Pex tubing used as heat exchanger?

[stefan66]

I,m thinking of using 200 ft. of 1"heat-pex in an aprox 1200 gallon (6x9x6ft high) storage
tank as the bottom heat exchanger instead of 80 ft. of 1"copper. anyboby out there done comparisons?
Also thinking of floating 150ft. on the surface for heat extraction.
Any guidance would be greatly appreciated

 

[EricV]

Yep did exactly that for my DHW. 200 feet of 3/4 pex. Doesn't work at all. The out feed pipe gets stone cold as soon as the volume in the 200 feet of pex runs through. But now I got the top on nice so I'm not going to remove it. It may work better for heating from the boiler for my experience I won't try it again.

 

[tom in maine]

You need a minimum of 4 times as much PEX as copper. With larger diameter tubing like you are talking about, I think that goes up to 6 times as much.
Use copper for heat exchangers, it is more expensive, but it will work the first time.

 

[stefan66]

You need a minimum of 4 times as much PEX as copper. With larger diameter tubing like you are talking about, I think that goes up to 6 times as much.
Use copper for heat exchangers, it is more expensive, but it will work the first time.

OK how about 2 runs of 3/4" copper fed from a manifold off of 1" pex.
Each run about 60ft. Will that be enough?

 

[Fred61]

I have an EKO 25 and I wouldn't go less than two runs of 100 feet each either for DHW or tank charging. What size boiler do you have?

 

[stefan66]

I have an EKO 25 and I wouldn't go less than two runs of 100 feet each either for DHW or tank charging. What size boiler do you have?

The boiler I have now is an old unit of aprox. 60,000 btu/hr
I'm probably going to have a large temp differential since I'm using the water
for in-floor heat.

 

[kabbott]

I have an EKO 25 and I wouldn't go less than two runs of 100 feet each either for DHW or tank charging. What size boiler do you have?

The boiler I have now is an old unit of aprox. 60,000 btu/hr
I'm probably going to have a large temp differential since I'm using the water
for in-floor heat.

Yes 2x60' of 3/4 copper should handle 60 kbtu fine. I have 2x100' 3/4 copper fed with 1 inch and it handles 110 kbtu or so with a 30 degree delta.
Do I wish I had more? YES, but as you know copper is pricey...

What pump are you planning to use for the copper coil? I use a Taco 00R on high, I could do better with more flow but next larger pump uses a good bit more power.
Bottom line it works like it is, no problems charging tank to 185+...