Veissman not making hot water in normal mode

John Umina

My Veissman trimatik MC boiler started having trouble producing hot water in the normal mode. It works in override. Test #4 is failing. I assume it is the hot water temp sensor although, I don't understand the tie in to test #4 (boiler shutoff) and a resistance check of the sensor, seems within limits.

heatboy

Questions.

John,

Is this a new installation? Meaning first heating season. Are you using the Viessmann indirect water heater with your Viessmann boiler? I hope you are. Trying to match Viessmann boiler that run on boiler reset to anything else but a Viessmann indirect is problematic at best, even with Viessmann controls.

When in override all of the pumps run, the burner fires to limit and the mixing valve closes. Test #4 is burner and pumps off. So, unless they are running in test 4, that is not the issue.

When you checked the tank sensor, what was your resistance? The manual says “Using an ohmmeter, measure the resistance between the two connector pins on sensor plug #3.” That is incorrect. Measure plug #5 for the sensor readings. Obvious, but incorrect, nonetheless.

Answer these questions and maybe we can help.


Warm Regards,

hb

"Expert in Silent Warmth"™

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"

John Umina

No hot water

Thank you for the quick response. This is not a new installation, about 8 years old. It is a Superstore hot water tank. The sensor read around 600 ohms. I have been experimenting with puttting some additional resistance across it. So far an 8.2 K seem to bring it down enough to get reasonable heated water. This seems to indicate that it is the sensor. Do you know where I can get a replacement sensor?

heatboy

Swap the .............

boiler and tank sensor. They are the same except for the lead length and see if that makes a difference. You may have to extend the sensor lead depending where the indirect is located. Super Stor indirects tanks have a nasty habit of having the fins on the heat exchanger get full of debris and slowing heat transfer. Does the tank just run out of hot water or is cool all of the time? Set the dial on the control to 60° C (140°F) to see if it helps. If it works fine on over ride, a dirty HX may be your problem, especially when running boiler reset. What boiler do you have? Getting a sensor should be easy, if needed. I may even have one in my Viessmann stash .

Warm Regards,

hb

"Expert in Silent Warmth"™

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"