SIP 150l wiring issue

[gretsch-drummer]

Hey all, just purchased a SIP belt 150l 13amp single phase compressor but we've come across a stange hic-up with wiring/plugging it in.

I've got it situated outside undercover were we installed an external socket which is wired to the sheds 16amp fused RCD socket with a ~3meter 1.5mm core lead.

The compressor trips this but when we plugged it into a 25meter 1.5mm core reel extension lead it works perfectly fine.

In basic terms, the compressor trips when using the short 1.5mm core, 3meter lead but works fine when using the thinner core 25meter extension reel.


Is there a minimum length of lead you should use when using a compressor?

(I'll find out the way the wiring is fed into the shed from the house extension tomorrow if it helps.)

 

[rtbcomp]

I'd check the wiring in the shorter extension first.

 

[Robotstar5]

Have you tried anything else in the "compressor socket"?

 

[gretsch-drummer]

We used a heat gun on the small extension and it worked perfectly and we re-wired the sockets 2/3 times over.

But another weird thing was if we plugged the smaller extension into the larger reeled extension (so daisy chaining them) the compressor would work fine ...strange, very strange.

Could the longer extension be reducing the start up amp'age 'just' enough to not trip the fuse?

 

[Julian_P]

1.5mm lead is too small for a 3hp compressor, needs to be 2.5mm min. 1.5mm is normally used for lighting circuits (fixed wiring) and will start to warm up if you're not careful.

What's 'tripping,' the compressor overload or the RCD? If it's the RCD then you're going to probably have to source one designed for motors (time delayed) as the standard issue domestic jobbies are not designed for 3hp motors with their large initial starting current draw.

Julian

 

[wheresmejumper]

are you plugging the 25 meter extension into a different socket?one that isnt protected by the 16amp rcd?

 

[zx9]

1.5mm lead is too small for a 3hp compressor, needs to be 2.5mm min. 1.5mm is normally used for lighting circuits (fixed wiring) and will start to warm up if you're not careful.

What's 'tripping,' the compressor overload or the RCD? If it's the RCD then you're going to probably have to source one designed for motors (time delayed) as the standard issue domestic jobbies are not designed for 3hp motors with their large initial starting current draw.

Julian

Julian might have it, is it a 'b' mcb? The 'd' ones are more suitable for high start up currents.

 

[rtbcomp]

Are we confusing MCBs and RCDs. An RCD isn't current dependent, if the current in the neutral is the same as in the live it won't trip.

 

[zx9]

Are we confusing MCBs and RCDs. An RCD isn't current dependent, if the current in the neutral is the same as in the live it won't trip.

Sorry, my mistake I had assumed if it was rated at 16A it must be a MCB.

 

[rtbcomp]

I was wondering if the OP was confusing the two.

 

[Julian_P]

Are we confusing MCBs and RCDs. An RCD isn't current dependent, if the current in the neutral is the same as in the live it won't trip.

Combined unit? My outbuildings supply comes from a 30mA 63Amp combined RCD/CB unit.

I think the point is that these domestic things are mainly tailored for resistive loads and hover lawnmowers and the like. A 16amp unit (without a delay) will not handle a 3hp motor with a starting current that's probably thrice normal - which is pushing a standard 13amp fuse when the motor is fully loaded.

Julian.

 

[rtbcomp]

I run a 3HP compressor through a 30mA RCD in a consumer unit and a 2HP compressor through a 30mA RCD protected socket and have never had any trouble with them tripping.

It doesn't make any difference whether the load is resistive, capacitive or inductive, the line & neutral currents will be equal under no-fault conditions.

 

[wheresmejumper]

i was thinking the rcd protected socket was in fact an rcbo,a or b curve,and tripping due to overcurrent.
where he plugged the 25m lead in was 20amp rated,the overcurrent on startup not long enough to trip 13amp fuse.
long shot though

 

[rtbcomp]

That's the problem with remote fault diagnosis, you can never be sure you have all the facts.

I'm sure any one of us could have fixed it by now if were on site.

 

[Julian_P]

I run a 3HP compressor through a 30mA RCD in a consumer unit and a 2HP compressor through a 30mA RCD protected socket and have never had any trouble with them tripping.

It doesn't make any difference whether the load is resistive, capacitive or inductive, the line & neutral currents will be equal under no-fault conditions.

Yes, but specifically in this case the OP informs us that it's a 16 amp unit (''16amp fused RCD socket'')- that's surely the problem here. Starting current well in excess of that - the RCD function of the trip is not _the_ issue.

Julian

 

[rtbcomp]

Yes, but specifically in this case the OP informs us that it's a 16 amp unit (''16amp fused RCD socket'')- that's surely the problem here. Starting current well in excess of that - the RCD function of the trip is not _the_ issue.

Julian

But the OP states it's an RCD protected socket that trips, that to me describes an earth leakage fault, overcurrent won't trip a dedicated RCD.

We need to be certain whether we are looking at an RCD trip or an MCB/RCBO trip

 

[gretsch-drummer]

Cheers for the comments guys, I'll forward them to my electric-minded friend.

This is the way we plugged it all together:

This is out RCD unit in the shed:

Fuse for the sockets and another for the tube light.

Outside socket:


Which uses a 3/4meter cable which we plugged into the sockets in the shed:


^This set up would trip the B16 fuse.

But if we plugged the small extension into the big 25m 1.5mm extension it would fire up fine:


The compressor would work fine when plugged directly into the long extension.

 

[rtbcomp]

Which of those three trips actually trips out?

 

[gretsch-drummer]

Sorry, it's the B16 fuse which is used for the sockets.

 

[rtbcomp]

Right.

That's an MCB not the RCD (that's the one on the left). The MCB is a B type, it wants replacing with a C or D type (as ZX9 says). They are slower to react so will not trip on the surge.

By using a longer extension you're increasing the resistance and thus reducing the current, so the MCB doesn't trip.