Monoflo Tee Placement?

Adam E · January 2015

Hi all, I've got a rancher with a monoflo system and cast-iron baseboards. I've always thought the the flow wasn't what it should be, but the house stays warm - at least most of the rooms.

A question I have is, should each radiator branch return to the main before another starts? My tees are staggered so that - for instance - on one zone, I have a plain tee feeding my living room, then a plain tee feeding the kitchen. Then, I have a monoflo tee for the living room return and then a monoflo for the kitchen return. The bedroom zone is piped the same way.

The kitchen radiator heats up fine (it's short), but the living room never gets more than half warm. Granted, the living room has 40 feet of 9" Base-Ray. Also, the end of the main near the boiler takes a looong time to get warm.

Is this normal? If I were to complete each branch before the next one starts, there would be some really long branch lines. Or could it be that my lone Taco 007 isn't up for the job?

Thanks (and now to formulate my question about replacing my boiler with a 93% AFUE condensing unit).

Harvey Ramer · January 2015

Adam E said:
A question I have is, should each radiator branch return to the main before another starts? My tees are staggered so that - for instance - on one zone, I have a plain tee feeding my living room, then a plain tee feeding the kitchen. Then, I have a monoflo tee for the living room return and then a monoflo for the kitchen return. The bedroom zone is piped the same way.

The kitchen radiator heats up fine (it's short), but the living room never gets more than half warm. Granted, the living room has 40 feet of 9" Base-Ray. Also, the end of the main near the boiler takes a looong time to get warm.

Staggering Monoflows is a neat trick to balance flows going to different heat emitters. A monoflow creates a pressure drop in the run of the tee, upstream of the branch in said tee (when the tee is on the return pipe from the emitter loop). That is what causes flow through the emitter. Lets call this PDa. The monoflow tee as a whole, creates a pressure drop on the circuit, emitter loop and main combined. Lets call this PDb. So if you have 2 regular tees followed by 2 monoflows, the emitter loop that ties into the first monoflow will get the induced flow of PDa. The emitter loop that ties into the second monoflow will get the induced flow of both PDa and PDb.

In your example, if you switch the return pipes, putting the living room return on the last monoflow, You will get more flow through the living room baseboard and less flow through the kitchen.
Make sense?

icesailor · January 2015

Is the 40' living radiator loop piped with 3/4" pipe? If not, it should be. Sometimes, they used "Super Tee's" or high flow tees'. Or used Two mono flows on a heavy flow circuit like you have in the living room. If the 40' living room has a corner, are both ells connected? I've seen where someone got cheap and only used one on the bottom.

The end valves usually sucked. They had a brass valve with a steel piece that acted as a stop for when the valve was open or closed. If the side stop rusted away, there is no way to tell if the valve is fully open. It only turns 1/4 turn. If the handle turns 360 degrees without stopping, the plate is gone. You can try starting at some point and turning it a few degrees. To see if you ever get flow.

If the circulator flanges on the pipes on either side of the circulator are red, it had a B&G Series 100 circulator. Usually, a Taco 007, works and falls into the realm of the curve, You might need a higher output circulator that pumps a little more water.

Adam E · January 2015

Thanks guys. I feel better knowing that it's acceptable to stagger the tees. I was thinking that the second branch would need the full flow after the first return so that it had enough pressure.

Yes, the big loop is 3/4" and you are correct that only the bottom ell is connected.

I'll check the valves...

Thanks!

Monoflo Tee Placement?

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