Cold start using L4006 vs. triple aquastat


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Old 12-14-06, 01:25 PM
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Lightbulb Cold start using L4006 vs. triple aquastat

Okay, I ran some math, someone tell me if I am wrong...
I'm figuring it takes about 50 BTU to heat the water in my boiler 1 degree F. (85% efficient, 4.7 gallons water.)For a 10 degree differential, that's about 500 BTU to maintain a boiler low limit with a ten degree differential... The boiler is pretty well insulated as well.

If 1 gallon of #2 fuel oil has 144,000 BTU, 1 gallon of fuel should last for at least 288 boiler firings to maintain the low limit. Even if it has to fire 10 times a day, 1 gallon of fuel should keep the silly thing warm for a month? Next question would be regarding it's being such a low mass unit would require other measures to keep the return water from cooling it too fast. I'm really not thinking about doing this, just thinking about stuff in my quest for knowledge.
 

Last edited by radioconnection; 12-14-06 at 02:53 PM.
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Old 12-18-06, 09:15 PM
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Hmm, It would probbably work ok, but I'm not sure. I've seen some giant old gravity feed boilers operating with them, but I wonder with a modern boiler if you would run into problems. Would it short cycle? A triple reccomends a minimum 20 degree difference between the high and low limits. 10 degrees doesn't seem like enough. Would the combustion gasses condense in the chimney if it doesn't run long enough to heat up the chimney? If you used 2 with one for high limit and the other for low limit, it would probbably be better.
 
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Old 12-19-06, 05:30 PM
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And after you have the two aquastats, add a circulator relay and you will have all the components of a triple aquastat with way more headaches. If you want to maintain a low limit of 120, your triple aquastat probably already does that. Then when there is a call for heat, the boiler will try to reach high limit. That's what is supposed to make the summer/winter control save energy. If you don't use the boiler for domestic hot water, you can just turn the low limit to its lowest point on the dial and achieve what you are after. There are probably other factors you didn't take into account with the heatloss of your boiler but you are on the right track.

Ken
 
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Old 12-19-06, 05:43 PM
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aquastat

Originally Posted by KField View Post
And after you have the two aquastats, add a circulator relay and you will have all the components of a triple aquastat with way more headaches.
Ken
Hi Ken

It is a cold-start Biasi boiler with a L4006 (30 differential). Actually, I've finally decided to add a Danfos 140-degree thermic valve on the return in the spring. That seems to be the most elegant, easiest and most foolproof solution to maintaining a good return temp and keeping the boiler hot while the burner's firing. Cheap insurance to keep the boiler happy.

Pete
 
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Old 12-19-06, 08:23 PM
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Originally Posted by radioconnection View Post
Hi Ken

It is a cold-start Biasi boiler with a L4006 (30 differential). Actually, I've finally decided to add a Danfos 140-degree thermic valve on the return in the spring. That seems to be the most elegant, easiest and most foolproof solution to maintaining a good return temp and keeping the boiler hot while the burner's firing. Cheap insurance to keep the boiler happy.

Pete
Biasi's seem to be pretty good boilers, although I've never installed one. The main reason for not setting the low limit too low, is you don't want condensation in your chimney. If you have your chimney on the outside of the house and it has a clay liner, this is easy to do. If you find a yellow crystallyn (sp?) substance coming from where your shokepipe goes into the chimney or from the cleanout and pieces of clay liner flakes, then this is the problem. I like the Buderus boilers personally because the G115 is shock resistant, and the G215 is shock proof, so you don't have to worry too much about return temps. Good Luck! Sound like you are an educated consumer!
 
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Old 12-19-06, 08:30 PM
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Do you think adding a carpet to the chamber would help raise the stack temp a bit (besides giving better combustion)? The stack temp is a bit low (about 425 gross/355 net on average).

Biasi originally supplied a combustion pad, then stopped, and I hear they've again gone back to using a pad. I did note some carbon building up on the chamber floor. Might be able to improve two things by adding the pad?

Pete
 
 

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