440V heating element insulation test

Hi

I do voluntary  work on a retired Royal Navy Fleet Tender vessel,  both electrical and engineering. We have a 440v ships galley oven and hot plates. There is no RCD, so as part of a safety check,

what insulation reading would I expect across the elements and their tubular casing, what would be considered as a pass/ fail figure

thanks

Mike A

id be considering anything below the value in the required standards as a fail. anything above and its a pass. youd have to check the standards for your installation type to find out what this value is

Anything under 2Mohm needs investigating, under 1Mohm needs replacing.

What are you using to measure the resistance??

There are I believe separate regulations for sea going craft. I’d also hazard a guess RN requirements are different to merchant shipping. As to whether the separate regulations or BS7671 apply to a laid up ship would be a very debatable subject.

Shipboard distribution can be weird, when you mentioned 440V, it suggested an earth free system to me. Dock side supplies can usually be swapped around for various voltages, the ships intake is equally variable.

Your best bet would be to contact the RN engineering depot your ship was previously assigned to for a definitive answer.

To carry on @apprentice87’s point, do you have the necessary test equipment?

Notwithstanding the above comments about varying regulations and standards to which you may need to be working, if you are effectively conducting an insulation resistance test at 500 Vdc on a heating appliance in accordance with the COP for in service testing then the minimum value for a heating or cooking appliance over 3 kW would be 300,000 Ω, possibly after a period of heating to drive off adsorbed moisture if they have been standing for a long time.

All other class I items should be minimum 1 MΩ.

Good evening gents - many thanks for your replies - I'm using a MEGGER BM80/MIN on the 500v range. I'll give the  elements a toast and see what happens to the insulation, and as also suggested, contact the RN and see what I can glean.

best regards

 Mike A

I’ve done work for the services (non electrical) and they’ve always been helpful, but you have to ask.

@Ardet R, what is the COP for shipboard electrical systems.

BS8450 is the BS for ships Tony.

"BS 8450:2006 Code of Practice for Installation of Electrical and Electronic Equipment in Ships"

I think Ardet's values are from the PAT CoP?

There is some guidance in old versions of the IEE wiring regulations wrt generic insulation testing.

Also, I think that Rob is not far away really.

Anything less than 1M Ohm needs looking at seriously to find out why it is so low IMHO.

Sidewinder said:

BS8450 is the BS for ships Tony.

"BS 8450:2006 Code of Practice for Installation of Electrical and Electronic Equipment in Ships"

I think Ardet's values are from the PAT CoP?

There is some guidance in old versions of the IEE wiring regulations wrt generic insulation testing.

Also, I think that Rob is not far away really.

Anything less than 1M Ohm needs looking at seriously to find out why it is so low IMHO.

Click to expand...

I would be inclined to agree with you on this one, to be honest I've often wondered where you'd stand with certain regs, regarding certain situations. For example, to drive a car on a public road you need a valid MOT certificate if the vehicle is over 3 years old, now if I wanted to run that vehicle on a private road, lets say as at a transport museum, then I would have no need to have it mot'd, although obviously I would have to make sure it was in a safe condition. How would this relate to say a ship, boat, or whatever you want to call it, if it was kept in dry dock and powered from a power supply on land? If the vessel was never going to sail again then which regs would you follow? Is it still classed as a seagoing vessel, or is it classed as part of a land based structure in the same way as lets say a portacabin.

Like where you are going with that Phil.

So thinking on that vein, those barge boat type things that I have seen done up as homes on programmes like Grand Designs and are moored for most of the time in one place, but could be moved on water. I presume they just got the local spark to wire it up probably qualified with his lets say 17th edition, I wonder if any consideration was given to any other sea going regs?

Sidewinder said:

BS8450 is the BS for ships Tony.

"BS 8450:2006 Code of Practice for Installation of Electrical and Electronic Equipment in Ships"

I think Ardet's values are from the PAT CoP?

There is some guidance in old versions of the IEE wiring regulations wrt generic insulation testing.

Also, I think that Rob is not far away really.

Anything less than 1M Ohm needs looking at seriously to find out why it is so low IMHO.

Click to expand...

Yes we went in to that a while back, maximum of 1/10,000th leakage of circuit FLC.