Supply for Glamping pods

[hockley14]

We are considering putting in two glamping pods on our farm.
The main house has a two phase supply (so im told). The house has a annex connected to it and also stables.
The pods will be situated 300 meters from the main consumer unit. Cables would need to be underground.
At the pods we will need to supply lighting and a few sockets for a kettle, toaster 2 ring hob, fridge and hairdryer. (no heating) A klargester sewerage plant will also be present.
We estimate that if everything is running at once we could have a draw of around 4kw.
So my question is simple!!!!!! what size/type SWA would be required. What volt drop would there be etc.
I look forward to anybodies help.

 

[pc1966]

By my rough reckoning parallel cables will be the most cost effective solution, as long as the design is done right.

I guess it would depend a lot on the details & suppliers. A quick comparison of 2-core SWA in both 25mm and 50mm from Superlec has 660m of 25 coming in at £2,962.08 and 330m of 50 coming in at £2,665.08 so no cost advantage in parallels there. But a whole lot easier to work with!
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Or maybe no long cable run at all and have two battery banks - one at the glamping site and the other being charged at the farm which are swapped over say daily. Especial care would have to be taken with the way the batteries are transported back and forth and connected because of the dangers associated with very high energy density batteries - this would not be a preferred practical way ahead so keep it at the back of your mind for now unless the cable run is very expensive. Nota bene - not a task for glampers to do.

The battery & inverter option (a makeshift UPS really) has many attractions but I really doubt about the sanity of battery swapping.

Having some solar PV for "free" electric (good from a green PR point of view) would help, but the main attraction and possible justification is you could run a much thinner cable for mains-charging at all times.

While bad from a power loss point of view, it might make economic sense to allow more than 5% drop at peak demand if the charger is OK with that level of AC variation and safe fault-clearing on the cable can be maintained. That suggestion might kick of a whole thread on its own...

 

[Lucien Nunes]

Is it worth including the split-phase option in the comparison? Unless one is relying on diversity between the two pods (i.e. the cable design load is less.than 2x the individual pod load) then it should show a saving. One 25mm 3-core on 230/460 will give the same worst-case VD as one 50mm 2-core on 230V single-phase.

Whether the smaller circuit's higher resistance creates or solves OCPD selectivity headaches might depend on whether the pods can be run with one radial, with just the lights fused down, hence allowing lower Ib at the source.

 

[pc1966]

Looking at the 25mm split-phase on 3-core and 50mm single phase on 2-core we have £2,245.32 versus £2,665.08 for the cable costs, so a modest saving of around £420 on basic cables cost. However I have not looked in to the implications for the OCPD arrangements. Quite probably a 3-pole delay RCD could be used for additional cable fault protection in the event fuses, etc, can't meet the disconnection times. Just have to take care about how the self-test works and so which of L1/L2/L3 is left vacant in this case.

Given the quite intermittent aspect of kettles & hair dryers I'm not sure it would be reasonably to assume enough neutral current cancellation to make, say, 16mm split-phase on 3-core a sound choice though, which is a shame as that would save another £500 or so (approaching what a transformer arrangement could offer).

But the diversity on single-phase shared between pods is probably quite reasonable!

 

[davesparks]

Is it worth including the split-phase option in the comparison? Unless one is relying on diversity between the two pods (i.e. the cable design load is less.than 2x the individual pod load) then it should show a saving. One 25mm 3-core on 230/460 will give the same worst-case VD as one 50mm 2-core on 230V single-phase.

Whether the smaller circuit's higher resistance creates or solves OCPD selectivity headaches might depend on whether the pods can be run with one radial, with just the lights fused down, hence allowing lower Ib at the source.

I doubt the one radial per pod with lights fused down will be sensible, the sewage treatment equipment doesn't really want to be on the same circuit as one of the pods in my opinion.

Of course that could have its own circuit, it wouldn't be a very large cable for a 300W appliance even over 330m.
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Very true, also 4kW max load seems small if any heating & cooking together is possible. But I have never "glamped" to know what sort of joys it provides in this way.

