I have a Navien NCB-240 ASME tankless water heater / combi-boiler. I've had a plumber look at it, and he said it is operating as expected, which apparently means I never have any hot water to wash my hands in the winter b/c it takes awhile to heat up the water. I've never had this problem in any other home where I've had a tank water heater, so I would like to install a small electrical tank water heater so that is plugged into the water outlet of my Navien. What size (and brand perhaps?) tank do you recommend for the 120V tank water heater given that it takes 30-60 seconds for the Navien to produce hot water? What specifications should I be looking for since I want it to be able to handle large inward flow of hot water from my Navien? [Once the Navien gets hot, it stays hot, as long as I'm calling for sufficient water pressure]

I've discussed this issue with plumbers, and they are skeptical this will help. My home is finished, so installing a recirculation pump, would likely be difficult. I figure if the small tank in my utility room doesn't help, I'll install a small water heater below my bathroom sink.

The Navien is also causing problems for my appliances like my dishwasher and washing machine, since when they draw hot water, it ends up being cold. [e.g. I have issues with the dishwasher detergent leaving residue below the compartment.]

I'd appreciate your advice!

thanks,
nurit



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i would toy around with putting a small water heater feeding the navien.
even a small tank will give you hot water for enough time until the navien kicks in.
you are saying the navien works ok in the summertime. so temper the winter water so it is warmer entering the navien. in the summer you can shut the power to the small electric tank to save electricity.

Hi Packy,

thanks for your reply. I was thinking of having the Navien feed the small electrical tank b/c then the less efficient tank would have to do less work. What do you think? also, what size tank do you suggest?

in the summer, washing my hands with cool water wasn't a big deal, but in the winter, washing my hands with ice cold water is unpleasant. however, even in the summer, I was having issues with detergent residue on my dishwasher door.

thanks
nurit

Update

I misunderstood the issue



Edited 1 times.

at 30-60 seconds to get hot water from the existing system i would do NOTHING


waiting 30-60 versus the cost of having a tank and waiting 10-20 seconds to purge the line of cold ANYWAY


your existing system is just fine

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



Edited 1 times.

i would think a 6 gallon tank tank set at 130 deg would help alot.

so... cold water into the small tank.

130 deg water out of tank into the navien

by the time the 6 gallon tank starts to run cold the navien is up to speed.

so much depends on how often you use hot water. the small tank would take a short while to heat up again.

realize this.. i'm not an engineer. i'm just a plumber taking a guess at how i would treat this problem

merry christmas..

the issue is the PURGING of the static cold water in the piping between the Navien and the sink


while the boiler is more efficient, the DW will heat the water internally


an 'under the sink' heater will supply enough 'insta hot' for hand washing


NOT a recommendation, merely an example:

Eccotemp EM-2.5 Electric 2.5 Gallon Mini Tank Water Heater



I WOULD LEAVE THE PERFECTLY WORKING SYSTEM ALONE


(next time install a recirc line)

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

bern, i understood the issue to be that the navien took more time to heat the water than the OP liked.

you know it could be that the coil just needs a cleaning because it isn't picking up the heat fast enough ??

noooooo

the issue is the cold water in the piping along the distance FROM the Navien

the Navien heats in mere seconds, but, just as if it were a tank full of hot water, the cold water already in the lines has to be 'purged'

the fact that it is acceptable in the summer .............................

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Both the cold water in the line and the Navien taking awhile to heat up the water are issues. It's not one or the other. There is a bathroom right next to my utility closet, and I used a timer to see how long it took to get warm/hot water to the bathroom first thing in the morning: over 30 seconds. It takes approximately 1 minute in my master bathroom where I usually wash my hands.

And that 1 minute is really a problem for me since I severely burned my leg 3 months ago, and I experience pain and pins-and-needles when standing.

I'd like to see how well a small electrical tank water heater plugged into the hot water outlet of my Navien works. I'm hoping packy can clarify why he is suggesting installing the tank before the Navien. I have a hydro-air heating system, so it seems inefficient to have the tank before the Navien.

The long-term and expensive solution would be installing a new combi-boiler with a small tank and a compatible recirculation valve. I know that combi-boilers with small tanks and combi-boilers with recirculation valves (like NaviCirc) exist, but not sure if there is a system with both.

thanks for all of your help! I appreciate it.



Edited 2 times.

i'm gonna back away from my original theory and shift my pile of chips over to ' something is wrong with the navien'.
shouldn't take 30 + seconds to get hot water to a faucet next to the heater.