Heat exchanger size

[Redbird]

What size heat exchanger for my residential hot water can someone reccommend and a good place to buy, I've got a Shaver 165 with upgrades and do not wish to use the "coilL setup in the back of the stove, Family of four. Thanks

 

[beagledog]

I just put in a 40 plate, flat plate exchanger. Mounted it on the wall next to my hot water tank. Breaker is shut off to the water heater. 4 showers per day plus hot washing machine water and never a problem. I wasn't sure which dhw heater to go with either, but the flat plate came with my owb so my decision was made for me. good luck