3phase to 240v

[333rocky333]

>63A then use a panel board.

Excuse my ignorance whats a panel board.

 

[RF Lighting]

It's like a DB on steroids

 

[Lectrician]

seems Rf thinks busbars are old hat so lets see how he would connect Two 3 phase boards to a single supply

Depends on the situation. Normally for a small second board ≤63A then just submain it off the first board. >63A then use a panel board.

Or one of the well thought out MEM ones

 

[Lectrician]

An 800amp Panel Board we did last year - replacing the busbar which was there. Not the best pic in the world!

 

[Lectrician]

Looking though my pics for a better shot, and can find these:

Kind of cross posting to the other thread.

The supply was actually a 630amp supply from the DNO, with an 800amp panel board. There was a 630amp changeover switch, which was based on two contactors with a tiny 20amp two position, centre off switch operating these. The generator side of this was simply an 800amp busbar chamber in the sheltered loading bay which would be used to connect a generator to from a company who would respond with in 4 hours to supply one.

Cables were doubled up 150mm tri-rated in 300x300 galv trunking.

Usually on supplies this size, motorised changeover switched are used, controlled by either a tiny two position/center off switch, or an automated panel. Due to a supplier mix up, we ended up fitting this dual contactor version at a hugely discounted price. I just wonder *when* the contactor will fail!

 

[mfarrow]

Apart from Lectrician, many of the posters seem to have confused the term 'way' with 'module'.

In a 3-phase board, each way is usually 3 18mm modules wide.

There are examples in BS 7671 where confusing the two would, and does, lead to a 'less safe' installation for the end user.

 

[SimonH2]

If I need more power, would that need a separate 3 phase supply or can more power be "sent" through the existing 3 way power supply ie increase A to more than 100A? (I'm guessing no, but thought I'd ask!).!

It depends
You discuss things with your lecky, then approach your supplier (who you pay the lecky bills to), and they will pass it up to the DNO (Distribution Network Operator).
It may be that the cable is suitable for a higher supply loading, in which case they would upgrade the fuses (and possibly the service head) accordingly. More likely they'll tell you that the cable is up to it's limit.
There are two many variables to call which way this would go before you ask them - I do know that standards and practices have changed over the years.

If your current supply isn't adequate, then you probably have two choices - upgrade the existing supply or have a second one added. I suspect that long terms, a single supply is cheaper, and it definitely simplifies a few things electrically - having two supplies to the building means more care needs to be taken with what runs from where and what is isolated when a supply is off. Both an upgrade and a new install will involve work - digging up the pavement for example. Whatever option you go with, it won't be cheap !


However, you really need to get some better power requirements sorted out - the figures quoted do not make sense and you are probably worrying unnecessarily. For example, you state the power requirement for a treadmill at 16A. This is not how much power it is going to use (nearly 4kW !, fan heaters are usually only 2 or 3kW), but what it's supply requirement is (which still seems OTT to me).
So you need to find out what they actually require - not the "unduly pessimistic" bovine excrement* you've had so far.
Worst case would be that you tried to start a lot of machines that have DOL** motors - they could not be started at the same time, but would happily run if started in sequence. In this case, the motors will not be DOL**, there will be an inverter to give a variable speed. Chances are you could run quite a few of these off one 16A supply, and the chances of 20 users synchronising their pressing of the start button is quite slim.

When you've got realistic figures, then you'll almost certainly find that your current supply is more than adequate.


* In my experience, manufacturer tend to be "a bit pessimistic", and just quote requirements for oversized supplies that remove requirements for thought or calculation. The classic situation is things like garage/workshop equipment where they just say "dedicated 30A supply" even for stuff that will run off a 20A or even 16A supply given the right design - they assume Type B protection for something with a big motor. it does, however, give them an easy get out if you provide a more realistic supply and have any problems.
In my own line of work, UPS manufacturers seem to like specifying supplies that are 100% (or more) over specced.

** DOL - Direct On line, where a motor is just switched straight onto the supply for power, and takes a huge inrush as it spins up.

 

[xr4x4]

For the op..

Are you sure the treadmills are actually 16amp each, or do they just need 16 amp plugs?

16 amp load each sounds a lot.

 

[ziggy1979]

Hi Xr4x4 and Simon H2

Tbh I'm not sure, that's simply what the supplier have told me. I will ask tomorrow and see what they say. So far they've just told me that each treadmill needs a 16A dedicated line (I know that other suppliers say the same thing for their treadmills too).

I do hope that the existing supply is fine as I am worried about the cost of bringing more power into the premises!

Thanks again for all your help!

 

[Lectrician]

I do hope that the existing supply is fine as I am worried about the cost of bringing more power into the premises!

And your monthly lecky bills.

 

[SimonH2]

Tbh I'm not sure, that's simply what the supplier have told me. I will ask tomorrow and see what they say. So far they've just told me that each treadmill needs a 16A dedicated line (I know that other suppliers say the same thing for their treadmills too).

Ask them the current rating shown on the rating plate, the typical startup current, and typical running current. They can probably tell you the first and will give you blank looks over the others

The rating plate value will be a lot less than 16A. You may have to take measurements of the others. Once you know how much each machine actually takes, your lecky will be able to do the rest.
There' won't be much reduction from the running current for diversity - but as long as you don't try and start up everything at the same moment, you can largely discount startup current.

Eg, say each machine takes 2A when running (that's a plausible figure) - that's still only 40A between 20 machines. A bit different from the 320A you seem to be thinking you need

 

[ziggy1979]

Thanks again for your help!

Just heard back from one supplier:

1. current rating - need a 10A dedicated supply
2. Startup current - approx 8A depending on weight of user
3. Typical running current - approx 3-4A

Does that sound about right or should I ask them to confirm anything else?

