Plate exchanger question

[hottubbrad]

I am installing a Garn 2000 and would like to run a closed system in the house.
Can I just run the Garn heated water through a plate heat exchanger and build my closed system like you would for a typical fossil fuel boiler.??
Will the plate exchanger idea work....what size is sufficient...?

My system is:
Air handler
Indirect hot water tank
In floor radiant
Snow melt (wish list)

Thanks

 

[deerefanatic]

Oh yes, plate heat exchanger will work just fine.... Now, for sizing, that's a different matter. If you have a primary secondary system, where you can re-use water over several loads, then you can get a large temp drop and use a smaller flat plate.....

for instance, I'd set up your system as follows:

Primary loop with water flow going clockwise and all loads tied off the bottom of the loop:

snowmelt -- Infloor radiant -- air handler -- Indirect tank

That way, the hottest water is first offered to the indirect tank, then the air handler is offered the slightly cooler, but not much cooler water. Then the quite cooled (about 130F) water is offered to the radiant. Then the very cool water (100F or so) is offered to the snowmelt, before going through the plate cooler for another trip around the system. of course, this is assuming that all the loads are on at the same time. If all the loads except for the snowmelt were off, then the snowmelt system would get hit with 180F water, so mixing valves on the snowmelt and radiant floor are necessary....

Hope this helps you!

 

[hkobus]

Good to see another Ontarian around here, welcome.

Looks to be a huge load to go through one plate HX. The air handler is already a HX, and you would lose efficiency running a plate ahead of it. The snowmelt I can see a need as it should have glycol.
The whole thing can work with Primary/Secundary ( and close spaced T's) like Deerefanatic discribes above. This leaves the question, why would you want to separate the system fron the Garn with a plate?

 

[Chief Ryan]

Plate heat exchangers work very well. It's amazing how much heat transfer you can get from them. The absolute most important thing with these type of HE's is water treatment.

I do HVAC for a living (not familiar with you setup) and the biggest problem with these HE's is scale filling the pathways inside the HE. I've acid washed these HE's for days with no luck. Wound up ripping them out, and there not cheap. Sierra Glycol is what we use (propylene glycol). We cool 100,000 sq ft buildings with a HE that's only 4' high 2' wide 16' deep.

Like i said, i'm not familiar with your setup but make sure you find out from the manufacturer about water treatment.

 

[hottubbrad]

I just like the idea and understand a closed system better as I have built a few of them before on Natural Gas.
Eventually, i will need glycol for the snow melt anyway.

* Is there anyway of Oversizing a plate exchanger. Or is bigger always better??

 

[Chief Ryan]

I'm not sure. As long as you have some type of bypass (three way valve, mixing valve) What is the primary and secondary water temps.