Multi-temp radiant design questions

Matt Connolly

Hey guys, it's been a while since I've been here but it's always comforting to know that the best and brightest are ready to help. Anyway, i'm finally getting around to properly repiping my house after 5 years of attaching zones here and there and having no comfort or control!

Anyway, i'm using a Monitor MZ25C condensing boiler and have 3 zones of in slab radiant with a load of 50 MBtu at design, a basement with radiant panels with a load of 15 MBtu at design and a garage with in slab radiant that has a flat plate heat exchanger to it since i'm using antifreeze there. I'm not sure of the load yet but if I have insulate it more to bring it in line I will. Half of it is 150 years old, but the slab is new thoughout. The garage slab is properly insulated with Insultarp underneath and R15 styrofoam on the sides.

Here's my dilemma: I want to maximze the condensing aspect of the MZ and use the Tekmar outdoor reset for comfort in the 3 house zones, but also want the higher temp for the panels and garage. What is the simplest way to not overheat the house when the high temps are calling (and I use the setpoint on the Tekmar) while keeping the system as simple as possible? There is a lot of flexibility in the design - I just don't want to go crazy with loops and pumps, as it usually ends up reducing efficiency although it does work for comfort. I saw some earlier posts on Taco's mixing injection system but have never used anything like that. In the past the house has tended to flywheel a bit, so i would like input on slab sensors or any other way to prevent that. My wife is really getting tired of going from sweaters to opening windows.

Thanks!

Matt

Tom Stayer_2

Multi temp radiant

Matt,

Your solution is simple. My system, like yours, has a requirement for diff temps. High temp for baseboard and some radiant wood floors. I have designed my very comfortable heating system as follows:

As you know there are many ways to do these systems, but I try to design so that there are very few mechanical parts involved. So, my preference is balancing valves and one or two pumps--constant circ.
Take a look at John Siegenthalar's "mini-tube" equation and you can constant circ to your garage and house at the same time via "mini-tubes", control heat output by adjusting balancing valve(s) to desired setting.
I think that constant circ on the MZ (use primary/secondary piping) to make MZ condense.
If you want drawings, call or email me, and I will hook you up with the drawings and some more ideas.

Your ball....

hr

I'd like to see you

add a buffer tank in the mix. With those various, and small, loads it will really cut down on the cycling.

I piped my MZ in series with a 32 gallon then pulled the mixed temperatures from that.

I run the tank, and MZ, 100-140° to spread the cycles even more.

Run some different "what ifs" on a copy of the HDS buffer tank module.

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

hydronicsmike

Matt...

Good to hear from you. Hope all is well.
Give me a call in the office, if I can help.

Mike