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I have 3 working devices avalon 920p , and when I turn on the fourth device, problems begin to occur, and one or two devices start restarting. I have good electricity and ventilation is also good.

Did you plug all these units into a single outlet with an extension?
Also, take note of how many amps can handle your wall outlet or your current circuit.

Here's the specs of this unit that I found on google


Power consumption is around 1700w so each unit requires a 10amp outlet since you have 4 units you should have around 40amp in your circuit to run these units normally because if below 40amp you may experience a power outage just like what you experienced.

thx alot for repling .

I actually connected each device to an outlet, but I cannot measure the amperage value entering the circuit

I can tell you that you simply are over loading the circuit.

They pull 1700 to 2100 watts each.

4 would be 6800 to 8400 watts.

that is too much for a 30 amp 240 volt circuit.

Do you have access to the circuit breakers?
Do you have 210/240 volt power?

What are your power supplies?

frist , thx for reply

I don't have a circuit breaker for the entire circuit but each device has an power switch breaker 16 amp
My electricity is 220 volts
I have electricity directly from the National Home Electricity Company

I think try to configure all the units first to static and maybe it is just an IP conflict that causes this issue or one of the units has the same Mac address. We do not sure but try it first.

If it doesn't work then you might need to consider hiring a professional electrician for inspection or to investigate why you've experienced some power outages and to ensure the safety of your units and your home.
If each of your units is working fine that's the best thing you need to do because a professional electrician can help address electrical issues.

thx , i found the problem and it is due to high temperature When it reaches 115, it restarts, and when I turn on the device alone, the temperature appears normal, but when I turn on more than one device, a problem begins. I think it is a problem with the Raspberry Pi or the AUC.

How far are these units from each other?
I don't know how you set up these units, but if it's just a temp issue, then make sure that the hot air from the unit does not hit each other and should be well positioned to avoid overheating issue.
If it still doesn't work try to force the unit to force the fan to run at high speed or full speed.

Here's the command below to set the fan I don't know if this command will work on this unit but on latest canaan units this command below works using the FMS tool you can download it from here https://download.canaan-creative.com/fms/

@BizMax - the A920 does not run FMS. It uses a modified cgminer same as the A6xx-A8xx did.
@OP - 115 deg is WAY too hot. I ran A921's and yes while they do run hotter than most miners, 115 is really pushing them. I played with Vcore and speed to keep them below 100.
ref https://bitcointalk.org/index.php?topic=5085231.msg48770866#msg48770866 and the posts around there for settings to play with.

In post #40 of that thread https://bitcointalk.org/index.php?topic=5085231.msg48823226#msg48823226 Philipma used
More Options  --avalon9-voltage-level -2 --avalon9-voltage-level-offset -2
to hash at 18.7 THs pulling 1,700w

A list of all the settings I used for the A741, A841, and A921 are here https://bitcointalk.org/index.php?topic=5085231.msg49168363#msg49168363  For all of the A9 setting I used the max temp was under 96C

No idea what the 920P is though I do see several for sale. AFAIK the 1st (and only) A9xx that Canaan released was the A921. The 920P I'm seeing specs a slightly lower hashrate than the 921 so perhaps it was their attempt to reign in the A921's hunger for power?

thanx alot i will try the set and post it soon

Good news today, the temperature dropped by 7 degrees, but the DH rose in more than one device by 30%. What effect does this have on the hashrate?

DH = Average error rate, it shouldn't be more than 1.5%, max 2%, it has been a while since I run any Avalon (never liked them, didn't have good luck with them, maybe because I bought them used/abused, but ya) IIRC the GHSavg which is the hourly rate will show the actual hashrate the unit runs at after taking into the account the DH, DH and HW are usually caused by incorrect voltage/frequency settings, too high or too low would increase DH and HW.

Most important however would be your pool hashrate and the reject rate at the pool, if your miners are expected to run at 100th and you get anything above 97~th with say 1-2% rejection rate on the pool, ignore everything else you see on the miner GUI, if that isn't the case -- you got a problem, start by lowering the frequency.

I think it may not have side effects but increase in your mining. Though I have gotten deep experience on this but believe that could be the results