Excuse the clickbait title, as to be fair the T21 is an awesome bit of kit, however having owned these for a month or so I have now discovered another flaw / problem (aside from them being 3-phase).

It appears that if one hashboard fails, the whole miner fails rather than just carry on hashing on the remaining (working) boards. I'm guessing this is something to do with the 3-phase power and needing the PSU to be balanced across the phases, however if anyone knows better please enlighten us.

Basically, one of my hashboards has failed (finding 0 Asics) and it has completely bricked the miner. I've tried updating firmware to no avail, so looks like this will be a warranty return.

Not knowing the connections and guessing seems like a bad idea to me. In the very first instance, I would have sent a support request to Bitmain and ask what the colour coding for the connections is.

I'd say it's feasible that your problem could be down to wrong wiring, but also you're lucky you haven't fried the miner completely.

Is the S21 Hydro designed to connect direct to your power distribution or is it meant to have some kind of control unit?

I know nothing about this scheme or situation, however I was originally using Poolin for all of my farms, had no problems for years, then suddenly the payouts stopped. I checked my control panels and everything looked normal (and therefore no reason to not receive the payouts). I waited a couple days but still no payouts, at which point I changed to F2pool and eventually forgot about it. I lost about $3000 of BTC, which today would have been worth much more.

Is what I encountered above related to the topic of this thread?

That room will no longer be usable as an office, once you have miners in there. They are incredibly noisy and exhaust vast amounts of hot air (which will require installation of cooling infrastructure, air in, and air out etc).

Well, my energy cost varies and I wouldn't want to put it here. I will say my farms are all on sites that generate electricity, and that is a big factor in the price per kWh that I pay.

As for consumption, at this farm I am running 36 x S21 and T21, which is about 130kW total with the fans. 3.1 MW per day, 94 MW over a 30-day period.

I don't sell Bitcoin unless I have to. I'm running around 200 rigs total, and I happened to get into mining at a very good time (shortly before the last halving, when coins were around $7000). Following the halving, over the course of several months, Bitcoin price exploded to 6x / 7x what it was when I got into it. I took out several large fiat loans to get into mining, but was able to pay them off in under a year (due to the explosion of Bitcoin price). Since then, I only buy new miners with BTC, so I have no outstanding loan payments to make - only the rent (which is peanuts as they are derelict buildings) and energy cost (which is low due to locations). So I sell bitcoin to cover costs, and also when I want something nice for myself But otherwise, my plan is to hold for long-term and watch it grow.

I'm not sure there is any system that could prevent a farm from catching fire, however this is an area I am currently thinking more about. My line of thought so far is that it would be beneficial to have some kind of suppression system that cuts power to the miners and fans via a contactor (e.g. when fire alarm is triggered) - but also Co2 extinguishers with heat activation (I have some in the engine bay of my yacht, they have a glass bulb that breaks at a certain temperature, causing the extinguisher to fully discharge).

In order for anyone to put together a meaningful response, we would first need to know the following:

*  How much is your unit cost (how much do you pay for electricity, per kWh)?
*  What type of supply do you have? Single phase? Three phase? 120V? 240V? What capacity is the supply?

Miners come in various different efficiency ratings (how much energy used to provide 1 TH of computing power). If you have free (or incredibly cheap) electricity and a huge / unlimited supply, it makes more sense to buy cheaper (less efficient) miners. If your electric cost is normal and power available is limited, you will probably be better off with the most efficient miners you can get hold of (current S21 Pro) - or S21 with aftermarket firmware.

Homes are generally unsuitable for bitcoin mining, at least on any scale. Unless you are rural with outbuildings, or live on a farm or a huge mansion, you will probably only have a small single-phase supply which could only run a handful of miners (e.g. 4 or 5 max). They're also incredibly noisy and generate vast amounts of heat. Once you have a bulk of miners, you will have a huge amount of heat to dissipate, this will require heavy airflow in and out of your farm. Whilst you can mount them in boxes and connect ducting etc, this is essentially misuse of the equipment and not how they are intended to be operated. It's also impractical on any kind of scale. Miners are designed to have neutral or negative pressure at the outlet fans, they are not designed to push air through ducting and this kind of use will likely shorten the life of the miner.

You would probably be better off buying $100k of miners and hosting externally IF (and that's a very big IF) you can find a reputable host that doesn't rip you off.

As for Whatsminers - they are brilliant. The only reason I didn't include in my examples is that none of my current suppliers have Whatsminers available. They are not typically as easy to source as Antminers, however (in my opinion) they are much better quality. You will pay more per TH though. Assuming you did have $90k left, today that would get you 21 x M60S 180T. Although the Whatsminers are better quality, I'd be inclined to suggest 32 x T21 vs. 21 x M60S would make you more money in the long-run (even after taking failures into account).

This question was asked, and answered earlier in the thread I'd estimate this setup was approx. $8000 for everything except the miners, however I did the electrical work myself so you'd probably need to allow an extra $1500 - $2000 if you needed an electrician.

