65+°C connections

[Zdb]

Looking for some advice regarding some connections on a heating contactor.

I picked up some readings using a thermal camera which I thought were a tad high. I remade the crimps as these were the "hot spots" however this has had no effect on the temperature.

The current draw is approximately 42 amps as its a radiant heating circuit.

Are these temperatures normal for this scenario? I haven't done a great deal of thermal imaging but when I do I set the camera to flag temperatures above 60 degrees.

See the attached image below:

 

[Lucien Nunes]

What's the current rating (Ith) of the contactor? and what sort of ambient temp was it in? If it is working near its limit I would say that is not abnormal unless in a low ambient, otherwise it might be suggestive of high contact resistance.

Care is needed to identify the specific source of the heat, which might not be the terminations even though the hotspots appear on the cables. The contactor contacts produce heat which is dissipated partly by conduction through the terminals and out along the cables. The cable insulation has high emissivity and tends to read high, compared to (e.g.) the terminal screws, which might be as hot but are of lower emissivity.

 

[pc1966]

Out of curiosity what camera was used?

I can't justify getting one really, but it is high on my "cool toys" list of things to get if any job came up where I could justify it!

 

[Zdb]

What's the current rating (Ith) of the contactor? and what sort of ambient temp was it in? If it is working near its limit I would say that is not abnormal unless in a low ambient, otherwise it might be suggestive of high contact resistance.

Care is needed to identify the specific source of the heat, which might not be the terminations even though the hotspots appear on the cables. The contactor contacts produce heat which is dissipated partly by conduction through the terminals and out along the cables. The cable insulation has high emissivity and tends to read high, compared to (e.g.) the terminal screws, which might be as hot but are of lower emissivity.

The Ith is 50A and the ambient temperature was 17 degrees.

Emissivity was set at 0.95. Is this correct for this type of use?

Yes i did think that the terminal temperature could be higher as the "hot spots" were on metal crimps with insulation tape wrapped around.

 

[Zdb]

Out of curiosity what camera was used?

I can't justify getting one really, but it is high on my "cool toys" list of things to get if any job came up where I could justify it!

I use a Cat S60 with an integrated Flir thermal camera with a resolution of 80x60.

Although only basic in terms of a thermal camera its a great tool to have. I'm looking to upgrade soon to the Cat S62 Pro which has an upgraded thermal sensor.

The biggest advantage of having it integrated into a phone is the operating system and apps you can use to tweak the images. You can also send images via Bluetooth, email etc rather than having to connect via USB.

Here are some of the Cat/Flir specs compared to some of Flir's stand alone devices:

 

[Darkwood]

As Lucien has pointed out, this could be related to the contactor itself that is warming up the terminations, having said that though my younger yrs of learning I realised very quickly that there is a lot more to making a crimp termination than simply picking one to fit the cable size and squeezing it with a £25 crimper, I had a reoccurring issue of termination burning out even after upsizing contactor feeding a bank of heating elements.
The resolve was to ditch budget crimps and crimpers, I do high temp and current equipment as part of my machine service and although my job sees some extremes of temp' I quickly learnt the value of using appropriate crimps and crimpers.
My current crimper is about £650 retail and I use thermal rated crimps that between them give a perfect crimp with no trapped air or deformity that is not by design, this of course is for the high temp' terminations which these should not require on the contactor but it highlights the need to pay a small fortune to ensure your crimper does the intended job for the job and that the crimps themselves are not budget.

You can do an experiment to rule out the crimp here, remove the lug, bare back the cable twice the termination length, twist it as tight as you can then fold the length in half and clamp in the contactor, it the temp issue is resolved then it is likely it is a cheap crimp and/or crimper in play, at £25 quid we are very budget there and you may need to invest at least £100 and use recommended lugs for the crimper to avoid this. Cheap crimpers often trap small pockets of air inside the crimp and if the temp' rises it can expand the air enough in these pockets to force the crimp to open slightly, this may not be visually noticeable but it will definitely show its presence on heavier loads.

PS - I am guessing the crimps are to blame as we see no hot spots on the contactor itself at any part.

 

[pc1966]

My current crimper is about £650 retail and I use thermal rated crimps that between them give a perfect crimp with no trapped air or deformity that is not by design

Out of curiosity, what tool and make of crimps do you use?

