Hi & Low Limit Setting - Oil Boiler, Forced HW - Cast Iron Radiators - HVAC - DIY Chatroom Home Improvement Forum


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Old 12-06-2009, 09:40 PM   #1
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Hi & Low Limit setting - Oil boiler, forced HW - Cast Iron radiators


OK, just saw another thread & post on high & low limits
My furnace is Oil fired hot water - B Smith
Radiators are Cast iron, no problems with heat
But I did notice that they do seem to get really hot
I just checked & my Hi Limit is set to 190....too high?
My Low limit is set to 160...so this will cycle more ?

Should I turn them to 140 & 180 ?
130 & 180 ?

Thanks

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Old 12-06-2009, 10:20 PM   #2
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Hi & Low Limit setting - Oil boiler, forced HW - Cast Iron radiators


It's a Honeywell controller, circuit board stamped 8805
The Diff control was set to 10
There is a HW loop, but it is not in use - capped off before we bought the house

I'm also wondering if it's better to use the Oil boiler HW loop VS electric in the winter while the heat is running ?
Then shut it off & use electric the rest of the year ?

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Old 12-07-2009, 05:44 AM   #3
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Hi & Low Limit setting - Oil boiler, forced HW - Cast Iron radiators


Your cast iron rads shouldn't need more then 160 water, if they are sized to the homes heat loss.

If the boiler isn't providing domestic hot water, I would set the low limit to 130, and the high to 160.

Actually. If it were my boiler. I would convert the control to make the boiler a cold start boiler, and set the high limit to 140, and see it that is enough to heat the house.

I use to work with a guy that had his water temp set to 110. His rads were so oversized that he didn't need any hotter water to heat his house.

Using the boiler for domestic in the winter. Just makes you use more oil then need be.
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Old 12-07-2009, 07:50 AM   #4
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Hi & Low Limit setting - Oil boiler, forced HW - Cast Iron radiators


Thanks
I turned it down to 180 last nite
I'ts about 24 out & heat is fine
I'm going to run it today & check the low Temp

Radiatiors are still plenty hot
So I will probably be turning it down to 160
On warmer (50) days heat would turn on & not come back on for about 90 minutes
And the radiatiors are still slightly warm 90 minutes later
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Old 12-07-2009, 11:13 AM   #5
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Hi & Low Limit setting - Oil boiler, forced HW - Cast Iron radiators


It was still going up as high as 190 with setting at 180
So I have turned it down to 170
But for now the heat is off as I have a fire going in the fireplace
It's up to 70 already....I like
I need to burn off all the wood this year as I have a large dead Oak that will be coming down in the Spring
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Old 12-07-2009, 02:13 PM   #6
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Hi & Low Limit setting - Oil boiler, forced HW - Cast Iron radiators


So your hoping for a cold winter.
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Old 12-07-2009, 03:14 PM   #7
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Hi & Low Limit setting - Oil boiler, forced HW - Cast Iron radiators


Hopefully not !!
I've already burned off over 1/3 of what I had
A lot was old Maple - burns very quickly & not a ton of heat
I burn that during the day & save the Oak for at nite when its colder
With burning wood I didn't turn the heat on until the day before Thanksgiving
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Old 12-07-2009, 03:40 PM   #8
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Hi & Low Limit setting - Oil boiler, forced HW - Cast Iron radiators


Wow. A 1/3 in a week and a half.

Better have a lot of oak, ash or locust.
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Old 12-07-2009, 04:17 PM   #9
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Hi & Low Limit setting - Oil boiler, forced HW - Cast Iron radiators


No, I started burning wood the beginning of Oct, so about 8 weeks
Usually we have the heat on sooner
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Old 12-07-2009, 04:36 PM   #10
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Hi & Low Limit setting - Oil boiler, forced HW - Cast Iron radiators


Ooops. I took it as you didn't use any heat until the day before TG.
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Old 12-07-2009, 04:41 PM   #11
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Hi & Low Limit setting - Oil boiler, forced HW - Cast Iron radiators


Oh...no...my bad - poor explanation
Fireplace grate heater is used in fall up until it gets really cold
Then we turn the oil heat on
Then in late winter when it warms up I switch back to wood again
I just hate running the oil boiler for a day or two - then we get 3 days of warm weather...back & forth in fall & spring

So I try to heat as much as I can with wood until it's cold enough to just leave the oil boiler going
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Old 12-07-2009, 04:53 PM   #12
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Hi & Low Limit setting - Oil boiler, forced HW - Cast Iron radiators


Yeah. I hate when I hear mine kick on.
One of these days I'm going to get an insert like yours.


Been saying that for 10 years I think.
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Old 12-07-2009, 05:05 PM   #13
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Hi & Low Limit setting - Oil boiler, forced HW - Cast Iron radiators


I lucked out & bought it off Craigslist brand new for less then 1/2 price
Wife was sort of like...what did you get now ??
But she likes it to keep the main room warmer
The other night she even asked why I didn't have a fire going
I didn't take the hint
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Old 12-07-2009, 06:06 PM   #14
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Hi & Low Limit setting - Oil boiler, forced HW - Cast Iron radiators


LOL...

You will if she ask tonight. Or she'll make life tough on ya.
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Old 12-09-2009, 09:15 AM   #15
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Hi & Low Limit setting - Oil boiler, forced HW - Cast Iron radiators


I would turn the control low side down as low as the lowest number and set the diff to 20. This will give you longer run times and longer off times which is better for the boiler. Work the high limit down as low as you can but don't go below 160.

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