tankless controlling two air handlers

[jmar]

hi folks, recently purchased a home with two AH, one up one down, with stats for each. they are currently fed by an old water heater and recirc. I would like to put an npe 240a in place of the HW heater and use for both AH's and DHW. I realize none can run simultaneously. my question is controls as the tankless will only control one AH and DHW at a time. One concern I have is delay time to not allow one air handler to completely shut down for second AH or DHW call and leave hot water in the coils. any comments appreciated on how best to control all this using a navien H2 air kit and ? .

Any suggestions appreciated.
I would add that the air handlers are 25 year old horizontal suntherms but appear in good working order, all of which are stuffed in very tight quarters in second floor.....

joe

 

[breplum]

Maybe try the HeatingHelp.com site forums 'the wall'. One of the dead men may have already answered.
My pure guess is a relay is needed.
Don't you want a Combi anyway?

 

[jmar]

Maybe try the HeatingHelp.com site forums 'the wall'. One of the dead men may have already answered.
My pure guess is a relay is needed.
Don't you want a Combi anyway?

I already have a an npe 240a and understand it can do the job as well. If the combi's have an advantage in this situation, then maybe I should take look at changing. It would be nice to have aside by side comparison on the navien website. maybe a better solution is two units. One for DHW and one for air handlers with a bypass in the event of failures. options... I'll check out your suggestion.

 

[breplum]

I know that the Navien fire tube series boilers has three landing spots for three separate air handlers.

 

[jmar]

that looks like a great option if tankless becomes the route. thanks.