Adding small radiant zone to 2 zone monoflow

Brian Chilton_2

I will not bore you with details, but this is a 1945 house. 2 large zones of monoflow running baseboard. Large Utica boiler(old and dependable and inefficient). Believe it or not, it has had a zone of radiant in the living room which is over an unheated garage, which was running at boiler temperature, off one of the monoflow loops. Since it has only been 71 years, I decided it is time to put the radiant on its own zone(this all came about because the master bed and the radiant were on same monoflow zone and controlled by same thermostat...so time to finally make sleeping comfortable.)

My question is what is best way to add a small zone of radiant (ideally constant circulation ) to a boiler with 2 zone of high temp monoflow.

House is about 4000 sq feet.

I would like to just put a new zone on with a mixing valve off the supply, Taco shows piping in the iseries mixing valve spec sheet - "3 way valve with high temperature zones". Drawing should be attached.

Seems like the easiest way.

I am not a professional but in the property management business, so know enough to get myself in trouble.

I though t about just putting on a separate zone and leaving the radiant on high temp water...it seems to have worked as is for 70 years....I guess Levittown ran boiler temp in the slabs, but those didn't stand the test of time.

One more thing: I have no idea what the tubing lay out is, size/length etc, if it is in concrete(my guess), because there is finished ceiling below and hardwood on top. The floor has not historically become "hot" and room stays comfortable.

This home was designed by a nationally know architectural firm in 1945....but some of the things they did(including the heating system) really makes me scratch my head.

Thanks for any ideas or suggestions.

Brian Chilton_2

Ok, here is my answer:

1. You should add a separate zone because you do not want to add a takeoff zone for radiant off of a monoglot circuit. It could interfered with the overall performance of the mono flow zones.

2. To add a single zone of radiant, the best way, and especially if you are going to add more radiant in the future, is to bite the bullet and add a primary secondary zone. But this requires 2 pumps and is probably overkill for one small zone of radiant. And, by the way, although your boiler is "large" , you should do a heat loss to make sure everything actually adds up thermodynamically.

3. If you do not want to do a primary/secondary loop, add a low temp zone by coming off boiler with a taco i series outdoor reset 3 way valve. Pump from mix port on valve to radiant load, return to cold side of valve and boiler return.

Because this is a small load on boiler, you will not have to worry about boiler condensing. Put outdoor reset control and let this run continuously based on load.

You could let this just run at boiler temperature and skip the mixing valve. But that will lead to bigger temperature swings and less comfort. But it sounds like it has been like that for a while and if it has been satisfactory, you could leave it alone, it must have a great thermal mass if boiler temp is not making it hot to the touch, so the fact that it was built in the 40's would suggest it is in a large concrete slab.

Hope that helps.

delta T

Could this radiant be just fin tube elements suspended beneath the floor? In that case your ODR curve would have to be set up pretty high