# tankless setup



## plumjoe (Oct 21, 2009)

trying to figure out best way for recirculating tankless system was thinking of this


----------



## GREENPLUM (Jul 27, 2008)

thats they way I like to do it.


----------



## ZL700 (Dec 8, 2009)

That's what many manufacturers call for to eliminate circulation through the heater, avoiding erosion & excessive pump size.

Heating a recirculation line with electric when you have gas makes no sense to me but make sure your lines are insulated well to eliminate heat loss/excessive current consumption.


----------



## plumjoe (Oct 21, 2009)

Just making sure recirculated water won't cool down hot water I'll have a 30 gal electric heater to but it's a big house like 7500 sq feet. And I have 3 tankless on a manifold system


----------



## ZL700 (Dec 8, 2009)

plumjoe said:


> Just making sure recirculated water won't cool down hot water I'll have a 30 gal electric heater to but it's a big house like 7500 sq feet. And I have 3 tankless on a manifold system


Unless you feel you need a buffer, a bigger tank only has larger standby losses.
However, with 3 tankless you will need a tank with bigger ports than 3/4" or you will be cutting flow potential of the 3 tankless. Unless your taking 35 degree water to 180 degrees a normal system running 70 degree rise with 3 units should be at least 1" water manifold. 

You can break off the recirculation line and put the tank at the end of recirculation line before it ties back into main water supply, thereby return line and tank is still 3/4" 

A small heater with a 1000 watt element is 3,400 BTU, lose more than that on your piping and they must not be insulated well.


----------



## bizzybeeplumbin (Jul 19, 2011)

I don't think the electric tank is a great idea either, defeats the purpose of the tankless in my opinion. I do think for larger homes, the electric tank on the recir is best, but in most cases I install the Metlund with either motion sensors or the push buttons at the sinks.

I either do the conventional return line with the Metlund, or have used the Metlund under the furthest sink, using the cold line as the return. The Metlund has a thermistor in the inlet so when the water gets to temp it turns off right away, pushing less hot into the cold line, also the Metlund is energy star rated.


----------



## deerslayer (Mar 29, 2012)

Looking at your design I see a problem with cold water sandwiches particularly if you have long term hot lowflow that doesn't trip the flow switches. I think you will be better served with rheem's piping arrangements for tankless whereby only the recirc goes to the heater and it tees into the hot supply. http://www.rheem.com/pdfs/_temp/11000Series/11126.pdf

Hope that helps!


----------



## Tim`s Plumbing (Jan 17, 2012)

Why not go with a Navien with built in circ pump and mini buffer tank instead ?


----------



## Titan Plumbing (Oct 8, 2009)

deerslayer said:


> Looking at your design I see a problem with cold water sandwiches particularly if you have long term hot lowflow that doesn't trip the flow switches. I think you will be better served with rheem's piping arrangements for tankless whereby only the recirc goes to the heater and it tees into the hot supply. http://www.rheem.com/pdfs/_temp/11000Series/11126.pdf
> 
> Hope that helps!


I have to agree, DS.


----------



## ZL700 (Dec 8, 2009)

deerslayer said:


> Looking at your design I see a problem with cold water sandwiches particularly if you have long term hot lowflow that doesn't trip the flow switches. I think you will be better served with rheem's piping arrangements for tankless whereby only the recirc goes to the heater and it tees into the hot supply. http://www.rheem.com/pdfs/_temp/11000Series/11126.pdf
> 
> Hope that helps!


That's what I said earlier, just didn't have that colorful diagram on my phone.


----------



## grandpa (Jul 13, 2008)

Are your 3 tankless all in the same location?? One of the advantages of tankless in new construction is that you can locate them fairly easily at scattered locations, thus possibly eliminating the need for recirc.\\

I definitely suggest contacting your tankless manual, or that manufacturer, for specific recommendations on recirc.


----------



## smellslike$tome (Jun 16, 2008)

Install Noritz, drop the electric tank, and use an on demand recirc system. He's right about the 1" manifold until you reach the last branch.

How many bathrooms? Any shower towers? 3 units sounds like a lot for 7500 sq. ft. Of course square footage is virtually meaningless in terms of production capacity but is important in terms of developed length from the unit(s).

Go with the on demand recirc. You can even get a remote for it. When their alarm clock goes off they hit the snooze button and then the recirc remote and when they get out of bed they have hot water.


----------



## Michaelcookplum (May 1, 2011)

Electric water heater not REQUIRED, , although preferred


----------



## plumjoe (Oct 21, 2009)

Thanks for all the help . Got it done. You are all awesome always enjoy the different perspective .


----------

