Themostaic bypass valve

A Whitman

I am installing a cast iron boiler for a low temp radiant system. I need a bypass (1/2"?) between the supply and return? What type (make and model)of valve should I use?

Paul Pollets

You'll need more than a Bypass...

Radiant mixed temperature is either done with a thermostatic 3 way (the least expensive), a 4 way mixing valve, or by injection mixing. Only a 4 way valve or injection mixing provides boiler protection. The various strategies have been discussed ad-infinitum on this forum. Protecting the boiler from condensation is critical...if the return temps cause the boiler to condense, the boiler will corrode...and quickly. This is most important with oil or gas fired cast iron boilers. How you obtain the radiant mix will often determine the bypass required. Usually, computer controls modulate the water temps and control the return temps. A 1/2" bypass probably won't cut it. See the manufacturer's piping schematics and follow them.

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clammy

taco i series valve

Pauls suggestion are correct but a cheaper alternative instead of a 4 way valve may be a taco i series valve they come with a return sensor for low temp return protection and can be order as a outdoor reset or a set point controller .i have used them and found there performace to be far better then a standard manual 3 way valve ,they will cost a bit more but it enables you to have more automatic control over the supply water temps as the system may require which you would not have with a manual mixing valve and also again gives you the return water temp protection.the 4 way valve that paul suugestes is yet another opition and it all depends on what you want to get out of the controller the 4 way valve would be a actuactor motor and a controller also which could be eitheer a set point or outdoor reset all this also depends on how much your willing to spend and if the system is also used for hi temperture like baseboard hydro air ect.The taco valve would probalbly be a little cheaper and way better then a standard manual mixing valve .peace and good luck clammy