So, assuming you were making a similar setup today, $100k would get you:

$10,000 - similar setup to mine including labour
$90,000 - lots of options here (depending on your available power and cost):

   * 64 x S19KPro - 120T
   * 27 x S21 - 188T
   * 23 x S21 - 200T
   * 32 x T21 - 190T

You would need a large commercial electricity supply though. I have 200A 3-phase 240V, which was already in the premises before I started mining. If you had to have a big supply like that installed, I imagine it would add several thousand $ to the setup cost

I look forward to hear how you get on with it. I understand the T21 (with standard PSU) will clock to 280TH / 5610W on Asic.to firmware

Video here re: converting T21 to single phase operation:

https://www.youtube.com/watch?app=desktop&v=0XR0nyLKroI

I guess it could work out ok if you could get a decent return on the unused 3-phase PSU's. There will be demand for them eventually (as they start to fail)

Ahh - that sounds like you were caught out too then. I think it's stupid that Bitmain named this the 'T21'. AFAIK they have never had a 3-phase air-cooled miner. By calling this a 'T21' it implies it is simply a 'T' version of the S21, but single phase vs. 3-phase is such a big difference. Maybe they should call it the T21-3, or something to make it more obvious.

Can you not return them for credit?

My supplier also suggested you can convert them to single phase with an aftermarket PSU

All my farms are 3-phase, so it's not the end of the world... however it does mean I need to rewire, and can't distribute them in the way I wanted to. They will also be very difficult to re-sell when I upgrade

Whatsminers are BY FAR the best quality miners I've ever seen. I've just sold a batch of 24 x M31s+ 82T. They were the first miners I ever bought (back in April 2020), and in 4 years only 1 x Whatsminer went faulty (dead PSU). No other problems whatsoever, no dead hashboards, not even a dead fan!

As for Antminer, I don't think I have any that have lasted more than 2.5 years.

The only reason I buy Bitmain is because they are easier to get hold of.

The supply at this address is 240V / 200A 3-Phase. The distribution board in the photos is rated for 250A, however it is fused at 160A at the supply end (due to using a 50mm cable). I have a second (smaller) distribution board in the mining room (not photographed) to spread load.

The 2.5mm cables were ESSENTIAL. I fitted 1.5mm cables first, they overheated (which is why I upgraded to 2.5mm). Bear in mind these were only for my Whatsminers which have only one power input, therefore you are delivering all power for the miner through one cable (vs. 2 x cables with old Antminers). I used 1mm flex cables for my Antminers. The Whatsminers draw up to 3700w each.

You should also consider cable length when calculating appropriate cable size. The longer the cable length, the more voltage-drop - so where 1.5mm cable might be fine for a 3m run, it may not be ok for a 25m run etc.

As for old rigs, they've all been replaced since this post was made (4 years old now)! It's just at the top of the forum because I fixed some missing photo links recently. I'm running S21 / T21 at this farm now.

Having recently ordered a batch of Antminer T21 190T, I have just learned that Antminer T21 are 3-phase.

I had absolutely no idea they are 3-phase, and at the time of ordering there was no info on Bitmain website so impossible to know. This is going to cause me a huge headache and will make them virtually impossible to sell when I replace them.

Nothing anybody can do, but I just wanted to warn others in the hope it may help someone else to avoid making the same mistake.

Brilliant - thank you! Photos updated and all working again.

P.s. interested to know why you have "mixed feelings" about wooden structures?

Could someone advise why my images no longer show in this post? I want to send this to someone I've sold some miners to (to help them build their first hot/cold setup).

The images have not been removed at the source site (imgur).

What do I need to do to fix this so images show again?

I must admit I just 'winged' my first setup (but also following advice from yourself and Mikeywith) - it worked very well. I took the total CFM of all my miners, added 20% and used that figure to determine the size / power of the extractor fans I would need. This setup has been flawless and I've copied it throughout all my other hot/cold setups.

As for filter material, this is what I use (I am UK based also):

https://sprayboothserviceandfiltration.com/collections/frontpage/products/https-spray-booth-service-filtration-myshopify-com-product-filter-extraction-secondary

20mm G4 spray booth filter

I find this interesting. Is this how most people approach a cold room / hot room setup? I've done 6 now, and I've never used fans for the air in. All my setups are passive on the air inlet, I only use fans to extract as follows:

air in >>> filter >>>  machines >>> fans >>> air out

Is there an advantage to 'pushing' the air through the farm instead of 'pulling' it out? My farms work brilliantly this way, and by having fans at the air outlet point, and 'pulling' more CFM than the miner outlet fans, the negative pressure ensures no hot air lingers or buffets in the hot room.

Is anyone offering a repair service for APW17 PSU's (for S21 / T21)?

I have one that is completely dead after 3 weeks of running. Obviously it is under warranty (miner is only a month or so old) however Bitmain will not accept a ticket, citing the following response: "I'm sorry that no repair site has enough materials to repair APW17 currently."

I have been arguing with them for the past two weeks (my approach being that they should just swap the PSU if they are unable to repair it) however they refuse and have said I have to wait until repair becomes available, or buy a new one from them.

The cost to buy 1 x APW17 PSU from Bitmain, including postage to UK - is over $1000. There would then be an additional 20% import duty on top of this (as technically it is a purchased part, not a free warranty replacement).

I am on virtually free electric so I have lost out almost $300 already wasting time arguing over the repair with Bitmain. I have since ordered a new PSU from ZeusBTC, however I would like to get this one repaired so I have a spare.