What nozzle to minimize fuel use?

bruce_21

Just finished installing a replacement Peerless EC/ECT-04. It was shipped with three nozzles for different capacities. A 1.25 was installed and a 1.10 and 1.50 were sent extra. They set the pump at 140 psi, so the 1.25 is like a 1.50 at 100 psi. I had measured the load at 565 sq. ft. Peerless rates the boiler at 563 sf. ft. at 1.50 gph so I was surprised when the unit would not raise steam pressure even though all the radiators heated fully and the weather is still mild. To make sure we had no steam leaks before we finished insulating the piping near the boiler, I put the 1.50 nozzle in today and it did finally raise the pressure to 1.5 and shut off.



My question is about fuel use. Which of these nozzles should I use to minimize the clients fuel use over the winter?

BobC

Raising Pressure

Bruce,



If it wasn't a very cold day the system probably able to supply enough heat without raising any noticeable pressure. How long did it take to satisfy the thermostat?



If the system raises enough pressure to trip the pressuretrol it might indicate the firing rate is a bit high. A few ounces is enough to move the steam as long as the venting is adequate. In a perfect world the system would run almost 24 hours a day at 0 degrees F, or whatever your area's design temperature is.



Low pressure is usually the customers friend and the oilman's nemesis.



Bob

Mike Kusiak_2

Firing rate and efficiency

I agree with Bob. In general, you really want the lowest firing rate that will meet the heat load while still being able to completely fill all the radiators with steam. In a perfectly matched system, the radiators would be capable of condensing all the steam the boiler could produce and the system would never build enough pressure to trip the pressuretrol. In the real world however, you need to be able to heat all the cold iron piping and insure the ability to quickly vent the air and bring the system up to temperature. So there is always some oversizing ( factor of 1.33 ) built in to the steam rating. Once you oversize (or overfire) above this optimum amount it may become counterproductive as the short cycling on pressure drops efficiency. So under normal operation you really want to satisfy the thermostat before any cycling of the burner on pressure.



Another benefit of a lower firing rate is an increase in thermal efficiency of the boiler. A low firing rate results in a lower stack temperature, and less wasted heat going up the chimney. There was a discussion of this in a previous posting:



http://www.heatinghelp.com/forum-thread/132371/Does-slightly-underfire-longer-cycle-save-money



For best efficiency and overall operation, I  would suggest going back to the original nozzle, which would fire the boiler at the rating matching the installed EDR

jpf321

lowering nozzle size...

bruce ... to save more .. you can fully insulate the boiler with K-Wool (mineral wool) .. on my new boiler, fully insulating the boiler raised the stack temp substantially. thus not losing heat to the surrounding boiler space, therefore being able to downfire the boiler.



the boiler is spec'd at 1.10GPH (effective firing) .. however, it looks like i may end up at around 0.75 or so after eliminating most static boiler losses. it may be the single best way to reduce fuel consumption. in fact, i've downfired it so much, that i should probably be in a Riello F3 rather than the Riello F5 that I have installed.



also keep in mind that your boiler can only produce enough steam as it has volume of water available. 1 cup of water will only yield the equivalent amount of steam, regardless of how much heat you provide.



you can see, in both regular photos and IR photos, my fully insulated  boiler in my thread over here: http://www.heatinghelp.com/forum-thread/132546/so-long-fitzy-hello-slantie#p1206036