Temp Fluctuations
 

I am having some trouble with my Denver EF200 furnace. It has a Bartlett RTC-1000 control. The temperature readout drops 15 deg. F when the power to the elements comes on. It is very consistent.
I checked to see if the thermocouple extension wire was running close to a coil or high power line, but it is not.
Any ideas?

Thanks!

Is this a new behavior? Have you updated the firmware recently? Can you update it? I see this when I start a ramp down on my Bartlett genesis controller.

Is this a actual temp reduction, or just on the readout? I've had issues before with old elements at high temps sending out signal "interference" on GB sending units.

I was having problems with the control not reading the thermocouple correctly. I was getting thermocouple errors so I sent the control back to Bartlett and they repaired it. (it was under warranty. Only 18 months old) While it was there they tested it, and returned it (2 weeks ago). While they had it, they deleted my programs and settings. I don't know where all of the settings were because Denver set them.
Anyway I have been watching it closely because of the previous problems so I do not know if this is a new "bonus" feature or if it has been there all of the time.
I'm thinking shielded thermocouple extension wire perhaps?

If there's power to the coil and it's "sensing" a temp drop that's not actually occurring, then it could be interference that shielding the wire could fix. If the coil is losing power and there's an actual drop then that won't do anything, then something is probably still wrong with the controller, but that could just possibly be changing a parameter that determines how fast it reacts to a temperature drop.

The readout drops 15 deg. almost instantly when the power comes on. Then it rises instantly when the power shuts off. This can't be actual temperature. It has to be misreading the thermocouple.

Does anybody have a source for shielded thermocouple extension wire?

The stuff wet dog uses is supposed to be shielded. You using type R? Alternatively you can try flexible conduit.

Yes it is an R Type.
It is in flex up to the control box, but it is not in flex inside the box. I think that is where it is picking up the noise as it passes by the mercury switches.

That'd do it. Like I said, wet dog has some type r shielded wire with a ground. Don't know where they get it, but they might sell you some. Omega looks like they have some, but they want to sell you the whole roll.

From what I'm hearing of the situation -- a short run inside the control panel is near some electromagnetic components -- I imagine that it would be a lot cheaper and easier to just slip shielding over the wire there, instead of replacing the whole run.

https://www.mcmaster.com/wire-shield...able-sleeving/

This. Hadn't seen that stuff before. Might have to try it on the kiln that's giving me issues.

The normal conduit would have probably been to stiff for a tight box.

You are correct. Short run inside control box
I like that idea! I've never seen that!
Hmm. I'm going to try that first.
I like simple solutions to complex problems!

As a quick diagnostic test, you could wrap tinfoil around the wires inside the controller -IF- you shut of the power first and can be certain the tinfoil would be nowhere near any source of live power (i.e. screw contacts for 120/220 v).

If the deviation is less with the tinfoil, then you would have some evidence that a proper shield on those wires would help/solve the problem. If there's no effect at all, then it might be something else.

I purchased some extension wire from Wet Dog. It was actually less expensive than the copper shielding because Wet Dog did not have a minimum purchase. It's nice because it is 20ga shielded instead of 22ga unshielded which is what came with the furnace. Can't go wrong!
I will let you know if the problem goes away.

The 20 ga thermocouple wire seems to have done the trick. I don't know if it was because of the heavier gage or something else, but the temp holds when the elements turn on and off now.
Thanks for the help!

I always loved Steve Smyers description of studio problems. He said "Then every thing breaks. You do this, you do that, you try everything for weeks and then the problem goes away by itself."

True dat.

My philosophy:
What goes away by itself comes back by itself.

This rarely lets me down.

true dat, except for virginity.

This should be included in the dictionary definition of "Transient Electrical Problems" as a warning.