I bought a new P12 last week,When i switch on the P12 unit, the fan will start up a moment then slow down the speed and the fan is still running, this is the new feature in 2.11 fw?
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Hi welcome to forum…
I have a P12 myslf…and yes the fan will come on briefly and then slow down
my amp is high bias and when I 1st turn it on the power meter may quickly momentarily jump upt to about 500 watts then instantly settle to about about
220 watts there abouts; even very loud fff might move watt meter on P12 to
between 350-450 watts…fan will come on…
I have a meat thermometer resting on the vent grill and temp is mostly 90F…
So things are really good…
I hope this helps you get an idea on your P12’s behaviour…
Happy listening
Sometime i try to use different power cord for P12 and then shutdown the p12 unit and reopen again, the fan will start to working, after testing the fan unit then stopped, the p12 will very hot and i try to shut down and reopen again, the fan running testing after will slow down the speed and still running , so i dunno it is a bug or normal operation. 
Call PS Audio tech support… no it doesn’t appear to be normal…
Btw what all is plugged into P12?
Sorry for my typo, that’s mean i testing the power cord for my p12 then power on or off the unit, instead of sometime shut down the unit. 
I just pluged dual mono two of devialet 200 in P12 Hc socket, but the fan still running in slow speed, so i want to know is it normal operation ? Or the fan should be not runing ?
Your 2 Devialet I think are a class D if so should be a very easy load for your P12…
The fans in the P12 come on and off and I don’t think they are a steady on…
I forgot to ask you earlier…what amount of physical space do you have below the P12
and above the the P12?
Myself b/c of my cabinet there is about 9" of open space below my P12 and
about 10" above allowing for plenty of free air circulation…which is very vert crucial
for the well being of the P12…
What amount of space above and below your P12?
Therein could be your answer…
You may need to rearrange the space around your P12…
Hope this helps …
Oh btw please give us a pic of the power meter with the watts used…will help…
I have put out the observation of my P12 fan here
In your case, if both fans do not stop after the initial main power on (wait for awhile to turn on main power back to let P12 cool down), might need to check with PSA support.
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No more space now 
The internal fan of P12 is running, the heatsink is cool but seem they would not stop, but luckly do not hear any noise come from the fan, but i worry thevfan running 7/24 will affect the fan life time. So i want to know your P12 normally those fans is stopped ?
Ok here is what ought be done…
Your P12 has no ventilation on the bottom or top
So create a minimum of at least 2" of space by lifting
Your P12 so air can flow up from under the bottom.
As it sits now there is not room at all for air circulation,
Next step get some anti vibration blocks to lift your turntable up some more …it seems you may have a little over an inch maybe inch and half…need room for
Air to exhaust…
Increasing the bottom space should solve a lot of the
Heat issues…
Increase the top space ensures more air flow…
As quick as you are able get on it right away…you
Don’t want to heat damage or shorten your P12 lifespan.
Your power meter reflects minimum power being
Used…and this is with your Devialets powered on.
If so this very good …in my system everything on
my power meter sits at about 220 watts…
My fans come on only briefly depending on load…
But then again I gave much more room in my cabinet
Below and above my P12.
So summarizing then:
Priority #1is main priority increase breathing room below P12 at least 2" if not more.
Priority 2 increase space above P12…
Didn’t mean to sound gruff or come off that way…
But you have cause for urgency…
Or upgrade to P15 and then airflow in your case no
Problemo
Happy lifting rearranging…
Now a day I tried put a tissue on the P12 cover then see the tissue is floding, but i cannot hear any noise come from the fan, so i found that the fan is running in slow speed.
In the set up guide of your P12 owners manual the set up guide states to make consideration of how you place the P12…it needs to breathe cooling air…
Your current set up leaves NO breathing air flow room for your P12…don’t let it gasp
for air…
Until you correct these issues your fans will run trying to cool down your P12…
because they can’t draw enough air to do the job…so they stay running…
It is up up to you now…
The P12 is designed to draw air from the base sittng on a flat surface, and exhaust out to top. The pictured install should be 100% fine. If the P12 can draw, as it is designed, from the base the exhaust clearance is more than adequate and exceeds the base intake restriction.
You should not have to darn near to hang the unit in free space to cool properly and, I doubt that’s the situation. The fan are controlled with a thermocouple and run as needed. They are high quality quiet PC case fans with very high MTBF 24/7 run times.
They will spin up at start, and then slow to a stop or low RPM based on the thermocouples signal. I checked with Paul McGowan about the fans.
I will be using the P12 unit for my source power, no power amps…that’s a P20, and as such it will likely not run hard enough to spin the fans up, ever. If the clearence on top of the unit meets or exceeds the intake area, it should cool fine.
Best,
Galen Gareis
Galen…why then does the manual state clearly to consider this bottom spacing when placing the P12…It wasn’t stated for no reason…
As you know the P12 draws air from the bottom…the op’s pix shows hardly any room
for airflow…
It is no wonder the op was concerned his P12 was getting hot…
Politely stating an opposite view to yours and what I would do if it
were my P12
Best wishes Galen…
BTW you have an amazing product line and have used BJC in my gear…
I made no mention of hanging it in free space at all…
It is good that the fans have such high mtbf…but the analogue amps
providing the power out may suffer heat damage…
Best wishes
Oh well it’s the op’s P12 in question not mine…he may do with it as he wishes…
Right?