It does seem as though a std 100A supply won't cut it...or am I missing something? Tbh I'm pretty confused, and even more concerned about the budget as i never really thought powering the treadmills would be an issue.

If we need more power, given the costs involved, would it be worthwhile increasing it a fair bit above our needs in case we need more down the line or does more power = more cost so don't go overboard?

Thanks again for all your help!!!

 

[SimonH2]

1. current rating - need a 10A dedicated supply
2. Startup current - approx 8A depending on weight of user
3. Typical running current - approx 3-4A

OK, if those are real values then a 10A supply makes sense. However 3-4A running current still sounds very high to me - it's over a horsepower ! Or about 3/4 to 1kW. Do these gyms really use that much power for the machines - must make the air conditioning bills horrendous.

Oh yes, if these machines really are using that much power, you'll need to consider how to keep the place cool.

It does seem as though a std 100A supply won't cut it...or am I missing something?

Lets look at the figures ...
20 treadmills at (say) 4A each = 80A
Assume the steppers are the same load, 10 of them would take a further 40A.
That's 120A total. That can be split between the phases*, so that's only 40A/phase. Yes, you could double that if you had 30 heavy users who carefully synchronised starting all the machines at once - but that's not likely.

So that leaves "quite a bit" available to cover startup surges on single machines, and your other loads. Unless you have loads, then computers, CCTV, etc won't take much. Lights could add a bit (your lecky will be able to talk about that), and then aircon if you need it, or ventilation if that is enough.
In rough figures, aircon will take about 1/3 of the current taken by the loads it's cooling. So lets say you get the total load up to around 50A/phase, then your aircon will take something like 16-18A/phase (at this load, the A/C will be 3 phase) and bring your total to near 70A. Stick to modern inverter driven designs and the startup loads shouldn't be too bad.

If you have a 100A supply, then I'm thinking your 30A headroom at full load should be enough to handle startup surges from various bits of equipment. I'm sure the professionals will be able to talk more about that.

If we need more power, given the costs involved, would it be worthwhile increasing it a fair bit above our needs in case we need more down the line or does more power = more cost so don't go overboard?

It will certainly cost you a lot more if you do one upgrade, and then need another. However, I suspect it will cost you on an ongoing basis in capacity based standing charges if you put in something that's significantly oversized. Based on the above guestimates, I think you'll be able to cope on your current supply.


In your position, I'd want to be looking at some of these machines in action, and getting my own figures. The new figures you have are less out of this world, but still seem very high to me.
There's also a factor of how you plan to open. Is this going to be one big "install everything, have a grand opening, and hope that people flood in ?" (presumably using their promotional vouchers to try you out), or do you expect to be installing stuff in phases ? If the latter, then you may well be able to get some of the kit in and monitor actual loads - then extrapolate to a full setup.

 

[Lectrician]

If you increase your supply to a larger one, you will pay an "availability charge" on your electricity bill. The larger the supply, the higher this charge. If you oversize a supply, you will be paying more than you need each month.

On the flip of the coin, if you have a standard 100amp supply, it is unlikely your supply agreement is actually for this full 70kva availability. The fuses may be 100amp, but your agreement is more than likely less. Check this, otherwise you will pay a penality for exceeding your agreed maximum demand.

Your best bet is to engage a decent sparky company now at the design stages and get them to calculate an anticipated maximum demand, and to determine what your supply is capable of.

This reminds me of a site close to me where 3 industrial units in a row were struggling to be let and some chap came along and took the lease on them all to set up something just like you propose. He had 3 separate TP supplies, but had issues with the supplier as they would only allow him to have a meter installed onto one supply if he knocked holes in the walls to create one unit. He argued for ages saying he had loads of capacity between the 3 units, and couldn't see why he could not use all 3 rather than increasing the size of one. He ended up running everything out of 3 individual units.......knocking holes in the walls many months down the line.

I wasn't the spark, just an observer!

 

[ziggy1979]

Hi and thanks (yet again)!

1. For the treadmills we are budgeting 10-12 for opening and hope to increase this up to 20 if the demand/money is there (it wouldn't go above 25 in any event because of a lack of space).

I want to have the wiring done for all of them though (20-25) so that if and when demand dictates we buy more, it's simply a case of plugging them in.

Basically I want to future proof the electrics as much as possible at install as everything from the DB will be new and would rather not have to run additional electrics at a future date.

2. Almost all of the other equipment is self powered (ie rowers, ellipticals, steppers, etc). There is only one other piece of cardio that has a 0.75A current rating on the plate and we'd probably start off with 4 of those.

3. Extra electrics will be needed for lighting, ac/ventilation, CcTV, water heaters (need to post in plumbing next door to determine options), alarms, office, plasmas, sound system and speakers, automated door system (I think that's it).

4. Thanks for explaining how the power would be shared across the three phases (I was missing more than a little something). It doesn't actually seem all that bad anymore and I'm hopeful that we can get it to work with what's there.

5. Does anyone know/work with or for a company that would handle this type of installation who'd come round, confirm what we need and quote for the job?

6. Is it allowed, safe, of any (cost) benefit, etc. to lay/run the wiring (eg from the sockets, lighting, office area, etc to the DB without making any connections and have the certified electricians connect everything up and test it? is this something they would even do? I've rewired a couple of residential premises in the past and have access to reasonably cheap labourers who could do the chasing, etc. Before reading about 3 phase power I was a little hesitant to consider doing any aspect of the electrics in this way but with a little more understanding I'm not too put off the idea any more (although being commercial premises I wouldn't want any insurance, etc being potentially voided in any such way).

Thank you all again for your help!