 

[Lucien Nunes]

I had not realised there were crimps there. Then yes I agree with DW there is a significant chance that they are at least partly to blame.

 

[Darkwood]

@pc1966
I'll have to look when I get home, I got it all in one box as there is about 2k in bits like cable, heatshrink, crimps etc... bag of 10 lug crimps m5 can cost more than most splash out on a crimper.

 

[Darkwood]

@Lucien Nunes
I am slightly guessing but cable 3 and 4 seem to thicken out a little going into the terminal... I may be wrong as its not that clear.

 

[Marvo]

With a temperature of 65C and given the high inaccuracies of thermal images in general I wouldn't stress too much. I'd just replace the crimped lugs, check the torque of the terminal screws on the contactor and if it's the type of contactor where you can see the actual switch contacts I'd visually check their condition. I'd then just monitor it over a few months and if it doesn't get any warmer I'd just leave it as is. Maybe flag it as requiring monitoring with the customer and sell them a 6 monthly thermal checkup.

 

[Darkwood]

@pc1966
Here you go, specifically designed for the high temp' crimps I used, strato-therm been the crimps in question mentioned in the link.

TE Connectivity CERTI-CRIMP Ratchet Crimping Tool, STRATO-THERM/SOLISTRAND Terminals and Splices, Minimum 22AWG | 46447 | ET16717667 | Enrgtech LTD

Buy the TE Connectivity CERTI-CRIMP Ratchet Crimping Tool, STRATO-THERM/SOLISTRAND Terminals and Splices, Minimum 22AWG. 46447 TE Connectivity Crimp Tools. FREE shipping for UK customers on ET16717667 product.

www.enrgtech.co.uk

 

[timbobelfast]

Looking for some advice regarding some connections on a heating contactor.

I picked up some readings using a thermal camera which I thought were a tad high. I remade the crimps as these were the "hot spots" however this has had no effect on the temperature.

The current draw is approximately 42 amps as its a radiant heating circuit.

Are these temperatures normal for this scenario? I haven't done a great deal of thermal imaging but when I do I set the camera to flag temperatures above 60 degrees.

See the attached image below:
View attachment 85690

Not much additional room inside that adaptable box, not surprised its running hot!

 

[Zdb]

Well if you thought the last one was bad, here is an image I took earlier this week. I used the lava pallette and set an isotherm for 70 degrees. Therefore everything showing as "lava" is potentially 70 degrees and higher.

Image taken using the Cat S62 pro.

 

[pc1966]

I still don't need a FLIR camera, but I still want one!

 

[Megawatt]

Looking for some advice regarding some connections on a heating contactor.

I picked up some readings using a thermal camera which I thought were a tad high. I remade the crimps as these were the "hot spots" however this has had no effect on the temperature.

The current draw is approximately 42 amps as its a radiant heating circuit.

Are these temperatures normal for this scenario? I haven't done a great deal of thermal imaging but when I do I set the camera to flag temperatures above 60 degrees.

See the attached image below:
View attachment 85690

Just out of curiosity have you put an amp meter on it to see what kind of load it’s pulling.

 

[Marvo]

Well if you thought the last one was bad, here is an image I took earlier this week. I used the lava pallette and set an isotherm for 70 degrees. Therefore everything showing as "lava" is potentially 70 degrees and higher.

Image taken using the Cat S62 pro.

View attachment 86924

Yeah...once you see temperatures above 65C in a CU or DB, for me it would be time to start investigating. I agree with PC1966, you don't really need a thermal camera above that kind of temperature, you can usually smell that there's a problem when you open the door. I'd assume the problem in the photo was either marginal overload or undersized wiring....or maybe a bit of both.

 

[Zdb]

Just out of curiosity have you put an amp meter on it to see what kind of load it’s pulling.

37.8A. 6mm² cable.

 

[newfutile]

6mm singles enclosed in conduit/trunking is only rated at 41 amps, at that current it would be at 70C, i would be looking at a bigger cable , 10mm will take 57 amps in similar conditions

 

[Darkwood]

It's not in conduit or trunking, the images clearly show the heat eminates from the connections otherwise the full length of the cable would be overheating, this is not a ccc issue, its either poor quality contactors or cheap terminations.