Adding radiant zone

williamgxxx

I’m adding a radiant zone to my Weil Mclain ultra 155 boiler. I have two high temp radiator zones already. The manual says that if the radiant zone is less then 30% loss then I do not need a mixing valve. What will happen when a high temp radiator calls at the same time?

DZoro

Your going to get the high temperature. What type of radiant are you adding? How large? A big picture of your current system will help tremendously.

williamgxxx

Thank you for your help.
I have primary/secordary piping with two circulators for radiators and a indirect fired water heater I’m thinking of adding a 300’ loop in 1/2” pex for a subfloor install under a kitchen.
Why would Mclain suggest this?

EBEBRATT-Ed

You need some type of mixing valve. If not the radiant which must be supplied with less than 120 degree water will get high temperature water

williamgxxx

Thank you.

DZoro

That means that particular zone should be less than 30% of your system design btu's. Not 30* lower water temperature. For radiant floor load in your case like Ed said will need some type of mixing device to lower the water temperature in that zone. Note: this device placement should be after all of your high temp. zones.

Mark Eatherton

Or, hang finned tube element in the joist bays. Ultra-Fin.com

ME