Issues for adding a standard zone to a hydronic "diverter tee" system?

Jells

I have an apartment heated by an old fashioned diverter loop, a 1" loop of pipe in the basement with 3/4 Monoflo tees going to cast iron baseboard on the ground floor. But the extension area of the apartment is cold, they didn't insulate it well when it was built many years ago, and it's exposed on 3 sides, the roof, and the uninsulated floor! Regardless of what could be done insulation-wise, I think it need to be it's own zone.

My plan is to cut out the Monoflos feeding it, run the lines directly to the boiler, and build a manifold with the one circulator feeding 2 zone valves. My main concern with this design is the balance of head pressure between the Monoflo loop and the simple loop if they are both calling for heat. Should I just use identical Honeywell zone valves, or perhaps a full port 3/4 for the Monoflo loop? The Monoflo loop has sections of 3/4 all around the boiler, so there's no point in sizing the valve 1", and Honeywell zone valves have tiny ports anyway. I used a full port 3/4 when I had issues with an indirect WH on a manifold with other zones taking forever to recover, it worked like a charm essentially doing what a priority valve control would do but better, but perhaps there would not be enough flow to the extension in that case.

Any comments on this plan are welcome. Including that it's stupid. It had occurred to me to simply put a gate valve between the tees to the extension and divert more water there, or eliminate the tees and make it part of the main loop, but the difference in heat loss between the main part of the building and the extension make having it's own thermostat seem like the best plan.

Jells

Nobody's got a comment? The plan is perfect?

clammy

Instead of doing zone valve just use a another pump being your single loop zone will have less resistance then your mono flow zone . Your liable to have less flow thru your mono flow zone when using zone valves and also if both zones are calling using valves you will have less flow to your mono flow due to the lesser restriction on your series loop which will get more flow . If your heat emitters are undersized for the area using zone valves could be even more promblems . Remember when using multi pumps to use check valves on pump outlets . For myself when faced w zoning off a mono flow system I use pumps w built in checks . You will need a circulator pump relay and thermostat to make life easy get a taco multi circulator relay This way u got 1 end switch to your aquastat unlesss u can handle doing some rewiring on the boiler aquastat circ relay If in the future u would like to expand more zoning n can add a zone valve controller and zone valves to your single loop zones and still have your mono flow by it lonesome all content to do it’s thing Remember sometimes it’s not as easy as u think u may have to increase the size of your boilers supply and return piping to handle higher flow that the piping will see .before all of this have you bleed ur emitters in the offending areas if hey have bleeders and if so have you tried balancing the baseboards I know that some of the system that I see similar to your have hand valves under the end cap on the supply side usually you may be able to throttle them to get more flow to where it is needed. One more note your issue may be related to the spacing of the tees for that single baseboard that is not giving u enough pressure differential to get you heat . I think I would look at that and maybe add two mono flow tees if the distance off the main loop was in excess of what the original distances to elemaents where . Some times when addition are built they just extend the pipe and do not even think about how it effects the flow to said emitter . Hope I gave u some junk to think bout peace and good luck clammy

clammy

Check and see if they installed the monflow tee in the correct direction also check the distance the tees are apart from each other .how many feet of baseboard are being served off that loop . Possible increase your tees distance apart and use two tees instead of one . On another note again do a heat lose on the room maybe u ain’t got enough emmiters in the first place if so it’s all nil even if you zone it it will still be cold and most likely your boiler will be short cycling peace and good luck clammy

EBEBRATT-Ed

I agree with @Clammy. Their is more was to skin a cat. If you put a second pump in and pipe your new zone back to the boiler it may not be the cheapest $$$ but will be a sure thing if piped right and any cost savings would be minimal

Jells

Thanks Clammy, a lot to think about. I was thinking that the higher resistance in the Monoflo loop could be compensated by using a 27Cv zone valve on it, and and a more typical 3.5Cv on the regular loop. Seems far less complex than adding another circulator and having to enlarge the manifolds too. It's not like it has to be perfectly balanced, it's only relevant when both are calling.

I could also make both 27Cv, but with a gate valve on the open loop, then dial it closed till the return water temps are exactly the same.

clammy

Don’t discount straighten out the mono flow increase your tee spacing and use two tees very cheap easy and follows one of my favorite rules kiss and don’t lie also don’t discount that heat lose 1 st thing first peace n good luck clammy

Jells

The system already uses 2 tees on the loops, but something I noticed is there's a capped loop (2 capped tees) which has to be lowering the flow rate.

As for zone valves vs pumps, I'm seeing the light as I look at relative pricing, it might even be cheaper to do one more pump rather than 2 valves. I guess the multiple valve system is just more familiar to me so I went there first.