Armoured cable for DC

[Tinbum]

I have a company in redoing one set of my solar panels through an insurance company and in the conversation with them we talked about running the DC through armoured SWR cable as it is at present and they say it's not allowed. Something to do with it not being double insulated.

Anyone heard of this?

[Stinsy]

Nonsense!

Armoured cable is indeed double-insulated and is perfectly fine for DC applications. Every rating table I've ever seen has made this clear.

Here is a document you can use for current ratings and voltage drop calculations: https://www.rm-electrical.com/wp-conten ... trical.pdf

SWA cable tends to be rated at 1000V between cores and 600V core-to-earth. Domestic PV installations tend not to exceed 500V so you shouldn't have a problem there either.

[nowty]

I agree Stinsy,

Armoured cable is double insulated anyway, in fact they are generally triple insulated. You could argue each conductor in the multicore cable would only be single insulated.

I recall looking at the spec of armoured cable I have used and it was well within the voltage capability of the cable in both DC or AC, so I don't have an issue of using it and I certainly would not use any other type underground.

Maybe its a general MCS recommendation for connected panels to an inverter ?, i.e, use double insulated solar cable with 1000v+ rating. And the company has interpreted it literally without taking any reasonable intelligence.

Or maybe its just cheaper not to use armoured cable !

[Tinbum]

I was surprised as armoured is rated for AC and DC.

As the wall the inverter is on is due to be knocked down I asked if they could relocate the inverter in the process which they are happy to do. I'd already put in a new armoured cable for the DC but they say they can't use it as explained above. They have been pulled up for using it on a big project. They think it's possibly because the DC can't be isolated.

The other strange thing is the inverter has to be mounted on a fire board which is then mounted on a brick wall!!

[nowty]

I was surprised as armoured is rated for AC and DC.

As the wall the inverter is on is due to be knocked down I asked if they could relocate the inverter in the process which they are happy to do. I'd already put in a new armoured cable for the DC but they say they can't use it as explained above. They have been pulled up for using it on a big project. They think it's possibly because the DC can't be isolated.

The other strange thing is the inverter has to be mounted on a fire board which is then mounted on a brick wall!!

I can understand that they might not have wanted to use the SWA because you'd installed it so its not theirs. I do recall having a hell of an argument with a BT man when they installed my broadband 11 years ago. I wanted the main termination socket in the lounge next to my router and not in the hallway were the cable came in. He wanted to staple the cable along the skirting board and drill through an internal wall. But I already had laid a twisted pair cable under the floor so all he had to do was connect it up. He did not want to use it but in the end he agreed although he grumbled, "I'm not supposed to do this."

[Fintray]

My latest PV system was installed by a MCS installer and they had no problem with me supplying and running in the 4 core SWA cable between the panels and the inverters.

[Stinsy]

The other strange thing is the inverter has to be mounted on a fire board which is then mounted on a brick wall!!

Mounting the inverter onto fireboard that is set away from the external wall is to reduce condensation. Because my inverter is in the attic attached to the gable-end wall, the installer who put my system in did as you describe.

[Tinbum]

I can see that is logical for some cases. This is actually mounted on the external brick leaf of a cavity wall that is inside a barn (so actually an internal wall) and the inverter is rated for external mounting.

[Tinbum]

I can understand that they might not have wanted to use the SWA because you'd installed it so its not theirs. I do recall having a hell of an argument with a BT man when they installed my broadband 11 years ago. I wanted the main termination socket in the lounge next to my router and not in the hallway were the cable came in. He wanted to staple the cable along the skirting board and drill through an internal wall. But I already had laid a twisted pair cable under the floor so all he had to do was connect it up. He did not want to use it but in the end he agreed although he grumbled, "I'm not supposed to do this."

I hate cables surface mounted like that but can understand why someone may not want to use a cable someone else ha put in. This SWR is about 8m long brand new and visible from one end to the other. I don't mind if they want to run their own cable but it would be much better and much safer in armoured.
4 cores of single core solar cable won't have the same physical protection that armoured does inside a barn.

[Stinsy]

I can understand an electrician's reluctance to use a cable installed by someone else. But common sense has to be applied. Particularly with SWA. If you can see both ends and have a good idea where it goes, insulation resistance tests OK, R1+R2 and R1+RN both test in line with the estimated length, then they should be very confident in using it. If there was an iffy hidden or buried junction box or something, the above tests would show it...