Connecting a one pipe wet return system to a two pipe wet return

Billurbs · April 2004

I have a very old church where the boiler on a single pipe wet return system is failing (breaching actually, but that's another storm) There is an adjacent boiler which feed a two pipe wet return system, with a boiler return trap assembly (could have been a vapor system). I'd like to interconnect the two systems with motorized valves. Any suggestions or comments. I know about trapping the motorized valves.

Ken_8 · April 2004

Unless you are very \"hip\" to...

actual and/or false water line dynamics, cross talk in common headers, pressure differential dynamics, lead-lag controls, wiring and control strategies, and the inevitable "surprises" steam "logic" always has in store, you may want to leave that sleeping tiger alone.

Simply replacing the bad pipe is the obvious starting point.

Yo what end would you want to "integrate" two entirely different ste systems? Or did I mis-read, and they're already interconnected?

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Steamhead · April 2004

> I have a very old church where the boiler on a

> single pipe wet return system is failing

> (breaching actually, but that's another storm)

> There is an adjacent boiler which feed a two pipe

> wet return system, with a boiler return trap

> assembly (could have been a vapor system). I'd

> like to interconnect the two systems with

> motorized valves. Any suggestions or comments.

> I know about trapping the motorized valves.

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Steamhead · April 2004

You don't want to use motorized valves

on that one-pipe system. The lack of "leftover" steam pressure in that system will cause the water to back up into the steam mains when the valve closes. This will cause banging.

The "2-pipe" system is very likely a Vapor system, designed to run on less than a pound of pressure. The Return Trap was there to make sure the water could return to the boiler if the pressure got too high. If you connected the two systems and both systems were calling for heat, the Vapor zone would heat but the one-pipe zone might not.

Your best choice here is simply to replace the boiler on the one-pipe system. This would also ensure that if one boiler stopped working, the other part of the building would still have heat.

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Billurbs · April 2004

The one pipe steam boiler (probably original) in question is in the center of the basement of a 100 year old church. The problem is that the chimney, which is incorporated into(framing) a rather elabotate stained glass window, leaks. Replacement would be impractible.
There is a newer steam boiler located ~ 30 ft away, which is probably 4 feet lower than the older one. I'm thinking of sharing this boiler on a priority basis.
I think I can get most of the condensate returns back by gravity, and pipe a new steam supply line to the two existing 3" distrubution mains. Problem would be that there are some wet returns that would remain trapped after the valve closes, although I don't see how this is much different, then when the current boiler cycles. (I quess pick-up speed could be an issue.)

Billurbs · April 2004

> on that one-pipe system. The lack of "leftover"

> steam pressure in that system will cause the

> water to back up into the steam mains when the

> valve closes. This will cause banging.

>

> The

> "2-pipe" system is very likely a Vapor system,

> designed to run on less than a pound of pressure.

> The Return Trap was there to make sure the water

> could return to the boiler if the pressure got

> too high. If you connected the two systems and

> both systems were calling for heat, the Vapor

> zone would heat but the one-pipe zone might not.

> Your best choice here is simply to replace the

> boiler on the one-pipe system. This would also

> ensure that if one boiler stopped working, the

> other part of the building would still have

> heat.

>

> _A

> 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 Professional"_/A_

> on that one-pipe system. The lack of "leftover"

> steam pressure in that system will cause the

> water to back up into the steam mains when the

> valve closes. This will cause banging.

>

> The

> "2-pipe" system is very likely a Vapor system,

> designed to run on less than a pound of pressure.

> The Return Trap was there to make sure the water

> could return to the boiler if the pressure got

> too high. If you connected the two systems and

> both systems were calling for heat, the Vapor

> zone would heat but the one-pipe zone might not.

> Your best choice here is simply to replace the

> boiler on the one-pipe system. This would also

> ensure that if one boiler stopped working, the

> other part of the building would still have

> heat.

>

> _A

> 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 Professional"_/A_

Thanks, the problem is with the chimney of the the existing 100 year old steam boiler (serviing the one pipe system. It's a masonry chimney that frames a very large stained glass window. Replacement or repair of this chimney would be very expensive and probably not warranted for such and old boiler and piping system. My thought is to use an adjacent steam boiler, located ~ 30 feet away and slightly lower (~4') to duplicate this boiler. The thought behind the motorized valve is that it would only operate when the other system is inactive. I'm thinking these loads can be diversified, so they wouldn't run together. I'm also thinking that the water left in the system wouldn't be much different that the amount remaining after the current cycling of the boiler. (Probably why these systems worked so well with coal.) A fast cycle up on the boiler could probably bang the pipes I suppose.
You're right about the vapor system, although I don't think they run it at such low pressures.

