On Demand supplement hot water

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WasVilla

Active Member
Joined
Oct 8, 2020
Messages
26
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12
Location
San Diego
We are looking at an in-line on demand electric water heater. The distance from the tankless to the kitchen requires a long wait time for cold water to be fed before the hot water gets there. Imagine the tankless is at one end of and below the house (basement) while the kitchen and master shower is at the far end.

My idea is to install an electric on demand heater which provides quicker hot water until the tankless supply kicks in. At that point, the on demand would cycle down (?) allowing the water to primarily be supplied by the tankless.

(1) Do on demand electric heaters sense the input water temp and adjust heating downward as the input temp gets hotter?
(2) Should the on demand heater be as close to the fixtures calling for hot water?
(3) Which brands can you recommend based on performance and longevity?
 
They are only going to heat too the temp. you select, and when the incoming supply is at the, temp. they are just a flow thru device.

Why not just install a recirculating system, with a timer and a pump.
 
I thought tankless and on demand are the same?
 
Here was my solution. It took 10 minutes to install, I adjusted it only to activate at 7AM and 7PM (for showers and dishes) and I get hot water instantly. It costs about $200 at the Orange Big Box store.
1653408087784.png
 
havasu said:
Here was my solution. It took 10 minutes to install, I adjusted it only to activate at 7AM and 7PM (for showers and dishes) and I get hot water instantly. It costs about $200 at the Orange Big Box store.
Click to expand...
What is it?
 
Isn't recirculation as wasteful as just purging the pipe as I do. I have a pipe run of around 65ft from water heater to bath shower or faucets. I ran water into a bucket finding that it's running warm with less than two gallons in the bucket. In my case shower is not my first activity so I have learned how much to crack the faucet to have hot water available. The kitchen sink has only around 12ft of pipe so less delay.
 
It's the convenience of not having to wait for the purge to achieve the desired results.
 
OK my solution works well for me, maybe not so much for others.
 
YEP, some just tuff it out, some need a lot of vaseline.
 
WasVilla said:
We are looking at an in-line on demand electric water heater. The distance from the tankless to the kitchen requires a long wait time for cold water to be fed before the hot water gets there. Imagine the tankless is at one end of and below the house (basement) while the kitchen and master shower is at the far end.

My idea is to install an electric on demand heater which provides quicker hot water until the tankless supply kicks in. At that point, the on demand would cycle down (?) allowing the water to primarily be supplied by the tankless.

(1) Do on demand electric heaters sense the input water temp and adjust heating downward as the input temp gets hotter?
(2) Should the on demand heater be as close to the fixtures calling for hot water?
(3) Which brands can you recommend based on performance and longevity?
Click to expand...

WHAT IS THE MAXIMUM INLET TEMPERATURE PERMITTED FOR A POINT OF USE WATER HEATER?
 
billshack said:
there is a thing called an instant hot . here it is
https://insinkerator.emerson.com/en-ca/insinkerator-products/water-dispensersIt supply's small quantities ( one gallon )of very hot water for making tea, coffee, It also has a temp setting.
It requires another water spout.
i do not know if this will meet your needs but check it out .
Click to expand...

We added this on our kitchen remodel - and LOVE it. Would highly recommend if "small" quantities of hot water are needed but it's not what the OP needs.

Along those lines, I do think what he's looking to do is a viable solution - assuming there is space & access to plumb it in.

We, also, have a similar situation - tankless is 100' away from the master bath - and wish we would have had the foresight to install a recirc line when it was built!
 
dsteinhorn said:
WHAT IS THE MAXIMUM INLET TEMPERATURE PERMITTED FOR A POINT OF USE WATER HEATER?
Click to expand...

@Snoonyb is right on - 97.35% sure there isn't a specification for (a maximum) inlet temp. I have seen manufacture charts showing the time differential for heating supply water starting at 33°, but it typically only goes to 100ish°
 
Snoonyb said:
The issue will be the temp. set by the user, and not by a governing agency.
Click to expand...
I AM ASKING ABOUT THE MANUFACTURER'S SPECIFICATIONS FOR ALLOWABLE INLET TEMPERATURE. MOST OF THESE UNITS ARE INTENDED TO TAKE A COLD WATER SOURCE. AS OTHERS HAVE SAID, USING POINT OF USE TO GET QUICK HOT WATER UNTIL THE HOT WATER ARRIVES FROM THE CENTRAL HEATER IS THE GOAL HERE.
 
dsteinhorn said:
I AM ASKING ABOUT THE MANUFACTURER'S SPECIFICATIONS FOR ALLOWABLE INLET TEMPERATURE. MOST OF THESE UNITS ARE INTENDED TO TAKE A COLD WATER SOURCE. AS OTHERS HAVE SAID, USING POINT OF USE TO GET QUICK HOT WATER UNTIL THE HOT WATER ARRIVES FROM THE CENTRAL HEATER IS THE GOAL HERE.
Click to expand...
stop yelling! Using all capital letters is plain rude.
 
Most of them don't list inlet temperatures, so I have written to customer/technical support.
 
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