Hydronic question...

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
  • Hope everyone has a wonderful and warm Thanksgiving!
  • Super Cedar firestarters 30% discount Use code Hearth2024 Click here

BrewerBob

New Member
Jan 22, 2020
1
Essex, MD
While searching for info on 1/2" pex flow rates and pumps, I came across a thread from this forum:


Lots of techno -geek info there. I am not going to pretend to understand much of it. I'm a complete newb at hydronics.

I'd like some advice for my application, which is:
I have a 40' skoolie with a single 300' loop of 1/2" pex in the floor with 6 3/4" diameter loops. Spacing is also about 6 3/4". That's roughly 270 sq ft of floor space. Figure 2,200 cu ft. I have 1" closed cell foam sprayed on the steel floor with 1 1/2" rigid foam board on top of that. Total R-value of about 13. On top of that is 5/8ths plywood. The final flooring is undecided but will be either laminate flooring or 3/4" solid wood. I'm using a 12KW (40K BTU) diesel coolant heater. Head will be about a foot. Max would be 3' if I got a wild hair and put the pump on a shelf but figure 1' for ease and most likely location.


I'm likely to add a heat exchanger (need help there too) and try to run an instant hot water loop for the shower if this is at all possible. If it's not, tell me as I will need to come up with another system for heating potable water. What kind (brand model) of heat exchanger would I need to go from 170°F to 105°? How many plates? How big of an expansion tank?

Eventually, I will plump the radiant floor into the 8.3L Cummins coolant system. Engine coolant runs under 180°F. Use the engine coolant to heat the floor while driving. Use the diesel heater while parked. Also use the diesel heater to reverse flow thru the engine as a block heater while boon-docking on cold days.

The pex is already installed and the diesel heater is scheduled for delivery today. Those are fixed. I don't have a pump, tanks or heat exchanger yet. The pump would be best at 12V DC. 120V AC is also acceptable. 1/2" NPT would be better than any goofy flange like the Taco pumps I've seen.

What flow rate do I need?
How many plates in the exchanger?
How much capacity for expansion?
Misc? What esle am I misiing?
 

Attachments

  • [Hearth.com] Hydronic question...
    Radiant 2.webp
    136.6 KB · Views: 335
Last edited:
I don’t see a problem with flanges for your system, but I know Grunfus makes bronze sweat fit pumps for hydronic systems.