Which nozzle to select

burbridgeb

We recently installed a Peerless WBV-04 oil fired boiler. I requested the 0.95 gph nozzle delivering 117,000 BTU output (we calculated we need 122,000) b/c it provides an 87.0 AFUE and has the Energy Star Rating (other size nozzles do not). My home is 2,600 sf with 4 zones, 217 ft of baseboard and a Superstore water heater as a 5th zone on the boiler. The house is older and somewhat drafty. The installer (my oil provider) instead provided a 1.25 gph nozzle which delivers 151,000 BTU's. I asked him to change to the nozzle I had requested. he said he would but didn't recommend it b/c that would make the boiler run more and use more oil. Is he correct or should I still switch to the smaller nozzle?

Charlie from wmass

A heat loss needs done to determine required boiler size, or fire rate.

Robert O'Brien

Hatterasguy said:

The installer, like most, hasn't a clue as to how a boiler operates..............the longer it runs before hitting high limit and shutting itself down (the usual life of a boiler), the happier it is and the less fuel it burns in a heating season.

If they had a clue they wouldn't be selling 150K pin boilers in houses that I would give 10-1 has a heat loss under 75K.

DJD775

I have a slightly smaller house (2500sq ft) in Rhode Island and a very similar sized boiler (Crown TWZ150). I have data from the previous owner when the boiler was fired at the maximum firing rate (1.5gph) and I have tried 2 different firing rates (0.9 and 1gph). Oil usage between the 0.9 and 1gph firing rate was within 1% of each other with degree days factored in. I haven't factored in the degree days for the 1.5gph firing rate but the previous owner reported using ~100 gallons less oil. He was single and I have a family of 3 so I'm assuming he kept the heat a little lower. I can tell you no matter what size nozzle you install you will be over sized as my boiler still short cycled at the lowest firing rate. I have the boiler setup at 1.25gph this season and I won't know the fuel usage until next year.

Patchogue Phil_2

Why go so much higher firing rate this year? You will admittedly short cycle.

DJD775

I'm trying to test/balance multiple theories. Short cycling wastes energy Input too small for the heat exchanger surface wastes energy. I know it would be best for me to install a small 3 pass boiler but I'm trying to justify the cost. I can justify the cost of the boiler and chimney liner install (DIY) until I factor the the investment income lost.

Patchogue Phil_2

Input too small doesn't waste energy, most of it will transfer and be more efficient. Longer burn cycles are better.

STEVEusaPA

TWZ 150 with:
AFG-1.10 X 45B HAGO 175psi Pump pressure
NX-1.20 X 60B HAGO 150psi Pump pressure.
If you downfire, make sure it's not condensing.

DJD775

Definitely signs of condensing in my exterior brick chimney at the lowest firing rate.
BTW, I have a Carlin EZ burner.

STEVEusaPA

Ah 1.25 X 60 B. If you go with another firing rate im sure youre aware to change the air band and the plate for the head depth.
I'd go with the factory specs for maximum efficiency and take care of condensing and short cycling with piping & components

DJD775

Oddly I'm more aware of the plate change for head depth than most technicians that have serviced the boiler. I'm a gear head so even though I don't perform the service on the burner I like to know as much as possible about them.