What is correct firing rate: Steamer

Steve Garson_2

Steve Garson_2

I am restoring a neglected steam system and just calculated that we have 1000 square feet of radiation on a system that has had radiators removed over the years. The mains are now well insulated and vented. How do I determine whether the present 2.5gpm nozzle is the correct firing rate?

Boiler: 6 section Smith Model 19 rated for 2308 square feet of steam. Can some sections of the boiler be removed to bring it closer in capacity to the load? Today it holds 57 gallons of water.

Burner: Carlin 301 with 2.50 60-A nozzle

The system seems to work just fine, but with the price of oil, I need advice. This is one of those old buildings that has two giant radiators (shut off and not counted) that heats fresh air.

Thanks for any advice. We're burning 5400 gallons for a 5662 degree days in 2007.

Steve

Steve Garson_2

Does this math make sense?

Total Square Foot Radiation: 1000

Pickup Factor: 1.33

Total load: 1330

BTU per square foot radiation: 240

Total BTU/Hour: 319,200

Adjust for 80% efficiency: 0.8

Total BTU/Hour: 399,000

Divide by 140,000 BTU/gallon= 2.85

Present nozzle is 2.5GPH


Should I use a 3GPH nozzle? Or should I simply measure how many minutes it takes for steam to heat the radiators? The system never seems to shut down from pressure, even though the pressuretrol is set for 4 ounces...it was set at 8 lbs.

Thanks!

Jamie Hall

Silly question?

do all the radiators heat OK? In a reasonable time? If so, sounds like I'd stick with what I had, on the theory that if it ain't broke, don't fix it...

Steve Garson_2

All the radiators heat. I just figure that the boiler should shut off on pressure at some point. With the amount of oil we use, I want to make sure we are doing everything possible to control the oil usage. My understanding was that slow steaming wastes oil and you should always fire to the load

Keith_8

system water clean

Steve,
Is the water in the guage glass clean?

If the water is dirty the boiler has a difficult time making steam, (read uses more oil).

Is the stack temperature high?

If everything seams to be in order with the boiler you should look into tightening up the building heat loss.

I wish I could claim this saying as my own but I can't
"The most efficient boiler is the one that doesn't come on"

BTW, My Smith book tells me a 19-6 should have Carlin 702CRD oil burner, firing @ 6.5 GPH. Something tells me that
someone has already tried to downfire the boiler as much as possible and any further derating is going to result in low stack temp causing more problems.

The Carlin 301 has a firing rate of 3.00 to 6.00 gallons per hour. You have a 2.5 gallon nozzle is the pump pressure set @ 150 psi? If so you are already at the lowest input the burner is rated for.

In order to derate the boiler further you would need to remove a couple sections entirely to get closer to your actual square feet of steam.

Good Luck,
Keith

Steve Garson_2

Boiler water is crystal clear as is the watch glass.

Is it practical/possible to remove a section? The piping is joined with Victaulic fittings, so my guess is that piping changes might be less time consuming than with threaded fittings.

My question about firing rate was whether it should be increased since pressure never shuts down the burner.

Steve

Keith_8

Victaulic?

I was not aware that Victaulic made couplings for a steam system?

If the boiler is in good shape I wouldn't hesitate to remove 2 sections. You will need to order a new jacket and a breaching adaptor.

If the burner is keeping up with the heat loss @ design conditions then I would suggest that the firing rate is basically on cruise control. If that is the case and cruise control does the job increasing the firing rate would not help your fuel consumption.

Keith

[Deleted User]

The original 19-6

(not the 19A-6) had an input of 5.5 GPH #2 for the net 2,013' EDR. That's 366' EDR per gallon. Divided into 1,000' = 2.73 GPH.

The 301 CRD is the correct burner. It may be the earlier version, rated @ 100# to the nozzle. The "PA" version is rated @150#. W/ a 2.50 nozzle - that's 3.00 GPH.

Looks like someone has already traveled your path. Before doing anything drastic, like removing sections, I'd do a thorough fireside cleaning, service the burner, & run combustion tests. That will tell you more about what the boiler is doing & should help w/ further decisions.

BTW. The 19 is a pressure fired boiler. +.10" WC. Measured @ tapping before the adjustable boiler damper. Not the barometric.

Steve Garson_2

Ron:

In reading the specs on the boiler, it seems to indicate that there shouldn't be an atmospheric damper, which there is. What do you think?

The boiler is tuned up and cleaned every year. It has 80* combustion efficiency when tuned. 12.5% CO2, no smoke. Although at this point in the season, I'm sure that is not the case.

Steve

[Deleted User]

If the boiler is

vented into an existing stack, a barometric is still required. That's to regulate the draft between boiler damper & stack. The new-fangled term for venting this way is Balanced Draft.

Something doesn't ring true. 80% w/ 12.5 CO2 works out to a net stack temp around 550*. Unless the fireside is really dirty, or the water side badly scaled, the net stack(underfired @ approx 2.5 GPH) should be around 300*.

Are you sure the boiler is a 19-6? Wouldn't be the first time somone affixed the wrong rating plate. 19-6 is 36" long.

Steve Garson_2

The plate clearly says Smith Model 19 Series 6 Boiler, but it is a lot bigger than 36-inches long. I guess I should measure it and count the sections. I would say it is closer to 50-inches deep. I'll measure and report back tomorrow.