Insulated Underground Pex Tubing

Lightning wrote: ↑

Fri. Mar. 06, 2020 5:22 am

Can 3 GPM deliver 30,000 BTUH?

I calculated the salon to need about 20K with design day temp of 2 degrees.

For the case of the classic expectation of 20 degree Delta-T the answer is yes.

BTUH = 20 x 3 x 8.34 x 60
BTUH = 30,024

If your primary is only sending 30,000 BTUH to the Salon, how can the added 007 circulator deliver more than that through the HWB's?

If the total feet of HWB's is sized to something less than 30,000 BTUH, then the Delta-T across the HWB's will be below 20 degrees. That's perfectly OK. For the flip-side case, if you needed 30K for the HWB's and the primary circulator was only sending out 20K, it would not be OK.

Lightning wrote: ↑

Fri. Mar. 06, 2020 5:22 am

I calculated the salon to need about 20K with design day temp of 2 degrees.

If your calculation is correct, then:

1.4 x 20,000 = 28,000

Therefore, on the coldest day anticipated to happen within any given span of 10 years your Salon will need 28,000 BTUH being delivered to it.

That's a lot of good information Larry, thank you. It seems that when we discussed this in the past you felt a bit on the fence about asking my one circulator setup to push water all the way to the salon and then also adding the burden of pushing it thru the radiators, which made sense to me. So I added the 007 to handle the job of getting the water thru the secondary loop.

But maybe its overkill to do it that way.

Lightning wrote: ↑

Fri. Mar. 06, 2020 3:49 pm

That's a lot of good information Larry, thank you. It seems that when we discussed this in the past you felt a bit on the fence about asking my one circulator setup to push water all the way to the salon and then also adding the burden of pushing it thru the radiators, which made sense to me.

I don't recall ever discussing this. What I do recall informing you was that with each subsequent zone that opens the friction head of the "system as a whole" actually drops, thus allowing the circulator to move to a new and higher total GPM output position along its pump curve (moving it to the right along the pump curve). You were concerned at that juncture that all zones friction heads must factually be additive, thus soon overburdening the single circulator, and as this presumption that you had is not correct, I merely corrected you on this point.

That said, the friction head of the Salon's HWB's and the underground run from the boiler to the Salon would indeed be additive, as if you eliminate the 007 circulator the two (meaning here their two lengths) must then be combined and therefore reside on one consecutive and thus noticeably longer zone loop, just as I described above when I added their friction heads together (while guessing liberally as to what may be the actual friction head across the HWB's).

You can lead a horse to water

lsayre wrote: ↑

Fri. Mar. 06, 2020 6:18 pm

I don't recall ever discussing this.

I thought it was in an email but I couldn't find it, maybe it was mentioned by someone else..

But anyways, as the seasons started to change last November I got into a hurry to get heat in the outbuilding. Currently the outbuilding has 2 rooms on one loop with 57 ft of baseboard. One of the things I need to do is split it into 2 zones since we don't use both rooms at the same time. If'n it'll work, it would be much simpler to install 2 zone valves triggered by a thermostat in each room and just have my basement pump do all the work. This would also eliminate the primary/secondary configuration, wouldn't need the taco 007 and make the underground run on demand instead of constant circulation.. This is what I'm leaning towards doing.

Lightning wrote: ↑

Fri. Mar. 06, 2020 6:52 pm

I thought it was in an email but I couldn't find it, maybe it was mentioned by someone else..

I reviewed my PM's before making my last comment.

To split the Salon into 2 zones, make the split as close to mid HWB's as you can, and then combine them once again upon discharge into a single (at least one size up in ID) return leg. This should have the effect of lowering the Salon's friction head a bit in a beneficial way. Though to balance the flows between the two split zones while feeding them from a single source and circulator you may have to throttle one side a bit via a throttling valve. Since you won't initially be likely to know in advance which split needs a bit of throttling, add such valves to the feed side of both split legs. Use full port valves. I very much like this idea of splitting the Salon's HWB flow into two HWB flows. 57 feet of baseboard is a lot to have on a single leg.

