have a spot for a panel radiator? How about radiant underneath?

Lightning wrote: ↑

Mon. Jan. 10, 2022 3:45 pm

My biggest zone will be the living room which used to be a garage. It has 3 exterior walls and seems to require a lot of heat. The heat loss calculator says to use 36 ft but I'm inclined to put in 45, 15 ft on each exterior wall. So 45 ft would be the longest zone.

If you split that up, you can have a 30ft and a 15ft, or you can split the middle baseboard if it makes sense with your room layout, and supply from that farthest point from the boiler. Be sure to include full flow ball valves on the RETURN side of the 3/4 before they rejoin the 1" return line, for balancing capability.

I'm not sure what to do with the kitchen. Its in the middle of the house with only 1 exterior wall. The heat loss calc says it should have 1530 BTUs worth but I'm struggling to find a place for it. Would it make sense to add a little baseboard to the adjacent rooms instead?

We added baseboard in an L-shape under the overhang of the island. There's never enough space in a kitchen It is perfectly happy at 65F, but 70F+ and it will just run solid. So far that is fine, with cooking and such. We added a small 5-column radiator in my in-laws' kitchen and it does just fine- and used to be where they put metal bread pans of water for humidity...until the cat decided he like "hottubbing" about 2 weeks ago. LOL

Then there is the far room on the other side of the house. The boiler room is directly underneath it. It current has no heating but only feels slightly cooler, its also where the cold air return is so heat gets dragged out there after being pulled thru the kitchen. But of course that won't be the case once its not windy in here anymore. I'm considering giving that room its own zone so that I don't overheat it since it gets some radiant heat from underneath. My cat loves to lay on the floor directly over the Axeman, a sure sign that he's found a warm spot

If it is near any other room with heat, you can tack it onto the end of the run. It won't be as warm, but who cares? Now if it was a small room that needs to be warm, like our main floor bathroom, we added a single 5ft baseboard behind the toilet and it is always warm and toasty in there.

My small workarea is directly above the boiler here. I didn't install baseboard there, but did do work to add 2" styrofoam an then OSB and then paneling over the outside wall (just one, it's in middle of side of house) and it is fine. May have to put slippers on if I'm going to be in there a while and it is really cold. Don't forget the rim joist.

If you stick with the split supply and return lines, adding a ball valve to balance on each return side, you can mix baseboard and radiators if needed. Just use the valves to balance. (Assuming you have a pump for the zone and use closely-spaced-tees coming off the main loop to avoid the need to balance a zone against other zones) Keep in mind that radiators can consume a LOT of BTUs. The more columns, the better.

Maybe this gives you some ideas.

Hydronics amateur with a few thoughts on the starting assumptions:

1. Use of daily averages based on OAT seems like it might overlook variation within a day - i.e., you generally need to pump out more of your btu's during nighttime, when solar gain is zero and temps are below daily average. Also might need more btu's if design conditions are going to cover above-average wind conditions.

2. If you want the system to get you to 73 deg. shouldn't that be the design criterion?

3. 10k btu/lb seems optimistic. Need to start with about 12250 btu/lb AR, deduct a percentage for unburned coal, and multiply what's left by the 0.8.

Mike

Rob R. wrote: ↑

Mon. Jan. 10, 2022 6:08 pm

Do you have a spot for a panel radiator? How about radiant underneath?

Actually I do have a place for a panel radiator, that's a good option .. as for radiant underneath it would be a real chore to install.. half of the kitchen is over a crawl space that is pretty much deplorable to work in.

CoalisCoolxWarm wrote: ↑

Mon. Jan. 10, 2022 7:27 pm

Maybe this gives you some ideas

Yes sir! Thank you for all your effort with that detailed post, I appreciate it.

