optimal steam system?

Fred P

i read dans latest we got steam and was interested in the oversize and undersized steamers.

Is there a such thing as a right sized steamer? One that can run for a hour without building up pressure and shutting off at 1.5 lbs?

Can you get a nice steamer to run at 4 ounces of pressure until your desired temp is hit?

Is it better to go slightly under the sq ft of steam that you need rather then go slightly over?

A calculated load of 100 sq feet for example ,minus your 1/3rd pick up factor is 66.7 sq feet. Why get a 125 sq ft steamer which leaves you oversized by 66 sq feet when all pipes are hot? According to what Ive seen all the steamer manufactures recommend going to the next highest rating when you are in between steamers...

Wouldnt it be more optimum to have a 75 sq ft steamer? Would this setup cause the steamer to run longer but never hit its pressuretrol limit?

It seems to me that if we elimate the pickup factor we would rely less on pressuretrols and vapor stats as well as avoiding accidents where the pressure release valves fail. And at the same time we could accomplish a steady steaming rate akin to the coal fired days where our beloved steamer ran for days at a time.

Boilerpro_3

While my opinion is in the minority

I have to agree with you on many points. Yes there are steam systems that run on only ounces of pressure... They are called vapor systems and work exceptionally well. While having a much more limited experience with steam than many of the excellent gentlemen at this site, I prefer to keep the boiler on the small side. To do this the pipes must be well insulated and very well vented, while the radiators will need to be vented slowly. This allows the steam to greatly favor the system piping, so even if it takes fives minutes for the steam to get to the end of the main, none of the rads will be getting much steam until the piping is full. Also, keeping the boiler small will reduce the load moving through the piping, reduing the pressure drop across the system, speeding distribution, helping counteract the fact that less steam is available to fill the piping. This will also result in longer burn times at lower input, which translates to better boiler efficiency.

There is alot to be said on this topic.

Boilerpro

Fred P

I am glad I made some sense

to somebody here at the wall.

Modern steamers product steam so rapidly that I think if you went with a steam at or a little below the connected load that it would be more beneficial that way. Why the 33% additional for the connected piping?

I am not talking about a steamer that is greatly undersized.. that would be a no-no.

Have any of you professional come across undersized steamer that work well? Would you even bother determing the sq ft ratings if the customer did not complain of poor heating?

Randy Berg_2

Food For Thought

You both make very good points. I will tell you a story of a job that I am doing now. I have been in the HVAC field for over 20 years, in the Commerical side. Never worked on small systems. A freind had bought a house with steam heat, the boiler had been replaced because it had dried fired. He never had really any problems with the system other than the oil bills were high. He called in a company that was the biggest HVAC contractor in the county where he lived. This company replaced the boiler. His problems started right after this replacement was started up. He called them back several times for problems. After the year was up he still had problems. He asked me to take a look at this system. When I went down in the basement the 1st thing that caught my eye was there was no insulation on any of the piping, also the near boiler piping just did not look correct. I made a call to the rep for the boiler and got the instructions for this boiler, and the near boiler piping was not correct, we repiped to the boilers instructions, also reinsulated all the supply piping. I then notice that the main vent looked that they had never been replaced. Not really knowing these smaller system, I purchased Dan's books also the dead man steam class on video. We caculated what size vents we needed and replaced both of the main vents and all the convector vents. Now here is where it threw me for a loop, this system is a two pipe steam with air vents, and no traps. The main problem he was having was short cycling of the burner, our thought was that with the near boiler piping corrected, supply piping reinsulted and all the vents replaced the shory cycling would stop. We were wrong, it still short cycled, after looking at the steam side we then looked at the fired side, I checked the firing rated and it was at the boiler specs, nozzle size angle and pump pressure. This is when I started to look at the load, and did complete load with out the pick up factor designed in the boiler. I did the whole piping system. This is where we found the real cause of the short cycling, the boiler is oversized. I don't know how they sized this boiler. This summer we are pulling this boiler out and installing a boiler that is closer to the connected load. Just remember that the newer boilers make steam alot faster then the one they are replacing. I tried down firing the burner but then ran into condensation problems in the vent side of the system. And by short cycling I'm saying a on cycle of three mins on 1 min off 1 min on until it cycles off thru the stat. And to think I'm just doing a freind a favor. The boiler is a 356 Sq ft and the one we will be installing is a 283, which is alittle smaller then the load.

