Raypak - Cupro Nickel or ASME copper?

[internet]

Replacing minimax NT 400 (400k btu) and going with RayPak low nox heater. There are two options and I am hoping to get some advice about which to choose. I can either get the ASME model that has copper heat exchangers, or go with the cupro nickel heat exchanger version that is NOT ASME. I know the headers are different - cupronickel is a polymer header, ASME is a cast iron header. The price difference is negligible.

So, the question remains: is one objectively better than the other, or is just a question of where I want to trade off? Everywhere I read says cupronickel is superior to copper. (Pool is SWG, plaster/shotcrete). I also read that ASME will outlast anything...but not if it uses copper that's inferior to cupronickel, right? I'm kind of in the woods on this one. Is ASME just complete overkill for a residential application anyway?

Our season is from about mid April to late November if we're lucky. Maybe longer once we get an actual hard working heater installed! Thanks for the advice.

 

[internet]

EDIT: cupronickel is available as an OPTION on the ASME models. So....still, is ASME overkill for residential? Thanks again.

 

[internet]

EDIT again: apparently raypak does not have a low-nox AND cupronickel option. (Learning as I go.) Back to the drawing board.

 

[JamesW]

In my opinion, there's no reason to choose cupronickel or ASME.

Cupronickel is less efficient than regular copper by about 1 or 2%. Usually 84% efficient for copper vs 82% efficient for cupronickel.

I don't think that the ASME version heat exchanger has enough extra copper to make a big difference. If the tubes are thicker, the efficiency will be reduced.

For the best longevity of the heater, maintain good chemistry and keep the flow rate to the heater within the recommended range but at the lower end of the range to reduce erosion.

Thicker tubes might give you a little bit more time. However, if the copper is being eaten through, it's only a matter of time before it leaks.