Dead shorts....

kcopp

I have run across two systems that are reading dead shorts in the sensor wires. Beyond the obvious that there is a break in the wire is it possible that the thermistor is the problem and that would give a dead short reading?
ty,kcopp

hot_rod

under the hood, this is what is inside the tip of those sensors. I suppose if someone put 120V to one it could short it out, and read as a dead short.

A nail thru the wire somewhere? Or a bad splice where two wires touch.

If the control reads 888.8 you have an open circuit
88.8 is a short in the wire.

If they are PT1000 sensors it will rad 1000 ohms at 32F. Put the tip in a glass of ice.

At 212F it will read 1385, put the tip in a couple of boiling water.

This way you check both ends of the temperature range.

Possibly from extreme over-heating on an vac tube array it could damage the sensor tip?

hot_rod

sensor exposed

kcopp

Thanks Hot rod.
Theses are two different units.
1 is a Stecca control w/ an 8 Buderus flat plate array.
The other a Puritan Controller on a Evac tube array...

Nails are possible but not probable. They worked fine for a few years then just stopped.

I need to follow some wires around...

hot_rod

check for any sensor wire splices outdoors. I've seen the wire melt against the copper tube near the collector. That would show a short. Or if they get wet inside a taped splice.

If you must splice outside use the automotive "weatherproof" trailer wiring splices. Or the small button type, telcom splice that the phone company uses.

ratio

You're going to have to unhook the sensor to check it and the wiring for faults separately.

The manual should have a table to check calibration - unless you are certain of the type of sensor use the table, as there are many different types, some quite (but not interchangeably) similar.

Sensors are critical for correct operation, if there's any doubt about it, replace it. (Check the calibration of the new one too...)

SWEI

hot rod said:

If you must splice outside use the automotive "weatherproof" trailer wiring splices. Or the small button type, telcom splice that the phone company uses.

The solder-filled heatshrink splices also work well.

margsuarez

the red insulation appears damaged in the picture. is it?

hot_rod

margsuarez said:

the red insulation appears damaged in the picture. is it?

That is a sensor tip I cut open to show folks what is inside.

kcopp

I found the issue.
It was the splice outside from the sensor wire to the 18 ga wire that went down stairs. I re-did the splice and sealed it up better.
ty,kcopp