ABSOLUTE Mystery Electric Tankless Problem : /

[hoosiermd]

Let me start by saying hello, and thank you in advance for all who read and attempt to offer advice.

We have a Richmond 18kW electric tankless. It is only around 18 months old, and it's been around 12 months since I last successfully flushed it. Now, it won't even flush. When running, the water begins heating, then it goes cold BUT the unit stays on...it then gets hot again...then cold, confirmed by holding the copper hot water exit line. It oscillates like thus until it throws an error (E4) which I believe is an overheat error. More oddly, the longer the water has been on (and before it errors), water flow at the fixture slows to a trickle. If power to the hot water heater is turned off (so only cold water flows through), it never slows to a trickle.

I purchased Rectorseal Calci Free (sulfamic acid) and attempted to flush it, but the same issue occurs. The flow starts high but then slows to a trickle. I disconnected the pump and tested it alone in a loop and got good flow. I reconnected the pump using the same hoses to the water heater using cold tap water instead of the acid solution, and it flowed through the water heater fairly well, for several minutes. I immediately put it back into the acid solution and within 30 seconds it slowed down to a trickle. I then put ice into the acid solution (where I know it works better warm but I wanted to take the temperature variable out), and it still slowed to a trickle. The filter screen on the cold in is clean.

Absolutely any advice is welcomed.

 

[Twowaxhack]

Call manufacturer tech support.

 

[hoosiermd]

Call manufacturer tech support.

I had spoken with them, and their first step for ME to disassemble the unit and begin testing on the heating elements...some of the steps with power ON (!), which I'm hesitant to do with live 220V connections. I'm not an electrician and don't know how to do these steps safely. The rep even hesitated when I asked if this was safe.

* If I purchased a set of electricians 1000V lineman gloves to perform the tests, is that adequate protection? I'm comfortable with a multimeter, but have never worked with these voltages and am being cautious.

* * I'm also unsure how even if the element(s) failed, how that would explain the flow rate issues even when the unit is powered off. I figure it must be some oddity of a physical obstruction, potentially exacerbated by thermal expansion? : /

 

[Twowaxhack]

Call a professional.

 

[hoosiermd]

Call a professional.

It would potentially be cheaper to just buy a new water heater, which is why I'm posting in a plumbing forum...for information about plumbing, even if for nothing other than a rational explanation that fits the data, even if I can't fix it myself.

 

[Aggie83]

Turn the power off and run the hot water to see if the water heater is clogged. The water has to flow for it to heat. I had a problem with one clogged with sediment.

 

[Twowaxhack]

It would potentially be cheaper to just buy a new water heater, which is why I'm posting in a plumbing forum...for information about plumbing, even if for nothing other than a rational explanation that fits the data, even if I can't fix it myself.

Buy and install a new one then.

. Just don’t get yourself killed at Christmas trying to use a multimeter. I don’t want to be a part of that…

 

[havasu]

Are you sure the error code was E4? I just Googled that code and searched the Richmond site. The error codes were 2 digits?
Honestly, this is exactly why I ripped my tankless water heater from my house and installed a never failing tanked water heater.

Unless a plumber has specific knowledge of what's it is doing, what codes it's throwing, and internal knowledge of this specific TWH, you'll end up paying big bucks to repair it.

Your unit does have a 5 year warranty so I'd be calling that damn company and either have them help you, or refer you to a local plumber who is certified to work on their units.

Remember, the squeaky wheel gets the grease.