Renovation With Radiant Heat

awaltiii

A friend of mine recently bought a 1750's house in Southern New England and renovated the kitchen and baths using radiant heat below the wood floors.

He has asked me to help with the heating system integrating the radiant heating loops to the existing HW heating system.

The existing heating system is a gas fired Weil Mclain CGI-6 boiler connected to cast iron radiators using a 2-pipe system.  He also has an indirect HW heater.

I was planning to use a couple of Taco RMB-1 (Radiant Mixing Blocks).  One for the radiator circuit and another for the radiant loop.

The existing system uses the same high temp water for the radiators as well as the indirect HW heater.  My experience with radiators in my own house shows they like to be in 110° to 135° F range (I monitored my heating system water temperatures for a number of years and found the water temperature never went over 135 with my high limit set at 135° F).  I never had temperature overshoot issues due to the low setting on the high limit of the boiler.

My question is... Do I need a Radiant Mixing Block for the radiator circuit?  Or should I just connect the radiator circuit as it is connected now to the high temperature part of the boiler output?

My friend is getting antsy as the heating system is nearing.  I want to get this right the first time and welcome your advice.

hot_rod

return protection

for the boiler is key, I assume that is a cast iron boiler? Look for a control that will run the boiler on outdoor reset, which will adjust the temperature based on the building load and outdoor temperature.



Generally these controls also have a function to watch the boiler return temperature. You don't want to run the boiler for extended periods with return temperatures below 140, or what the manufacturer requires. Then a mixing device to bring down to radiant requirements. The Taco blocks may have all of those functions available or able to be added on.



hr

hot_rod

DP

EricAune

RMB

This is a perfect place for the RMB.  Hot Rod is right on with the outdoor reset.  The Mixing block has it built in and will provide a perfect separation of a two temperature system, easy to pipe in and eliminate the need for an additional pump to be added for the new radiant (provided the RMB pump size is correct for your application).