Central Boiler FORGE 3500 Outdoor Coal Boiler

 
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Lightning
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Post by Lightning » Wed. Dec. 05, 2018 6:35 pm

We counted roughly 90 feet total of baseboard in the house. I got some conflicting numbers on the IR gun, though it seems to be around a 21-22 delta between the supply and return. The pex at the boiler appears to at least 1 inch. Some of the radiator lines I saw were 3/4. I believe there to be a lot of friction head since many of the radiator runs come down from the ceiling and then back up and over to the next room. There isn't very much exposed lines in the attic, maybe a few feet.

Most of the print on the circulator was illegible. Here's a pic of it. After blowing up the pic, I guess you can read it.

I'm thinking he needs a bigger pump along with more radiation.

What's your thoughts?

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lsayre
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Post by lsayre » Wed. Dec. 05, 2018 7:37 pm

It looks like a Grundfos 15-58 Three-Speed. On high speed it will deliver 7 GPM in the presence of 12 ft. of friction head. A well respected circulator.

Downs and ups are irrelevant. No head contribution from that. What matters is the ID of the 1" PEX (which will be 0.863" if it is standard PEX, and not PEX-AL-PEX) and the total run length for the single zone loop.

 
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Post by Olllotj » Wed. Dec. 05, 2018 8:01 pm

2500sq ft x30 btu needed per sq ft=75000 btu required

500 btu per ft x 90 ft of baseboard means 45000 btu going in in a perfect world.

Not to mention 3/4 can only carry so much before it cools down towards the end of the loop.

Time for a second loop with lots more base board
Last edited by Olllotj on Wed. Dec. 05, 2018 8:06 pm, edited 1 time in total.

 
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Post by CapeCoaler » Wed. Dec. 05, 2018 8:05 pm

Nice thing is you can zone up some rooms with the up to the ceiling pattern...

 
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Post by lsayre » Wed. Dec. 05, 2018 8:06 pm

If we guess at an average of 500 BTUH per foot of radiators, and use your figure of 22 degrees of Delta-T, we get:

(500 BTUH/ft. x 90 ft.) = (22 x 8.34 x 60) x GPM

GPM = ~4

Looking at the 3 available pump curve(s), his friction head "ballpark" for a "ballpark" of 4 GPM flow is as follows (multiple choice):

1) For the case whereby he is running the circulator on low speed, friction head = ~6.5 ft.
2) For the case whereby he is running the circulator on medium speed, friction head = ~12.2 ft.
3) For the case whereby he is running the circulator on high speed, friction head = ~15.4 ft.
Last edited by lsayre on Wed. Dec. 05, 2018 8:16 pm, edited 1 time in total.

 
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Post by Lightning » Wed. Dec. 05, 2018 8:12 pm

Suppose the total length is 200 ft because of all the ups and downs and distance to and from the outside boiler which includes the 90 ft of baseboard. What kind of friction are we looking at? And based on that, how many BTUs are actually being delivered?

He told me the pump is on its highest setting.

 
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Post by Lightning » Wed. Dec. 05, 2018 8:18 pm

I also advised him to pull the covers and vacuum the fin tubes, just to be sure it's getting proper air convection.


 
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Post by lsayre » Wed. Dec. 05, 2018 8:28 pm

At best flow is 5 GPM, and at worst perhaps 4 GPM. At 22 degrees of Delta-T and 5 GPM, the system is capable of putting 55,000 BTUH into the home. At 4 GPM the system is capable of putting 44,000 BTUH into the home. Best guess is therefore ~50,000 BTUH.

If he actually needs 70,000 BTUH he needs a higher output circulator. And even the Taco VT2218 I mentioned earlier will not be sufficient for the task.

 
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Post by Lightning » Wed. Dec. 05, 2018 8:30 pm

What's the ballpark decent price on baseboard radiators? He priced some at Home Depot around $85 for an 8 foot section, I believe. Is that the goin rate?

 
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Post by Lightning » Wed. Dec. 05, 2018 8:33 pm

lsayre wrote:
Wed. Dec. 05, 2018 8:28 pm
If he actually needs 70,000 BTUH he needs a higher output circulator. And even the Taco VT2218 I mentioned earlier will not be sufficient for the task.
I like that pump you suggested, I might have to have a couple lol.

His house is block with no insulation in the walls. Ceiling is well insulated. So he probably requires the high side, BTU wise. There are a couple rooms with a lot of glass too.

 
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lsayre
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Post by lsayre » Wed. Dec. 05, 2018 8:53 pm

Lightning wrote:
Wed. Dec. 05, 2018 8:12 pm
What kind of friction are we looking at?
Friction is a combined function of the system and the circulator. They are tied at the hip. Change the circulator brand/model and you change the friction head.

For the Grundfos 15-58 I believe he is within the ballpark of 4 to 5 GPM flow. Call it 4.5 GPM. The lower figure is highly predicated upon a reliable measure of an observed 22 degree Delta-T and a presumed 500 BTUH per foot of radiators. If the Delta-T is not 22 degrees and the radiators are not a nominal 500 BTUH the nominal 4 GPM guess is off also. The higher figure of "not more than 5 GPM" is a stab taken via the use of my spreadsheet and applying your total run length of 200 feet and guessing at a nominal pipe ID.
Last edited by lsayre on Wed. Dec. 05, 2018 9:03 pm, edited 2 times in total.

 
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Post by Lightning » Wed. Dec. 05, 2018 9:01 pm

I'm sure everything has a little variance. The ballpark figures do help though. I'm sure it can't be too far from the truth.

 
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Post by Olllotj » Wed. Dec. 05, 2018 9:10 pm


 
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Post by lsayre » Wed. Dec. 05, 2018 9:11 pm

Lightning wrote:
Wed. Dec. 05, 2018 9:01 pm
I'm sure everything has a little variance. The ballpark figures do help though. I'm sure it can't be too far from the truth.
I'm speculating (as in guessing) here, and consulting an HVAC professional would clearly be wise, but if you can find a circulator capable of delivering at least 7.5 GPM of flow at 15.5 ft of head, his house should be a lot warmer for it on the coldest few days of the year. One concern here is whether or not velocity noise becomes problematic in 3/4" copper pipe for the case of 7-8 GPM flow.
Last edited by lsayre on Wed. Dec. 05, 2018 9:14 pm, edited 1 time in total.

 
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Post by Olllotj » Wed. Dec. 05, 2018 9:12 pm

On top of more radiation and circulator he needs some distribution work. Zoning!


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