UPS Project

[dan86]

Hi Guys,

Please tell me if this is in the wrong place. I currently run about 10 machines including servers etc at home on my ring main 240vac supply and each machine has its own psu. However when I plug in any more machines or forget and plug in a laptop the rcd breaker trips. I have a apc ups which i could connect my machines to however i believe the 240vac pwr runs straight through that to the outlets and so doesn't solve the trip problem.

I am considering the following:

A number of 12v leisure batteries or better, a 1000watt inverter or better and a 12v car battery charger to charge the battery bank normally. Esentially I am creating a basic ups system where if the mains pwr trips or has an outage the machines connected to the inverter would remain on for however long the batteries lasted.

I just need to confirm something before this is planned or non-planned depending on what you guys advise me as I know you know your stuff. If I have the following setup:

12v mains charger > battery bank 12v batteries > 12v > 1000water inverter 240vac > socket strip and a couple of machines connected will my main rcd know about the machines psu capicaters? Say if my ring mains rcd limit was 10 machines and a 11th machine would trip the breaker ( I have been told it causes an inbalance because of the caps in the psu) would adding the machine that normally tripped my ring main still trip the breaker if it was on my home made ups system? I am sure my main rcd would't trip however many machines I had running on the battery bank within reason as the 12v car charger > batteries are feeding the machines.

Any advice would be greatful. Apologies for the long post. Please tell me if this is a bad idea. If this is a good idea then it solves 3-4 problems.

Daniel

[Pyr0Beast]

Re: UPS Project

It is not imbalance of capacitors it is the noise filtering of PSU which causes that some current always flows thru the grounding wire, this tripping the breaker which detects any imbalance.

[stj]

Re: UPS Project

maybe, but the ring is 32a and the breakers are very fast at stopping surges.
i'v had one trip because a lightbulb failed!

maybe wire a second ring into the cab and put another breaker on the bussbar.

[dan86]

Re: UPS Project

Thanks guys. I believe the the rcd is 30mA and because its for domestic use it senstive.

[dan86]

Re: UPS Project

It is not imbalance of capacitors it is the noise filtering of PSU which causes that some current always flows thru the grounding wire, this tripping the breaker which detects any imbalance.

Would that mean if the machines were connected like the following below the rcd would still trip?

12v car charger > inverter > 240vac > machines

[dan86]

Re: UPS Project

Any updates or advice on this? Please.

[willawake]

Re: UPS Project

why dont you just get an electrician in?

[Eagle2a]

Re: UPS Project

I finally figured out an RCD breaker is what we call a GFCI breaker here in the USA. Are you sure you aren't exceeding the max current capacity of the breaker rather than tripping its leaky current detection circuit? And can you move the computers to a non-RCD breaker protected circuit? That would be the preferred solution.

[Pyr0Beast]

Re: UPS Project

Would that mean if the machines were connected like the following below the rcd would still trip?

12v car charger > inverter > 240vac > machines

With galvanic insulation no.

Current can flow thru grounds, like monitor cable, keyboard cable, KVM switch etc.

[MixMasta]

Re: UPS Project

Get a different circuit breaker.

[japlytic]

Re: UPS Project

I have handled two models of UPS (not live chassis - the battery negative is connected directly to the USB communication port) which are an APC Back-UPS CS Series and a Belkin F6C800auUNV.
In these two models, the mains input and output are monitored directly (no isolation transformers) via high value resistors (2M0 per side in Belkin, with 800K per side in APC) while the output current is monitored by a current transformer.

[Pyr0Beast]

Re: UPS Project

Mustek Powermust 600VA monitors input voltage the same way. The whole PCB except the COM port is under voltage.

[dan86]

Re: UPS Project

why dont you just get an electrician in?

Thanks for the replies, i've not checked the forums in a few days. The breaker is working correctly and has been tested. However because its a domestic premise we canno't have it changed. I've been told in large computer rooms such has a college campus it room they aren;'t on these breakers but its allowed because theres someone there keeping an eye on things.

I'm not exceeding the breakers spec ie 32amps. The solution to my problem is make it so no matter how many machines were running on the inverter the electric won't trip due to the rcd being so sensitive. 99.99% of the time the power is fine and doesn't trip but does sometimes causing downtime etc.

I mean would running the machines earth elsewhere from the rest of the mains circuit make a difference?

[kc8adu]

Re: UPS Project

big isolation transformer?

[dan86]

Re: UPS Project

big isolation transformer?

Infact I was just reading up about that and then saw your reply.