Using 400v transformer pair to avoid cable runs...

[Energetic]

I've been asked to look at putting a new supply to a pool for a heater. It's a long run and there's currently a 1.5mm SWA to run the pump.

We're being asked to quote on a 16A heatpump or similar and they've been told that to up the current carrying capacity for the supply cable they should put a 400v transformer at each end of the run, the idea for this being that this will be cheaper than upgrading the cable and digging up 50m + of playground.

I've never heard of this approach, has anyone done something similar?

 

[malcolmsanford]

Well in theory it may just work, after all HV transmission works on very similar principles, higher voltage transporting less current.

I have to admit that I have never personally done anything like this, and well I suppose there is more than one way to skin a cat. I would love to see some figures on this

 

[Knobhead]

I've been asked to look at putting a new supply to a pool for a heater. It's a long run and there's currently a 1.5mm SWA to run the pump.

We're being asked to quote on a 16A heatpump or similar and they've been told that to up the current carrying capacity for the supply cable they should put a 400v transformer at each end of the run, the idea for this being that this will be cheaper than upgrading the cable and digging up 50m + of playground.

I've never heard of this approach, has anyone done something similar?

Yes but not in a bloody garden!

Before you go any further concider the cost of two transformers as against the correct cable. Then you will have the earthing of the secondary output of the remote transformer to contend with. Current inrush will be a problem with two transformers. Finaly to use the exsisting cable i would be looking at 660V.

Has the client got deep pockets? If he has tell im to employ a landscape gardener to repair the damage done putting the correct cable in.

 

[Energetic]

Sorry got my numbers wrong, it's a 12kw output HP (allow 3.5-4kW input) + the pool pump/filter 500-800w so the demand is only say 5kW...

That makes more sense...

 

[Knobhead]

The whole idea doesn't make sense. Get digging!

 

[Guest111]

if you are going to that trouble why not go all the way and step up to 11kv that should counteract any losses in the cable,if you can get them use transformers with on load tap changers that way you can adjust to compensate for any difference in voltage outside your needs.

 

[Engineer54]

I've been asked to look at putting a new supply to a pool for a heater. It's a long run and there's currently a 1.5mm SWA to run the pump.

We're being asked to quote on a 16A heat pump or similar and they've been told that to up the current carrying capacity for the supply cable they should put a 400v transformer at each end of the run, the idea for this being that this will be cheaper than upgrading the cable and digging up 50m + of playground.

I've never heard of this approach, has anyone done something similar?

Not to boost the CCC of a tiny 1.5mm SWA cable i haven't!! lol!! The cable was too small when it was first installed, for the type of distances your talking about. I take it there is a good few metres to add to that 50m either side of this playground?? Is this installation for a school of some sort??

 

[Guest111]

Not to boost the CCC of a tiny 1.5mm SWA cable i haven't!! lol!! The cable was too small when it was first installed, for the type of distances your talking about. I take it there is a good few metres to add to that 50m either side of this playground?? Is this installation for a school of some sort??

Well mate you,ve disappointed me!we are all taking the mick in a roundabout way and then you come on and don,t even mention earthing.how disapointing lol.

 

[Engineer54]

Well mate you've disappointed me!we are all taking the mick in a roundabout way and then you come on and don,t even mention earthing.how disappointing lol.

The scenario is in my opinion a none starter, so no point in going into the earthing side of things.... lol!!

 

[Knobhead]

Well I've got to admit, it's a novel approach to the problem.

 

[Marvo]

...the idea for this being that this will be cheaper than upgrading the cable and digging up 50m + of playground.

Don't you have directional moling contractors in he UK?

We installed transformers for remote pump and booster station supplies before and it's a very expensive exercise. It will only be worth it if the playground repairs will for some reason cost an arm and a leg or if the distance is over a kilometer.

Edit.
Why did they suggest 400v? You may as well go 1kV if the SWA is rated high enough.

 

[Knobhead]

For gods sake Marvo, 1KV! 960V and stay in the realms of LV.

 

[Engineer54]

For gods sake Marvo, 1KV! 960V and stay in the realms of LV.

All of our projects LV cables are rated 1 KV!! lol!!

 

[Marvo]

Okay, okay, easy chaps... we also run 1kV under low voltage regs. I'm sure we're not to a volt or two amongst friends

 

[Knobhead]

All the cables I used were 600/1000 but I wouldn't go shoving 1000V down them.

 

[DPG]

Well mate you,ve disappointed me!we are all taking the mick in a roundabout way and then you come on and don,t even mention earthing.how disapointing lol.

Playground - roundabout way. I take it you intended that one! Daz

 

[Energetic]

Glad you've all amused yourselves for a bit, I've been out and about but enjoying the responses as they came in

It all seemed a bit dubious to me so thought i'd ask some proper sparks. First venture out of the sun lounge for a while... Cold out here...

It is for a school so they are pretty sensitive to price, perhaps need 50 or so small spades or an army of dads...

 

[Knobhead]

I'm afraid you're stuck with digging.

BTW at 960V the volt drop would be 2%

 

[DPG]

33kV and lattice pylons - no digging that way either. Lattice, not lettuce. Daz.

 

[Knobhead]

Just spoken to Phil, how many pylons do you need? He's got a couple knocking about.