Maximum Demand

S

scotteng

Main fuse in the property is a bs1362 type 2, 60amp.

Customer has 6x storage heaters at 2.55kw each, there is already a 9.5kw shower, no water heating ot cooking, 2x 32 amp rings and 3 x lighting circuits 6 amps each.

Customer wants me to add an additional 9.5kw shower in the on-suite. Already the demand is in excess of the 60 amp main fuse.

Its hard to get a clamp meter on due to the economy 7, i think the main supply needs to be upgraded to take this extra demand. It looks like the main supply is only 10mm swa!! ill be having a proper look on monday.

But what you recommend to do? whats the best way in this situation to calculate the true demand?

thankyou for your help

Scott
 
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Speak to DNO to see if it possible to increase size of fuse - incoming tails should be uprated - by them - normally at a cost to the customer. Customer responsible for tails from the meter onwards.

You should also advise them (DNO) that you are going to put two large demands on the circuit - as per manufactuers instructions.

Alternatively Split load - have two consumer units with load equally divided.
increase the size of the tails to 25mm

RCD's on the showers - as per manufactuers instructions.
 
S

scotteng

thankyou riveralt

when you say split the load, to two consumer boxes. How will this help? currently the storage heaters are on their own consumr box on the economy 7, and the new shower will go on its own dedicated consumer box wth rcd.

thanks
 
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By splitting the load I mean that you use a Henley block to split the tails from the meter to the either two consumer units or a consumer unit and as you appear to be doing a shower unit - the tails from the henley block should be 25mm.

The assumption for this is that you have managed to get an increase in the main fuse and the incoming meter tails.

However, unless there is some form of isolation switch between the meter and the current consumer unit you are going to have to get the DNO out anyway to turn the power off - cause we cannot touch there property.

The main fuse is probably capable of taking much more than Holmshaw indicates but I would not give such advice.

Also contrary to what Holmshaw says about manufacturers instructions, all showers I have fitted recently clearly state that if you are fitting more than one shower in domestic property you should inform the DNO.

The reasoning behind this is this is especially relevant when your customer has a 60 amp fuse and is fed by a 10mm cable. If both showers are operated at the same time as other equipment then demand on the 10mm cable will probably exceed its rating.

If you cannot get an increase in the main fuse and the incoming tails then the customer cannot have an additional shower.

It is also worth noting that in a recent job I did with similar circumstances the DNO would not upgrade the main fuse because they would also have to upgrade the cables. Furthermore they would also have to upgrade the cables and fuses of the two neighbours linked to that line - proposed cost to customer min £3000. They stayed with one shower and a bath...
 
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You should also advise them (DNO) that you are going to put two large demands on the circuit - as per manufactuers instructions.

The end result of that could be they cut you off, and whats manufacturers instructions got to do with the dno?.

You should always follow the manufacturers instructions - especially when the customers guarantee will depend on it. Don't you?
 
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You can install a changeover switch near the CU but it's far from an ideal solution. AAB in Ireland (iirc) make a shower board which allows the first shower to be turned on to have priority (and cut supply to the 2nd shower until it is switched off) but haven't been able to find them here.
 
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You can install a changeover switch near the CU but it's far from an ideal solution. AAB in Ireland (iirc) make a shower board which allows the first shower to be turned on to have priority (and cut supply to the 2nd shower until it is switched off) but haven't been able to find them here.

One of these, maybe? (phew, that took some time to find).

They makE a unit for up to seven showers!
 

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