On studying the requirements, it would appear that the standard allows panel internal temperatures to be limited only by values above ambient, which suggests that any max temperature would be allowed, e.g., if the ambient was theoretically 60deg C then the limitation for plastic covers would be 60+40degC!!.

Another limitation seems to be on internal components. This limitation appears to be, that which the component manufacturer stipulates, e.g., if the lowest manufacturer,s max is say 40degC, then the whole internal of the panel cannot be above 40degC?
Would this be a correct interpretation of the standard?

Does the new standard BS61439 make any change to this?

GMAC

Starting with the last first.

Any component that has a max temp lower then any other components derates the system to the lower temperature. The reasoning is quite simple, anything above the max temp of a component means that it could fail and possibly put the "system" at risk.

First query.

In theory you are right but most components have a max temp and if you exceed this you put the system at risk. Also there are max touch temperatures on the panel front at at 60 + 40 = 100C the panel exterior would be to hot to touch and put persons at risk.

Cheers

Oh and whatch out for 61439 as things change a bit when that one comes into force.

GMAC & Fredman
I know this is an old topic, but there are some corrections need to be made.

The standard is based upon a maximum 24h average ambient of 35C with a max limit of 40C, so your 60C ambient is not inside the scope of the standard. If you want to use this scenario, then you would need to reduce the rise in K by the temperature that your ambient is above the standard. I assume you would have 60C max, so in this case you would reduce the rise by 20K to 60 + 20 = 80c being the same absolute temperature that you would hae had if you used the limits inside that standard.

Also note that 61439 uses the same limits, so no change there.

If you want to know a bit more about 61439 I would reciommend www.3phasedesign.com the training section has some good data