520 df gives very little hot water with municipal water

 
Pacowy
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Post by Pacowy » Tue. Dec. 12, 2017 4:03 pm

Yes it should be abundant without any help, provided that an appropriate low limit setting is used. Larry I think the AA GPM numbers you referenced earlier may be conservative because they assume a 100 deg F rise; I think others may assume 80.

Mike

 
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Post by lsayre » Tue. Dec. 12, 2017 4:09 pm

Pacowy wrote:
Tue. Dec. 12, 2017 4:03 pm
Yes it should be abundant without any help, provided that an appropriate low limit setting is used. Larry I think the AA GPM numbers you referenced earlier may be conservative because they assume a 100 deg F rise; I think others may assume 80.

Mike
My calculations were based on 80 degrees rise. Should I have based them on 100 degrees rise? If so, the maximum potential GPM figures will drop.

 
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Post by europachris » Tue. Dec. 12, 2017 4:35 pm

Something else to think about - well pumps are typically set to 30 psi on/50 psi off (or even 20/40). I've yet to see incoming city water less than 60 psi anywhere I've had it and usually quite a bit more (70 or even 80 psi). More water pressure is going to mean higher flow rates through any device (faucet, shower head, dishwasher fill) and that's going to mean less temperature rise thru the boiler coil.

Combine that with any temperature difference of the incoming water and....brrrr.

Chris


 
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Post by lsayre » Tue. Dec. 12, 2017 4:39 pm

europachris wrote:
Tue. Dec. 12, 2017 4:35 pm
Something else to think about - well pumps are typically set to 30 psi on/50 psi off (or even 20/40). I've yet to see incoming city water less than 60 psi anywhere I've had it and usually quite a bit more (70 or even 80 psi). More water pressure is going to mean higher flow rates through any device (faucet, shower head, dishwasher fill) and that's going to mean less temperature rise thru the boiler coil.

Combine that with any temperature difference of the incoming water and....brrrr.

Chris
Good point!

 
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Post by Pacowy » Tue. Dec. 12, 2017 4:55 pm

x2.

Larry on the GPM numbers I thought you were quoting AA but I see their literature shows different numbers representing the capacity of the coils themselves, not the coils installed in specific boilers. So, for example, they say an IN 117 coil has a capacity of 3.5 GPM @100 deg rise, but in an AA-130 from the 130,000 btu/hr gross output I would estimate a capacity of approx. 3.25 GPM @80 deg rise. I think the AA comes out higher than AHS because their 130 is an output, while AHS says theirs is an input. I think 80 is the more representative rise, because if you really take it to 140 deg you're going to have to temper it anyway for most uses other than dishwasher and laundry.

Mike

 
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Post by coaledsweat » Tue. Dec. 12, 2017 5:19 pm

Pacowy wrote:
Tue. Dec. 12, 2017 2:03 pm
Regarding the supposed uniformity of city water temp, it might make sense if the city draws from wells. Around here, my understanding is a lot of municipal water comes from surface reservoirs, where the water temps routinely plummet after early October.
Even if drawn from surface water, it will spend a very long time in underground pipes before delivery to its final destination. Whether draw from well or surface, it will be the ground temp when it reaches the tap.


 
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Post by lincolnmania » Tue. Dec. 12, 2017 6:00 pm

that water tank in newtown is on the side of the mountain. that water is ice cold!
i just moved from newtown over the summer. the place i was living at was too far from the road to get municipal water.

 
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Post by gaw » Tue. Dec. 12, 2017 6:28 pm

lincolnmania wrote:
Tue. Dec. 12, 2017 6:00 pm
that water tank in newtown is on the side of the mountain. that water is ice cold!
i just moved from newtown over the summer. the place i was living at was too far from the road to get municipal water.
But which Newtown is the OP from? The one you moved from or the one just north of Philly?

 
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Post by Pacowy » Tue. Dec. 12, 2017 6:51 pm

coaledsweat wrote:
Tue. Dec. 12, 2017 5:19 pm
Even if drawn from surface water, it will spend a very long time in underground pipes before delivery to its final destination. Whether draw from well or surface, it will be the ground temp when it reaches the tap.
I took the liberty of Googling "seasonal tap water temperature variation" and this interview with a municipal water plant manager was the first thing that came up - https://patch.com/ohio/avon-oh/from-the-expert-ta ... the-winter . He specifically rejects your statement and describes how source water temps largely carry through to the tap. Then there were some academic articles about how the solubility of harmful substances changes between seasons due to changes in the temperature of the water in the water distribution system. Those don't seem to weigh in your favor, either. The point I was making did not depend on whether the temperature difference was caused by differences in the source vs. the ground temp you mention. Whatever the cause, there is lots of evidence that the difference exists, beyond my nonscientific sampling.

Mike

 
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Post by Rob R. » Tue. Dec. 12, 2017 7:25 pm

europachris wrote:
Tue. Dec. 12, 2017 4:35 pm
Something else to think about - well pumps are typically set to 30 psi on/50 psi off (or even 20/40). I've yet to see incoming city water less than 60 psi anywhere I've had it and usually quite a bit more (70 or even 80 psi). More water pressure is going to mean higher flow rates through any device (faucet, shower head, dishwasher fill) and that's going to mean less temperature rise thru the boiler coil.

Combine that with any temperature difference of the incoming water and....brrrr.

Chris
I am glad to see you back on the board. I mentioned the water pressure back on page 1 and no one noticed...glad you brought it back into the light. Whatever has changed with this setup is very simple, and probably easily fixed...just needs some troubleshooting.

Lets stick with trying to determine what is wrong.

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