Need all expert to advice and thanks in advance.
Do I need to have a isolation transformer if the individual equipment in my endoscopy system meets IEC60601-1 standards. In addition, they are all plugged to individual power socket on the pendant with 10mA RCCB.
I understand that for Endoscopy system installed on mobile trolley with ganged-socket an isolation transformer is required on the trolley so that the leakage current is keep within safe limit.

It's good that your equipment meets IEC60601-1, but what really matters here is the practicality of the situation.

Are you wondering if each item of equipment needs an isolating transformer ...?

Can we assume that the pendant you mention is in an operating theatre?

Is the pendant part of an isolated power system? Is there a LIM (what does it tell you)?

The RCCB(s) won't offer much protection against high leakage current(s), but rather against equipment faults (short to earth, etc.). But having said that, 10 mA sounds a bit low to me. After all, the main reason (these days) for an isolated power system is to prevent power interruptions (even in the event of "minor" equipment faults).

Where are you using the "system installed on mobile trolley"? Outside of the OR? You may or may not need an isolating transformer - it all depends on the total leakage current the system delivers.

How many items of equipment in the "system" on the trolley? Which items are they?

Lastly, how good is the electrical system in general where you are? Can you rely on decent earths, for example? And is neutral connected to earth - or floating about at some other level?

In short - more information required!

Geoff, thank you for the reply.
1) I am wondering if I should connect all the endoscopy system equipment, ie CCU, lightsource, CO2 insufflator and flush pump, needs to be connected to a isolation transformer if they are all from the same electrical power circuit.
2) the pendant is in a Endo procedure suite not in operating theatre
3) The pendant is having a grounded power supply not isolation power supply. Would you consider a Endoscopy suite wet location like operating theatre?
4)When you say the RCCB is a bit low, do you mean it is not sensitive to prevent a leakage current fault?
5)We were using the isolation transformer on the trolley because we were using non-medical grade video recording system with the endoscopy system.
5)This site is a new endoscopy center so the power system has just passed commissioning and it is a grounded system.

OK, so we are talking about a normal (grounded) electrical system.

As it's a brand new system that has just been commissioned maybe it's a bit late to second-guess the designers' solutions!

But back to the 10 mA RCCB(s). Where is this (are these) actually in circuit? I read your earlier post to mean one for each power outlet on the pendant.

Are you saying (as I think you are) that each item of equipment is plugged in to a separate power outlet on the pendant? Or are you using the trolley (complete with isolation transformer) in the Endo suite - and just plugging in the cable from the ganged connector on the trolley to a single outlet on the pendant? Let's be specific here.

With regard to the trolley - I would prefer a "medical grade" video recorder; otherwise I had better let others on here give you "chapter and verse" on that one.

An isolating transformer is not required it is only needed if the sum of the leakage currents is more than the acceptable limit as only one plug is connecting it to the mains supply. In this case all the equipment together is treated like a single item because of the single plug.
When the system is connected to a pendant each piece of equipment has its own supply so they are treated as individual pieces of equipment. Assuming each piece of equipment has a leakage current within limits there is no need of an isolating transformer.
Robert

See also this earlier thread.

Thank you, Geoff and RoJo!

Geoff,
1)Where is this (are these) actually in circuit?
I understand each electrical circuit with 10mA RCCB are connected to 5 power outlet on the pendant.
2)Let's be specific here
Yes, Geoff you are right the individual equipment is plug to each power outlet.

Without an opportunity to take a look at the circuit (diagram) I can't be sure ... but from what you're saying I can't see the point of those 10 mA RCCBs. Moreover, I would anticipate that the only "service" they'll perform will be the amount of "nuisance tripping"* that the staff will enjoy!

However; see my post under your other thread - maybe they have been provided to meet a spec about "wet locations" - but I would still question the 10 mA setting.

No doubt this reference will muddy the waters for you even further! In other words, when it comes to "wet location(s)" - versus - IPS(s) it seems to be an "either-or" situation (and it sounds like your hospital may have chosen the "wrong" one)!

Meanwhile, are there any line circuit breakers anywhere in evidence (at a panel on the wall, perhaps)?

By the way:- I see you are in Singapore; do you still use the British-style 13-A (polarized) plugs (with fuse) and socket outlets?

* Due to "inrush current" on switch-on, for example.

OK - I've got it now; it seems there are basically two types of RCDs:-

1) Type 1 : nominal tripping current 10 mA AC
2) Type 2 : nominal tripping current 30 mA AC


See here.

Here is another good reference document:- HTM 06-01.

This document is a good guide but is now outdated and in the process of being updated. Always refer to the latest version of the standards (BS 7671 in this case).

Just out of interest in the USA there is now a move to specify RCDs with a 5.6mA trip rating for medical locations.

Also remember an isolation transformer only provides protection against electric shock before a first fault to earth occurs. Once a fault has occurred then any subsequent fault would provide no protection! If each socket-outlet were protected by an individual RCD then safety is always maintained and there can be no issue from false tripping due to too many items being supplied by a single RCD.

How many devices that suffer a first fault to earth would be still working safely?

I have asked before on this forum for the number of times a LIM sounds as a result of a first fault to earth and the answer came back as almost never! The monitoring tends to operate when there is a circuit overload (drawing too much current) rather than some breakdown in equipment insulation.

