# Radiant heat



## RealLivePlumber (Jun 22, 2008)

So, we are in the design stages for a small (600 sq. ft.) addition for my house. It will be a new family room. 

As you might recall from my previous thread, I have a WM CGs boiler, 2 zone, (1st and 2nd floor) tube and fin baseboard. I'll be repiping the near boiler piping and adding outdoor reset. 

I think I will install radiant heat in the addition. So, do you all prefer staple up, or alum heat transfer plates.? 

What is the best way to temper the water to the radiant zone. I was thinking of using a Taco radiant mixing block. 

Ideas/suggestions?


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## rex (Jun 13, 2008)

staple up/basic mixing valve 

you already have a simple system keep your new zone simple


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## njoy plumbing (May 19, 2009)

Transfer plates, insulation & the mixing block is a great idea.


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## Scott K (Oct 12, 2008)

Heat Transfer plates DO make a noticeable difference in allowing significantly lower water temps to be run by helping distribute and conduct the heat better. Most recommend 140-160 degree water temp for "staple up" (in joist/below floor) and 110-140 for heat transfer plates (again, in joist/below floor). In both cases you MUST put at the minimum, some insulatin (R-14-R-20) below it to help reflect the heat up. 

I'm assuming your new radiant addition will be just one zone, which means 3 zones total (2 baseboard/1 radiant). I'll assume you'll fork out the $$$ for the heat transfer plates as they will save you $$$. 

In this case this is what I have dreamt up for you. Coming out of the supply side of your boiler, have a bleed hose bib coming out of the vertical portion of a tee. This will be your system purge line that allows you to purge your entire system including the boiler. On the horizontal section coming out of the tee, have ball valve, then an air seperator (e.g. spirovent) of which you'll tie your expansion tank and fill valves into and allow about 6-12" before you install a pump to prevent cavitation from the air seperator on the pumps impeller blades. This pump will be a Grundfos Alpha variable speed ECM pump (or as I recommend anyways). Now you will split off pump into 3 zone valves. 2 zone valves obviously feed the existing zones. The third zone valve will feed a 4 way mixing valve. The 4 way mixing valve can run off of a controller (e.g. Tekmar, or maybe the X-block you speak of, not familiar with the unit, assuming it does the same thing as a 4 way zone valve). Either way, I believe you know the job of a 4 way mixing valve - to protect the zones from too hot of water, while at the same time ensuring the boiler doesn't receive too cool of water which would cause flue gas condensation ending the boilers life prematurely. 

On the supply side of the radiant coming out of the 4 way mixing valve, you would have a 2nd pump to pull heat out and push it into the radiant piping (a fixed speed pump like a grundfos 15-18, probably on low or medium speed would fit the bill here as you don't have much radiant to worry about). 

On a call for heat, hot water is sent through the open zone valves either to your 2 high temp loads, or to your 4 way mixing valve (or similar). 

The 2 returns from the high temp loads would tie into the return of the boiler coming from the 4 way mixing valve.

The Grundfos alpha does not need an end switch but instead can just be plugged in to a conventional pug and you can set it on auto adapt or a fixed head and it will react to the zone valves opening and closing and pump accordingly.


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## HonestPlumb (Jan 25, 2015)

Nice design Scott. Amazing how many designs people will come up with for this application. Including some horrific jobs I have seen that obviously no idea what they were doing. I think your system is nice and simple because it is a small radiant job. Not a big Grundfos fan though. But that was 15-20 years ago, I remember them seizing up. I think they had a small slot at the end or an Allen screw to spin it. It would operate fine after that. They probably have come a long way since then. Most times anyway. If it had been there a while I would replace it with a Taco. ( Now everyone can start with the Taco"s are delicious jokes) Small radiant job like that , I do a loop with an injector to maintain temp as needed. With Aquastat or the Weil-McLain set up they have, but usually theirs is meant for a larger radiant job with a manifold for several radiant loops. More controls and labor. mine is essentially the same thing as yours just a different manner,if that makes any sense ?


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## FRMA2Z (Mar 30, 2014)

Keep another item in mind as you design , keep floor coverings ex:carpet wood to be a heat release product designed for radiant use . I've seen many jobs that they did not listen to this advise and it ends up not working as designed. Good luck seems like youve got a grip on it


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## rjbphd (Feb 5, 2010)

FRMA2Z said:


> Keep another item in mind as you design , keep floor coverings ex:carpet wood to be a heat release product designed for radiant use . I've seen many jobs that they did not listen to this advise and it ends up not working as designed. Good luck seems like youve got a grip on it


Had a job where I knew they will be using heavy padding and carpet,.. forewarned them.. said do it right.. so I added supplenet heat ( cast iron baseboard )..with 2 stage thermostat.. baseboard comes on at about 15 degrees outside.. ( using the ODR control on boiler)


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