Two Pipe Vapor System Help Needed

Randy Berg_2

I need some help with this system. This is a two pipe vapor system that was installed in 1947. The boiler was dried fired and replaced with a W/M Sgo 3 several years ago. The near boiler piping was not correct and has been redone as per W/M specs, also all the supply piping has been reinsulated. They were using a pressuretrol, which has been replaced with a vaporstat. All of the vents have been replaced with gorton's. The boiler has been downfired to the point where it can not be downfired anymore, due to the acid dewpoint in the chimney.With all of Dan's wonderful books, I have done a load caculation of the entire system without the pickup factor included in the boiler rating. The total load of the system is 305 sq ft, the boiler is rated at 356 sq ft. I have looked for a boiler that has a IBR of 300 sq ft but can only find a 283 sq ft which Burham,Crown and also Smith produces. The basement is not heated, and I was thinking of possible solutions are, installing a loop of hot water baseboard, or a steam unit heater, if in fact I can find one that size. The bottom line is that this boiler is oversized and it seems that noone makes a boiler oil fired with a rating of around 300 sq ft of steam. Please give me your thoughts and suggestions on this one. The problem is short cycling.

Steamhead

356 square feet

is not that much oversized..... have you checked the thermostat anticipator? Try sliding it toward the "longer" end of the scale and see if that helps.

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Randy Berg_2

> is not that much oversized..... have you checked

> the thermostat anticipator? Try sliding it toward

> the "longer" end of the scale and see if that

> helps.

>

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> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 157&Step=30"_To Learn More About This

> Professional, Click Here to Visit Their Ad in

> "Find A Contractor"_/A_



Steamhead, that has been done, it had a Honeywell programable stat on the system,which has been removed and a new T87F installed, its not short cycling on the stat, but pressure.

Ken_8

The only answer...

The parameters of the burner are the problem.

In an area dominated by NG, I don't get my hands on too many smaller burners other than the 'plane jane' Becketts, Carlins, Riello's, etc.

I know of no model that small, that has true "step" modulation. "Full" mod would be unheard of - but is exactly what you should have. Adding a phantom "modulation load" seems wasteful in such a great system.

Could always do the SS liner thing and not worry about the chimney? But you still wouldn't have the modulation you should have. A few burners have a 2-staged potential (but always run a tad rich on light off because there's no air shutter inter-action) - but rarely if ever have staged air shutter linkage in your BTU input range.

A cheap "fix" might be to allow the vaporstat off-to-back-on "event" to take longer! This could be easily done by adding one of those little solid state delay timers - set to 6 minutes? (the typical max. setting). The longer the off cycle, the longer the run cycle right? That may be the ticket.

Ya never know. You may make that thing sing and dance after all!

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Mad Dog

I concur with Steamhead....I really wouldn't call that

oversized. My rule is one extra section is ok. 2 over starts to be on the overrsized scale. You replaced the rad vents, but how about the main vent/s? Mad Dog

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[Deleted User]

just for the heck of it,

remove the main vent and see how the system runs,,,does steam appear?? does the short cycling stop when the main vent is removed??let us know these answers and we may be able to help better.

Randy Berg_2

Yes the main vents have been replaced as well. When the stat calls for heat, the boiler starts and will run about three mins until it cycles off on pressure, then off for one min then back on for about a min, this occurs until the stat shuts the system off on temp. The system has been cleaned also the ph is correct, as per W/M at 9.0 ph. The pigtail is clear, no crud in it. Also all returns have been cleaned.

Randy Berg_2

Also this is at a setting of 10 oz and the diff. set at 6 ozs. The system heats very well, and even.

Mad Dog

New vents, but what kind? how many?

how big and long are the mains? As Gerry says..take the vents off and see what happens. MD

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Randy Berg_2

The mains are 1 1/2 and the total lenght is 100 ft.

Randy Berg_2

Vent's installed on the Mains are Gorton's # 2, one on each end of the main's

Mad Dog

Hmmmm...try taking them off

MD

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Steamhead

Main vents sound OK

but how about the dry return? How does the air vent from the dry return?

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Randy Berg_2

I was thinking about taking them off as well to see what would happen. This job has been a hair puller and some sleeplest nights. I have been going over everything to see if I have overlooked anything. Thank's and I will get back to you all after removing the main vents and let you all know what happens.

Randy Berg_2

Steamhead the main vents are at the end of the mains,then the main does a 90 down into a 45 then into the return, this is on both mains. The house next store has the same setup, piped the same way.

Randy Berg_2

Also a very big chested boiler, that does not short cycle as per the owner but then again she is 80 years old.

Unknown

Think about this

the cycle may get longer if you turn the pressure down.

Of course, this won't make the boiler smaller, so it isn't magic, or anything. I've found the longest cycles, both on and off (the sweet spot) are at the lowest pressure that it will still heat at.

Once you find out how many ounces of pressure it takes to keep the last radiators hot, that would be your cut-in pressure. You can make your cut-out any differential that works for you.

The higher the setpoints, the shorter the cycles. Compression is more.

You may need to set your pressures using a manometer.

Noel

Steamhead

But

since this is a 2-pipe Vapor system, there are no vents on the radiators, correct? If so, air from the radiators goes into the dry (overhead) return and out thru a vent or vents on this return.

With this type of system, the steam mains aren't the only place you need main vents.

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[Deleted User]

what is stopping the steam from

getting from the supply pipe to the dry return?? you say the main does a 90 degree turn down, then a 45 degree turn then into the dry return...but what kept the steam from crossing into the return?

Fred Harwood

steam

What sort of radiator trap/vents are there. Small orifices may be holding back air.