Fix for non-optimum piping to (non-hot) baseboards ?

MrCofDG

Our house has a family room addition (c. 1991), with 3 exterior walls.
It has two 4' long copper & fin baseboards and two 12' long baseboards, fed by a single loop under the floor (accessible via crawl space). One end of that copper pipe loop is tied in to the original house's 1 1/4 inch black steel return pipe via a 1960's vintage Bell&Gossett mono-flow tee; the other end of that copper pipe loop is connected to the same black steel return pipe via a regular tee, about 8" away from the aforementioned mono-flow tee. And, alas, those copper&fin baseboards are tied in to the in-crawl-space loop via regular tees. Result: the family room baseboards don't heat up worth beans (other baseboards in the house heat up just fine after bleeding).
My question is - would it be sufficient to replace the 4 tees in the crawl space copper loop with mono-flow/venturi tees ?
Or should an in-line circulator (with t-stat) also be added to that crawl space copper loop ?

mattmia2

So there is a loop that goes to the addition with one monoflow and one regular tee off the monoflow loop then the baseboard in the addition it is teed off a loop instead of in series or parallel between the tees off the main loop?

MrCofDG

Yes, I think - hopefully attached diagram (roughly to scale) clarifies.

EBEBRATT-Ed

Because the addition has 3 exposed walls it's heat loss is larger that other rooms in the house.

My advise is to disconnect the addition and make it a seperate zone piped to the boiler with it's own circulator and a thermostat.

Can you fix it without making it a seperate zone? Maybe but trial and error gets expensive

mattmia2

you could try capping the tees where they bypass the baseboard and see if that is enough, you will have to do that anyhow to make that zone flow properly, or at least put a balancing valve in it to force some or all of the flow through the baseboards, unless those are copper monoflow tees and are misidentified.

Is there any zoning in the addition or are they all on at once? i don't see a reason to do a loop in the addition, especially if you are trying to feed it off of a monoflow system.

MrCofDG

Thanks gents.
Ed, your suggestion makes sense.

Mattmia2, they are not copper monoflow tees. And no zoning in the addition - it's just part of the overall 1st floor zone (and the t-stat for that is 2 rooms away from the addition). When you say "don't see a reason to do a loop in the addition," do you mean it's better to have the addition's radiators just run in a straight series from the existing B&G Mono-flow T ?

MrCofDG

FYI, the original diagram wasn't 100% accurate WRT where the copper loop was tied into the black steel return piping; I've attached an updated diagram above.

mattmia2

I mean it sounds like they tried to make a monoflow loop with regular tees in the addition, which won't work, the water will follow the bypass almost exclusively without using diverter tees, and even if they used diverter tees the small flow from the main loop would get divided again at the diverter tees and you wouldn't get much flow to the baseboards.(your drawing didn't format right when i tried to open it with libre office but i think this is how it is set up)

the baseboards need to be in series or parallel to get flow through them, so yes, i'm saying remove the section that bypasses them or put a valve in the bypass section so you can divide the flow between the bypass and the baseboard section.

mattmia2

This might help as well:
https://heatinghelp.com/systems-help-center/diverter-tee-q-and-a/

MrCofDG

Yeah, that's a very good article.
So, at this point I'm leaning towards having a valve
put in each of the two "bypass sections" in the crawlspace; with (2) valves I can adjust the amount of flow/heat into the west side of the room's radiators vs. the amount of flow/heat into the east side of the room's radiators.
FYI, the diagram is a MS Word document. I'll comment again after the plumbing change. Cheers.

mattmia2

You still might not have enough flow out of the monoflow system to satisfy that demand, but you need to do something to make the water go up in to the radiation either way, even if you ultimately end up making it a separate zone.

If it still isn't enough then the make it a second zone with its own pump is probably the best idea. You could add a second monoflow tee at the other main loop connection, that would increase flow but then you are just experimenting. With a separate zone you can have a separate t-stat that will accommodate the bigger load of the addition.

MrCofDG

Thought: Is it possible for an old Bell&Gossett Mono-flow T (40-50 years old) to fail ??

Jamie Hall

MrCofDG said:

Thought: Is it possible for an old Bell&Gossett Mono-flow T (40-50 years old) to fail ??

No -- there are no moving parts.

But. A monoflo system only works -- if it works at all -- because the monoflow T causes the pressures in the main and the branch to change enough to cause some of the flow to go through the branch. I note above that your baseboard loop is tied into the main -- much larger -- pipe with a monoflow T and, only 8 inches farther away on the main, a return.

Nope. Not going to work. If as has been suggested you put a restriction in the main between the supply and the return from the baseboards, such as a ball valve, you could control it so as to get as much flow through the baseboards as needed. Probably... depending on the pump and the rest of the system...

Paul Pollets

8" separation between the tees will be tough to overcome. I'd pipe this as a separate zone with it's own pump, thermostat and relay. There's appx 17K btu's of baseboard with 3 exposed walls. Needs some reliable flow and BTU's.

MrCofDG

The funny thing is, those baseboards were getting heat from original install in 1991 thru ~2015..... Jamie, I like the idea of putting a ball valve between the Mono-flow T and the Regular T on the 1 1/4" black steel main. There's a ~6" nipple there now.
Paul, you're right, definitely needs reliable flow; I have considered making it a separate zone (and probably should have been originally); a valid alternative solution.

MrCofDG

One note re "If as has been suggested you put a restriction in the main between the supply and the return from the baseboards, such as a ball valve, you could control it so as to get as much flow through the baseboards as needed" - I've read that a gate valve should not be used for throttling - I assume you'd agree, since you (Jamie) mentioned ball valve.

hot_rod

Diverter tee systems are high pressure drop, adding more restriction between the tees may require more pump head possibly getting farther from your goal. I’d separate zone it.

Jamie Hall

Quite correct. Never use a gate valve for throttling. They are built, quite specifically, to be either open or closed. Ball valves aren't the best throttling valves in the world -- they're not very linear -- but they do work. Globe valves are better, but have much higher head loss even when open. There do exist special throttling valves, but they are overkill for this application.

MrCofDG

hot_rod, your comment above induces me to ask this question - what if I just replaced the current circ pump with a higher head circ pump (instead of adding more restriction between the two aforementioned tees) ??

MrCofDG

Updated diagram (a couple added labels near bottom). 11/28 edit: I crawled into the crawl space with a mirror and LED flashlight to double check what a plumber (not the original installer) had told me about the copper T's in the crawlspace, and discovered that two of the four are monoflo T's. Updated the diagram accordingly, with a couple added notes at bottom.....

Jamie Hall

MrCofDG said:

hot_rod, your comment above induces me to ask this question - what if I just replaced the current circ pump with a higher head circ pump (instead of adding more restriction between the two aforementioned tees) ??

Won't help. All that will accomplish is to push more water faster through the shortcut. You might get a little more through the baseboards, but not much.

MrCofDG

An update: surprisingly (to me) there is now heat in the west/north baseboards of the room, and a little heat in the north/east baseboards. The only thing I did was bleed some air out of a couple 2nd floor baseboards last night and the night before...... maybe that implies that because the B&G monoflo tee that supplies this copper loop is so close (8") to its associated return tee, getting flow into this copper loop is very sensitive to the presence of air(?)