The idea I had in mind would be to rebuild the primary/secondary intersection into 2 headers (a supply and return) each 1.5 inch header would have two 3/4 inch nipples (one for each zone). Since we wouldn't be using both rooms at the same time one room could be left at 50 instead of heating the whole building every time one of us needed to use it.

Scottscoaled wrote: ↑

Fri. Mar. 06, 2020 6:43 pm

You can lead a horse to water

But you can't make him drink.
Thank you for the helpful contribution.

An interesting observation while doing the loop time test. The underground run lost about 50 degrees in two hours.

7.6 gal x 8.34/gal = 63.4 pounds
63.4 × 50 = 3160 BTU
3160/2 hours = 1580 BTUH heat loss

Would this have any relevance is determining the heat loss while running constant circulation?

Lightning wrote: ↑

Fri. Mar. 06, 2020 8:10 pm

An interesting observation while doing the loop time test. The underground run lost about 50 degrees in two hours.

7.6 gal x 8.34/gal = 63.4 pounds
63.4 × 50 = 3160 BTU
3160/2 hours = 1580 BTUH heat loss

Would this have any relevance is determining the heat loss while running constant circulation?

I believe it does, and if correct, it implies that the loss to the underground loop is on the order of 4.2 Lbs. per day for the case of 24/7 circulation.

If we may assume that anthracite yields ballpark 9,000 output BTU's per pound, then:

1,580 BTU's/Hr x 24 Hrs/Day = 37,920 BTU's/Day (lost)

37,920 BTU's per Day/9,000 BTU's per Pound. = 4.2 Lbs. lost per day to the underground run

I haven't searched for it, but somewhere rather recently (perhaps in a completely different thread. ???) I recall that I suggested that your DHW cost was likely on the order of 7 Lbs. per day, and your underground loss was likely on the order of 4 Lbs. per day, and I summed them to 11 Lbs. of daily loss that you didn't have concern for with respect to the Hotblast, such that you could forgive these 11 Lbs. when attempting to compare the home heating consumption for the AA vs. the home heating consumption for the Hotblast

Yes I remember you mentioned around 4 pounds, its gotta be right around there somewhere. I think we're very close to verifying it

lsayre wrote: ↑

Fri. Mar. 06, 2020 9:07 pm

such that you could forgive these 11 Lbs. when attempting to compare the home heating consumption for the AA vs. the home heating consumption for the Hotblast

To make a real comparison I'd somehow also have to forgive the coal that keeps the outbuilding between 50-70 degrees to make it a more apples to apples..

So even if generously rounding it up to 5 pounds per day it's only around 1/2 ton per heating season to keep the primary loop hot.

I'm realizing that in either case there is going to be heat loss in the underground loop whether its constant circulation or not. The savings by running it on demand would only amount to a small portion of that half ton.

Lightning wrote: ↑

Sat. Mar. 07, 2020 4:37 am

To make a real comparison I'd somehow also have to forgive the coal that keeps the outbuilding between 50-70 degrees to make it a more apples to apples..

Correct!

Oh boy!! I averaged all 97 data points for each (supply and return) and come up with a delta T of .866 degrees on the underground pex loop.. These data points were taken during a consecutive 97 minutes whereas there were 40 complete loops of water based on 2:25 loop time. Should be legitimate, Im thinkin

Factoring in the primary/secondary intersection we get about 7.6 gallons.
3.140 gallons per minute
.866 x 3.14 x 8.34 x 60 = 1,360.7 BTU per hour heat loss..

Feel free to double check that..

My assumption above with the loss of 50 degrees in 2 hours was an approximate observation and by no means exact to any extent. But interestingly enough it does help verify the findings of being in the 1500 BTUH heat loss ballpark..
I like it.
I'm happy with the results of the BTU loss tests...
I think that about wraps up this thread for me
But feel free to keep the comments coming if you so desire..