I’ll check with Paul, but I doubt the standard mount on a table should be inadequate to cool the unit. The customer should not have to essentially replace the existing feet to give adequate ventilation into the unit.
The fans are high pressure low RPM fans, and the top clearance shown in the picture should be MORE than adequate to cool a properly designed unit.
The manual does not state the unit needs additional intake area clearance over what the current feet have designed in. The exhaust impedance needs to match or exceed the intake. The intake impedance is the bottleneck in this design. You can’t move more air than you can pull in.
Once you match the output exhaust air impedance to the input exhaust impedance, you’re done. Thermodynamics says it can’t get better past that.
So that’s the physics of the cooling.
Best,
Galen Gareis
Then read for yourself Galen…not my word’s but PS Audio engineering…
from page 4
Location Considerations
Once your new Power Plant 12 is unpacked, you’ll need to find a convenient place to set it.
Mounting
The Power Plant 12 should be placed with consideration of providing air circulation to the unit. If you wish to install the P12 into your component rack, the purchase of an aftermarket, custom-designed shelf may be necessary.
So Galen there it is in black and white right from the owner’s manual
Getting started section…
Galen if the op’s P12 unit goes down due to heat failure…will you replace it for him
in light of this?
Best wishes Galen
For the op…how you care for your P12 is up to you …read through my suggestions on raising your P12 just a couple of inches ( this not an exaggerated amount) at the bottom for air flow …also consider the effect of the rising heat on your turntable…
This the last I will say about this on this thread…
The steps you take are yours alone to decide.
Thanks everyone for help, l try to find a best place to setup let it have enough space to breath the air and see the fan it is still running in slow speed. 
If the fan can running 7/24 thats is not a problem 
Hi David,
I have the manual, and 35 years of experience with test equipment in HOT manufacturing plants that cool the exact same way.
Facts are not present in your interpretation of the manual’s statements. It isn’t your fault, though. The manual really doesn’t factually say ANYTHING more specific than don’t limit the airflow. That’s not much. So what limits the airflow, really?
The lower air flow input impedance is with the STANDARD feet installed. It does not suggest the units input airflow impedance is inadequate, or that the top clearance has to reach an exhaust impedance that is lower, verses equal, to the input impedance airflow.
The UPPER impedance has to have clearence to match the lower…THAT is what the manual VERY loosely suggests. The cooling is the DELTA of the incoming air to the heat sink’s BTU/watt dissipation rating and CFM of the fan airflow amplifies that, same as any heat sink. Cooler air and more of it past the heatsink equals more BTU/watt cooling. Once the limit of either the input (likely on this unit) or output airflow impedance is reach more fan RPM is just noise.
As far as “ventilation” that reference is such that you don’t install it inside a box with no natural air circulation as this diminishes the DELTA of the input to outputs max air temperature, the lower the ambient air coming in, the more BTU/watt you can cool at a given CFM fan speed before the max temperature is hit.
The unit will protect itself from too high temps with a feedback loop on the thermistor that controls the units internal device temperature. This is not a long term suggestion for operation, but a process that encourages better ventilation when it is tripped.
This unit cools no different than a PC, or any electronic device. Again, the clearance on top of the unit in the picture is MORE than ample with 20C ambient air in the open stand it is on. If this unit gets too hot in this configuration, we have real problems mission control.
The long term internal temperature of silicone can be as high as 95C, even higher for VRM MOSFETS, to 105C even. What constitutes “hot” depends on the devices efficiency load line range and cooling efficiency.
Like a thermostat in a car which determines the units operating temp and adjust accordingly to keep it in steady range. You don’t need to know the operating temp or the incomng air temp. You do need to know if it is “too high” based on the water temp “OK” range. Running the car at 120F in a windless state won’t allow the same conditions of the car MOVING at 70F. The thermostate will adjust within reason to keep the internal temp near the same all the time. Electronics are the same. Fans are variable to not be on all the time unless the unit reaches a set recommended device temp. Same as on your car, the radiator fan does not run UNTIL it reaches a max set temp. Same as a good PC fan set-up or this regenerator.
I agree with you that the manual “suggest” to keep it cool, but no, it doesn’t really give a proper technical set of poperties to do so. High-End test equipment DOES give clearence and with high variable ambient temperature charts to adjust the units clearances based on ambient air to reach a suitable internal temperature. As the temps around the unit go up, the clearances need to increase to a MAXIMUM, and after that Scotty’s given it all she’s got unless you ramp up the cooling efficiency (lower the airflow impedance and more CFM at that ambient temperature). More space won’t work anymore and faster fan RPM is just noise.
So yes, more space above the unit is the “best case” for lowest fan speeds even if it isn’t needed, but the unit will operate properly with less than an “open air” installation as long as the output airflow impedance matches the input and the CFM of the fan prevents the upper temp limit from being tripped. If your fans are running at max, consider why. If not, you should be fine with well designed electronics.
Best,
Galen Gareis
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The unit will do this at startup - it’s checking the fans are working.
It then, like a computer, will run at a slow speed to keep air moving and only ramp up again when the unit needs it.
If it was running the fans 100% no matter what, then we have a problem.