1950's monoflow tee hydronic system

John Luebbers_2

Ok, here goes, Doing a boiler change out, putting in a 4 section weil mclean gold, House was built in the 50's and has 2, 1 inch zones. half inch take offs to radiation, I suspect monoflow tee. Going to install diaphram expansion, and pump away with zone circs. Going to build 1.5 inch supply and return headers to accomodate 2, 1 inch zones and 2, .75 inch stub outs for future zoning. Any one have any input I might want to consider?

Firedragon_4

Leave the mono-flo system alone,

I've never regretted following that advice in my own home.

Steamhead

I've seen these systems

installed as Monoflo and also as two-pipe. The key is whether the piping to a radiator takes off from one particular pipe and then returns to that very same pipe. If this is the case, it's Monoflo, and the special tee is installed where the radiator pipe returns to the main. The exception would be if the radiator is below the main, in which case there should be a Monoflo tee on both radiator connections.

Firedragon is right, leave the Monoflo loops as they are. You sound like you're on the right track, leaving stub-outs for future zones. And Pumping Away is the only way to go. If the customer wants to, you might install a separate circulator, flo-check and relay for each of the Monoflo loops to set them up as individual zones.

The only thing I might do differently is, if the system now has a plain-steel expansion tank, use an air separator with a 1/2-inch tapping in the top and run a pipe from here to the steel tank. This will keep the tank from waterlogging. I have a bunch of these setups in the area and they work perfectly. Diaphragm tanks are OK but if the old one ain't broke.....

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Mellow_2

I would see if it was working with the old unit. It might have air in some rads or you could have piping problems. It's much easyer to fix when the system is empty. Most piping is going to be right and with a pump away system, the increaced psi will help your flow. This type of system likes to trap air so... I would spring for the diaphram tank. It is worth it.If the rads are not heating and are blead you can spread the tees for that radiator apartand it should improve. Anything to get the air out and keep the psi up is the key......The old steel tank could keep air in the system and if they bleed the rads alot the tank will fill up.....have fun....

Joe_30

When we moved the circulator to pump away, our monoflo system really worked well. Well, except one under-radiated room at the end of a long horizontal riser. Am adding radiation. Dan's book "Pumping away" was great. We went to a Taco 007 from a bigger circulator. AND, we put in a simple B&G IAS inline air separator device [that has an air pipe up to the tank] and the matching devices to keep the tank with the corect cushion of air and water. The IAS goes before the pump but after the boiler. Leave about 18 inches of straight line before the IAS and about 10 before the pump to smooth out the water flow. Put in a gate valve just at supply side of the boiler. But have a drain and hose just before that. Then, when you fill the system zone by zone [with the fill water coming in the bottom tap of the IAS, it rushes through a monoflo zone, and through [filling] the boiler, and out that drain and hose. [the gate valve being shut for filling stops the flow there]. As the zone fills and the hose stops spitting air, shut that zone at the supply manifold and open the next, etc. When all have been flushed of air, shut that drain and open the gate valve to open the boiler supply to the system. you will have little air trapped in the system now. Open all the service valves at each zone. It is kind of a rush to move from zone to zone opening and closing valves with the water and air spitting out to the drain in the floor. Monoflo works when it was designed in the first place, but this helps it.. joe