radiant heating zoning

EMC PLUMBING

so your saying the mixing valve is probally limiting the amount of flow, that would make sense, didnt install the system but was called out to fix it they only used 3/4 copper with 3 way mixing valve out to a 007 then to 4 zone valves.it comming off a storage tank indirect water heater, do i even need the mixing valve cant i just use the aquastat on tank all loops are gonna be the same temp anyway?
thanks for your help

EMC PLUMBING

radiant heat zoning

quick question, a radiant system with one, say 007 circulator after the mixing valve going out to 4 zone valves, What is the max amount of 1/2 say 200ft run pex loops, that the pump would be able to handle.

never had a problem doing it this way,but had a problem recently with some loops not getting hot, not air bound,
any suggestions
thanks
Eddie

Brad White_184

With oh so many variables....

Typically 1/2" PEX has a limitation of 300 feet total per circuit. That is not to say that one pushes it too much and it depends on the manufacturer. There are sometimes slight diameter differences hence capacity differences.

Personally I think your 200 feet is safe for 1/2"

The other reason I like shorter runs is that it would tend to make the floor more even in temperature.

Now, what you really need to do though is assess the total of your manifold, mixing valve, flow meters and the PEX itself including home-runs. Know your flow rate especially.

Do yourself a favor and go to the Online Store and buy yourself a Radiant Panel Association "Rad Pad". A good investment and it can help you with all of the "what-if" questions early on. A great way to make book knowledge more instinctive, in my opinion.

Rich L.

Rad-Pad

Unfortunatley the Rad-Pad hasn't been available for quite some time now. I received one in a Radiant Basics class some years back and misplaced it about 6 months ago. I've been trying to buy a new one ever since and they're telling me they are on order from the printer. I keep checking thier web site and it's still not available. It's a shame because I used mine to run the what ifs a lot too. They last told me they would be getting them after the first of the year, I'm still waiting! If anybody else has one they don't want, let me know!

Thanks, Rich L

hot_rod

the mix valve may be

your bottle neck. most of the 3/4 or 1" 3 way thermostatic will only handle 3- 3.2 GPM. The circ could easily move 70- 100K without a problem, but at a 20 delta t, probably only 30K through most 3 way thermostatic mixers.

If you are going to use another type of mixer check the flow rate, most will have a Cv factor on the installation manual.

hot rod

hot_rod

Yeah, maybe

if all the zones require the same supply temperature. Remember many indirects have a fickle differential on their aquastats. I'd suggest a setpoint control with an adjustable differential to control the indirect temperature.

Now your limiting factor will be the 3/4" pex.

As Brad mentioned, determine what your loads are and then build the distribution to handle it. four zones with what kind of load per zone?

hot rod