Low temp radiant off of existing baseboard system

tk92

Hi all I am looking for some help with installing a small section of radiant in my house. An additional was put on and I would like to put radiant in this room. The house currently has baseboard heat. I have been doing a lot of research but not sure of the best/simplest way to go. I came across the taco rmb-1 which seems like it would be a simple solution for reducing the temp for the radiant loop and would tie into my sr relay. When I look at the taco recommended piping the show p/s piping however that isn’t not how my boiler is currently piped. I’ve attached a picture of what I thought would be and easy was to hook it up but I don’t know if it will work. Thanks in advanced.

tk92

I am also open to other ideas of stepping the temp down/controls just didn’t want anything overly complicated. 

Jamie Hall

Pretty much any mixing valve which would allow you to mix the return from the radiant with a feed from the boiler, the excess going back to the boiler. The problem is, of course, to get circulation in the radiant loop. You may need a separate circulator.

tk92

Yes I had looked at a simple 3 way mixing valve but would be sending cold water back to a non condensing boiler.

Jamie Hall

Eh? Well, cooler perhaps -- the rejected water from the radiant loop, which would have mixed with the return from the rest of the system... but seems to me that if that's too cool, you should be running primary/secondary on everything

hot_rod

It depends on the size of that low temperature load in relation the boiler as far as if bit will pull the boiler return down for extended periods.
If that radiant zone is 20% or less of the total load, you should be fine.
You could connect and observe on a design day, typically you want the return up around 130F within ten minutes of boiler run time.
Certainly no harm in adding a return protection valve. if you go that far, I'd change the piping to primary secondary or better yet use a hydro sep.
Kinda depends on how involved you want to get? It is best to pull that low temperature load of a better piping arrangement.

Here are some ideas for connecting a low temperature loop into a conventional boiler and high temperature distribution.

https://www.pmmag.com/articles/84495-a-little-floor-warming-please-john-siegenthaler

tk92

Thanks hot rod. This setup would be an easy way to add the radiant.I would assume the the 2 new circulator would be wired to both turn on the off the same time? 

Paul Pollets

The Oventrop Unibox does this easily, as long as the connected load is under 12K btu's.
https://www.oventrop-us.com/unibox

hot_rod

Yes, both circulators need to run together