External recirculating pump

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jhalt

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Hi all,

What are my options for a TWH that I can use with an external recirculating pump? I'm aware of the Navien 240-A series, but it's not clear how well it actually integrates with an external pump, and also it comes with an internal pump which I wouldn't need. What other options are there?

Thanks
 

Jadnashua

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The warranty on a tankless, depending on the brand and configuration, may be voided with a recirculation system, so first thing is to study the installation manual carefully.

Unless you have a small tank to act as a buffer, you may defeat the whole purpose of installing a tankless, since when the recirculation system is running, the burner must be on. The ideal location for a tankless system is close to the point of use, otherwise, the combination of the delay in turning the system on, then purging the water line of room temperature water will end up wasting a fair amount of energy. In a large house, the wait can be substantial, and, in many places like CA, water is a very precious commodity.

WHile tankless systems can work well in some circumstances, they do have some operational differences from a conventional tank system. IF you don't like those, it may not be a good choice.
 

jhalt

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Thanks for the info. Is it possible to have a tankless that allows water to recirculate but only fires up when needed to keep that recirculating water warm, basically, the same way a non-tankless recirculating setup does?
 

djdavenport

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Our house was set up with a circulating system, so when they installed my tankless--it's actually a combi--they also put in a 10 gallon electric water heater downstream of the tankless, isolated with check valves. The pump--it's a bronze Taco 006--recirculates the water through the electric tank (it's got a smart pump, so it learns your usage patterns) and the tankless won't fire up unless there is demand. I have the electric set a little cooler than the output of the tankless, so the water, if left running, will get a little hotter once the electric tank has been filled with the output of the tankless. Those little electric tanks (which I think are often used as point of use tanks) are pretty reasonable. Couple hundred bucks, IICR. But so far the setup has worked fine. No cold water sandwiches.
 

Jadnashua

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There are some tankless systems with an internal tank that are designed to operate with a recirculation system. But, other than that, you need some sort of storage tank to buffer the output so you don't have the tank trying to fire all of the time. Take a look at the installation instructions...some show how to add recirculation without voiding the warranty.
 
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