big gravity conversion question

The Steam Whisperer (Formerly Boilerpro)

those probably aren't divertor tees. If the radiator supplies come from the top of the main and the returns come in the sides, it's gravity one pipe. You need a real low flow pump. Basically the pump justs need to overcome any smaller piping near the new boiler. If you pump the system too much the water temp at the top of the main and bottom of the main will be the same and you will get no flow to the radiators. Also when tying in your new smaller piping into the old main be sure to leave a couple feet or more between the increasing coupling and the first take off. If you make the connection too close you will disturb the gravity flow to the first radiator. You may want to use eccentric coupling to direct the supply flow to the top of the main and the return flow pulled off the bottom of the main. I recently did a system with 2 3 inch mains and am running a UP15-58 pump with the flow throttled with a TT Solo 110 boiler piped P/S. A 15 -58FC may be all you need.. REMEMBER...the pump is not pumping water through the radiators...they still need to run gravity flow.

Boilerpro

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Timco

I have done several, but this one is a bit different. House is 2 stories, and I am guessing the heatloss will come in around 200K just by looking around. Thing is, this gravity system has a 6" main running all the way around the basement and back to the boiler, and is a diverter tee type system. How does one size the circ for a system like this? I am putting together a proposal.

Thanks, Tim

mark ransley

200k btu,6" pipe, T, I have one in the Basement below me that was converted, if you want to know the pump used or anything, I know its a B&G pump.

Timco

I am fairly certain it is monoflow as the takeoffs are both from the top of the special diverter fitting and it has that telltale bulge on the supply takeoff side. At 6" they are HUGE fittings. Boiler will be P/S because the giant pipes will eventually be removed for head room but not for the next few years or more. There must be a threshold where even though there is very little resistance in those giant pipes, it is a ton of water to move...thus the P/S piping so the boiler can have it's own GPM.

Tim

tim smith

Tim, how big of house is this?? I have never seen a underfed

monoflow system on gravity. Plenty of overhead feed systems in larrrrge houses. 7 - 10,000ft. Be that said, I would probably not pipe it primary secondary if using TT boiler. I would use smallest pump allowed for boiler and then maybe put a manual bypass between supply and return and throttle down to keep flow up in boiler and reduce flow to system as needed to get proper circulation. I think that would give best return temps for condensing and you the latitude for adjusting flow. Maybe a TT 175 will do?? depending on heat loss. Tim

Timco

I have spec'ed out and given literature on the Ray boiler from mestek. House is around 4-5K sq' by guessing, but when the estimate is OK'd I will do a full heatloss. I was shocked to see the size of the mains running at the 5'10" line all the way around the basement with HUGE diverter tees where each rad takes off from the main. Y'all think a small pump (15-58) would still move the entire house, both stories? I do not want the main floor to get circulation and not the top floor...I just put in a larger grund pump on a house with a single 15-42 running a huge conv grav system and it immediately got heat to the second floor.

Tim

tim smith

If it did it with gravity it sure as heck will with a 15-58.

nicholas bonham-carter

a ton of water

there is probably a ton of water to move upstairs--but luckily there is also another ton trying to get back to the basement!--nbc

Steamhead (in transit)

Tim, that's called

a "one-pipe gravity system". I'm sure it inspired the more-recent Monoflo system.

You want to pump that system real slow. Mimic the gravity flow and it should circulate OK.

Use this chart and article to size your circ:

http://www.heatinghelp.com/newsletter.cfm?Id=125

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