Boiler/indirect temp settings


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Old 10-10-20, 08:34 AM
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Boiler/indirect temp settings

2001 gas fired Weil-Mclain CGI. Unlike many of the posts I read my boiler does not have Hi/Low temp settings. It only has a 1 dial to set the high temp where boiler stops firing. The temp where boiler fires back on is automatic. I think about 25-30 degree difference to the high depending if it's still calling for heat). In the winter I have it set to 180-190. My question is, with my indirect heater set at 120, what is the lowest boiler temp setting I can go to which is safe for the boiler and conserve energy at the same time?
 
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Old 10-10-20, 10:45 AM
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Welcome to the forums.

The 25-30 is the differential from turn on to turn off.

with my indirect heater
Do you have a separate DHW storage tank ?

In other words you want to know what you can set the boiler down to when it's not required for house heating.... like say for summer time ?

I don't know that exact temperature. The boiler guys can help you there. I do know that as you lower the boiler temperature.... the tankless coil does not get as hot and requires longer time to replenish the storage tank.

 
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Old 10-10-20, 05:37 PM
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Hi Pete and thank you for the welcome. Yes, I am trying to determine a good summertime set temp for the boiler. I have a separate "indirect" hot water tank called "Superstor" It has it's own aquastat which I have set at 120 for now. Any higher and my water feels scalding so thinking about a mixing valve.....that's a separate issue.
So I was figuring that any boiler temp above the 120 will sufficiently heat the indirect coils. But what you said makes sense. It will take longer to do so at a lower temp. I'm in the process of testing boiler temp at about 150-160, a bit lower then a winter set temp and see how that goes. Was also wondering if having only a single dial as opposed to separate high and low settings on the boiler made any difference to what my setting should be.

Thank you for the input!

 
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Old 10-11-20, 06:30 AM
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You would not need a high/low setting aquastat since you don't have a domestic hot water coil in the boiler that would need to keep the boiler at a minimum temperature all the time to keep your water hot.
 
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Old 10-11-20, 06:53 AM
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Thank you. I think I may have misunderstood Pete when he said tankless coil. I have a separate tank. But i'm guessing it still makes sense for the boiler set temp not to be too low even in the summertime so as to heat the hot water storage tank efficiently.
 
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Old 10-11-20, 11:09 AM
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since you don't have a domestic hot water coil in the boiler
@ poorplmbr.... YES ..... there is a hot water coil in the boiler. He's using a storage tank connected to that.
 
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Old 10-12-20, 10:07 AM
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joshua59 issues of boiler temp and saving money can best be solved by installing an out-door-reset / aqustat.

ODRs save up to 20% on fuel cost and provide high low temperature control and delta-T at 1 degree with digital display and extensive menus.

Condensation at 133F can lead to in sulfuric acid. Older controls were not accurate so 140F was commonly used for low setting 180F for high.

ODR's by slowly changing water temp over season make homes more comfortable.

https://www.supplyhouse.com/Tekmar-2...iler-4150000-p

Click on Installation Instructions to see detailed description of ODR unit.
 

Last edited by doughess; 10-12-20 at 10:29 AM.
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Old 10-13-20, 12:18 PM
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I have my storage tank set for 120 and my boiler set for 150 year round and have no problems with hot water, condensate, or heating. (My emitters are large cast iron radiators.)

One exception is a greenhouse room with 3 glass walls, glass ceiling, and copper baseboard emitters. That zone alone is on ODR control that can vary the boiler set point from 130 to 180 depending on outside temperature.

The boiler (with a 30 degree differential) will come on at 120 and heat up to 150 degrees except on days with outside temperatures below 40 degrees when the ODR may take it as high as 180 depending on outside temperature to satisfy the greenhouse.
 
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Old 10-15-20, 04:24 PM
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@Pjmax...
YES ..... there is a hot water coil in the boiler. He's using a storage tank connected to that.
He's got an HTP Super-Stor indirect, not a storage tank off a coil!
 
 

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