Where is the fuse? 5

[MarkGallimore]

Hi, I've been asked to send a piece of laboratory equipment over to North America for use in a laboratory. It's intended to sit on a bench and plug into a receptacle. In the UK this apparatus has a 240v single phase plug which contains a 13amp fuse and all runs well - (note that the fuse protects the equipment and cable downsteam of the plug and not the upstream branch circuit). I understand that to power it in the US it will run off a 230v receptacle in the lab and will not be wired directly to a branch circuit as you might do with a large motor. The US plug will be added by the lab owner. I'm confused about fusing. In the current configuration the fuse is in the UK plug. If this is swapped for a North American plug then the only protective fuse will be that on the brach circuit (I think that's correct - could be wrong though). If the lab owner's branch circuit is fused with a 20 or 30 amp mcb then how does this protect my equipment in the event of a short or overload inside the equipment? Should I add a lower rated fuse inside my equipment or can the applicable US plug / receptacle hold fuses rated at a lower and more appropriate current for my equipment? In case it's necessary info the equipment is built to iec61010-1 and contains a heater and two servo motors and their controllers. Thanks for any advice offered.

 

[Skogsgurra]

All US instruments that I have seen do have the fuse in the equipment. A fused plug is not very common outside the Commonwelth. In fact, "the Claw" is the only one I know about that has a fuse built in.

I guess that you have to put a fuse in the back panel of your equipment.

Wait until they wake up on the other side. You will get better informed advice then.



Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[waross]

Yes Gunnar, you are correct.
Branch circuit protection in North America protects the branch circuit conductors.
Equipment needing fuse protection has protection built into the equipment.
For 220/230/240 volt equipment in North America you must fuse both leads.
respectfully

 

[LionelHutz]

I've never seen a fused power cord over here. I would expect you need to put a fuse on the back panel.

 

[davidbeach]

waross is correct in that it will require two fuses.

 

[rbulsara]

It is very common (even in the USA) to have dedicated receptacle for certain equipment, wired to its own branch circuit breaker or fused disconnect. Just ask the owner to do so.

 

[rbulsara]

In fact, 230V outlets in the USA are uncommon, meaning they are not general purpose outlets (they will be 120V). So most 230V outlets are separately wired here.

 

[MarkGallimore]

Thanks to all who've responded. All points noted with interest. Re rbulsara's comment's - I'd been under the impression that in most large laboratories 230v was readily available via receptacles to allow for easy use of small / easily portable specialist gear that might be sourced in western europe. Good job you guy's are here - this is a very helpful website.

 

[rbulsara]

Mark:

No, that is not the case. 230V outlets are easily available but are only provided where required. The installer will also have to change out the plug to match NEMA receptacle here or only provide leads for hard wiring.

Also, the 230/240 or 208V single phase source here requires 2-pole breakers/fuses as both are line conductors coming off a 240/120 single phase, 3-wire or 240V or 208V 3-phase systems. Leave that up to the Owner.

 

[itsmoked]

You should consider something like:

http://rocky.digikey.com/WebLib/ETA/Web Data/3130 Series.pdf

If you just use two fuses one will blow on a fault leaving 120V still live in the device.

If you use an instrument type double pole breaker then if one is tripped it takes the other with it.

There are several different types.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com