I have two different pairs of speakers- 1st pair is yamaha ns-8390 floor standing speakers and 2nd pair is mission mx1 bookshelf speakers. M facing the problem with both pairs of speakers.
Cabinet of the av receiver gets very hot after an hour of use.
I don't know how to help you.
I assume the receiver has plenty of space around it for ventilation, 6" all around at least.
Pioneer are not what they used to be.
Either that unit is faulty or it does not like those speakers.
I note a high incidence of problems with that receiver but not the issue you are having.
The receiver has no 4 ohm rating.
Therein my lie the problem. A speaker manufacturer giving a speaker an 8 ohm nominal impedance rating means nothing. Mission do provide more complete specs. The minimum impedance is stated as 4.2 ohms. A good rule of thumb is that the actual impedance is likely to be the minimal impedance plus 10%. So that would make the Mission speakers about 4.6 ohms.
The Yamaha speakers seem to be just available in Asia. I can only find the manufacturers impedance rating and no third party measurements. I suspect the nominal 8 ohm impedance may be just that nominal and in fact the impedance is nearer 4 than 8 ohms.
Either way that receiver is not going to do the job for you, either because it is defective or your speakers are not suitable for it.
You need to return it to the dealer as unsatisfactory if still under warranty.
You need a receiver 4 ohm stable with a manufacturer rating for 4 ohm speakers.
Finally it occurs to me that since you are in India it is very hot. What is the temperature inside your home? On thing that might help is to put a computer fan right over the top of the receiver.