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Tankless hot water heater and recirculator pumps

I saw your program where you recommended using a recirculating hot water system to help prime the hot water line on a Tankless hot water system. I believe the system you used was a TACO D'MAND recirculator. What I would like to know is, when the recirculator kicks in and draws the cold water out of the hot water line, where does the recirculator send the cold water from the hot water line? I do not have a hot water tank, so is the water being fed back to? If the water is being fed to the Tankless water heater will this type of setup void my Rinnai warrant?

Re: Tankless hot water heater and recirculator pumps

It can't be done without a tank. There are some tankless heaters that do have a small tank but yours doesn't.


Re: Tankless hot water heater and recirculator pumps

You can install a small electric 2 gallon tank and circulate through that only, then you tankless just heats any ditional cold water. The power consumption to maintain 105F or so in that tank would be minimal.

One better, would be to use a 2nd circulator pump with an aquastat and circulate the small storage tank through hte tankless heater when needed.

I almost went this route, but I;m going ot have a Nvien "a" model installed whcih has a built-in circulation pump and 1/2 gallon buffer tank. It's designed for external circulation out of hte bax and has a 24 hour timer on the controls.

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