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[RSI]

$80 for a 30 plate? So it is a 3" x 8"  with 3/4" ports?

How much pipe is in that system? It sounds like the boiler flow is way too low.

[willieG]

i dont think the size of the plate exchanger matters..it is the flow of the domestic water and the flow of the OWB that makes things work

most homes have an output of about 2 gpm at the tap

so if that water was 60 degrees on the way in to the exchanger and 180 on the way out you would have an increase of 120 degrees  how ever most folks are not using 180 degree water at the tap and some of that 2 gpm will be cold water mixing in to cool the water.

lets say we need 2 gpm at 120 degrees  and the incoming water is 60 so we need to raise it 60  2gpm is about 16 pounds times 60 960 btu per minute or 57600 btu per hour

everything i read says 180 degree water can deliver 10,000 btu per hour with a delta t of 20 degrees so if this is all figured out right (it may not be)  6 gpm from the owb should be able to heat 2 gpm of domestic water going through the plate exchanger to 120 degrees  and still have a retrun temp of 160

yes? no? maybe so?

[RSI]

The size of the plate matters if it has excessive head pressure loss.
If it is the bottleneck and drops the boiler flow rate from 6 gpm to 3 gpm it will cause problems on the whole system.

[willieG]

i agree witht he low flow and the plate exchanger causing flow problems RSI

i was jsut thinking the other way...your plate exchngerer could not be too big unless your domestic flow was large also?

[baldwin racing]

RSI, no doubt easier to buy a couple or just buy the sidearm but have been experimenting with metal spinning anyway.

kelly, thats a sweet little metal lathe.

thanks....
I figured I could make a side arm easy.....figured the stainless would last and it's free even better....lol 
kelly

[yoderheating]

 But you can run to large of a flat plate depending on flow on both sides. I've taken a 3/4 30 plate and produced 142 degree water out of the tap with the furnace on 180 with a 10 degree differential. Thats with the furnace 100ft from the house and having a 007 pumping the furnace. The reason I checked was because the customer was complaining the water wasn't hot enough for him. Of course I told him I wasn't going to make it hotter. lol
 My point is that water flow on the domestic side determines a lot and if you have a bigger flat plate it will only jack it up more. 

[RSI]

RSI, no doubt easier to buy a couple or just buy the sidearm but have been experimenting with metal spinning anyway.

kelly, thats a sweet little metal lathe.

thanks....
I figured I could make a side arm easy.....figured the stainless would last and it's free even better....lol 
kelly

It is certainly worth a try. Just add as much heat transfer surface area as possible if you can.

It will work even if you just do a simple pipe in pipe but probably won't keep up unless you add a large storage tank.