Mono-flo Tee

Brad White_9 · March 2006

I would assess where the moisture is coming from. If it just air-borne or minor dampness a little heat will be a good thing. If a bona-fide standing wetness, heating it will drive it to other parts of the house by evaporation. Just one thought.

I think the monoflow with TRV or thermostat and zone valve is a good idea, for it does not add parasitic horsepower (ok... Watts) in the case of Option 2.

My only caution is that when the TRV or CV is closed, the main may suffer a bit of series pressure drop. Especially so if it is downfed because you know you will need two (2) Monoflow tees to counter buoyancy.

Option 3 has merit too in that it is rather passive and provided it does not drop your HWR temperature overall below the boiler critcal level.

"If" you had a condensing boiler this is the tack I would take, and do so in my own house, using occasional basement heat to depress my HWR temperature to boost condensing efficiency.

Eric Johnson · March 2006

Mono-flo Tee

There's a small storage room in my basement that I would like to heat in order to drive out some of the moisture. I have 1" copper supply and return lines running right past the room I want to heat. They're the supply and return lines from a wood-fired boiler running to a heat exchanger on my gas-fired boiler.

To provide thermostatically-controlled heat to this space, sould I:

1.) Put in a pair of 1" to 3/4" monoflo tees and regulate the flow with a thermostat and a zone valve.

or

2.) Put in a set of conventional 1" to 3/4" tees and regulate the flow with a thermostat and a circ pump, like a Taco 007.

or

3.) Some variation on the above or something else entirely.

In the room, I was thinking about installing a cast iron radiator connected to the 3/4" line and running it off of the boiler return line.

Eric Johnson · March 2006

On supply & return only?

My gas boiler is a circa 1960 (or earlier) Weil McLain cast iron job, so I doubt that it's a condensing boiler.

Anyway, when you say I would need two mono-flo tees, are you saying one on the 3/4-inch supply line and one on the 3/4-inch return, or an additional two somewhere else?

Slightly OT, my home's heating system is a typical cast-iron radiator arrangement that probably dates from around 1900, with the rads branching off main supply lines. Did they have mono-flo tees in those days? If not, what channels the water up into the radiators on these old systems?

Brad White_9 · March 2006

Yes, both supply and return

The water has to complete a circuit and with monoflow tees that is from main to radiator to main, thus diluting the water to subsequent radiators. The tees have to be part of that circuit or they would have no effect.

I did assume you did not have a condensing boiler, just offering a what-if where it may benefit you in the future.

Are you sure that the current set-up does not go from supply to radiator then to return? I do not think monoflow tees were in vogue until the late 1940's/early 1950's. Dan H. would know even though he is MUCH younger than most heating systems

My guess and a good one is that what you have was gravity HW at one time.

Eric Johnson · March 2006

gravity

Thanks.

I'm sure my system was a coal-fired gravity/convection arrangement when it was first installed. But it works fine with zones and circ pumps. I love cast iron radiators. On my old house we had a wood-fired boiler in the basement, big pipes and radiators and no circulators or zone valves. All you did was heat the water and the house stayed nice and warm. It was way up in the Adirondacks where the power would periodically go out for long periods. Still does. IMO, that's the way to heat an old house.

Brad White_9 · March 2006

Gravity Cast Iron

is how God would heat her house, given a choice.

Uni R · March 2006

Monoflo fittings

Your original system predates Monoflo fittings (and unfortunately in this day and age it is very difficult to get ones that aren't copper). The spacing of the Monoflos will be a critical factor for how much heat goes through the rad.

Eric Johnson · March 2006

spacing recommendations

Is there a good way to determine the proper spacing?

Brad White_42 · March 2006

Rule o' Thumb is

at least as wide as the risers are apart. IOW if the stub-ups to the radiator (or whatever) are 5 feet apart, so should your tees be spaced on the mains.

Theory is if the tees are close together and the runouts/stub-ups are far apart, you waste precious differential pressure chasing those errant riser points with offsets from the mains.

Truth is, I had monoflow in my house for years with the tees less than 6 inches apart and the place heated fine. The risers were 3/4" off of a 1-1/4" main loop so might have been some gravity at work too. Piddly flow per radiator.

Mono-flo Tee

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