Can somebody help me with sizes?

[83trekker]

I have a 23 x 26’ garage, 10ft walls 12 foot ceiling. I have radiant heating in the slab.
I have around est 680ft of ¾ pex w/oxygen barrier tubing.
2 loops , each loop is 340ft ea.
Ran 6” OC from the walls, 12” OC for the runs.
No insulation under the pad just packed sand/gravel.
Its is running off of a BTU Input 75,100--BTU Output 60,080---- 70 gallon Apollo Hydro heat hot water tank that’s made to work with in floor heat. I know this is a very large hot water tank but its worth close to $1700-2000 and I got it for 100 bucks brand new cause it has a dent on the bottom of it. So I couldn’t turn it down. This is a closed loop set up.

The help I need is what size pump especially with ¾ tubing and what size of exspansion tank should I use. All the plumbers I talk to say just goto your local store and pick up a pump and exp tank. These don’t seem necessary to size these up, yet I read about that it should be sized up and its very important. Any prof plumbers or radiant people on here? I talk to one radiant company and once they heard I was using a closed loop with a water heater and not the $5000 boiler system they said I should use didn’t want to help me any more.

So what do yall think?

 

[83trekker]

anybody have a setup close to mine?

 

[Nosman]

My setup is reasonably close to yours, 600ft, 2 loops, 3/4" Heat Link tubing. With a 37,000 btu tankless heater, and a Grundfos UPS15-58C pump, everything seems to be working wonderfully so far. The pump is a 3 speed, and I normally run it on high. Let me know of you have any questions.

http://grundfos.com/Web/HomeUs.nsf/GrafikOpslag/PDFs/$File/L_UP_SL_027.pdf

 

[83trekker]

What do you think your paying per month to run it, do you have insulation under the pad?

What made you go with the tankless?

 

[Nosman]

Monthly is questionable since I just finished it about 2 wks ago, but I did a little math. Based on a 11,000 watt heater, running for 15 min, off for 1:15(16%), it would run 4 hours a day total at about 60 cents an hour. Extend that out to a month, and you get about $72/month. Our electricity is about 5.5 cents per kw/hr. Right now that schedule gets me about 60 degrees in the shop, but it's not real cold outside.
As the colder weather approaches, I will adjust the schedule to keep it comfortable with an eye towards keeping the electrical bill reasonable.
It is ok insulation wise at R22 in the walls and R14 in the ceiling although I will be increasing the R14 at a later date. The floor is insulated with 1.5" Celfort and a perimeter Celfort skirt that goes 2' down. I'll load some pictures up as soon as I can.
On the tankless decision, it was mostly a matter of space. The heater takes up very little space on the wall, and is powerful for it's size. I have no gas service to the house, so the electric decision was made easier, although your service has to be pretty stout(46A at full chat). Let me know if I'm forgetting anything, later.