I've never 'glamped' personally, but I have looked after power distribution for a couple of VIP campsites at Glastonbury festival a few years ago. I don't think anyone had coined the phrase 'glamping' at that point, but the biggest 'pods' they had their are what I would imagine is being discussed here.

If I remember correctly there were around 12 of the big pods on the second site, each one had a 16A inlet on it and I ran the whole lot from a 200KVA generator. Why 200KVA? Because that's what turned up on the truck despite my having requested something more suited to the actual load. They had lights, underfloor heating, a radio and not much else in them I think.

The first site had over a hundred smaller pods which all got fitted with small 12V batteries (the typical Yuasa burglar alarm style), a maplin solar trickle charger, a bit of led tape and a car cigarette lighter socket with USB adaptor.

 

[DPG]

I doubt the one radial per pod with lights fused down will be sensible, the sewage treatment equipment doesn't really want to be on the same circuit as one of the pods in my opinion.

Of course that could have its own circuit, it wouldn't be a very large cable for a 300W appliance even over 330m.
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I've never 'glamped' personally, but I have looked after power distribution for a couple of VIP campsites at Glastonbury festival a few years ago. I don't think anyone had coined the phrase 'glamping' at that point, but the biggest 'pods' they had their are what I would imagine is being discussed here.

If I remember correctly there were around 12 of the big pods on the second site, each one had a 16A inlet on it and I ran the whole lot from a 200KVA generator. Why 200KVA? Because that's what turned up on the truck despite my having requested something more suited to the actual load. They had lights, underfloor heating, a radio and not much else in them I think.

The first site had over a hundred smaller pods which all got fitted with small 12V batteries (the typical Yuasa burglar alarm style), a maplin solar trickle charger, a bit of led tape and a car cigarette lighter socket with USB adaptor.

Dave, why would you not put the sewage plant on the same circuit as one of the pods? It's only a small load. Just interested.

 

[Midwest]

Dave, why would you not put the sewage plant on the same circuit as one of the pods? It's only a small load. Just interested.

Having had lots to do with our site cess pit recently. They can get really messy, if the pump gets tripped. Needs to be on its own circuit, for that reason.

 

[DPG]

Having had lots to do with our site cess pit recently. They can get really messy, if the pump gets tripped. Needs to be on its own circuit, for that reason.

Fair point, cheers!

 

[pc1966]

I would assume that the sub-main feed would be designed to be reliable and at the end you would have a board with separate circuits for each pod and with the sewage plant on a dedicated circuit!

 

[davesparks]

Dave, why would you not put the sewage plant on the same circuit as one of the pods? It's only a small load. Just interested.

If the pod which supplies the sewage plant was to trip out and go unnoticed, maybe because it is unoccupied for a couple of days, then the people in the other pod would continue to use the facilities.
If that happens then it won't hit the fan, but it will probably backup and cause a rather unpleasant mess.

 

[westward10]

It is a requirement for this type of plant to have a power failure alarm.

 

[David Prosser]

Klargesters are gravity fed in and out. The power is for a blower to Corse air to aid the bacteria in arobic digestion and the reduction in ammonia.

 

[Midwest]

It is a requirement for this type of plant to have a power failure alarm.

It may well be; our system is linked into our BMS. Well it should be, but someone forgot to connect the cat cable.

Mind, three foot of brown water, is a good indication something is not right.

 

[davesparks]

Klargesters are gravity fed in and out. The power is for a blower to Corse air to aid the bacteria in arobic digestion and the reduction in ammonia.

Klargester make a variety of products which work in a variety of ways, from simple tanks up to full sewage pumping and traatment plants.

 

[DPG]

Klargester make a variety of products which work in a variety of ways, from simple tanks up to full sewage pumping and traatment plants.

Dave knows his sewage processing.

 

[pc1966]

Dave knows his sewage processing.

Works in the entertainment industry...