Laptop Trolley through UPS - prevent circuit tripping?

[docboggle]

We have a couple of 16x laptop trolleys in the school. However, staff are not very good at following instructions, and forget to turn off the switches inside, and subsequently trip the circuit breaker. To make things worse, it is the same circuit as our servers.

 

I was wondering if connecting the laptops up to a UPS to charge would prevent this sudden surge of 16 power packs from tripping the fuse breaker, with the UPS dealing with the surge? Was looking at something like Extra Value 500VA UPS - GREAT PRICE | Ebuyer.com

 

Would this work? Has anyone faced something similar and found a solution?

[soveryapt]

Could you not fit something like PRO ELEC|RCD2-UK|RCD ADAPTOR REWIREABLE | CPC to the trollies that would help? Or get a sparky to fit a surge protected plug socket where they get stored?

[docboggle]

Have tried RCDs and both the RCD and main circuit breaker go, so no good

[soveryapt]

Have tried RCDs and both the RCD and main circuit breaker go, so no good

 

Wowsers .. have you had the trollies or circuit you're plugging into tested as that sounds a bit extreme to be doing all of that ..

 

I guess a UPS would soak up some of the surge, but it's how you would go about making sure the staff plug into that if they can't follow your other instructions too.

[steveg]

What model laptop trolley's do you have? I know the ones we buy offer a 'soft start' (or some similar name) charging option to prevent this happening.

 

Steve

[bossman]

@docboggle:

 

I would be suggesting another circuit for the 2 laptop trolley's to plug into probably a 16 amp breaker. As with all our ICT suites it is a recommendation that between 6 - 8 computers per trip on each circuit. What you have in effect is 2 x 16 = 32 on one circuit which carries your servers also, no wonder your laptop trolley's are tripping everything.

 

That would be my advice from a health and safety point of view.

[westom]

We have a couple of 16x laptop trolleys in the school. However, staff are not very good at following instructions, and forget to turn off the switches inside, and subsequently trip the circuit breaker. To make things worse, it is the same circuit as our servers.

That circuit breaker is not reporting staff mistakes. The circuit that is ghastly overloaded.

 

You are suppose to know how much power is connected to that circuit. Every appliance has a label (where the power cord connects) that says how much power (watts or amps) that appliance consumes. You are expected to add those numbers.

 

Circuit breakers are only emergency safety backups to report when a human has made an addition error. For example, a 20 amp circuit breaker will conduct an overload - 25 amps - for up to two hours before the breaker trips. Your laptops could be drawing more than 30 amps when combined with the power consumptions of the server. That is an overloaded circuit - a human safety threat.

 

Also scary is recommeneding a surge protector plug to cure an overload.

 

Circuit breaker is repeatedly reporting an overloaded circuit. A 16 amp breaker will easily provide 32 amps for 12 or 25 seconds without tripping. The circuit can be overloaded for that long because breakers are only emgerency backup protection. Stop trying to cure symptoms. You need another circuit. The existing circuit is very much overloaded. That simple. That existing overloaded circuit was obviously a potential fire.

 

A mistake started by not summing power numbers from each appliance label. Circuit breaker is reporting a human created failure. Switching off laptops to reduce the still existing overload is another bad solution.

Edited October 19, 2011 by westom

[docboggle]

but it's how you would go about making sure the staff plug into that if they can't follow your other instructions too.

Signs, posters and lessons. Short of using them as the circuit breaker, I'm not sure what to do!

 

What model laptop trolley's do you have? I know the ones we buy offer a 'soft start' (or some similar name) charging option to prevent this happening.

 

We have Bretford trolleys through RM. One of them is quite old now, but even the newer one we had in August doesn't have this facility.

The 'soft start' seems to be a Loxit product, with the Bretford equivalent being 'EPM'. These upgrades look to be in the region of £200 each and are design to fit inside the trolley.

This is the type of system that I am after, but would be happy with something that is just attached to the wall where the trolleys are charged (they are never plugged in anywhere else). Is there such a product?

[plexer]

Having a new circuit with commodo plugs but that would probablu be more than £200

 

Ben

[Chris_Cook]

If the rcds are tripping (rather than circuit breakers), then it isn't just current, it will be the number of devices as well.

 

RCDs detect an imbalance between the current flowing in the live and neutral wires. Each device will have a small earth leakage, which isn't a problem on its own, but if you add 32+ computers/laptops/servers onto one rcd, the cumulative imbalance will trip the breaker.

 

The advice above about adding up the current is correct. If you are in any doubt, get someone qualified in to check it over. Messing up mains electrics could cause a fire which would be much more expensive getting an electrician in.

 

You need to get a properly qualified electrician in to look at this circuit.

 

Adding a ups will make things worse at this stage, as it will increase the electrical load and earth leakage, although your servers probably should be on one anyway. You should probably get your servers on their own dedicated circuit that isn't used for anything else, not hoovers, not laptop trolleys, not anything.