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Old 02-21-2011, 11:14 PM   #16
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Lowering The Thermostat


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Originally Posted by beenthere View Post
Oil has a high discharge temp because most of them are either over sized for the house and duct system, or the duct system is under sized for the furnace. Temp rise is a function of CFM per BTU.

I run my oil furnace at a temp rise of 55 degrees. So my register temps are never over 125 when the house is at normal/occupied indoor temp. Which is what many gas furnaces run.

Many people think it takes more to recover then what you save. Its a common false hood that will be around for decades to come.

Tight well insulated houses(actually tight) will see very little savings.

A properly sized furnace will have long run times, but still won't use more fuel then what was saved. Simply because the house can't lose more heat at a lower indoor temp then what it does at a higher indoor temp.

Many many years ago, I thought it used more to recover also. Then I did some testing of my own. Since I found it hard to believe that so many people could be claiming to save money by using set backs. If it indeed used more fuel to recover. Found out they were right and I was wrong. And so were the people that taught me it used more fuel.
Isn't the temp rise range for oil higher though (like 45-75 on average, I know it varies depending on the unit)? Just about every type of system is oversized most of the time but oil always feels a little warmer.

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Old 02-22-2011, 07:34 AM   #17
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Lowering The Thermostat


This is a great post! Lots of good information.

I have an oil boiler servicing old cast iron radiators. my current programmable thermostat is something like +/-1 degree. I am interested in finding a programmable thermostat which will give me a greater temperature swing around a given setting (+/-5?). For example, rather than setting the heating call for 68 degrees, I would like the furnace to come on at 64 and turn off at 68 (or on at 60 and off at 64.)

Is this possible, or even a good idea?
All useful input is welcome!
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Old 02-22-2011, 01:09 PM   #18
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Lowering The Thermostat


Quote:
Originally Posted by unicursalhex View Post
Isn't the temp rise range for oil higher though (like 45-75 on average, I know it varies depending on the unit)? Just about every type of system is oversized most of the time but oil always feels a little warmer.

Because of the duct system being undersized.
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Old 02-22-2011, 03:23 PM   #19
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Lowering The Thermostat


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Originally Posted by 1910NE View Post
This is a great post! Lots of good information.

I have an oil boiler servicing old cast iron radiators. my current programmable thermostat is something like +/-1 degree. I am interested in finding a programmable thermostat which will give me a greater temperature swing around a given setting (+/-5?). For example, rather than setting the heating call for 68 degrees, I would like the furnace to come on at 64 and turn off at 68 (or on at 60 and off at 64.)

Is this possible, or even a good idea?
All useful input is welcome!
You could probably get this to happen with the old Honeywell round thermostat-- if you set the anticipator improperly. I don't see it as being productive. It would just make you uncomfortable, and I doubt it would save any money unless your heating system was horribly oversized.
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Old 02-23-2011, 12:21 AM   #20
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Lowering The Thermostat


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Originally Posted by seatonheating View Post
Because of the duct system being undersized.
I'm talking about the temp rise range on the furnace rating plate, not case by case
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Old 02-23-2011, 04:13 AM   #21
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Lowering The Thermostat


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Originally Posted by unicursalhex View Post
I'm talking about the temp rise range on the furnace rating plate, not case by case
The heavier gauge heat exchanger of an oil furnace can take a lot higher temp rise then the thin heat exchanger of a gas furnace.

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