PLC Enclosure in Canada - Minus 40 degrees

[DrDrreeeaaa]

Hi All

My company is contracted to supply PLC panels to a site in Canada. The ambient temperature is minus 5 degrees Celcius and the PLC etc. is rated to zero degrees Celcius.

I hope someone outthere has had this problem and can share their solution(s).

One requirement we have is that the heating apparatus is powered via 24VDC, but I expect this will go out the window.

Cheers

Michael

 

[roydm]

So you just put a small heater in the panel, don't forget a thermostat.
-5°C is mild
Give us the panel dimensions
Is it outside or inside?
Stainless steel. plastic or painted steel?
Regards
Roy (Canada)

 

[DrDrreeeaaa]

Hey mate

I thought something was out of place in your reply

The ambient is minus 40 degrees Celcius, not minus 5 as I said earlier

Board is painted steel

1000mm wide x 600mm high x 300mm deep

 

[DrDrreeeaaa]

And board is outside.

The problem is it is powered from a 24VDC battery - hence 24VDC is the preferred supply voltage.

 

[waross]

Try propane. You won't keep it warm with a battery. You also need to keep the battery warm.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[DrDrreeeaaa]

hhmm interesting suggestion. You would need to refill the supply regularly. However, it is a mining site, hence they may have a supply they can plumb it to. Thanks.

 

[ScottyUK]

Bill,

Do you lag or insulate the enclosures in that sort of environment? -40C is not the sort of temperature we have to worry about in the UK: -20C is about as bad as it gets even in the highlands on cold night.


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[DrDrreeeaaa]

Does anyone have a product reference I can't find any purpose-made heaters for electrical enclosures.

Insulation is a notable point.

 

[itsmoked]

Go to

http://www.grainger.com

Page 3852 and xxx3.

These are enclosure heaters.

You aren't going to find low DC voltage ones, I don't think.

The enclosure you're proposing needs to be engineered. Not just built and heated.

It should be carefully insulated and properly arranged internally. If it's done correctly you shouldn't need a whole bunch of added heat.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[DrDrreeeaaa]

Yes well I've already chewed some people out about this but the bottom line is that both the panel and battery have already been delivered to site and are sitting in the ice on a skid.

 

[edison123]

Very interesting problem. Want to see how this turns out.

123MB - I can only give wishes since I am out of ideas.

 

[roydm]

123MB,
I have never tried a PLC outside at -40 but I know they have been tried on haul trucks. I wonder what part of the PLC suffers from the cold, if it's just the processor perhaps it can be kept warm by a small stick on element or a thermal blanket, they do generate some internal heat.
Usually the storage temperature is much lower than the operating temperature so the present situation should be OK.
As Waross said a lead acid battery will also freeze at -40°C, doesn't seem to harm it, just looses all it's power below about -35°C until it warms up again.
How are you charging the battery in mid winter?
What is the PLC monitoring, perhaps there's a source of heat there e.g. water tank.
What part of Canada, I'm sure someone has some local experience.
Good thing is, you have all summer to come up with a solution.
Good Luck
Roy

 

[waross]

I see a couple of types of enclosures for instruments used in the upgrader plants in Northern Canada. I would try a question in the petroleum and or instrumentation forums for specific information.
ScottyUK, If it's heated it will probably be lagged. I remember years ago dropping a temperature controller into the dry ice chest to confirm that it would function at low temperatures.
It was for use in an unheated, uninsulated cabinet in Toronto.
Possibly -20 deg. worst case.
The other side of heating and lagging is ventilation in the sunshine season.
Can you tell us what part of Canada?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

Hey 123MB, can you get us an inside and outside shot of this 'problem'? We might be able to provide more help. I am really very unclear on what this thing is comprised of.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[DrDrreeeaaa]

So the application is a moving mining rig. The panel in question is mounted on a 'cart' that moves about inside a mining facility. The panel houses PLC, controlgear and switchgear for the movable 'cart'.

The cart is by others and is powered from a 24VDC battery. Our panel is also powered from the battery. I am waiting for information from the cart manufacturer as how they are keeping the battery within operational temperatures.

The panel is of sheet metal type construction, with doors, 1000mm wide by 600mm high and 300mm deep. No insulation has been provided and the panel has been constructed to IP20.

I am told that the minus 40 degrees Celcius is a real restraint. The mine is located near Toronto. The work site will be enclosed in a 'tent' type enclosure I gather is common practice for work in extreme cold to keep some heat/light in.

One solution floating around is using silicon strip heaters powered from the 24VDC supply. I have not yet had a look at the feasibility of this option.

 

[DrDrreeeaaa]

An electric 'blanket' keeps the battery warm.

The idea with the silicon strip heaters is something about wrapping them around a tube and protuding the tube into the panel... I dont exactly know. Sounds a bit silly.

itsmoked, when you said an 'inside and outside shot' did you mean a photo?

 

[roydm]

Near Toronto, it doesn't get to -40°C. It can be quite miserable but inside a tent you will be out of the worst of it.
Since you don't have to worry about the supply, heres a couple of ideas.
Instead of heating the whole enclosure, mount a small heater just below the PLC powered thru a DO. Monitor the temperature of air leaving the top of housing with a sensor (RTD or T/C) and control the heater with a routine to keep it at at > 0°C. (the advantage of monitoring the actual temperature is you can display / alarm /record it).
If you don't have a spare analog use a thermostat set for zero (this has an advantage if the PLC is powered down). Monitor the heater ON time with a DI and hour counter, I think you will be surprised how little it is ON, the processor generates some heat internally.
If your system includes an LCD screen you will need to protect that also.
If you can't find a suitable heater something like a 60 Ohm 10W wire wound resistor or 24V lamp might do
BTW, 24VDC systems can have some nasty voltage spikes if there are any motors or coils involved, you might want to think about some form of power conditioning.
Regards
Roy

 

[controlsdude]

I did a freezer job where we had these sick scanners that was 24vdc. Sick said they had internal heaters that ran off of the 24vdc. Just by chance the ac blower blew across where the scanner was mounted The scanner failed like 3 times, then we went back in and mounted the scanner in an enclosure that had 120vac heater. I do not put much faith in 24vdc to keep the scanner going or a plc for that matter.

Then we also had these cranes that ran off of battery power, I believe it was 48vdc, anyway, it was used just to change aisles in the freezer. But when the power went out and then it came up, these comm devices would fail because the temp was at -20F. This would be your similar situation, to make sure before you APPLY POWER in that enclosure to the PLC that the ambient temp in the enclosure is above the minumum spec on the electronics, I believe it is around -20 for commercial products.

just a thought

 

[itsmoked]

Lots of good (important) points here.

Yes do not consider starting the unit if it is below the screen's/PLC's operating temps. Also you must watch for condensation. For instance when you first turn on the heater in an enclosure everything else in the enclosure suddenly looks cold to any moisture in the space. So everything else gets water condensation on it until it warms up too.

So you really do need a standalone heater system that comes on. Then the rest of your system should not start(interlocked) until it reaches minimum operating temperature. This can be done with just a timer but there are risks of doing it fast - with just a timer.

While your description was quite detailed 123MB, thank you, yes, I did mean a photo as a photo would probably allow a much better discussion of solutions.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[DrDrreeeaaa]

Stand by for photos