Conversion of Gravity Hot Water to Forced Hot Water.

loubee

loubee

this system was converted by others some time ago. the problems are customer needs a new boiler, most of the radiators and baseboards don't heat very well and the supply and returnpiping is a mess and all needs redone. There are tees everywhere in the system. My question is when we repipe this system should we use mono-flo tees? Should we take apart the radator valves to check for flow restritors? also this is a 2 storey house set up with 2 zone valves. Should we go to a pump for each zone?

Steamhead

My 2 cents

I would definitely use two circulators on this one. But don't oversize them- if you pump those zones too fast, the water will rocket thru the radiators and not have a chance to give off any heat. Use the circ sizing chart in Hot Tech Topics to see how much flow you need, then pick your circs. The resulting choice may seem smaller than you're used to- but remember, there's so little resistance in an old gravity system that a small circ will work beautifuly.

I tried this sizing technique on my system last fall. It worked so well that I was able to down-fire the boiler by one nozzle size. I'll bet the oil company wonders what happened....

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Mark J Strawcutter

while you're at it

taking the radiator valves off to check for restrictors, replace them with TRVs. Add them to the baseboards, too.
Or start out with TRVs on the 2nd floor only.

While repiping, go with 2-pipe direct return instead of monoflow. Consider constant circ with outdoor reset.

Mark