# central boiler:lowering the water temp.



## ant (Mar 18, 2008)

with the outside temp in the high of 40's and the night temp in the low to mid 30's. i lowered my Set point from 170 to 160 to conserve Wood. did i do the right thing?
i am two weeks old with my boiler.


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## Sawmill (Mar 18, 2008)

I have a Woodmaster and when the temp start staying in the 40's in the day and 30's at night I lower mine to 140on and 160 off. If the temp stays warm and you don't turn the stove down it gets kind of hot I run ours all summer and then I lower the stove temp to 120 and I only fill it up once a week,


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## Husky137 (Mar 18, 2008)

Is there really any wood savings by adjusting the thermostat to a lower temp range? After all, once your boiler reaches the range you are only heating water 10 degrees. In my mind (and maybe I'm missing something in thermo dynamics) it takes the same amount of energy to heat water 10 degrees whether you are going from 120 - 130 or 170-180.


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## Blazin (Mar 18, 2008)

I say lowering the temp is'nt gonna save you anything. I tried it..No difference... Your still heating water no matter what! Mine stays a 195 all heating season.


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## nathandrews (Mar 18, 2008)

I fall on the "no noticeable difference" side of this fence based on 2 years experience with mine. I can't say I've done much of a scientific study on the topic either.


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## HUSKYMAN (Mar 18, 2008)

Sawmill can you PM on how you control the temp on the Woodmaster? I have a 4400. Thanks


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## mimilkman1 (Mar 18, 2008)

It says in the manual not to lower the water temp below 165 on CBs. I only notice the difference in the temperature in the house because my furnace is on the first floor living area.


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## windthrown (Mar 18, 2008)

ant said:


> with the outside temp in the high of 40's and the night temp in the low to mid 30's. i lowered my Set point from 170 to 160 to conserve Wood. did i do the right thing?
> i am two weeks old with my boiler.



I have been using a Central Boiler OWB for 3 heating seasons now... 

I origially left it set at 185 F. (CB factory temp setting), but that was too hot for us. You will use more energy to get the water to that temp, and burn more wood (my experience). They claim that the higher the temp, the more efficient. But I have not found that to be the case. I set the temp to 165 last year (lowest allowed setting on a CB), and that was OK. But after a while it seems to be too low, and the creosote built up too much. So this year I rasied it to 170, and that seems to be just the right setting for our needs. In a cold snap, I will raise the temp to 175 or 180, to get more heat storage in the boiler water, and heat demand really goes up here below 20 degrees F. I keep the temperatre lower for several reasons, mainly becasue we have a tile and wood floor, and the floor loop temp only needs to be run at 100 degrees F. 

Several factors are at issue here though. The biggest factor of where to set your temp is the type of heating that you have, the heating demand that you have, and the temperature that you set your thermostats at. Case in point; if you have hydronic floor heating, you are going to need to set your floor loop temperature somewhere between 100 and 140 degrees F. If you have huge pile carpets in your house, you want about 140 degrees in your floor loop. If you have tile and hardwood floors like we do, then the floor loop should be set at 100 degrees F. Factoring for about a 20 degree drop across the heat exchangers (we have flat plate heat exchangers here), _and _ a heat cycle range of 20 degrees (below the setting) in the boiler loop, and a potential 10 or so degree drop in temp in the water heater exchanger and/or PEX line run, (I ran our boiler loop through the water heater exchanger first and then the floor loop) you would need to set the temperature to 150 at a minimum and 190 degrees at the max to cover the heat exchanger and variation in boiler temp. This is not an exact science though, and if you use a lot of hot water all the time that can really suck the heat out of the boiler loop. 

A note about CB thermostats and controllers: if you set the temp at say, 180 degrees, F., the controller will shut the damper off at 180 degrees. Most of the time the fire is roaring at that point and the fire will die down when the damper is closed, but typically overshoot the setting by 5-10 degrees. So at a setting of 180, expect the temp to max out at 190. The same thing happens when the damper opens, at 10 degrees below the setting. Set at 180, the damper will open at 170. In many cases, the fire will be cool, and the damper being open will cool the air insude the firebox and lower the water temp in the boiler. I have found that the boiler will undershoot and typically drop to 10 degrees below the open threshold, or 20 degrees below the setting on the controller. So set at 180 the boiler loop can typically go from a low of 160 to a high of 190. Usually it is more like 165 to 185. Now, subtract 10 degrees for the PEX run and 10-20 degrees from the low for the hot water heat exchanger and you will have typically 145 degree hot water for the hot water and floor loops. For us, we have 135-145 degree hot water, which is fine for or needs for hot water and floor heating here. I have a mixing valve on the hydronic floor loop (Honywell) and it is set to 100 degrees. The house thremostat turns on the floor loop pump at 69 degrees (set at 70). The hot water heater is passive; the heat exchanger is at the bottom of the hot water tank and convenctin does it all. We have more than enough hot water here in winter when the boiler is running.

Now heating demand is another factor as well as heat recovery. If you have a family that runs though hot water like there is no tomorrow, then set the boiler at a higher temp. If the outside temps are milder, then the demand for heat will certainly be lower. I have found that 40 degree days/nights are so mild that there is little demand for heat, and can get by with half the wood as at 30 degrees, and at 30 degrees we require half the wood as at 20 degrees. I do not set the boiler lower than 170, but I do set it higher in cold snaps though, up to 175 or 180, but only so we can store more heat in the boiler loop. You will have to fiddle with it for a while to get it right for your needs. It takes about a year to get the process down to where you know what the boiler is doing and the heating is set correctly.


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## Husky137 (Mar 18, 2008)

windthrown said:


> Also a note about CB thermostats and controllers: if you set the temp at say, 180 degrees, F., the controller will shut the damper off at 180 degrees. Most of the time the fire is roaring at that point and the fire will die down when the damper is closed, but typically overshoot the setting by 5-10 degrees. So at a setting of 180, expect the temp to max out at 190. The same thing happens when the damper opens, at 10 degrees below the setting. Set at 180, the damper will open at 170. In many cases, the fire will be cool, and the damper being open will cool the air insude the firebx down. I have found that the boiler will undershoot and typically drop to 10 degrees below the open threshold, or 20 degrees below the setting on the controller.



Really???? My CB will only overshoot after damper shutdown or fall after damper opening by 2-3 degrees.


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## Blazin (Mar 19, 2008)

Husky137 said:


> Really???? My CB will only overshoot after damper shutdown or fall after damper opening by 2-3 degrees.



Same here...


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## tanker (Mar 19, 2008)

Husky137 said:


> Really???? My CB will only overshoot after damper shutdown or fall after damper opening by 2-3 degrees.



Mine too,and I get a more efficient burn at 170deg. or higher and that has'nt changed in 3 years


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## Husky137 (Mar 19, 2008)

tanker said:


> Mine too,and I get a more efficient burn at 170deg. or higher and that has'nt changed in 3 years




I definitley stick with CB's suggestions. They designed it and have more experience with these things than all of us combined. I think some people really like to over think the simple things.


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