What is with "maximum copel" thermocouples

archibald tuttle

Just ordering in additional winter stock and I noticed some residios that were labeled "maximum copel". are there really ones that are minimum copel?

I guess maybe you can save money on precious metals by having them put out the minimum needed voltage/amperage/signal ? But when one says maximum i'm not sure what that really connotes and how to compare options.

of course I'd pay more for one that is likely to last longer and give more trouble free operation but I don't need to pay double for name brand. is there a specification that gives an indication in this regard?

Teemok

Slaps the hood. "These babies got maximum copel in them. They'll take care a ya family for years"

tim smith

We almost sleepy use base k16bt-36. Been air fave for decades. They way outlive and produce better mv than the hw q340. Only issue is the don't fit some of the mini pilots like on gas water heaters. But fit most if not all older standing pilot boilers and furnaces.

Steamhead

@tim smith , try the Baso K19 series. They'll fit almost anything. R.E. Michel carries them, though your branch may have to order them in.

archibald tuttle

@tim smith my bad to ask and run. just put my high kopel unit in stock the other day and it reminded me to return to this question.

i'm seeing the labeling for e.g. the Baso alternative recommended as 25-35 mv

but as best I can tell if you use an inline tester such as UEI atha1 then you will read less mv under load (i've seen some testing videos that talk about the low teens. but maybe hi kopel unit falls off less so it actually provides more milliamps? and as it ages, if it degrades it is still able to maintain requiste volts to the coil?

or . . . ?

brian

PS-the old thermopiles are labeled in the 250 to 750 millivolt range. i guess the coils on the gas valves are a little different. these have the two wire connections vs. coaxial.

maybe the power pile provides more capacity for systems in which the entire circuit out and back to the thermostat is not on the other side of a 24V relay. in the old days these were the steam systems that would run even when there was blackout!

Doug_7

Check your Copel here - no precious metals involved. See attached Honeywell article on Thermocouple Quality. Higher quality = longer life.

tim smith

you will always read less under load as the magnet is using some of the energy produced. Other losses of course are main coil, switches, limits, wires etc etc.

archibald tuttle

@Doug_7
well, these days copper and nickle are getting to be precious metals but I guess that is semantics and they didn't meet the traditional definition until all the obstruction of mining in our country that thinks everything comes from somewhere else these days . . . but i digress. thanks for the honeywell explanation paper. so it speaks of thicker copel element so I presume when a manufacturer touts "maximum copel" that is to which they refer.

@tim smith
get that I will read less under load. although they seem to sell by nameplate voltage and at least some testing approaches look at no load voltage. I presume the relation between no load and load voltage is dependent both on the no load voltage but also on the current (milliamps) actually generated to maintain that voltage under load? I assume there is a minimum voltage for operation and have seen a few informal offerings on that in the the mid teens.

I'll be the first to concede. if the pilot doesn't hold i put another thermocouple. when i have had one seem to go quickly then I get about testing for voltage but not typically. honeywell is recommending to do that on any visit without a voltage test for condition which seems maybe a little excessive. maybe on installs regularly serviced you could date the last replacement (thank god for sharpies). and then gotta think about logical life, as in best practice replace smoke alarm after 10 years even if it still tests alright.

also, in accordance with the honeywell write up, it might favor adjusting pilots down and insuring proper placement of thermocouple tip relative to flame. but it would be nice if they had test points and gave you new and degraded targets so you could quickly monitor. by the time you unscrew the lead to put in the tester you might as well replace it. not really a lot of resources involved one way or another but I just like to be able to monitor stuff. I suppose I could buy a gross of the adapters and just leave them in place. it is one extra connection which I suppose itself puts a little bit more resistance in the circuit which is why built in test taps would be nice. although with pilots headed to the dustbin of history in and of themselves I guess this is a shrinkingly small market for innovation.

tim smith

We have thermocouples that are in for 10+ years. We clean pilot every time we service and clean thermocouple. When we start seeing pitting on end of thermocouple we replace. I know you can replace them every time but we see no need. Love Johnson K16 thermocouples, they have been the workhorse for us. Along with the 72" heavy duties for the old commercial dual and single pilot cast iron burner boilers. Pretty amazing how well they hold up.