Lochinvar Noble "COMBI SENSOR FAULT"

josephny

I have a Lochinvar Noble combi boiler installed about 5 years ago by a professional who has since passed away.

The unit displays COMBI SENSOR FAULT.

On the main interior manifold I see the following sensors: Outlet, Out Temp, Flow, In Temp.

I see from the service manual that the Combi Sensor is connected to CN4-5 and CN4-6, and I think (not sure) that those go to the Out Temp sensor.

But, disconnecting each sensor one by one results in the display showing a different error message, like, "OUTLET SENSOR FAULT" or the in and out temps disappearing.

And, when DHW is running, the little light on the Flow sensor lights up.

I removed the flow switch and cleaned the filter, but that didn't help.

Also, I don't know the password. Not sure if that is relevant. Maybe need to manually reset the COMBI SENSOR FAULT error?

Can anyone steer me on this?

Thank you!

Zman

I think you are having an issue with the combi sensor shown on page 96. https://lochinvar.com/lit/417276100275091_2000533998 Rev Y_Noble Boiler_Combi_I-S (35690).pdf My guess would be a bad sensor or loose connection.

Do you remember the last 4 digits Jenny's phone number from the Tommy Tutone hit? Lochinvar does have a sense of humor....

josephny

Zman said:

I think you are having an issue with the combi sensor shown on page 96. https://lochinvar.com/lit/417276100275091_2000533998 Rev Y_Noble Boiler_Combi_I-S (35690).pdf My guess would be a bad sensor or loose connection.

Do you remember the last 4 digits Jenny's phone number from the Tommy Tutone hit? Lochinvar does have a sense of humor....

I don't know physically which sensor that it?

Red, yellow, green or purple (or none of the above) in the pic below?

LOL -- I am indeed old enough to know (and unable to forget) Jenny's # -- thank you!

josephny

From the schematics showing that the diverter valve has 3 wires at positions 1, 2 and 7 on the connector I deduced where positions 5 and 6 are, as the schematic shows 5 & 6 are the combi sensor.

They are the yellow/yellow-red wires going to the sensor circled in yellow above.

When I pull the wires off the sensor the display stops showing the out temp.

But nothing makes the COMBI SENSOR FAULT go away.

Oh, and Jenny came through like a champ.

Zman

The sensor wired to those terminals is the one you are looking for. It is probably sending the error if it is getting an incorrect reading or no reading at all.
I would recommend Ohming the sensor, replacing the sensor, or calling tech support (tell them you are a contractor, they get plenty of calls from actual contractors that know less than you .)

josephny

Took your advice and measured the resistance across the sensor.

Varied from 60 to 190 ohms. Did it 4 times to make sure.

According to the manual (below), I've (well, you've) found the problem.

I've ID'd the part as Lochinvar 100208560

https://www.supplyhouse.com/Lochinvar-100208560-Sensor-Inlet-Dhw

WIll order, replace and report back.

Thank you!

josephny

UPDATE: Got sensor from supplyhouse, installed it, and everything works great.

Thank you all so much.

It's hard to explain to people not interested in how things work how great it is to be constantly learning -- and this forum makes that possible.