CoalisCoolxWarm wrote: ↑

Mon. Jan. 10, 2022 7:27 pm

.until the cat decided he like "hottubbing" about 2 weeks ago. LOL

I bet he didn't enjoy that very much

Pacowy wrote: ↑

Mon. Jan. 10, 2022 9:57 pm

Hydronics amateur with a few thoughts on the starting assumptions:

I appreciate your insight partner thank you..

Pacowy wrote: ↑

Mon. Jan. 10, 2022 9:57 pm

If you want the system to get you to 73 deg. shouldn't that be the design criterion?

When I did the heat loss calculator I used -2 degrees OAT (which is the design temperature for this area) with inside temp of 72.

As for calculating coal usage per HDD, a 65 degree base is used because under 65 degrees outside is where heating requirement generally begins.

Sorry for the confusion there

Lightning wrote: ↑

Tue. Jan. 11, 2022 4:50 pm

When I did the heat loss calculator I used -2 degrees OAT (which is the design temperature for this area) with inside temp of 72.

As for calculating coal usage per HDD, a 65 degree base is used because under 65 degrees outside is where heating requirement generally begins.

I think I'm following, but it still seems like your coal use #'s and radiation are only going to get you from -2 to 65 on your design day, even if it's true that you wouldn't run the heat if it was 65 out. Your actual heat loss is higher with 74 vs 67 deg diff, so it seems like that needs to get worked in somehow. I guess if you used "standard" HDD's with your actual consumption when computing your consumption rate that might address it.

When I've done this type of analysis in the past IIRC I generally used HDD's computed from the set temp being used. Sorry I never looked at whether that made a difference in predictive accuracy.

Mike

Pacowy wrote: ↑

Tue. Jan. 11, 2022 5:50 pm

I think I'm following, but it still seems like your coal use #'s and radiation are only going to get you from -2 to 65 on your design day, even if it's true that you wouldn't run the heat if it was 65 out.

So my coal use #s are based on HDDs.. A base of 65 is used in HDDs because (and I don't know if its documented this way) but there are already things in the house that produce some heat that close the gap between 65 and 72 (average preferred temperature) and they should be taken into consideration for factoring your HDDs so that your "coal per degree heated" doesn't get skewed. These other things I'm referring to are occupants, TVs, Computers, Refrigerator compressors, light bulbs, ect you get the idea..

Now that I think of it, it seems that the heat loss calc doesn't consider any auxiliary heat from these other things.. So in reality if I put in -2 outside air temp to 72 inside, maybe its over estimating radiation requirement just slightly.

Or if I have that all wrong somebody let me know But that is what makes sense to me

I did a little digging and it turns out that its called balance point temperature.. per Wikipedia

"The building balance point temperature is the outdoor air temperature when the heat gains of the building are equal to the heat losses. Internal heat sources due to electric lighting, mechanical equipment, body heat, and solar radiation may offset the need for additional heating although the outdoor temperature may be below the thermostat set-point temperature. The building balance point temperature is the base temperature necessary to calculate heating degree day to anticipate the annual energy demand to heat a building. The balance point temperature is a consequence of building design and function rather than outdoor weather conditions."

So I suppose the balance point temperature of 65 degrees could be a little different for each situation

Thanks very much for your digging. That clarifies a few things for me, and probably covers my original #2 (above).

If you have any comments or questions on my #1 and #3, please fire away.

Thanks.

Mike

Your welcome

Pacowy wrote: ↑

Mon. Jan. 10, 2022 9:57 pm

3. 10k btu/lb seems optimistic. Need to start with about 12250 btu/lb AR, deduct a percentage for unburned coal, and multiply what's left by the 0.8.

I used 80% of 12500 btu per pound to cover a little loss in the ash pan and to cover a little efficiency loss since it doesn't run continuously. Efficiency came from the Bureau of Mines report. See pics below.

Pacowy wrote: ↑

Mon. Jan. 10, 2022 9:57 pm

Use of daily averages based on OAT seems like it might overlook variation within a day - i.e., you generally need to pump out more of your btu's during nighttime, when solar gain is zero and temps are below daily average. Also might need more btu's if design conditions are going to cover above-average wind conditions.

