Tips for dealing with an oversized boiler?

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Old 11-15-08, 12:11 PM
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Tips for dealing with an oversized boiler?

Is there anything that can be done to make an oversized boiler run a bit more efficiently?

Currently i have a Burnham SGC 6 boiler that is rated at 150k BTU. A rough Heatloss of my entire house is 84k, however the house is divided into 3 zones, and 2 of the zones hardly ever run.

Generally the boiler will run for ~2.5 minutes then shut off for 5 minutes, over and over, this seems like it cant be very efficient or good for the boiler over the long term.

Is there anything i can do? or am i just stuck with it?
 
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Old 11-15-08, 01:35 PM
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Probably more or less stuck ... you could probably make some improvement by installing a buffer tank, but that's big ticket ... and a bit of room for the tank ...

But, make sure the settings on all the controls are in order first and that there's no other reasons for the short cycles ...

What kind of radiation ? fin-tube ? cast iron ? radiant ?
 
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Old 11-15-08, 01:45 PM
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As far as i know everything is set correctly. The aquastat is set for 180, and really that is the only control i see. Are there other things i should check?

I forgot to mention that i have indirect hot water, i am not sure if that would make any different to my problem tho.

I have fin-tube radiation.
 
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Old 11-15-08, 04:16 PM
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What might help also ... if you had a wider differential on the boiler, the cycles would be longer, but spaced further apart ...

I wonder if this would be a good case for an add-on Heat Manger? That magic little box promises to save 10% ... and in your situation might help the boiler not short cycle so much. MAYBE... I've observed the way they work, and with the way your boiler is running, I think it would tend to widen your differential ... and lengthen the cycles ... but I ain't sure ...

What a 'buffer tank' could do for you is store a bunch of heated water... which would be pumped out to the baseboards ... the boiler would be piped into the storage tank and only fire up when the tank cooled ... so you would get one nice long efficient burn cycle, and then it would be off a good long time while the system used the heated water in the tank ... but like I said, pretty big ticket ...

The indirect gets treated just like another zone ... but I would think that you get nice long cycles when the indirect calls for heat ? Is the indirect piped with 1" and it's own pump ? or on a zone valve ? Are the other zones pumped or valved ?
 
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Old 11-15-08, 05:15 PM
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Is this LP or natural gas? If it is natural it can be de-rated slightly. The heat manager as Trooper suggested is a good add. What type of thermostat do you have?
If it can be de-rated it will need all the orifices replaced.
 
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Old 11-15-08, 05:16 PM
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There is 1 pump, all the zones including the indirect use a valve.

The indirect is piped with 3/4.
 
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Old 11-15-08, 05:44 PM
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Its Natural Gas.
I've looked into the heatmanager a bit, i think am leaning towards giving it a try.

as far as replacing the orifices how do i determine if thats possible with my boiler? Is it expensive?

Does all the short cycling reduce the life of the boiler? or just put a big hit in the efficiency?

My thermostats are Ritetemp 7 Day programmable, i didnt see a model number on them.
 
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Old 11-16-08, 08:36 AM
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My experience with boilers is with large oil fired commercial steam types but I have been involved with a couple of projects where a small electric boiler was added for use during low demand.
Apparently the cost was more than offset by the efficiencies gained, even with our higher cost of electricity over oil..

Pros, would this be practical in a case like this if sid had enough power available for even a third of his properly calculated load?
 
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Old 11-16-08, 04:05 PM
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Orifices are cheap and easy to change. The boiler will need to be tested after it is done to check O2 and CO levels.
 
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Old 11-16-08, 05:23 PM
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Originally Posted by sid77 View Post
Is there anything i can do? or am i just stuck with it?
You could bite the bullet and buy a mod-con.

They really save during the shoulder seasons like right now.

What's your annual gas bill? You might want to ballpark about a quarter to a third of that as potential savings.
 
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