Medical Device With 2 Power Cords

[Ohad Barsheshet]

Hey Anyone willing to help out

Our design team is considering an action.

our medical device is required the use of a pressure gauge (we have one that is clinical approved)

the pressure gauge comes with a transformer of its own, for safety reasons we are going to implement the pressure gauge inside our device enclosure.

we are considering if to power the pressure gauge through our medically approved power supply or just to make another power cord entry for it (basically 2 power cords one for the power supply and the second one for the pressure gauge)

did anyone tried something like that before?

or do you guys know what is the regulatory meaning for said action?

since now its 2 power sources for the same device.

Thanks In Advance,
Ohad.

 

[yodon]

Just from a risk management perspective, having 2 power cords doesn't seem like the best approach (incorrect connections, entanglement, etc.).

The reason they are "medical grade" (which I'm told is a misnomer anyway) is to support safety requirements. So if the other one isn't "medical grade" then there would be considerable testing and a high likelihood of test failure.

 

[Ohad Barsheshet]

Hi Yodon!

I appreciate your reply, After some data collecting i found out that the Provided transformer produce : 5V, 2A, 10W, 60Hertz Its Load Regulation is 5% Basically he can provide 4.75V-5.25V

While my Medically approved Power Supply can produce the same thing and his Load Regulation is 4.95V-5.05V
Essentially making it a more stable option.

Side note Obviously my power supply since being medical grade has more layers of protection against power spikes, EMC, Shorts, ETC...

Where the provided "dumb" Transformer doesn't have.

Apart the data i took into consideration is there anything else i should look at?

Thanks In Advance,
Ohad.

 

[Tidge]

I am familiar with ME equipment designs for which:

• There is a central device, designed to connect to an AC wall outlet (MAINS)
• The central device also distributes AC (not MAINS) to peripherals
• The peripherals can run on AC (MAINS) if necessary

The distribution of "wall AC" from the central device to the peripherals was using what anyone would casually recognize as a 'rated power cord', but those didn't have 'plugs' for wall outlets... but it certainly was possible to have a perfectly appropriate power cable between the peripheral and MAINS.

For those designs (of which I am familiar), each of the peripherals (and the central device itself) had all the necessary means-of-protection individually (and collectively, obviously).

I want to disclose: The devices I am familiar with date from the "second edition" era of 60601-1; it is entirely possible that a 14971-inspired risk analysis of such a design (as required by 3rd edition) could determine that allowing a connection of a peripheral to MAINS isn't free of unacceptable risk. Our design teams long ago stopped trying to make the peripherals work as 'stand-alones'. I suspect this was driven mostly by some sort of marketing strategy, with a little bit of cost consideration (cost of components, but also required cost of brainpower). I do know that we used to have plenty of customers who LOVED being able to run the peripheral devices without having to be connected to the central device... and as far as I know, all of the varied separate uses of the peripherals as stand-alones were understood and considered in risk management files, so I felt (and still feel) that we have sacrificed market share (and customer goodwill) by following this strategy.

 

[Peter Selvey]

In the 2nd edition having two power cords (two connections to mains) was explicitly prohibited (Clause 57.3).

This was (quietly?) transferred to the definition of MEDICAL ELECTRICAL EQUIPMENT (3.63) in the 3rd edition, but I guess the intention was the same, to allow only one connection.

It's been a while but I used to see equipment like Tidge mentioned with a single connection to the mains and then internally ac was distributed to devices already "approved" for direct connection to mains and even used normal mains plugs, power boards for distributing the ac, but kept fully inside the enclosure so the end user would be none the wiser. It was OK as long as fusing, leakage, internal temperatures etc were verified as OK. For example, inside temperatures might be hotter than a normal room, cumulative leakage etc.

There is a weak point legally if the manufacturer of the "large" product does not have a good relation with the "smaller" product manufacturers. For example, you could "type test" a system and show everything is OK, but the the manufacturer of the smaller product changes something that is still OK for use as standalone, but conflicts when used inside the larger device. But that's only likely to be an issue if things are running close to limits, and of there is good relationship the smaller manufacturer can advise of any changes in advance to allow for re-evaluation.

 

[Ohad Barsheshet]

Hey Guys, For those interested in closure haha

After consulting with your guys input and the company of the pressure gauge we have come to the conclusion we can indeed use the power supply to feed the pressure gauge instead of a second power cord entry and the use of that generic transformer.

Appreciate your help!!

Best,
Ohad.