Need Help! My Class A Amp Is Running Very Hot

the cabinet on the top temperature is 28C which I think is just a little warm but acceptable but when I put my hand on top of the plastic vents (over the heat shrinks) it is extremely hot, way over my thermometer maximum temperature of 50C

To add perspective, my Pass XA25 amp operates in class A and consumes an amount of power (240 watts at idle) that is very similar to yours. The XA25 is stated to be designed such that after it warms up to a stable temperature its heatsinks will be about 25 degrees C higher than the temperature of the room. (Elizabeth makes a good point about the significance of room temperature, btw. Each degree of difference in room temperature will make the same difference in the temperature the amp stabilizes at, following warmup).

So under typical room temperature conditions the heatsinks on my amp will approach 50 degrees C. Very significantly, however, in contrast to yours the heatsinks on my amp are on the outside of its cabinet:

https://www.passlabs.com/amplifier/xa25#lg=1&slide=8

The heatsinks on my amp also appear to have much greater total surface area from which to radiate the heat than the heatsinks that are inside of your amp.

So, again, it seems to me to be very possible that what you have described is normal, although I am not in a position to be certain about that.

Regards,
-- Al

If you just bought the amp and are that worried, perhaps Class A isn't for you.  In that case, I would return the amp and buy the Class AB version instead.

Questions: How much SPACE is open above the amplifier? How much space is under the amplifier? How much space is open behind and to the sides of the amplifier. Is it on the floor, on carpet? Is in on a hard shelf?     
Ambient temps? This is how HOT is your ROOM? If you live in the tropics or like me, regularly are at 80F/ 27C or higher, then the amp will be hotter. just the way it goes... If you room is at 74F / 23C that is not an issue.   
Does the 'too hot' mean if you left you fingers on it for thirty seconds you would have a second degree burn? Or just a bit of pain??    
If just some pain. then I say it is NOT too hot.     
I own a PREAMP that is a blast furnace. It gets really hot. I spoke to the guy who built them, and he said, normal.  
Things you can do: Raise it up a little higher off the shelf or floor. So small bits of wood under the feet. 1/2inch .. 10 to 15 mm is all you need. If the amp is on a shelt, it needs at least three or four inches free space above it. If it has less, you need to solve the lack of free space above it.    
All the "Danger Will Robinson Danger" nonsense spouted in other folks posts means nothing if the amp is designed to run that hot.

 Thanks for the feedback, to answer your questions, the Amp is placed on a  open wood shelf, the top and the sides are wide open, the room temperature is about 70 degrees. I can put my hands on the cabinet for a period of time no issue but when I put my hand on the vents it is very hot can’t hold it for 30seconds I will get burn

If it is so hot on the vents that you would get burned, I find it hard to believe, that Luxman would use a material such as plastic, as vents. 

Given what you have reported and Al's usual helpful stats it sounds like the amp is operating at normal temps for a Class A design. This is the main reason I am not a big fan of some of these designs--it's not so much the heat they produce and the impact on room temperatures. I have concerns about parts longevity in an enclosure that produces so much heat. Things get stressed at those temperature levels regardless of what specs they might cite and the repeated heating and cooling as you power up and down will also likely take their toll over time. I feel the same way about tube units that are not designed to allow the heat to dissipate easily from inside the cabinet. One of the reasons I love a ZOTL design like my LTA Ultralinear is that it runs remarkably cool for a tube unit. This will likely contribute to less parts failure down the road.