Two-pipe, direct return system, ADVICE!!

Matt L.

I have a residential, closed loop system, standing cast iron radiators, hot water boiler system, my situation is that my boiler is placed in the center of the basement near the chimney for venting, I would like to change my circulator to the supply side, pumping away from the expansion tank, and switch to a two-pipe, direct return system, which would mean that my supply and return mains would have to run from one end of the house to the other along the center of the basement right above the boiler,
but how can I pipe the supply side properly to get the benefit of pumping away when some of the supply water has to move forward toward one end of the piping then backward to the other end?? would I just tee off the main then 90 elbow it back?? wouldn't that cause a problem with the overall discharge pressure of the circulator?? please be technical !! thanks !!

Steamhead

When you say it's a \"closed loop\"

do you mean it uses special tees that divert water into the radiators?

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Matt L.

Closed loop meaning, one-pipe, in one radiator and out to another in a continuous loop, simple system...

Steamhead

That's a series loop

How about using a two-pipe, reverse-return system? That way the system's basic configuration could still be a loop- but a double loop instead of a single one, with the return starting at the first radiator on the supply loop. This would get around the situation where you'd have to run the mains down the middle of the basement.

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Matt L.

I like that idea also..my present series loop system offers me no control over the individual radiators, I was thinking about the two-pipe system so I can utilize radiator valves and/or TRV's. but I also like the idea of using a diverter tee method then I can heat my basement with radiators also, using a one-pipe method, would I be taking a risk with a diverter tee system , because of air related problems ?, or will pumping away solve this too??

Steamhead

Pumping Away

when done right, will solve almost any air problem. It is possible to retrofit TRVs to diverter-tee systems, but if you're starting from scratch I'd go with two-pipe. This way there's much less chance that a closed TRV would impede flow to other rads in the system.

And you can heat your basement from a two-pipe system.

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Matt L.

I wasn't aware of a method of heating my basement which is "below the main" other than a diverter tee system which would force the water downward, what other way could that work using cast iron standing radiators that are bottom connected??

Steamhead

What you need

is enough delta-P (pressure differential, produced by the circulator in this case) to overcome the tendency of the hot water to rise, and make it go down into the radiator. Two-pipe systems with radiation below the mains are all over the place- there's plenty of delta-P in this type of system.

When connecting radiation below the mains, I like to pipe the supply into the top and the return into the bottom. This will keep air from accumulating in the radiator. Also install a drain in the other bottom tapping so that part of the system can be drained for service or to prevent freezing if the house is unoccupied.

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Matt_29

Does the connection of piping the standing cast iron radiators that are below the main such as, supply into the top and the return into the bottom with a drain apply to all method of piping systems such as diverter tee/ two-pipe, direct return and etc. ??

Steamhead

Yes

it does. This only covers how the piping connects to the radiators, not to the mains.

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Unknown

Loop System Modification to Reverse Return

can be accomplished this way. Pressure drops in the system do not change. Pumping away will work with this system and TRVs can be installed.

Jacob Myron

Unknown

Loop System Modification to Reverse Return

can be accomplished this way. Pressure drops in the system do not change. Pumping away will work with this system and TRVs can be installed.

Jacob Myron

Unknown

Converting a loop system to a mixed loop and

reverse return system can be done this way.