Tankless and Recirculation in two directions

[Will Nicholson]

Hi all,

I'm in the final stages of building my own home in Bowie, Texas, and I have an opportunity to plumb the house with hot water recirculation lines, but I have a question about that.

My water heater (propane tankless -- I'm open to suggestions) will be located in a room in the corner of the house. The kitchen and master suite with bathroom will go off to one side, but the guest bathroom will go off to the other side.

In order to complete the loop, it seems like the simplest option is to go all the way to the master suite (roughly 55 feet, then turn around come all the way back, PASS the water heater and continue around to the guest bath, and the loop the recirculation line back from there. So, about 155' of hot water supply (3/4" pex insulated), and another 50' of recirculation to get back to the WH.

Is 200 feet of insulated PEX too far to maintain hot water for a system like this?

Also, any suggestions for Tankless Propane water heaters, pumps, etc? I haven't purchased any of the equipment yet, so I'm in a good place for advice.

One other thing I didn't mention is that I'm also going to have radiant heat flooring, so the water heater COULD run double duty on that, or be completely separate.

For reference, it's an 1800 sqft building at 50x36 feet.

Thanks.

 

[wwhitney]

Maybe make each double lavatory the end of line, and put an on-demand recirculation pump under each lav? Those often pump into the cold water line, but you could install dedicated return lines, since this is new construction.

Cheers, Wayne

 

[Sponsor]

 

[Bannerman]

A single recirculation pump may be located on a single return line where the return enters the WH. The return loop from each area would be combined prior to the pump so the pump will be drawing from both return loops.

Placing a balancing valve in each return loop will allow adjustment of the flow through each loop, to prevent the majority of flow from taking the path through the shortest loop. To reduce the likelihood for cavitation occurring before the circulation pump, suggest locating each balancing valve and also a check valve where each feed line is connected to the return line such as in the Master suite bath and Guest bath. The check valves will prevent flow from the return line from flowing backwards to each faucet.

Using two pumps as Whitney suggested, would allow each circulation loop to operate independently. Hot water flowing through a feed and return line will lose some amount of heat even while insulated, so there will be some energy savings in eliminating recirculation to the guest bath when no guests are present, particularly during warm weather when space heating is not also required.

Instead of running circulation 24/7 or on a daily schedule, suggest locating a momentary contact switch in each bathroom, kitchen and laundry to activate the pump for ~5-minutes. Many times, hot water will not be needed immediately so activating the pump only a few minutes in advance will likely provide sufficient time for hot water to arrive before it will be used. A 5- 10-minute run time will prevent needless circulation and energy use when hot water is not actually being used.

Navien is one tankless brand that offers tankless combi-boilers for both space heating and domestic hot water applications.
https://www.navieninc.com/residenti...rg37binn2Guw0860quTaqfsjfi4jJ85RoC4pgQAvD_BwE

https://www.navieninc.com/accessories/hotbutton

 

[Will Nicholson]

A single recirculation pump may be located on a single return line where the return enters the WH. The return loop from each area would be combined prior to the pump so the pump will be drawing from both return loops.

Placing a balancing valve in each return loop will allow adjustment of the flow through each loop, to prevent the majority of flow from taking the path through the shortest loop. To reduce the likelihood for cavitation occurring before the circulation pump, suggest locating each balancing valve and also a check valve where each feed line is connected to the return line such as in the Master suite bath and Guest bath. The check valves will prevent flow from the return line from flowing backwards to each faucet.

Using two pumps as Whitney suggested, would allow each circulation loop to operate independently. Hot water flowing through a feed and return line will lose some amount of heat even while insulated, so there will be some energy savings in eliminating recirculation to the guest bath when no guests are present, particularly during warm weather when space heating is not also required.

Instead of running circulation 24/7 or on a daily schedule, suggest locating a momentary contact switch in each bathroom, kitchen and laundry to activate the pump for ~5-minutes. Many times, hot water will not be needed immediately so activating the pump only a few minutes in advance will likely provide sufficient time for hot water to arrive before it will be used. A 5- 10-minute run time will prevent needless circulation and energy use when hot water is not actually being used.

Navien is one tankless brand that offers tankless combi-boilers for both space heating and domestic hot water applications.
https://www.navieninc.com/residenti...rg37binn2Guw0860quTaqfsjfi4jJ85RoC4pgQAvD_BwE

https://www.navieninc.com/accessories/hotbutton

So, you're suggesting something along these lines?

 

[Bannerman]

Yes. The balancing valves be as simple as two globe valves which probably only one would be partially closed to reduce the flow rate through that loop so as to increase the flow rate through the opposite loop.

 

[Breplum]

I recommend and use Navien NPE A series with a terrific recirculation pump built in.
The specs say that it can support 500' equivalent length 3/4" copper pipe. 3/4" PEX should be fine but you can call their support number to confirm.
The models also support push button add on control, or have a setting that continuously learns the household use patterns and predicts when you will typically need hot water recirculating.
It also supports NaviLink that can utilize home WiFi and smart apps.
The best efficiency is with user initiated hot water recirculation at all locations, but with that big a loop, you would need to plan on a delay based on where in the big loop the fixture is.

 

[Tanklees]

I recommend and use Navien NPE A series with a terrific recirculation pump built in.
The specs say that it can support 500' equivalent length 3/4" copper pipe. 3/4" PEX should be fine but you can call their support number to confirm.
The models also support push button add on control, or have a setting that continuously learns the household use patterns and predicts when you will typically need hot water recirculating.
It also supports NaviLink that can utilize home WiFi and smart apps.
The best efficiency is with user initiated hot water recirculation at all locations, but with that big a loop, you would need to plan on a delay based on where in the big loop the fixture is.

Hello what DIP switch setting is the "learning" use pattern?

I currently had the hotbutton setup with remote clickers. However the ideal addition would be to have the unit kick on 8am and 7pm so I would like it to learn that on its own.