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plumbit

Thank you for all the help

Larry Weingarten

Hi, Mostly questions... Did you do a heat loss calculation to size the heating system?... Have you considered turning up the heater to 140F and setting the mixing valve to 140F as well? It might be the slab is losing heat faster than it's being added with the current settings... It's not going to change now, but is there perimeter and under-slab insulation? That would affect the heat input needed... The pump is mounted in a vertical position. Does the manufacturer OK this position? Other manufacturers don't, as air can get trapped in the pump and damage the bearings. And lastly, do I see Knipex pliers on the water heater? Good tool!

Yours, Larry

Alan (California Radiant) Forbes

Without details, I'm guessing:

5 loops at .5 gpm/loop = 2.5 gpm flow
2.5 gpm x 10,000 BTU/gal.@ 20°ΔT = 25,000 BTU
25,000 BTU/3,413 BTU's/kw = 7.32 kw = 7,320 watts

So, it looks as though your water heater is too small, the pump is in the wrong location and mounted improperly, there is no microbubble air eliminator and no pressure or temperature gauges.

What are your tubing lengths? Tube spacing? Pump model? It looks like a Taco bronze.

And as Larry surmised, you probably don't need that mixing valve.

plumbit

Yea I’ve changed rotation of the pump and added a taco air eliminator before the pump. What location should the pump be in? And the spacing is 12” apart with insulation under slab and perimeter insulation. What is an ideal return temperature? And of the 5 loops the last 2 return lines are fairly cold coming back. So I should have .5 gallon per minute going through each loopI have  Unfortunately electricity is out only option for heating.

hot_rod

There needs to be a pump on the mixed port of the mixing valve if you decide to keep it in the piping. It is not needed.

A heat load would add some clarity. 1500 x 20 btu/ ft would require 30,000. But your location and typical outdoor temperature,insulation, etc can make a difference

HVACNUT

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realliveplumber

I'll never understand why people decide to use a piece of equipment that is designed to heat domestic hot water, and attempt to use it for space heating.

GroundUp

Because it's piped wrong, you're getting minimal flow through the loops, which is causing the high delta T. If you were to repipe it with the circulator downstream of the mixing valve would remedy that issue, but the mixing valve isn't doing anything besides adding resistance. Eliminating it altogether would at least have you close to correct, but then you're still faced with the too-small water heater trying to do a correctly sized boiler's job. The best fix here would be to start all over and install an electric boiler of the proper size. Maybe a 90* supply and a 70* return to maintain a 60* air temp.

plumbit

GroundUp said:

Because it's piped wrong, you're getting minimal flow through the loops, which is causing the high delta T. If you were to repipe it with the circulator downstream of the mixing valve would remedy that issue, but the mixing valve isn't doing anything besides adding resistance. Eliminating it altogether would at least have you close to correct, but then you're still faced with the too-small water heater trying to do a correctly sized boiler's job. The best fix here would be to start all over and install an electric boiler of the proper size. Maybe a 90* supply and a 70* return to maintain a 60* air temp.

Thank you for the advice. I appreciate the help. I’m just learning. It’s actually at my cousins and I’m just trying to help him out. What other piping changes would you recommend? 

hot_rod

We are all guessing until you get an accurate heat load number. Find free calculators with a google search.

An electric boiler is always the best answer.

However I have done many electric water heater systems for budget /starter family systems.
You could run two elements in the tank. You need two 30A 240V circuits however, two of the temperature controls that you see under the covers on the tank.
Same with an electric boiler, you will need more than one 30A circuit.

Two 4500W elements gets you 30,690 BTU/ hr
Two 6000W elements gets you 40,920 BTU/ hr

Hopefully you have very low KWh electric rates. It can be expensive heating with electric.

It could be this simple, the tank, an air purger/ expansion tank, pump and some valves.
I like to add a 30 psi relief valve into the piping also, in addition to the factory installed T&P safety.