Thoughts on this heavy load set up... (Bitcoin Mining Farm)

[ToastyToes]

Hi all,

I have recently set up a bitcoin mining farm in my garage for a small passive income. The equipment takes quite the load and runs 24/7/365.

Garage is fed by a 10mm SWA connected to a 60amp cartridge fuse.
Garage has an RCD protected DB with 3 circuits... 2x 6mm radials and 1x 4mm radial.

4mm Radial - 16amp MCB
Serves the cooling side of the operation, AC, Fans, pedant light, CCTV etc.... about 1.6kw max load..

2x 6mm Radials - 32amps MCB each
Each 6mm radial connects to 5 double sockets
Each double socket connects to 1 bitcoin miner. Approx 1.2kW load for each device
Each 6mm radial has 5 miners which totals approx 6kW load per radial, 24/7/365

The purpose built room in the garage which houses all the equipment has an ambient temp of around 22-33 degrees C. The hot air from the room pumps out in to the garage with an ambient temp of up to 40 degrees C. Radials are all clipped for the entire run (Under 10m each run)

The 6mm radials are warm to the touch in the garage. 10mm SWA is warm to the touch right by the DB but is cool by the floor where it comes in.

The DB is warm to the touch all away around.

Its been up and running for around a week now with only 1 issue. One of the 6mm radials trips. I removed one of the miners from the radial so the load is less but after 2 days it tripped again. The only thing I can think of is that the MCB is in the middle of the board thus having a higher ambient temperature compared to the other 6mm radial which is at the end.

I have thought about upping the MCB to a 40amp as 6mm clipped is rated over 50amps but with the load being 24/7 and a hot garage, I am not sure this is safe to do.

Thoughts on the entire setup greatly appreciated!

Thanks

 

[JohnW2]

I have recently set up a bitcoin mining farm in my garage for a small passive income. .... 2x 6mm Radials - 32amps MCB each .... Each 6mm radial has 5 miners which totals approx 6kW load per radial, 24/7/365

If those figures are correct, I hope that your 'small passive income' exceeds your 'not-so-small passive overheads' - you've hopefully found a more cost-effective tariff but, by my reckoning 12 kW for 24/7/365 at, say, 16p per kWh would cost almost £17,000 per year

Its been up and running for around a week now with only 1 issue. One of the 6mm radials trips. I removed one of the miners from the radial so the load is less but after 2 days it tripped again. The only thing I can think of is that the MCB is in the middle of the board thus having a higher ambient temperature compared to the other 6mm radial which is at the end.

Running adjacent MCBs fairly close to their ratings continuously can certainly be an issue. Wylex say thsi:

Adjacent thermal-magnetic MCBs should not be continuously loaded at or approaching their nominal rated currents when mounted in enclosures. It is good engineering practice to apply generous derating factors or make provision for adequate free air between devices. In these situations, and in common with other manufacturers, we recommend a 66% diversity factor is applied to the MCB nominal rated current where it is intended to load the MCBs continuously (in excess of 1 hour).

it may require a larger enclosures, but you could try spreading the MCBs out more (with gaps between them). Alternatively (again might need a larger enclosure) you could consider splitting each of the 6mm² radials into two, again each on 32A MCBs, so they were running far below their limits.

I have thought about upping the MCB to a 40amp as 6mm clipped is rated over 50amps but with the load being 24/7 and a hot garage, I am not sure this is safe to do.

As for the MCB, again quoting Wylex, they recommend downrating by a factor of 0.9 for an ambient temp of 60 °C -hence 28.8A for a 32A one and 36A for a 40A one. As for the cable, one could check what degree of de-rating it required at your ambient temp (when clipped direct). The difference between a 32A and 40A MCB is not all that great, although I suppose it might be 'just enough' to alleviate your problem - particularly if you also implemented one of the other options I've mentioned.

Kind Regards, John

 

[ToastyToes]

If those figures are correct, I hope that your 'small passive income' exceeds your 'not-so-small passive overheads' - you've hopefully found a more cost-effective tariff but, by my reckoning 12 kW for 24/7/365 at, say, 16p per kWh would cost almost £17,000 per year
Running adjacent MCBs fairly close to their ratings continuously can certainly be an issue. Wylex say thsi:
it may require a larger enclosures, but you could try spreading the MCBs out more (with gaps between them). Alternatively (again might need a larger enclosure) you could consider splitting each of the 6mm² radials into two, again each on 32A MCBs, so they were running far below their limits.
As for the MCB, again quoting Wylex, they recommend downrating by a factor of 0.9 for an ambient temp of 60 °C -hence 28.8A for a 32A one and 36A for a 40A one. As for the cable, one could check what degree of de-rating it required at your ambient temp (when clipped direct). The difference between a 32A and 40A MCB is not all that great, although I suppose it might be 'just enough' to alleviate your problem - particularly if you also implemented one of the other options I've mentioned.

Kind Regards, John

Hi John (Ward?)

Thanks for your reply.

I will pop the 20amp MCB between the 32s to see if it makes any difference. The board is at max capacity so if it doesn't work I will have to upgrade the DB and split the load further. Possibly 4x 6mms if I have the cable, but definitely 3 radials.

In regards to 66% diversity factor, in layman terms, does that mean expect 66% capacity (21amps) from the MCB rather then 100% (32amps)?

Thanks!

 

[AndyPRK]

He's not John Ward. He is a user on here though

 

[JohnW2]

Hi John (Ward?)

No, but he does participate here, as "flameport".

Thanks for your reply. .... I will pop the 20amp MCB between the 32s to see if it makes any difference. The board is at max capacity so if it doesn't work I will have to upgrade the DB and split the load further. Possibly 4x 6mms if I have the cable, but definitely 3 radials.

That all sounds reasonable. If you do end up having to 'upgrade the DB', as I implied, you'd probably only have to buy a larger ('unpopulated') enclosure of the same make and then could use all of the existing devices.

In regards to 66% diversity factor, in layman terms, does that mean expect 66% capacity (21amps) from the MCB rather then 100% (32amps)?

It's rather strange language for them to be using, but I can but assume that their intended meaning is as you have surmised. "Diversity" usually relates to the fact that not all possible loads on a particular circuit, cable or device will be drawing their maximum possible currents at the same time, such that the average load over any reasonable period of time will be a lot less than the theoretical maximum - but that is not really a relevant concept here.

Kind Regards, John

 

[ToastyToes]

No, but he does participate here, as "flameport".
That all sounds reasonable. If you do end up having to 'upgrade the DB', as I implied, you'd probably only have to buy a larger ('unpopulated') enclosure of the same make and then could use all of the existing devices.
It's rather strange language for them to be using, but I can but assume that their intended meaning is as you have surmised. "Diversity" usually relates to the fact that not all possible loads on a particular circuit, cable or device will be drawing their maximum possible currents at the same time, such that the average load over any reasonable period of time will be a lot less than the theoretical maximum - but that is not really a relevant concept here.

Kind Regards, John

Thanks a lot John.
Much appreciated response.