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Topic Title: Holiday Chalet Park.
Topic Summary: Potential Overloading.
Created On: 16 March 2019 08:00 AM
Status: Read Only
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 16 March 2019 08:00 AM
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Zoomup

Posts: 6117
Joined: 20 February 2014

Mornin' All,
on this grey windy day.

I have recently been given the task of electrically maintaining a local holiday chalet park. There are about 70 to 80 chalets, I haven't counted them all yet. There is no gas on site. The chalets date back to the 50s and are just wooden summer houses really. All chalets are TT earthed and supplied via a B50 M.C.B. in each chalet.

Initially I imagine that each chalet may have had lighting and a socket for a kettle, another socket for a heater and possibly a small cooker as well.

Some fuse boxes are original and are museum pieces with hot wire fuses and ceramic carriers. Many dodgy D.I.Y. alterations are present.

Now the thing is this. Just how soon will overloading occur and blackouts. Owners are adding 9kW electrical showers, cookers, additional electric heating, dish washers and space heaters etc.

The main supply is 3 phase and the site's main fused switch has three 200 Amp cartridge fuses. One has blown before and has been replaced.

Just when can I expect main fuses blowing?

Bye,

Z.
 16 March 2019 11:32 AM
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AJJewsbury

Posts: 17795
Joined: 13 August 2003

Just when can I expect main fuses blowing?

Usually the first weekend the site opens in the spring - (presuming it's the kind of site that shuts down over winter). I've seen it happen over Easter a couple of times on a static caravan site

Generally it'll probably be OK - 200A x3 gives you 138kW or about 1.725kW per chalet - which probably isn't much adrift from what the DNOs allocate for a house. If you're worried about peak demand then consider some load shedding relays - e.g. switch off the space heating when the shower or cooker is in use. Diversity might be a bit better than normal domestics as well - being holiday lets people will be more variable in the times they cook and shower and presumably during colder periods more of the chalets will be unoccupied, especially if the site doesn't allow sub-letting.

- Andy.
 16 March 2019 12:12 PM
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broadgage

Posts: 3170
Joined: 07 August 2007

The supply sounds very inadequate to me.

Whilst it is true that DNOs allow for a surprisingly small load per dwelling, this tends to presume the availability of gas. They allow more per dwelling if gas is not available.
Do many of the chalets use bottled gas for heating or cooking ? that would help a bit in reducing electricity demand.

Does your remit include the internal wiring of the chalets ? or only the site infrastructure thereto.

Load shedding relays within the chalets will reduce the risk of operating the supply OCPD, but will not in my view reduce the chances of operating the 200 amp DNO fuses.

Will the DNO provide a larger supply, is there space for a new packaged substation ?
How much work will be required to improve the site distribution to handle a larger supply.
 16 March 2019 12:46 PM
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daveparry1

Posts: 8020
Joined: 04 July 2007

I'd have talked my way out of that job Zoom, much more trouble than it's worth!
 16 March 2019 02:50 PM
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Weirdbeard2

Posts: 753
Joined: 29 November 2017

Originally posted by: Zoomup

Mornin' All,

on this grey windy day.

I have recently been given the task of electrically maintaining a local holiday chalet park. There are about 70 to 80 chalets, I haven't counted them all yet. There is no gas on site. The chalets date back to the 50s and are just wooden summer houses really. All chalets are TT earthed and supplied via a B50 M.C.B. in each chalet.

Initially I imagine that each chalet may have had lighting and a socket for a kettle, another socket for a heater and possibly a small cooker as well.

Some fuse boxes are original and are museum pieces with hot wire fuses and ceramic carriers. Many dodgy D.I.Y. alterations are present.

Now the thing is this. Just how soon will overloading occur and blackouts. Owners are adding 9kW electrical showers, cookers, additional electric heating, dish washers and space heaters etc.

The main supply is 3 phase and the site's main fused switch has three 200 Amp cartridge fuses. One has blown before and has been replaced.

Just when can I expect main fuses blowing?

Bye,

Z.


Hi, are the chalets metered at all and are you allowed to see the last years electric bills? These may indicate an average usage.
 16 March 2019 03:49 PM
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Zoomup

Posts: 6117
Joined: 20 February 2014

There is no gas allowed on site at all Broadgage.

There are some nice local H.V. overheads nearby so upgrading may be possible.

The chalets contains electricity meters owned by the site owners to allow usage billing.

I was primarily called in to test the site owners' pre-meter R.C.D.s in some chalets, and external lighting. But I have been given a key to the main intake building. To order some spare main fuses I took a look at their rating before the park opened in March. That is when I noted the 200 Amp rating. Being "industrial" I ordered some for emergency use. I don't expect to be able to obtain them quickly locally.

Z.
 16 March 2019 05:56 PM
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perspicacious

Posts: 8055
Joined: 18 April 2006

The main supply is 3 phase and the site's main fused switch has three 200 Amp cartridge fuses. One has blown before and has been replaced.
Just when can I expect main fuses blowing?


What is the site's ASC? Likely to be on the landlord's bill.

Has anyone queried the accuracy of the sub-meters?

Regards

BOD
 16 March 2019 06:07 PM
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broadgage

Posts: 3170
Joined: 07 August 2007

With no bottled gas, I would consider the supply inadequate.

Another factor to consider, Is that with a growing housing shortage, that some former holiday accommodation may end up as permanent housing. (even if not permitted)
Occupation in the winter months will clearly increase the heating demand.

It might be worth use of a data logger to determine the actual demand at peak times.

In cool weather, a reasonable estimate of load might be;

Heating at an average of 9 amps per unit.
Lighting, refrigeration and small appliances, 1 amp per unit.
No diversity allowed as these are continual average loads.

Now consider the large but short term loads, cookers and showers.
A good guide, IMHO is to allow for 100% of the first two appliances and a very much smaller average for the remainder.

Assume 25 chalets per phase, each with a 30 amp shower and a 30 amp cooker.
100% of the first two appliances---------------60 amps.
5% of the remaining 48 appliances----about 70 amps.
Heating and small appliances------------------250 amps.

Others may calculate differently, it comes down to a certain amount of judgement, but 200 amps per phase still sounds inadequate unless one assumes only mild weather, and hopes that not all units are occupied at the same time.
 16 March 2019 06:50 PM
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perspicacious

Posts: 8055
Joined: 18 April 2006

All chalets are TT earthed and supplied via a B50 M.C.B. in each chalet.

That suggests to me that there is a common distribution system on the site with service cables to each chalet tapped off it, very much in the way the DNO's provide a supply. Quite possibly with a large distribution aluminium cable, especially in your area,

I was asked to track and trace a cable this morning on a 28 pitch park home site with all year permanent residences. It was an odd design to me, with a 12 way 3-ph Ryefield incomer feeding the 29 meters and from the meters, the installer had used split concentric cable to each pitch. Not sure if it was a DNO job from start to finish or DNO to the metering and a contractor using split concentric for the BS7671 side......

Regards

BOD
 16 March 2019 08:11 PM
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sparkingchip

Posts: 11682
Joined: 18 January 2003

Is there actually a schedule showing which phase each chalet is connected to and how many chalets are actually connected each phase?

There no saying that the chalets are evenly distributed across the phases without seeing some decent installation records or some onsite testing.
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