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drh 02-15-2008 10:29 PM

Wanted: Second opinion on radiant floor/boiler hookup
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Hi Everyone,

Recently I had a new tankless boiler/domestic hot water unit installed that I am thrilled with. Recently however, we had added a radiant floor system to this boiler which has changed the way in which the unit, not to mention the sheer vast amount of new piping, that I'd like a second opinion.

The tankless unit has a built in pump, which up until now has worked perfectly for all the rads throughout the house (a small house, around 1000 sq ft). Adding the radiant floor aspect has added TWO additional pumps to the system, which I'm still questioning whether they are needed.

The attached pictures give you an idea of what was installed for us. I understand the concept of an additional pump required to circulate the floor water, but why a new pump to circulate rad water? Our HVAC guys tell me it's because we've gone to two zones, but I"m still confused. Does this seem right?

This all feels like overkill to me? Do two loops of in-floor radiant PEX require such a complex (and unsightly) setup?

skymaster 02-16-2008 12:05 PM

I cant answer that question but I wanted to say that whoever did the plumbing on the right side did a GREAT job isolating your circulator so any repairs in the future would be real easy. Cant say the same for the left side. Personally I dont see anything wrong with having a second circ pump. I would say it was far easier to plumb that way it is than trying to replumb everything to use the single pump. Had to be cheaper also

sgthvac 02-16-2008 08:04 PM

Yes, it is better to have one pump for each zone, but it is more expensive for inital install. In my house, I have 4 zones, but to save money I use one pump and yes it works just fine. My concern about your system is radiant floor heat normally operates at 100 degrees F. and normally at 4-6psi. I didn't see a mixing valve to lower the water temp. for the radiant zone. I'm not as concerned about psi as temp. because at 180 degrees it could burn your toes.

cracklin 01-16-2010 05:20 PM

two zones
That set-up looks like par.
I want to do the same thing in my house.
Two zones, one boiler.
I' getting estimates. What is ball park figure for the hookup if I already have a boiler and the radiant pex tubing is installed with just the pipe ends coming up out of the slab....quite similar to what you have in the two photos?

Home Air Direct 01-16-2010 08:41 PM

Nice set up. The pump that is included with your boiler is generally used as a circulation for the boiler loop, and subsequent additional "zones" would require an additional pump and a zone control, or additional pump(s).

Since your home is small, you would probably get along with the single pump, but why not do it right considering your overall investment.

Curious?? how long are the two pex loops? What is your input water temp and temp drop across the loops?

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