How long is too long

 
Trumpeterb
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Post by Trumpeterb » Wed. Jul. 01, 2020 8:28 pm

I finally got my pool heater plumber into my coal gun 130. The heater actually drains the heat from the boiler fast, and the boiler struggled to keep up. It will hit around 130°-135° And hold steady there when the pool heater is running. This also means the boiler is constantly running while the pool heater is on. My question is this—how long is too long in terms of long heat calls? Is it safe to keep the pool heater on for several hours or all day and just allow the boiler to run without ever shutting off?


 
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Scottscoaled
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Post by Scottscoaled » Wed. Jul. 01, 2020 8:44 pm

Just a quick question. What is your stack temperature compared to when your heating your house? It is lower isn't it?

 
Trumpeterb
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Post by Trumpeterb » Wed. Jul. 01, 2020 8:51 pm

Scottscoaled wrote:
Wed. Jul. 01, 2020 8:44 pm
Just a quick question. What is your stack temperature compared to when your heating your house? It is lower isn't it?
Good question. I don’t know. I don’t have a thermometer on the stack, but it would make sense that it would be lower.

 
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coaledsweat
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Post by coaledsweat » Wed. Jul. 01, 2020 8:58 pm

Question, while heating the pool and the boiler runs continuously, what is the minimum temperature of the boiler? Does it fall below the low limit? If so, throttle the pool loop to slow the flow until the boiler maintains the low setpoint. I wouldn't be concerned about it running continuously as long as it keeps up with the demand.

 
Trumpeterb
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Post by Trumpeterb » Wed. Jul. 01, 2020 9:17 pm

I may try throttling it back. I have the operating temp set at 170°, and the boiler kicks on at 160°. The temp keeps dropping to 135° or so and keeps running around there while heating. The temp never really recovers beyond the 130-135° range.

 
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lsayre
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Post by lsayre » Thu. Jul. 02, 2020 3:45 am

What is the dimensional size of the pool, and how many gallons of water does it contain? What pool temperature are you targeting? In ground or above ground?

 
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lsayre
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Post by lsayre » Thu. Jul. 02, 2020 5:03 am

If your pool water is at 75 degrees and your boiler is maintaining 135 degrees, the Delta-T is 135-75 = 60 degrees

BTUH = GPM x Delta-T x 500

Per an old Bureau Of Mines study the output of the AA-130 is ~115,000 BTUH (off the top of my head)

Putting numbers to the equation:

115,000 = GPM x 60 x 500
GPM = 115,000/(60 x 500)
GPM = 3.83

What you need in order for the boiler to hold at 160 degrees is a Delta-T of 160-75 = 85 degrees

Revising the equation:

GPM = 115,000/(85 x 500)
GPM = 2.70

Conclusion:

If you throttle the circulators flow from 3.83 GPM to 2.7 GPM you will raise the boilers temperature to 160 degrees. Coaledsweat already advised a GPM reduction.


 
Trumpeterb
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Post by Trumpeterb » Thu. Jul. 02, 2020 7:26 am

lsayre wrote:
Thu. Jul. 02, 2020 3:45 am
What is the dimensional size of the pool, and how many gallons of water does it contain? What pool temperature are you targeting? In ground or above ground?
Pool is 29’ round above ground. Water is 83° now. Wife wants 88°. Roughly 19000 gallons.

 
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Post by Rob R. » Thu. Jul. 02, 2020 7:52 am

Throttling the flow through the boiler will allow you to raise the operating temperature. I would keep tweaking it until the boiler levels out at 160 degrees or so.

Running the boiler continuously is not a problem.

 
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Post by coaledsweat » Thu. Jul. 02, 2020 7:54 am

Actually, continuous runs are going to be the most efficient for your process.

 
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Post by lzaharis » Thu. Jul. 02, 2020 8:11 am

Let's see here:

29 foot diameter pool
660 square feet of surface area rounded lower; 95067 square inches Pi*R*R= square area
4 gallons per minute (estimate)
240 gallons per hour 5,760 gallons per day
5 days- 28,880 gallons
30 days-172,800 gallons
120 days water circulation-1,536,000 gallons
120 days/2,880 hours of boiler operation minus 50+ percent hold fire time after solar cover is installed :)
Save coal, save heat, save chlorine; warm pool=happy spouse
YESH!!!! as Mooch The Cat from the "Mutts" comic strip would say

You need a round solar pool cover to save gas, coal and heat and reduce chlorine loss.
The spouse will enjoy the pool sooner.

PS; the pool will be like bath water and get rid of a lot of aches and pains too.



Keep in mind that the conventional pool heater is also sucking heat out of the water as it is circulating the pool water in the loop at a higher flow and lower pressure per minute.

You will need to be a bit more proactive about vacuuming the pool or running a robot pool cleaner at night.
In my parents 16 by 32 inground pool we had an octopus sprayer in the bottom of the pool that we connected to the return to pool discharge outlet and moved it as needed to break up any dirt or algae to keep it in suspension.


So you may just want to buy a pool cover as soon as possible and shut the other pool heater off and let the solar pool cover and coal stoker do all the work for you as the solar pool cover will hold in so much heat the bottom of the pool will be warm to the touch and you will need to be more diligent about the PH level in the pool water as the chlorine will be evaporating into gas at a slower rate per day.


Edited today to fix my math mistakes :0
Last edited by lzaharis on Thu. Jul. 02, 2020 12:47 pm, edited 1 time in total.

 
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Post by lsayre » Thu. Jul. 02, 2020 8:29 am

I'm guessing that with losses factored in it will take you about roughly 8 additional hours of heating to hit 88 degrees.

A ballpark average of several methods I found online comes to a guesstimated need (ideally) for ~220,000 BTUH boiler output for a pool of your size. Your boiler should take about twice as long as the typical expectation of 24 hours for the initial heat-up phase, or 48 hours. Does that sound about right based on how long you've been heating so far?

 
Trumpeterb
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Post by Trumpeterb » Thu. Jul. 02, 2020 8:57 am

lsayre wrote:
Thu. Jul. 02, 2020 8:29 am
I'm guessing that with losses factored in it will take you about roughly 8 additional hours of heating to hit 88 degrees.

A ballpark average of several methods I found online comes to a guesstimated need (ideally) for ~220,000 BTUH boiler output for a pool of your size. Your boiler should take about twice as long as the typical expectation of 24 hours for the initial heat-up phase, or 48 hours. Does that sound about right based on how long you've been heating so far?
I just got the exchanger installed yesterday and ran it for about 3 hours. It is all still relatively new to me.

 
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lsayre
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Post by lsayre » Thu. Jul. 02, 2020 9:04 am

Trumpeterb wrote:
Thu. Jul. 02, 2020 8:57 am
I just got the exchanger installed yesterday and ran it for about 3 hours. It is all still relatively new to me.
I was presuming ~48 hours for a ballpark initial 30 degree rise. If you accomplished that much with 19,000 gallons of water in only 3 hours with merely an AA-130, I'll back down, as clearly I'm all wet here. Your initial post made it seem that you were frustrated and becoming more frustrated over what appeared to be an extended period of time, and I took that to mean that things were not going well for perhaps a few days on end. 3 hours is simply amazing.
Last edited by lsayre on Thu. Jul. 02, 2020 9:14 am, edited 2 times in total.

 
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Post by Rob R. » Thu. Jul. 02, 2020 9:12 am

Most pool heaters are designed around a 1 degree per hour rise. If you want to keep the pool warm all the time you can get away with a smaller heater. If you want to flip the switch on Friday and have it steaming on Saturday, you will have to adjust your calculations accordingly. 😀


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