maximum devices for 32A ring

[theo2001]

Hi all

We are setting up a IT training company and we are trying to work out how many devices he can have in training room. There are 5 double sockets in the room, and they all go back to a 32A fuse.

We want to have the following in the room, will this be ok with the fuses/amps etc.

45W cisco switch – 30 Units – Total Maximum Watts = 1350W
160W cisco Router – 24 Units – Total Maximum Watts = 3840WTotal Number of Devices = 54

The maximum potential power usage from the above units will be 5190W or 5.190Kw

We will also have 10-12 Laptops (which use very little power) and also 1x Projector.

Based on the above configuration, will this be doable using the existing 32A Ring Main?

Any advice appreciated.

 

[Darkwood]

Welcome to the forum theo2001

What you are asking will need to be carefully designed and isn't just a case of the load, computer equipment has a designed earth leakage and this can cause many issues with regards to nuisance tripping also the ring main would need to conform to extra regulation regarding the high earth currents, so I recommend you get an Electrician in to weigh up the existing and what measures are required to allow for your equipment.

 

[Pete999]

What Darkwood said is true not just a case of loading the circuits need to be designed for this particular application, the regulations are quit strict (543.7.2.201) I could quote but the guy doing the work should have a copy of BS7671.

 

[Octopus]

Putting all your eggs in one basket is asking for trouble - especially if you are training people unless you are focusing on rebooting and starting up! lol

 

[Leesparkykent]

I agree with all of the above probably best to get your electrician to assess, as not as straight forward as just focusing on loadings.

 

[theo2001]

Hi
thanks for the advice the unit has an electrician looking into it. Just though I would ask to have a better understanding of it all.

For the loads and stuff is this where pdu's come into it? All the devices are going to be used for very basic stuff and will never reach anywhere near capacity but the unit want it done at capacity just in case which I guess makes sense on their part.

 

[davesparks]

Hi
thanks for the advice the unit has an electrician looking into it. Just though I would ask to have a better understanding of it all.

For the loads and stuff is this where pdu's come into it? All the devices are going to be used for very basic stuff and will never reach anywhere near capacity but the unit want it done at capacity just in case which I guess makes sense on their part.

It's not just the power consumption which you need to consider. Every piece of equipment will produce a legitimate amount of earth leakage current, the regulations set strict limits on how much earth leakage current can be present in any one circuit before special precautions must be taken to prevent the very significant danger that this could present.

 

[Phil Thompson]

Also as well as the above, as far as I recall without actually going and checking, laptop psu/chargers run at 85w do they not? So there's an extra 850w-1020w and a projector is around 200-300w, that you aren't factoring in either. So you'd actually be around the 6.5kw load. If there's laptops, there could now or in future be printers, and other possible equipment.

 

[Pete999]

What Darkwood said is true not just a case of loading the circuits need to be designed for this particular application, the regulations are quit strict (543.7.2.201) I could quote but the guy doing the work should have a copy of BS7671.

There are specif circuit arrangements described in the On Site Guide which your Electrician should have a copy of, some folk denigrate this guide as an idiots guide, but the chapter on high earth leakage is worth a read.

 

[Marvo]

^^My thoughts as well, the standing functional leakage could well be sky high so this would certainly be one of the design considerations.

 

[telectrix]

my computers have a very low earth leakage. < 3mA each. the main issue is the factor of the valve heaters, running on 6V d.c. each. 32 valves with the heaters wired in series. 1 heater blows. the lot's dead.

 

[theo2001]

Telectix what do you mean when You refer to valve heaters.

thanks for the advice everyone.

 

[Octopus]

Telectix what do you mean when You refer to valve heaters.

thanks for the advice everyone.

Out of interest, given the advice above, what do you plan to do next?

 

[theo2001]

Well before I do anything going to wait for the unit electrician to get back and see what he advises.

 

[Pete999]

Well before I do anything going to wait for the unit electrician to get back and see what he advises.

Tell him to bring his copy of the OSG for reference.

 

[davesparks]

Telectix what do you mean when You refer to valve heaters.

thanks for the advice everyone.

I believe he is referring to thermionic valves by way of a joke, they were the analogue predecessor to the modern diode and transistors.
They look a little bit like a lamp and get hot and glow when in use.

 

[Lucien Nunes]

my computers have a very low earth leakage. < 3mA each. the main issue is the factor of the valve heaters, running on 6V d.c. each. 32 valves with the heaters wired in series. 1 heater blows. the lot's dead.

What are you on about Tel? Series heaters were never used in computers, unless you've got one of those Dansette portable computers that take the big black 12" discs, they often have a UL84 and a UY81 run in series off a 90V tap in the motor winding, or the Decca Colour 625/405 Desktop which uses a 300mA heater chain. BTW watch out for x-rays from the PD500 EHT shunt stabiliser triode.