Fred Harwood

Example

I many have found an example of what you're describing. Burnham V74 boiler w/Becket burner rated at 392 sq. ft EDR at 1 gallon fuel oil per hour feeding steam into 90 feet of 2-inch main (half-inch insulation) and 330 EDR of radiation (various 3 and 4-column, 20-inch water-tube style). In this small system, that's just 16 percent more boiler capacity than radiation, plus the burner nozzel has been lowered to 0.85 gph.
The house during the week is kept at 55 degrees, and takes just about 40 minutes to hit 66 degrees on weekends, all without either cycling or significant pressure. At 66 degrees, when the outside temp is below 10 degrees, the boiler runs a bit more than 3 minutes on and 10 off to hold the house temp stable.
Also, showering, clothes washing, etc. do not seem to bother the heating (direct boiler coil).
This system would appear to be about the best match one could have.

Steamhead

It's all a matter

of doing your homework, and not just throwing a boiler in there and walking away.

In this case, you have to know how much radiation the system has and how much heat the building actually needs. The firing rate of the boiler should match the radiation. Note that on some Vapor systems, the radiation was sized about 20% larger than needed. These systems had orifices that limited the amount of steam to each radiator, and the slight oversizing made sure that all the steam was condensed in the rad and none got in the dry return.

If a stock boiler size is too big for the system and the next smaller one is too small, of course we'd use the bigger one and down-fire it (no more than 20% or so) to match the load. There are some who frown on down-firing, but in this case it's the right way to go.

Boilerpro has been experimenting with steam boilers whose ratings are smaller than the installed radiation (but enough to heat the building), and his results look promising. We'll keep watching to see how his methods work out.

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Fred P

would you say then it might make more sense

to raise the pressure on a steamer to allow it to run longer, assuming that all radiators do heat properly and do not shut off on pressure before becoming hot.

For instance raising the pressure from 1.5 to 5 would allow the steamer to run longer and subsequently when hitting 5lbs would give it more time to settle down as steam begins to turn into condensate.

I am trying to think outside the box on this.

Steamhead

Raising the pressure

only wastes fuel. These systems were designed to heat the building with no more than 2 pounds at the boiler. If you're building pressure, you're not moving steam to the radiators.

You should be able to get all radiators completely hot without showing pressure on a standard 0-30 PSI gauge. If you can't, there's a problem such as improper venting, bad traps, missing insulation etc. that needs to be fixed.

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Fred P

Steamhead to clarify,

I am talking about getting steam to all the radiators with a pressure reading of 0. After all radiators have steam in them wouldnt the steamer continue to produce steam because the thermostat has not been satisifed?

At this point a steamer set to cut out at 2 PSI would do that due to the buildup of steam pressure and then restart at 1/2 PSI ,am I correct?

Would it be beneficial to allow the steamer to hit 5 PSI?

I was thinking that a cut out of 2 PSI and the subsequent drop to 1/2 PSI would take a few minutes

But a cut out of 5 PSI and the drop to 1/2 PSI would take longer to achieve, theoretically resulting in less cycle time of steamer.

On a per hour basis, would this result in less overall fuel usuage?

If not, would the less cycling off and on result in less equipment wear?

If you project a 5 year period, would the wasted fuel of running at 5 PSI outweigh the cost associated with parts replacement associated with more frequent cycle times?

Dave_23

Tenths of an ounce

My two pipe Trane vapor system operates at a peak pressure of 0.4 ounces per square inch. On shorter cycles/warmer days, it may only make 0.2 osi. It's proof to me that ounces of pressure is just fine in a vapor system. BTW, my rads seem to be oversized, thus they condense the steam before it can enter the return. Most of my rads don't have traps, which doesn't seem to affect operation. The traps would never see steam anyway on my system, with it's oversized rads. Maybe this is a feature?

Dale

IMHO

I like a little over size since that way you have more water in the system and the time of condensate return isn't as critical. Sure, run the system with as low as possible a pressure, and if the pipes are large enough and the vents good enough you may just match heat loss to steam output. Remember that if the world was perfect the boiler on a winter design day with inside design conditions would not shut off at all once the pipes came up to temp. In this perfect world the heat loss would exactly match the heat generated.

scrook_2

at higher pressure

you just spend more time and fuel pressurizing and heating the steam, offsetting any gain later when the burner's off as the pressure drops again. The heat that is dilivered to the radiators comes not from steap pressure but the steam reconvensing to liquid.

Also at the higher pressures your vents won't work right either. A conventional one pipe system should run fine at 0.5-1 psi or less and a vapor system will run fine at much less, a few oz./in sq.

Boilerpro_3

I have come across some too

One is in a one pipe system....which nearly everbody says it can't work... but the boiler is now about 100 years old and the conversion burner probably about 40 years old and it heats evenly....all the rads have adjustable air vents. Also, a frequent poster here in the past up in Minnesota also has a greatly underfired steam boiler ina a very large home and it works quite well now too.... now that he has greatly increased the venting of the mains.

Boilerpro

Ken_8

It's coming

As soon as full mod burners are available on small house type boilers, there will be true nirvana.

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Boilerpro_3

Oh, yeah! NM