H07RN-F FLEX MAINS suitability

[Midwest]

At work in our main kitchen, the 6kW (26A sp) water packed up. The restaurant staff were in turmoil, as they had no hot water to make the tea. Luckily we had a new spare one lying around.

The old one was fed by a 32A supply, 4mm 6242B (LSOH) cable 32A RCBO. From the rotary isolator, the appliance was fed by a 3 core 4mm H07RN-F cable (about 1m). So I was just going to disconnect that from the old appliance, and reconnect to the new one.

However, once I disconnected it, I found the insulation on the cores had failed, it was crumbling away in places. The sheath was fine. The stranded conductors were slightly rigid. As the flex was too short to cut back, we got a new piece. No ferrules had been used on the terminations, but there was no sign of thermal damage on the terminals.

When I removed the old flex, it was pretty much the same throughout its length. No obvious sign of similar damage to the 6242B cable. I see that the 4mm H07RN-F cable is rated at 30-34A, depending on manufacturers.

So I can’t see the flex is being overloaded, terminals could of been a bit tighter.

No pic of cable I’m afraid. Thoughts?

 

[Pretty Mouth]

Had the CPC insulation perished too?

 

[DPG]

Had the CPC insulation perished too?

Perfect question.

 

[pc1966]

Any idea how old it was?

Typical lifetime for cables is 25 years at max running temp, which could be the case here. But it might just have been a poor batch, or maybe the environment was rather hot so cable really running above its specification. Typically for chemical degradation effects lifetime is halved for every 10-20C increase in temperature, so maybe not burning but could have its lifetime brought down to a decade or so.

 

[Midwest]

All cores suffered some damage, cable can’t be more than five years old. It’s situated in a warm environment, about 23’.

 

[DPG]

All cores suffered some damage, cable can’t be more than five years old. It’s situated in a warm environment, about 23’.

Got to be a bad batch surely.

 

[Midwest]

Got to be a bad batch surely.

Possibly, might check round all the other appliances we have.

 

[Midwest]

Found the old cable, pics.

 

[Rockingit]

That doesn’t look like H07 to me.

 

[Midwest]

That doesn’t look like H07 to me.

Its marked as Vede H07RN.

The shorter stripped end was terminated in a junction box (in 15A strip connector!) and the longer end was terminated in the appliance. These longer stripped core's, were me pulling off the outer sheathing, before I realised the cable had had it.

The cable is not very flexible!

Started to have a look at the other appliances in the kitchen, seems to be the same sort of cable. None seem to have the same rigidity as this damaged cable, but I think further inspection is needed. I think if they are same source of cable, they might need replacing. We've got fryers, steam ovens etc.

 

[pc1966]

...I think further inspection is needed. I think if they are same source of cable, they might need replacing. We've got fryers, steam ovens etc.

Yes, very good call!

H07RN is typically only rated to 60C anyway, but you can pay a bit more and get the butyl TQ flex that is 90C rated.

 

[pc1966]

OK, here it says 85C:

4.0mm² 3 core Butyl Flex - Black - 50M Drum

 

[Rockingit]

Its marked as Vede H07RN.

The shorter stripped end was terminated in a junction box (in 15A strip connector!) and the longer end was terminated in the appliance. These longer stripped core's, were me pulling off the outer sheathing, before I realised the cable had had it.

The cable is not very flexible!

Started to have a look at the other appliances in the kitchen, seems to be the same sort of cable. None seem to have the same rigidity as this damaged cable, but I think further inspection is needed. I think if they are same source of cable, they might need replacing. We've got fryers, steam ovens etc.

The whole point of H07RNF is its ability to be flexible and take the knocks and abuse because of it being rubber - that‘s why we use it by the mile in the events industry. Depending on the use/method it’s normally rated 60c to 85c. I‘ve also rarely seen it with a cotton core below 10mm sizes for 3c. As others said originally - I suspect what you‘ve got there is a rogue knock-off used at the initial installation - you might want to look at swapping it all out. Regardless…… it shouldn‘t have deteriorated like that.

 

[nicebutdim]

Its marked as Vede H07RN.

Vede or VDE (visible in images) which is a German standard. Is there a manufacturer's name or any more characters after 'RN'?

 

[James]

rubber is not resistant to oils, could it be airborne oil mist or fume has helped it deteriorate faster?

 

[Rockingit]

rubber is not resistant to oils, could it be airborne oil mist or fume has helped it deteriorate faster?

H07 is a funny tigger…. Inner cores are Rubber (EPR) but the outer sheath is actually Polychloroprene which IS oil resistant. And from practical experience of having retrieved enough over the years where its been used to supply catering concessions I can absolutely vouch for that!!

For even more extreme uses there’s H07 BN-F but that’s a different animal again.

 

[Midwest]

Vede or VDE (visible in images) which is a German standard. Is there a manufacturer's name or any more characters after 'RN'?

I’ll post a pic later.

 

[Midwest]

rubber is not resistant to oils, could it be airborne oil mist or fume has helped it deteriorate faster?

The appliances is situated in a vestibule between kitchen and restaurant, not subjected to oil mists etc.

 

[Midwest]

picture as requested.

 

[mattg4321]

I’d be thinking the cable is a fake/not to the standards it purports to be.