New tankless water heater

[srqguy]

Moved into a newly built house with a tankless heater. The heater is only about 10ft from master bath, and maybe 50 ft from kitchen. It takes several minutes to get water to kitchen and 2-3 mins to get hit water in master bath sink. But, in both cases once i get hot water, i lose it. Via the remite controller, i can see that the heater shuts off once i mix in a little cold water. Water stays hot though in shower.

Builder plans to replace the circuit board. I think that might nit be the problem. I notice the specs on the unit sa that at flow rate of 0.5 gpm the heater will not turn on, and on e on will go off if kess than 0.4 gpm. So I am thinking it is actually the plumbing itself that may be the problem, not the heater.

Possible? Likely?
But since house is already built & being lived in is there anything that can be done?

thnks

 

[srqguy]

Moved into a newly built house with a tankless heater. The heater is only about 10ft from master bath, and maybe 50 ft from kitchen. It takes several minutes to get water to kitchen and 2-3 mins to get hit water in master bath sink. But, in both cases once i get hot water, i lose it. Via the remite controller, i can see that the heater shuts off once i mix in a little cold water. Water stays hot though in shower.

Builder plans to replace the circuit board. I think that might nit be the problem. I notice the specs on the unit sa that at flow rate of 0.5 gpm the heater will not turn on, and on e on will go off if kess than 0.4 gpm. So I am thinking it is actually the plumbing itself that may be the problem, not the heater.

Possible? Likely?
But since house is already built & being lived in is there anything that can be done?

thnks

moved to tankless heater forum

 

[Sponsor]

 

[Jadnashua]

Tankless systems have a minimum flow requirement. If you're trying to get warm water, there may not be enough flow to turn it on. Kitchen and vanity faucets are flow restricted, so to get the heater to turn on, your valve would typically need to be moderately warm. Your shower is also flow restricted, but you may be running mostly hot, with only some cold mixed in, and it's enough to keep the thing on.

So, what you're seeing may be just one of the gotchas with a tankless system. It's possible that the flow sensor isn't working properly. It's also possible that the heat exchanger in the unit needs to be de-limed. The harder the water, the more often that must be done. Recommendation is often to perform that task annually, taking away most of the savings you might get over a tank.

The other issue, and this would be true for any hot water distribution, would be how big the pipes are, and how long. It can take awhile to purge the ambient temperature water in the pipes out before you get hot at the end, especially if their length is long.

You might find it gets hot quicker in the winter, as to get warm, you'd need more hot in the mix because the incoming cold will be lower in temperature. It will also limit how hot the water can get as it passes through the heat exchanger of the tankless system.