Insta-Hot and Voltage Drop Solution

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mgookin said:
I just made a little calculator in Excel for kW vs. temp rise vs. GPM.

That unit at 100% efficiency (which they all are close to when they're properly working) will raise 1 GPM by 24 degrees in 1 minute. A shower head is around 2 GPM, but they can vary greatly.

If the person is not getting enough hot water, we know they're running 100% hot water, so they may indeed be putting a flow rate of 2 GPM on it which means it's only going to raise the water temperature by 12 degrees.

How satisfactory is the water coming out the one that works? Is it good and hot?
Do both showers have the same head? Go buy a 0.4 GPM head and problem solved. It would raise that by 62 degrees!
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The two showers are identical the one with the smaller conductors has water that is lukewarm and people have complained about it being too cold to use. The other is warm enough to the point where no one has complained. I haven't had a chance to get back there and test them myself with a thermometer, if they were both outputing the same lukewarm water then they would blame whoever spec'd that small HWH.
 
Another point to check: according to the manufacturer website, these water heaters have some sort of microprocessor control for output temperature.

If we assume that the heating element is in fact sufficient for the load (low enough flow, warm enough input, etc.) then perhaps the supply voltage drop is causing problems with the _controller_.

-Jon
 
infinity said:
No the water is a one pipe cold water supply system and it tees off to the HWH adjacent to the shower.
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Do both of them have same incoming water temp? If one has a long run of supply line it may be "preconditioned" in that run and needs less heating at the outlet, especially if no other outlets are on the run.
 
If the supply is a copper pipe he could smash it with a hammer to reduce the flow!
 
winnie said:
If we assume that the heating element is in fact sufficient for the load (low enough flow, warm enough input, etc.) then perhaps the supply voltage drop is causing problems with the _controller_.

-Jon
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Considering the supply voltage at the heater while under load has not been checked I still think we are not in a position to say voltage drop is the problem.
 
ptonsparky said:
We know what the label says it is supposed to be, but the replacement element someone installed at a forgotten time may be a 240V.
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I thought this was new install. Am I wrong?

And I don't think you can replace an element in an insta-hot.

They do have problems with scale on the heat exchanger though, if you have hard water.
 
mgookin said:
I thought this was new install. Am I wrong?

And I don't think you can replace an element in an insta-hot.

They do have problems with scale on the heat exchanger though, if you have hard water.
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Yes, new building, new showers and new HWH's.
 
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