Commercial steam heating question

Tony Conner

... "old systems" that fire to maintain pressure, it's just how big industrial or institutional steam systems work the best. (New ones like this go in all of the time.) The only other way to do it is to install like 50 little boilers, all over the place, and that's a maintenance nightmare.

t. tekushan

150 HP boiler question

I have a question regarding a system of great magitude (the system, not the question).

Situation: A friend has purchased a 110,000 square foot factory building for redevelopment. Its got an overhead steam system with unit heaters, greenhouse type pipe coils along the skylighting, radiant overhead radiators, and lots of wall radiators. The boiler is a 150hp Sellers fire tube boiler with a forced induction natural gas burner. The interior thermostat operates a gate valve. There is no outdoor reset. The boiler sits there maintaining pressure 24/7. Naturally, it comes on periodically to maintain pressure. So the building is sitting at 50 degrees and the boiler is firing every 10 minutes. He wonders why it costs so much to maintain 50 degrees!

The questions: 1) A timing system based on outdoor temp seems like a good idea. Any recommendations?

2) (and this is important) What are the implications for thermal shock when starting a non modulating boiler? I really have no idea if the Honeywell burner control allows for a slow temperature controlled warm up. The burner's blower turns on first, then it goes to "pilot" which is a low flame level. Shortly thereafter, WHAMMO. Full steam ahead... (its awesome to watch the burn through the sight glasses; looks like iridescent light sabers (star wars) aimed perfectly into each individual fire tube). I'm thinking this 1969 boiler is in such good condition because it was always run this way.

Is it common for these systems to be able to preheat from cold before full power is applied?

I don't intend to do this work myself. I just want to make sure my friend knows what to ask and that we will be able to spot a pile of bull when we see it.

-Terry

c.t.kay

controls

call heat timer corp in new jersey. ask for ed eidelman, or someone else in tech dept.tell the the system requirements and the existing equptment. they are the best control system for steam and water systems over 100hp +/-. good luck it is just a bigger boiler / burner and more controls.

EBEBRATT-Ed

Most of those old systems were designed to maintain pressure. You may be able to rework the controls, adjust the firing rate etc. maybe avreging thermostats would help conserve fuel.

As far as full fire on a cold start that is the usual method. You can wire a aqustat into the circuit to keep the burner on low fire until the water reaches 190--and when the aqustat makes on a temp. rise -let it steam.

Check out "Heat Timer" they have timing devices that utilize outside air for controlling this boiler

Unknown

Heat Timer is good

I'm with these guys.

Noel

Mike20

150 HP boiler

Terry,
Without knowing all the particulars, The answer is simple. Have the thermostat control the boiler directly so that it only fires on a call for heat. This will eliminate the need to maintain pressure at all times and will permit the boiler to actually cycle off thus saving fuel.

As far as the size if the fire, in some cases this will only require a simple adjustment of the control system - On a 150 HP boiler you will likely be able to incorporate a steam pressure control that will automatically change the size of the fire based upon steam pressure. When the boiler is cold the burner will operate at full High Fire to get the steam up, then as soon as you make steam pressure the control gradually reduces the size of the fire until you reach an equilibrium point where the size of the fire matches the rate that steam is being used in the building, thus eliminating short cycling and providing for more efficient operations.

The control is Manufactured by Honeywell and is best installed by a professional. Honeywell L91A1037 proportional controller
Good Luck- please e mail me if I can be of further assistance- Mike G

t. tekushan

thank you

thank you for all your input.

I now have an excellent starting point to investigate and weigh the options.

You may not be surprised, but I was called out of desperation. Its amazing what consultants and engineers told him what was required to improve efficiency. To a one, they told him to scrap the steam system. Two of them told him to completely repipe and use multiple hot water boilers, one of whom recommended scrapping the radiators in favor of fin tube because radiators are less "efficient."
Forced air augmented with electric baseboard was also recommended. My friend's English isn't so great but he sure understood me when I asserted that keeping and tuning what he's already got is actually the most efficient and cost effective option for a building like that.

Thanks again. Now its time for me to do my homework!

-Terry

tim smith

commercial steam

I would maybe consider a new full modulating burner, install it in existing boiler, but the burner can be ordered so it will fit in a new boiler block when time. Then also install a Heattimer control. You wont have the short cycles any more and having the burner already is a big deal when the old boiler goes it takes 6 weeks or so to get a new burner usually, but iron is usually very available. Good luck.

Ken_8

THAT'S the

bingo! answer. Get the butrner to modulate based on system demand and keep the pressuretrol down a round 2 pounds or less!

If the pipes are insulated, 2 # should do the job all around.

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bob_44

sellers

Terry, It's been 25 ywers sincei've installed any of these but I don't think you can modulate the burner and you definitely can't change the burner. The air and gas is mixed before the burner and there is a seperate burner for each tube. bob

bob_44

That huge picture

ain't my fault, blame it on Constantin. He told me to buy this software from this guy in Deutschland. It was supposed to solve all my problems posting pictures:) I'm old but I can still pull a 36 better than I can run this confuser. bob

t. tekushan

laughing out loud

while I write this! Love your replies, Bob :-)

Back to the subject at hand...

Looking at the burner set up, I assumed that modulation is not possible with this one. As it turns out, Sellers still makes the very same boiler, a single pass with 80+ efficiency. So is the '69 in the building I am speaking of. This is one heck of a good boiler. Sellers claims low thermal shock risk, but still I wonder if the risks are higher on a 36 year old boiler.

Since I've found that Sellers is still very much in business, I'm going to contact them to see if the intermediate "pilot" flame level is enough to prewarm the boiler in a reasonable amount of time.

I'll say it again, but watching those individual "rods" of perfect blue flame shooting into each individual fire tube is impressive. The refinement level of the boiler/burner set up is terrific.

-Terry

bob_44

Shock