Correct.. according to design temperature data, those points in your statement above should be covered 99% of the time.

https://www.energyvanguard.com/blog/we-are-the-99 ... c-systems/

In my mind heat loss calculations should only be a starting point.. I don't think think oversizing 15-20% would be any harm.

In my first post of this thread I was just surprised that my real world usage was close to the heat loss calculator. I didn't really have much faith in it lol

On #1, you originally described the -2 as OAT, not 99%, so I was going from that. I think lsayre had some numbers related to the variations within a day. Because of those variations, a person might be unhappy if they designed based on an "average hour of the coldest day".

I object both in principle and empirically to the use of the 99 percent standard. I originally switched to coal to get away from the pressure to live in a cold house created by high (at the time) oil prices. I cannot fathom deliberately spending money to create a system designed to regularly underperform during reasonably foreseeable conditions. Especially when you look at the distributions over multiple years, you are ensuring that your system won't keep you warm when you need it the most.

Empirically, based on experiences with different systems of different sizes, I do not accept the proposition that smaller systems are inherently more efficient, or that excess capacity is inherently bad. I think this is also illustrated by the efficiency LL reports when it uses an (oversized) AA boiler head with its comparatively small stokers. So I haven't bought into the 99 percent standard.

Mike

Pacowy wrote: ↑

Wed. Jan. 12, 2022 11:46 am

you originally described the -2 as OAT, not 99%, so I was going from that.

Sorry about that. I tried to make it clear that -2 was the design temperature..

Pacowy wrote: ↑

Wed. Jan. 12, 2022 11:46 am

I object both in principle and empirically to the use of the 99 percent standard.

So where would you draw the line on over sizing a heating system? I've seen -25 here once in the 30 years I've lived in this house. I see -10 about once every 3 to 5 years. I don't recall it going below -2 at all last year. I think the 99% rule is ok (or oversizing it 15-20% is better) as long as you have something to supplement at times of unusual occurrence. For example I would occasionally fire the pellet stove at -10 when I had the hand fired coal furnace just so it wouldn't have to work so hard.

Thank you for replying, I value your opinion.

Sure if you have a reasonable way to cover the shortage, that's fine. But for someone designing a system, buying, installing and periodically operating supplemental equipment (like a pellet stove) is likely to be more expensive and less convenient than adding some boiler and radiation capacity.

I don't have a specific amount of recommended "oversizing" in mind. On the back of my envelope, it would take about 1/3 more capacity to fully cover your -25 deg scenario. Maybe you can get away with less than that, and maybe you don't mind falling short of your preferred low-70's comfort level every once in a while.

Years ago, when we were still in the big house, we had a polar vortex event that reached -20 deg air temp with pretty strong winds, so like -50 wind chill. In the coldest 24 hour period the coal boiler ran 14 hours, and maintained the set temp the whole time. Probably could have gotten by with less capacity, but that's what the Dead Men put in and I was glad they did.

Mike

Degree days and how much coal you burn is useful for sizing a boiler, but you have already crossed that bridge.

If you want a balanced system with some built in "insurance", download the Hydronic Explorer app from Slant Fin (https://www.slantfin.com/slantfin-heat-loss-calculator/) and enter the information for your house room by room. Go ahead and use the heating design temperature for your area, and pick the indoor temperature you want - but use an average system temperature of 160 degrees. This will require you to buy more linear feet of baseboard (or you could buy high-output baseboard), but in the event the next Polar Vortex hits us and your living room is stalled out at 65 degrees...you can nudge the Axeman up to 180 degrees and get a third more btu output from the baseboard.

Rob R. wrote: ↑

Wed. Jan. 12, 2022 3:00 pm

download the Hydronic Explorer app from Slant Fin

I downloaded and looked at it. Wow that is pretty extensive! Looks like it should be pretty accurate. Thank you