EBME Forums Forums Maintenance Technical Assistance Isolated Rooms

Hi,
Did anyone deal with this issue before? So few suggestion/point of view would be fine. Thnks

In my hospital we have the standard 230V supply, Live-Earth=230v, Live-Neutral=230v and Neutral-Earth=0v. EST in these areas is straight forward with our BioTek tester.

Recently some of our clinical areas have been supplied with a transformer isolated supply i.e. Earth is now taken from a center tap on the secondary side of an isolation transformer and our supply is as follows Live-Earth=115v, Live-Neutral=230v and Neutral-Earth=115v.

When testing to the 601 Standard, the values for Earth Leakage are much lower in the Isolated case, approx 50% of the values measures in the standard case for the same piece of Class1 Type CF equipment.

My concern is that if a piece of equipment was EST'd in an isolated room and the measurement for Earth Leakage Current was close to the limit of 1000uA, it would effectively have passed EST, but if this piece of equipment was to move to a standard supply room the Earth Leakage Current could be in breech of the limit of 1000uA (as the leakage current seems to double from an isolated room to a standard room).

Is there a different standard that we should test to when our supply is from an Isolation Transformer?

What is considered best practice when ESTing equipment running on an Isolated supply?

Any help with thus would be greatly appreciated.

"When testing to the 601 Standard, the values for Earth Leakage are much lower in the isolated case, approx 50% of the values measures in the standard case for the same piece of Class1 Type CF equipment"

The limiting values for earth leakage that presumably you are referring to for Class 1 B, BF and CF are in Single Fault Condition 500 uA, and Double Fault Condition 1000 uA.

If you EST'd a piece of equipment in a room powered by an isolated supply, the safety tester should flag up "open earth" on boot up, and this would indicate you cant proceed. Perform the EST in a non-isolated supply environment, if it passes there, it should be fit to be placed within the isolated supply area.

If you plug in a 601PRO and try to perform automated EST tests within the isolated clinical area, the can cause fault indications to be recorded within the sensitive isolated supply monitoring system. Also the use of "martindale" type power testers cause similar problems. Failure to note this may lead you to receive a "not too pleasant" call from Estates / Facilities.

There are a number of excellent downloads in this forum available which will help you understand the principles involved.

See the attached for guidance

http://www.mhra.gov.uk/home/idcplg?IdcSe...p;Rendition=WEB

Pleased to see that you've posted at long last, Buddy.

Surely the short answer to the question you pose is to move the kit into a non-isolated (ie, normal mains) room to carry out your EST?

And Sean is right ... (in my experience) the Bio-Tek won't "pass go" in the situation you describe. I seem to recall that an earlier tester would only "allow" something like 8 volts between neutral and earth.

Thanks guys, long time a looking.. first time a posting!

I agree that the best solution would be to move the kit to a different non isolated room. However the whole of our ICU is now isolated and taking each piece of kit (which are all on a wall mount) to another room each time we do routine/reapir isn't really something I would like to comtemplate.

The only solution that we could come up with was to run a cable (to power the EST) into the ICU from an outside socket. Again this poses some real problems!

Are you saying that there are no normal L-N-E power outlets in that department?

How come? Where are the cleaners supposed to plug in their appliances, for instance? And what about the mobile x-ray unit?

In my experience, even Operating Theatre suites have non-isolated outlets provided somewhere.

Is (was) this a New-Build? Sounds a bit like someone slipped up there, to me.

I spoke to the contractor that refurbished the ICU he told me there was just one normal plug for a washer on one side of the unit.

I must admit I had not considered the cleaners or the mobile X-Ray unit. However I have not heard of any issues with either of these. I will be asking some quaetions now though!!