Those are all good points, Mike.

So it seems that we can now look forward to an RCD at every isolated outlet. Sounds good to me; it would also help in identifying them, which would be another "plus".

Do you have any idea how the 5.6 mA value comes about?

On the last point, I suspect that any faulty equipment would just have been removed, then repaired and returned to service without any further investigation being carried out (or recorded). Also, is it normal practice for theatre staff to keep a log of LIM alarms (and the action taken to silence)? Somehow, I doubt it.

Well, the 2nd edition of 60601-1 allows 5mA earth leakage current (to allow for the BF fault of 5mA) and this single fault limit is the same for most domestic products.

I see UL943 also requires automatic testing of these devices, which tend to be rated 4-6mA Class A.

I must admit that I thought the lowest available RCD tripping value was 10 mA.

Is the 5 mA actually an "alarm" value, I wonder?

I ask as I have been unable (thus far) to find any reference to a 5 mA tripping RCD on line (aha, yet another pun)!

But see this catalogue.

No, these trip out like RCDs but you need to use the correct USA terms to be able to find them with Google!

Take a look at this NEMA GFCI information about the matter.

Yes; we should call them GFCIs!

In general (and to keep things simple) I would suggest that an GFCI protects just a single circuit (hence the low tripping value of 5 mA) whilst an RCD typically protects more than one circuit (30 mA tripping). So I believe that, for the circumstances being explored in this thread (one at each isolated outlet), GFCI (albeit apparently a "non-British" term) is the appropriate terminology.

GFCI : Ground Fault Circuit Interrupter
RCD : Residual Current Device

For further comments, opinions (and confusion) see this link.

Geoff,
Yes, we are still using the British-style 13-A (polarized) plugs (with fuse) and socket outlets. ;-)
I think you are right as they have catergories the endoscopy suite as "wet location" and they could not use IPS due to space constraint therefore the 10mA RCCB was installed.
"your hospital may have chosen the "wrong" one)! frown" >> you mean we should insist for a IPS for the Endoscopy system?

It's good to hear that you're still using the world's best arrangement(s) of mains plugs and sockets!

Regarding all the other stuff, it probably depends which Code(s) (Standard(s)) are being followed. As I have already mentioned, I like NFPA 99 myself (even though it is American).

Lastly, "wet location" (or not) is a local judgement call - again, I hope and presume, based upon the relevant Code(s) being followed.

The link I gave at the post to which you refer was really to indicate how "muddy the waters are" on these issues. NFPA 99 does encourage IPS in wet locations (as this .pdf makes clear). But it sounds like, in your case, you may have to tolerate an occasional interruption of power if certain fault conditions occur (that is, due to the lack of IPS).

See also this earlier thread ...

Care needs to be taken when reading documents like this, which have been produced by the electrical installation equipment manufacturers as they have a vested interest in selling more product.

A 5mA RCD will provide the same shock protection as the 5mA leakage current from an isolated supply transformer (USA specifications, in Europe the transformer limit is 0.5mA). In fact it could provide more protection, as once a first fault to earth occurs in an IPS you have no protection if another fault occurs! The only real reason for using an IPS is when continuity of supply is critical (life support and life sustaining equipment).

If the locations were truly "wet" then the only effective protection is by using safety isolated low voltage supplies as would be used for pools. (See section 702 of BS 7671.)

Yes; and I think that's what NFPA 99 is saying.

Myself, I think that the "problem" here is the business of the "wet location". It seems to suggest an "either/or" situation.

Many folk might argue that all OR's (and Endoscopy suites etc.) are "wet"; whilst others may insist that the intention is that only places like Hydrotherapy should be considered "wet".

I believe we need a new set of definitions (and corresponding "guidelines" regarding electrical safety and protection) to suit contemporary (Real World) situations!

The notion of "wet" locations is something that has crept in by manufacturers in order to sell more IPS units. The reality is unless a low voltage supply is used (12V AC inside the pool and 25V AC outside the pool) then no adequate protection will be provided.

The leakage current from an isolated supply (IPS) transformer is still hazardous to a patient if it reaches a sensitive intracardiac site.

If the continuity of supply is not critical then an RCD will provide suitable protection, especially at the low USA trip value.

When was the last time anyone received an unintentional electric shock (not static discharge) while using medical electrical equipment? Given the volume of equipment used outside of a theatre, so not connected to an IPS, we would have expected many reports if this was a real issue. We don't see this as modern equipment is well designed, to meet the regulatory requirements, and well maintained, to meet legal obligations, that the opportunity for an electrical hazard is almost none existent.

I agree Mike ... but we need to be careful that the Bean Counters don't seize upon all that as a reason (excuse) to cut back (even more) on tech support (regular EST and PM - in a word vigilance - by in-house biomed departments).

Remember that the "push" for biomed departments came about, by and large, due to the "fanfare" surrounding electrical safety in hospitals. In short, a whole industry* has grown out of a few well-documented cases (many years ago now) of hazardous equipment, environments ... and er, incompetent staff.

Don't knock it, Mate!

* Similar to quite a few of the more modern "industries" ("climate change" being but one example).