Steamhead · April 2004

Why not use

a boiler that can vent thru a sidewall? Burnham makes the Independence power-vented gas steamer in sizes from 163 to 454 square feet EDR. Or you could fit a power-venter to an oil or larger gas boiler if desired.

This would be a much better solution than tying the two systems together.

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Boilerpro_3 · April 2004

Say steamhead

I think he said that the old boiler was about 4 feet higher than the new one he wanted to tie into. I imagine 4 feet plus the original A dimension should do a good job of holding water in the boiler when the Vapor side is running and the supply valve is off to the one pipe. Haven't got a complete picture in my head of this, but I thought this might help.

Sounds like any wet returns on the one pipe would need false water lines, as I understand them, but not sure I see any other serious problems. I wouldn't be surpised if both systems would run at vapor pressure.

One thing that you may want to look at is if the radiation is too big. Do a heat load and find out. It is very likely that it is. With the vapor, it would be easy to either shut off unnecessary rads or throttle them down. With the one pipe, unecessary rads could be shut off (or removed, swapped etc), especially if they serve one large space like the sanctuary. This would reduce the steam load if the boiler is not big enough to handle all the radiation at ounce. It would also reduce the pressure drop across the one pipe to help insure that when both zones are open, both will get steam fully.

Looking at LA, pg 237, couldn't the one pipe return be connected to the bottom right capped pipe returning to the hartford loop. The 4 foot plus the added original A dimension should deep the water from backing out, as long as the pressure is not too high. This would give us a nice big B dimension for the returning condensate from the one pipe side.

I'd do my heat loads, shut off one pipe rads as necessary and then see what boiler pressure it takes to fill all the rads( and/or you could calculate it). I bet it will be well under 1 psi, so a four feet or more B dimension should be plenty to get the one pipe return water back to the boiler and prevent water from backing out when the vapor side is running, with a vaporstat in use, oh course.

Am I crazy, or would this work?

Boilerpro

Steamhead · April 2004

It might

but unless you're running a high-low-fire or modulating burner, you'd still be dumping the full load of the boiler into one zone if both are not calling for heat. Dan calls this "trying to put ten pounds of sugar in a five-pound bag". One side effect of this might be to increase the pressure drop across the active zone, which might be enough to overcome the added "B" dimension.

I realize that's a lot of "mights" but those "mights" can add up to a nightmare. We'd need to know the boiler's capacity and the radiation load of each zone. Also if there is any time both zones would have to be fully heated at the same time, for example maintaining the sanctuary at a certain temperature to keep the pipe organ in tune while simultaneously heating up the Sunday-school wing. Considering the age of the church, I'm 90% sure it has a pipe organ and we do NOT want it to get out of tune from the sanctuary not getting enough heat!

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Boilerpro_3 · April 2004

I agree on the 5/10 problem

It appears on nearly all zoned two pipe systems I've seen....lots of banging as the steam from a large single boiler rushes into a single small zone. Zoning any steam system never did seem to make sense to me. Ever seen any solutions for this? I suppose you could always start on low fire and time out a high fire pressure control. If pressure is developed in the time out period, boiler stays on low fire.
This is a case where homework is required, but it appears to have potential in the hands of a good "Steamhead". 48 inchs plus the usual minimum of 28 inches of the old A dimension would give you a nice big B to carry about 2.5 psi, more than enough for most any one pipe, as you know.

It would be a fun one to work out. I always like exploring beyond the edges of typical practice, especially when the homework supports it.

Boilerpro

Boilerpro_3 · April 2004

Oh and pipe organs

Pipe organs will last much longer in minimally heated spaces (45F) than in heated spaces, because the humidity in heated churches is typically is way too low (10 to 15 %) and destroys the chests, leather valves, bellows, wooden action parts and consoles. I understand this is purely an American belief.

European pipe organs have lasted hundreds of years in unheated spaces, while organs in heated spaces usually require major repairs every 20 to 50 years due to damage to natural materials. If you work with old churches in Baltimore, have them contact the Amercian pipe organ builders guild, they will confirm the need for low temps to increase pipe organ life in most church settings. Once the organ is warmed back up the reeds (which are what usually go out of tune) come right back in. Also the density of the air changes at low temps, so the pitch of most ranks of an organ go sharp...it makes the reeds sound reallll bad!

Boilerpro

Christian Egli · April 2004

How about thermostatic valves

Well, here is one more other opinion. I don't see why it would be a problem to feed the old system from the new one, the owner said the piping should flow and he must also think the new boiler is big enough.

What I wonder is what he plans to achieve with the single motorized zone. If the idea is to heat one part of the church more than the other, it might be of interest to go with thermostatic valves on each radiator and control the different areas that way.

At any rate, if this idea makes no sense, it does not matter, all I really wanted to say is that I am happy we are not talking about a steam conversion.

Connecting a one pipe wet return system to a two pipe wet return

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