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[woodman]

Hi all! I was wondering what the difference there is in head loss between a 10 plate with 3/4" fittings vs a 20 plate with 1" fittings. 

[RSI]

Are both 5x12 inches?

[woodman]

No, the 10 plate is 3x8. The 20 plate is 5x12. Sorry, I did not know a 10 plate was available 5x12.

[RSI]

I am not sure what the 3x8 10 plate will have as far as head loss but it would be very excessive. I wouldn't even try using it.

[woodman]

OK, what about the 3x8 20 plate? The reason I am asking is I am toying around the idea of a snow melt system for a new garage apron. I just don't want to put too much of a strain on my pump. I was planning on using a mix of glycol on the apron side so I could run it only when I wanted. The apron will be approx 10'X30', what exchanger would you recommend?   

[willieG]

100 btu per foot recomended on the net for snow melt..size your exchanger for more to be safe
and insulate below the slab as if it were a new basement in your home

[RSI]

You might be able to use it if you run it on a secondary loop but that would require an extra pump. I don't like to use anything smaller than a 5x12 20 plate because of the restriction.

How many BTU's do you need to transfer for it? A small shell in tube pool heat exchanger might be a better option and they are make so have very little restriction.

[woodman]

OK guys, thanks for the thoughts. Sounds like I will need a minumum of 30k btu/hr. As I said I am just kicking around the idea and never thought about a shell in tube. I won't be doing anything till next spring so I have some time to figure it out. My concern is I already have a fairly high load on my pump as it is going through 3 hx's currently. Its looking like I will have to run another line set as I plan on also adding a hot tub in the next 4 or 5 years.     

[willieG]

woodman..reading on the net it says (in the article i read)  that insulation under the slab of a snow melt system is not required as you would only lose between 15 and 20 btu's per hour per square foot to the ground and insulation is expensive. To me insulation is cheap! losing 20 btu to the earth  is 20 btu of the 100 the article says you need to melt the snow. if you insulate and drop that loss to 8 or 10 btu i  would say your wood pile would last a lot longer?

[RSI]

OK guys, thanks for the thoughts. Sounds like I will need a minumum of 30k btu/hr. As I said I am just kicking around the idea and never thought about a shell in tube. I won't be doing anything till next spring so I have some time to figure it out. My concern is I already have a fairly high load on my pump as it is going through 3 hx's currently. Its looking like I will have to run another line set as I plan on also adding a hot tub in the next 4 or 5 years.   

The return temperature is what you need to watch when adding too many heat exchangers. If it is still plenty hot there is no need to run more pipes underground.
Putting the heat exchangers on secondary loops with their own pumps is a good way to get rid of restrictions. Also doing this way you could set it up so all can't run at the same time to not put too much load on the system.