Extending a Spur

[JohnW2]

It's also worth noting, with reference to a recent thread regarding spurs, that had the OP had a double socket (and drier in the same room) we would have heard nothing about it - yet, electrically, everything would be exactly the same as he wants to do.

Indeed so.

Kind Regards, John

 

[steve271]

I suppose it's not impossible that could happen if compressor and dryer motor started absolutely simultaneously but, despite echoes' experience, I would have thought it extremely unlikely.

It takes at least around 22A to blow a 13A plug/FCU fuse ever, and a lot more current than that that to blow the fuse very quickly (i.e. if the excessive current is very brief, as with a start-up current). The running current of your fridge is only a bit over 0.3A, so even if the start-up current of the compression were (for a second or two) 20 times that (which I imagine is unlikely), that would not be much over 6A or so.

The dryer's start-up current is more difficult to estimate, since the great majority of the 2600W is the heater, rather than the motor. However, I would have thought that if dryer+fridge was likely to blow a fuse if they both 'started up' simultaneously, it would not be uncommon for a dryer alone to do it - and that's not something we hear of happening.

If it were me, I wouldn't be at all concerned, but it's obviously your choice/decision. Looked at pragmatically, if I'm wrong not to worry, it would only happen once (since I/you would then realise the need to change the electrical supply arrangements) - so, although annoying, would not be the end of the world.

Kind Regards, John

Thanks John. I didn't explain what I meant very well. When I said tumble dryer starting I should have said when it is turned on initially for the first 15 minutes or so. i.e when the drum is getting up to full temperature. Presumably it would be drawing nearly 2600 amps for that time. It would be fairly likely that the fridge might come on in that time. I had not actually even thought about the extra start up current of the dryer motor as well. I suppose what you said in this post still holds true. i.e it will still stay below 22A.

Kind regards

Steven

 

[steve271]

It's also worth noting, with reference to a recent thread regarding spurs, that had the OP had a double socket (and drier in the same room) we would have heard nothing about it - yet, electrically, everything would be exactly the same as he wants to do.

Hi, thanks for your response. I am not sure what you mean by this. Can you direct me tothat post?

Kind regards

Steven

 

[JohnW2]

Thanks John. I didn't explain what I meant very well. When I said tumble dryer starting I should have said when it is turned on initially for the first 15 minutes or so. i.e when the drum is getting up to full temperature. Presumably it would be drawing nearly 2600 amps for that time. It would be fairly likely that the fridge might come on in that time. I had not actually even thought about the extra start up current of the dryer motor as well. I suppose what you said in this post still holds true. i.e it will still stay below 22A.

Fair enough, but if you weren't even considering the start-up current of the dryer's motor, then that makes it even less likely that there would be a problem.

Dryer's don't seem to actually use the full heating current continuously (they cycle on and off - well, at least mine always have). However, even if it were 2,600W continuously, that's around 11A - which leaves 2A (5-6 times normal running current) for the fridge's start-up current before the total even gets to 13A, let alone 22A.

As I said, for what it's worth, I would personally not be concerned. I can't explain echoes' experiences, but it's something one very really hears of happening.

Kind REgards, John

 

[EFLImpudence]

Hi, thanks for your response. I am not sure what you mean by this. Can you direct me tothat post?

It doesn't really have anything to do with your situation.

It's just that for some reason, in an informative part of the regulations book although not actually a regulation, it states that on a spur from a ring circuit like you have, only one socket is allowed - be that socket a single or a double.
This obviously makes no sense.

I'll try to find it.

 

[EFLImpudence]

https://www.diynot.com/diy/threads/single-wall-socket-connected-to-two-mini-circuit-breakers.551119/

 

[steve271]

Fair enough, but if you weren't even considering the start-up current of the dryer's motor, then that makes it even less likely that there would be a problem.

Dryer's don't seem to actually use the full heating current continuously (they cycle on and off - well, at least mine always have). However, even if it were 2,600W continuously, that's around 11A - which leaves 2A (5-6 times normal running current) for the fridge's start-up current before the total even gets to 13A, let alone 22A.

As I said, for what it's worth, I would personally not be concerned. I can't explain echoes' experiences, but it's something one very really hears of happening.

Kind REgards, John

Thanks John for your reassurance, I will go ahead and do it within the next week.

Kind regards

Steven.

 

[steve271]

https://www.diynot.com/diy/threads/single-wall-socket-connected-to-two-mini-circuit-breakers.551119/

Thank you.

 

[JohnW2]

Thanks John for your reassurance, I will go ahead and do it within the next week.

You're welcome. As I said, even if the reassurance you are getting from most of us proved to be unjustified, the 'worst case' is probably only for a blown fuse to take out your fridge once - since, if that happened, you'd probably mutter some nasty things about all of us and then immediately re-think how you should be arranging the electrical supplies for these appliances!

Kind Regards, John

 

[echoes]

I have to admit that I also thought the chances of an overload high enough to blow a fuse were very low, especially as I was responsible for the wiring of those appliances via a 13A FCU!
The best explanation I came up with, is that the dryer's heater and motor, and *one* of the fridge/freezer's compressors had been on at the same time, running the fuse close to It's rated value and perhaps warming it somewhat, and then the *other* compressor in the FF kicked in with a surge current.

I ended up moving the dryer's socket from the spur onto the ring after the second time it happened. It was rather an old dryer and FF, as well!

 

[steve271]

I have to admit that I also thought the chances of an overload high enough to blow a fuse were very low, especially as I was responsible for the wiring of those appliances via a 13A FCU!
The best explanation I came up with, is that the dryer's heater and motor, and *one* of the fridge/freezer's compressors had been on at the same time, running the fuse close to It's rated value and perhaps warming it somewhat, and then the *other* compressor in the FF kicked in with a surge current.

I ended up moving the dryer's socket from the spur onto the ring after the second time it happened. It was rather an old dryer and FF, as well!

I have fitted the socket into the dry wall and led the cable. Will wire it up tonight. Hopefully I will have cold drinks and dry cloths tomorrow lol

 

[JohnW2]

I have to admit that I also thought the chances of an overload high enough to blow a fuse were very low, especially as I was responsible for the wiring of those appliances via a 13A FCU! The best explanation I came up with, is that the dryer's heater and motor, and *one* of the fridge/freezer's compressors had been on at the same time, running the fuse close to It's rated value and perhaps warming it somewhat, and then the *other* compressor in the FF kicked in with a surge current.

Fair enough. I certainly can't think of a better explanation, but remain surprised. The start-up current of a compressor would be very short-lived, so I would suspect that (even with a 'warm fuse'), it would probably take a total of at least 30A for such a short period of time to blow the fuse - and that would require the compressor to have an extremely high start-up current.

Kind Regards, John

 

[SUNRAY]

It doesn't really have anything to do with your situation.

It's just that for some reason, in an informative part of the regulations book although not actually a regulation, it states that on a spur from a ring circuit like you have, only one socket is allowed - be that socket a single or a double.
This obviously makes no sense.

I'll try to find it.

Do we know the grid switches are on a [the] ring? or is it on a dedicated circuit?

 

[JohnW2]

Do we know the grid switches are on a [the] ring? or is it on a dedicated circuit?

I don't think we know, but does is make any material difference, given that each one has a (13A max) fuse?

Kind Regards, John

 

[EFLImpudence]

Do we know the grid switches are on a [the] ring? or is it on a dedicated circuit?

Different thread? https://www.diynot.com/diy/threads/first-fix-kitchen-wiring.551297/#post-4714488