Lochinvar WH55 Lockout in DHW- Outlet Temperature Diff-

ced48

I am getting a lockout in the domestic hot water run. Error message of "outlet temperature difference" sensor 1- 123 degrees, sensor 2-143 degrees. System runs fine in space heating mode, so sensor error, or heat exchanger issues seem to be ruled out. After resetting, I ran DHW, and delta t continued to drop thru the run, untill lockock. Any suggestions would be appreciated.

Zman

The boiler thinks you have a flow issue based what it is reading for in vs out temps. You either have an actual flow issue or a sensor issue.

ced48

Too much flow, or too little? Numbers say too much, unless I am missing something?

ced48

Well, after talking to Lochinvar, this lockout is for a temperature difference between two different sensing units in the same outlet sensor reading the same temps to assure an accurate reading. It does not give an inlet reading as I assumed. So, most likely a bad sensor. If one sensor, say A1, reads differently than sensor A2, by x degrees, the control board shuts down the boiler.

Eastman

I think you are the third temp difference error I've seen on heating help in the past few weeks. Bad sensor.

ced48

Yes, bad sensor-$26 for the part, 15 minutes to swap out, back up and running-

NY_Rob

^ Seeing that this particular sensor has proven problematic, if I was the homeowner... for $26 I would keep a spare sensor onhand.

Le John

this has me thinking. Does anyone know if the Lochinvar Noble use the same sensor?

DZoro

@Le John Yes the Noble does use the same one, have changed a few of them out...…
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Le John

@DZoro thanks for info.

Adolfo2

NY_Rob said:

^ Seeing that this particular sensor has proven problematic, if I was the homeowner... for $26 I would keep a spare sensor onhand.

CED48 should try to eventually stock a replacement sensor (TSD91A2) with a date code of 20-18 (or later) as this is the break-in date for when Tasseron made the improvement.

ced48

After I picked up the part, I was kicking myself for not buying more than one. I will get a fresh one, as soon as I can find one-Thanks for that information.

On a side note, I have never had a Lochinvar tech guy so on top of a problem. Obviously they get a lot of calls on this lockout. It would have been nice if he had told me about the replacement part upgrade-

Adolfo2

ced48 said:

After I picked up the part, I was kicking myself for not buying more than one. I will get a fresh one, as soon as I can find one-Thanks for that information.

On a side note, I have never had a Lochinvar tech guy so on top of a problem. Obviously they get a lot of calls on this lockout. It would have been nice if he had told me about the replacement part upgrade-

I phoned Lochinvar Parts Department & Tech Support and they both denied any premature failure issue(s) or re-design of the Tasseron TSD91A2 sensor. This was after speaking with TasseronUSA who immediately recognized the part number as belonging to Lochinvar (must be a custom #) and who were very open about the reliability issue & re-design efforts.

Steve Ebels_3

For what it's worth. The Knight boilers will also shut down if delta T becomes to wide. I think it's like 45* differential or something around there.

We had that issue with a couple under the following circumstance.
Boiler on and firing. Water temp sitting at setpoint.
A zone with a lot of cold water opens up and the boiler temp drops rapidly.
Once the Delta T got past that 40-45* mark it would lock out and show a fault code.

Speaking with my area service rep about it and he said it is designed that way because too much delta T causes stress on the HX they do not want to see. Especially in low flow applications.

This is also the reason they will not use the Triangle tube type HX for domestic hot water type boilers such as the Armor series.

Eastman

@Steve Ebels_3
How did you solve that problem?

3zht

bump...how did this problem with the delta get solved?