Three Phase Tumble dryer!

[scotteng]

hello all, been asked to quote to install supply for a tp tumble dryer. They are telling me that it does not require a neutral, just tp. Doesnt sound right to me surely the control grear will need the neutral, i can understand the motors being balanced.

Has anyone had any experience with just tp tumble dryers not requiring a neutral?? The customer is awaiting conformation from the supplier, but just though id see if anyone has seen any?

cheers

 

[RF Lighting]

Sounds normal. The control usually uses a step down transfomer connected across two of the phases.

 

[ricicle]

Whats the harm in running an extra conductor for the Neutral anyway if you are using singles, or properly terminated 4 core swa ?

 

[ericmark]

Many large three phase items use 24v or 110v control circuits and step down 400 to 24 is just as easy as 230 to 24 so often they do not require neutral but this is all to do with design.

 

[ban-all-sheds]

Whats the harm in running an extra conductor for the Neutral anyway if you are using singles, or properly terminated 4 core swa ?

Would there be any point with singles? Couldn't a neutral be pulled in in the future if it was ever needed?

 

[Adam_151]

Couldn't a neutral be pulled in in the future if it was ever needed?

If all the conduit boxes remained accessible, then when push comes to shove if one is needed, then yes it could be, but would mean pulling it over the top of cables already drawn in, which makes the job harder and more at risk of damaging them, so plenty of yellow

We've all had times when we have had to do it, but its something which should be avoided.

but that said,if its high level trunking, then a short drop down to iso then not big job

Perhaps the OP should gave customer a price for with and without neutral and outline the situation, then its the customers call if he wants to save money now, over the expense of having neutral installed if he ever changes dryer

 

[RF Lighting]

It's a hell of a lot easier to pull a neutral in at the same time, and very little extra cost.

I cant remember the last time I put in a straight TP supply without a neutral.

I have been on so many jobs where a neutral has been required for a new machine etc, and one hasn't been available. It can be a nightmare to get one, and you wouldn't beleive the number of times I have seen where people have just borrowed one from another local circuit, which can be very dangerous.

 

[Adam_151]

It's a hell of a lot easier to pull a neutral in at the same time, and very little extra cost.

I cant remember the last time I put in a straight TP supply without a neutral.

I have been on so many jobs where a neutral has been required for a new machine etc, and one hasn't been available. It can be a nightmare to get one, and you wouldn't beleive the number of times I have seen where people have just borrowed one from another local circuit, which can be very dangerous.

Just tie wrap a single to the SWA... seen it loads of times..

 

[1john]

put a neutral in, you never know, you may be called back to install a different machine that required one in the future.

 

[ColJack]

Just tie wrap a single to the SWA... seen it loads of times..

did that with a 25mm earth once.. 300m run along an outside wall at a factory complex ( effectively in the narrow space between the boundary wall and the series of small buildings along that side.. )..
all because the Ze was too high at one of the buildings..

told them it would have been easier to just whack in a couple of earth rods...

 

[mfarrow]

did that with a 25mm earth once..

In all fairness an earth's slightly different, I wouldn't tie a live conductor in singles to a SWA cable.

I would also prefer the installation of a separate earth to using a TT as you could get nuisance tripping of the RCD in an industrial setting.