Is there any way to shrink an oil boiler?

[EatenByLimestone]

I've inherited my father's house. It's a post war cape where the upstairs was never finished off. I'll be finishing it off in the next few years, but for the time being it's a 1000 sq ft house.

The house has been upgraded with newer (last 10 years) windows. It has insulation (vermiculite) in the walls. The ceiling is insulated with cellulose and I'm currently working on insulating the attic in anticipation of the finishing off part. I plan on having it sided where there will be more insulation added under the siding.

So the house is/will be much tighter than it was originally constructed.

The problem I see is a brand new (Installed in December '97) 115K Energy Star boiler. This is larger than the one in my 1600 sq ft 90 year old house! Can I change the jet or burner size? I don't think I need a third of this size. Especially considering the 30-NC that will be burning in the basement.

Matt

 

[velvetfoot]

You can put in different nozzles. The oil guy has to set everything up though.
Plus, is that gross or net?
My boiler is a Burnham V83 and the catalog here http://tinyurl.com/nxbyxz says it can be fired with a .75 gph nozzle for 91,000 btu/hr or 1.05 gph nozzle for 123,000 but/hr. These are DOE numbers, I think gross.
My oil guy said said I have the .75 nozzle. I have a 2000 ft2 colonial about 5 years old or so.
You need extra capacity if you heat the upstairs (no baseboards up there?) plus you have less insulation in the walls.

 

[pybyr]

It is possible to change nozzles within an oil burner head (the basic burner head remains pretty much the same)(though you adjust the air feed as well) to achieve different firing rates.

That said, there are not only various burner nozzle sizes, but also entirely different patterns-- both in intended pattern and varying between make of nozzles-- and you'd want to make very sure that you select a new nozzle that gives you the right length and shape of flame for your boiler. Too short a flame and you'll lose efficiency- too long a flame and you may blow through some steel...

Some reading for you--

(broken link removed to http://www.beckettcorp.com/protect/techsuppt/product-manuals/RWB_Oilheat_Guide.pdf)

and

(broken link removed to http://www.delavaninc.com/pdf/total_look.pdf)

and this fellow's DVD's are remarkably informative, though they'll never win an award for slick style or production quality

(broken link removed)

To get into changing fuel feed rates, you'll definitely be getting into some adjustment and trial and error. It's not rocket science, but you'll probably need to borrow or get some instrumentation-- there are settings that "look OK" but that will gum up the works one way or another. If you try to do this, see if you can get a second-hand or left-over version of what oil service folks call a "wet kit"- which is a flue manometer, a flue temperature gauge, a smoke-tester (using filter paper) and a reagent-based combustion analyzer. All of the service techs these days want electronic gizmos, but the retro Bacharach "wet kit" will give good results if you're not in a hurry. As a bonus, you will become able to do your own yearly tune-ups on your burner, which will save you back the cost of the "wet kit" in a few years.

Hope that's a helpful start (I dug into all of this stuff a few winters back when I was hoping to adapt my oil burner to run on used cooking oil (which some people have done with real success) only to find that, where I live, the used cooking oil stream is already "spoken for" by biodieselers, etc.). Then I, luckily, ran across the technology of wood gasification + heat storage- which suited me well since I was already cutting and burning wood.

 

[heaterman]

What brand of boiler and burner? What size nozzle is in it now?

It's not simply a matter of changing the nozzle to a smaller size. The corresponding air shutter setting will have to be found or the O2/CO2 ratio will go down the crapper and leave you with a sooted mess. In some cases the burner head will need to be changed. All this can be found out and done yourself except the final air adjustment. Unless of course you have a combustion analyzer. In which case, have at it.

 

[Eric Johnson]

That's the problem with sizing a replacement boiler by looking at the tag on the old one. Whoever did the installation really should have done a heat loss calculation on the house since, as you point out, it's been significantly upgraded since the old one was spec'd. As a practical matter, it ain't the same house.

For that reason, I think it's fair to say that most older boilers in most older houses are oversized. By the same logic, most hydronic heating systems in most older homes are oversized, but the boiler is where the rubber meets the road.

I agree on the nozzle sizing, and I agree that you should get somebody who knows what they're doing to set it up. Also, bear in mind that a .75 nozzle has pretty narrow tolerances. Dirty fuel will clog it up in a heartbeat. If the tank is old and/or suspect, you might want to consider flushing it out. At minimum, change the filter.

Good luck, Matt.

 

[EatenByLimestone]

I need to have it cleaned still so I'll have the guy look into sizing when he's cleaning it.


Matt