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Old 11-12-2014, 05:29 PM   #1
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Tankless water heaters

I have a new 2015 Bay Hill 5th wheel, that came with a tankless water heater. I first thought that this is a great idea for RVs, as I have friends that have them in their homes, and love them. Then reality set in. After several attempts the operation was hit or miss. Sometimes hot water came quickly, but most of the time nothing, with the system constantly going to the "fault" mode. I did figure out that all the water lines had to be free of any air, but the operation was still sporadic. I did discover, mostly by accident, that if I opened more then one hot water valve; like the kitchen sink and bathroom faucet I began having more luck. This lead me to believe that I needed more flow, so I removed the pressure relief device, and bango! I had all the hot water I could use, and 15 mins. later I was still in hot water!!!!! Has anyone else had this same experience. The dealer was no help, and honestly didn't know how these systems worked. The only issue I have is with the toilet; the valve bangs a little harder now that the pressure relief device is gone.
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Old 11-12-2014, 05:40 PM   #2
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Your tankless heater has a few major parts.
The heat exchanger, Short of a leak not much can go wrong with it.
The Flow Sensor, #1 complaint on them is the flow sensor will not activate heater if there is not enough flow.. NOT YOUR PROBLME.

Finally we have he burner and control.

And this is where the FAULT light lives.. The Fault light means it sensed flow, attempted to light but FAILED to detect the flame.

This does not mean it did not light.. Only that it failed to detect it.

Possible issues: Dirty burner oriface
Points set wrong (ignition points) likely too wide
Bad or dirty flame sensor (May be one of the points)
Bad or dirty connection ignition or flame sense wire.
Improper burner adjustment (Not hot enough)
Bad control board.

I think that about covers it but... there is always the ever popular "OTHER that I missed"

Suggest you have someone turn on the water (After resetting it if in fault) while you stand near it..

When water flows you should hear the SNAP SNAP of the direct spark ignighter, YOu may hear the CLUNK of the gas valve (solenoid) and you may hear the burner light.. OR NOT

Report what you hear.

Note the only tools needed for this test are a partner to turn on the water and your ears/brain, NO wrenches, no screwdrivers, no meters, no "Hardware" of any kind other than the water heater itself.
Home is where I park it!
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Old 11-12-2014, 05:49 PM   #3
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I would look at removing flow restrictors and put a pressure regulator back on it. High pressure will damage your system. The most common problem I have found is construction debris in the lines plugging up the flow restrictors. There will be a restriction at the shower head and in the sink aerators these have very small holes and plug very easy. Use a quart jug and see what your flow is it should take between 12 and 15 sec to fill a quart jug from the hot side only if it takes longer your flow is to low for it to work well. What happens in low flow and in hot weather is people turn the temp setting way up and it will trip the limit switch so keep your temp control as low as you can that still gives you hot water. Turning it up will not increase output temp it will increase burner temp. The output temp is controlled by the mixing valve. Another issue I have seen is a few companies still plumb them with water heater bypass kits make sure the by pass is closed if it is partly open it will mix and also cause the heater to act up.
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Old 11-12-2014, 06:15 PM   #4
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"Your tankless heater has a few major parts.
The heat exchanger, Short of a leak not much can go wrong with it.
The Flow Sensor, #1 complaint on them is the flow sensor will not activate heater if there is not enough flow.. NOT YOUR PROBLME."

Read his problem and answer again. It sounds like he has low flow faucets that are not letting enough water flow to meet the minimum requirement for the heater. When he removed the flow restrictor regulator or opened two faucets it the system worked. From what I have seen looking at faucet aerators at Home Depot they are really restricting the flow on many of the newer faucets irrationally low amounts. It really sounds like an dumb engineer problem. Faucets with low flow that is marginal for the minimum flow for the heater. I'd see if I could get less restrictive aerators for his faucets.
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Old 11-13-2014, 09:13 AM   #5
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Tankless water heaters

Thanks to all for the advise. I never gave the faucet flow/aerators a thought, figuring that would have been figured into the requirements for the heater. My bad!! I am told that this heater is a second generation, and a mix of components from two major manufacturers, but still carries the Atwood name. As an example, older models supposedly had a mix valve under the bathroom sink. This valve was a major issue according to some web reviews. Also, original heater was not fitted with a boiler drain plug, and was prone to freezing. The burner ignites immediately, and the flame is strong and steady, as long as the flow is there. Turn off one faucet, and the burner shuts down and "fault" light displays.
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