Very informative. 

Thank you

An 100A fuse would have made my life much easier.

I just applied to the DNO for a fuse upgrade as octopus after their heat pump survey said I needed one. 

Getting in contact with the DNO was easy and fuse upgraded within days for free but stated their policy will only allow up to 80A fuse.

As I've already mentioned they removed neighbours 100A fuse and replaced it with an 80A

I've just addressed this issue here in the topic DIY solar upgrade.

I've spoken with the senior NGED engineer who issues their operational specifications and represents their interest at the Electricity Networks Association.
He's friendly, helpful... and deeply knowledgeable.

When he says they need to downgrade to 80A Service Fuses, then he won't have done that lightly.

As others here have pointed out, a Service Fuse is a very long time-delay device!
You can draw 100A through it for maybe an hour before it gives out.

A high proportion of homes which need to draw more than 80A (19kW) have inefficiencies within them which really ought to be addressed!

Yes, an electric shower is a very high demand appliance... more so than an EV charger.
And there's a lot of them in houses which have had additional loft insulation installed by morons on top of the electrical supply cable!

Let's hope that the need to downgrade to an 80A Service Fuse will cause more home-owners to re-evaluate their 10kW electric shower !

Let me end with a photograph showing 'loft flooring' which has been done properly:

A shows the original ceiling joists.
The span length is 4.6m, so these old 3-inch deep timbers aren't capable of taking the new floor.

B are the new floor joists which have been placed alongside the ceiling joists.

That leaves plenty of space below the new chipboard floor (C) for insulation,
and the re-routing of power cables (2.5mm² and larger) above the insulation layer.

Yes NG for me too.

They even rang me up 2 days after application was sent in to say

"I thought you like to know it was accepted"

That's 2 dealings I've had on the phone with NG with upgrade to fuse and the heat pump and both very pleasant and quickly sorted.

I've had the DNO application back and they've passed it. 

Taking out the 40A electric shower made it ok. 

When I say take out, I just mean out the equation not physically off the wall, not yet anyway till heat pump is so up and running then I won't need it anyway so it'll be removed permanently .They just want it down on paper.

Still got solar, induction hob, double oven microwave and soon to be installed heat pump so it'll still be way up there.

But chatting to electrician says 80A will easily take 100A for a few hours anyway.

The DNO were not best impressed when I requested an 80A fuse upgrade due to the installed heat pump - I only really requested it as sometime we do hammer the supply when Agile has negative pricing and 80A is sufficient for us. To be fair, once they had the retrospective application, they were quick to do the upgrade.

During the process I came across the ENA heat pump database which lists the Maximum Demand of many heat pumps. My own Samsung 12kW model is listed as 6.44kW (28A) which matches the spec sheet for 55C flow temps at -5C. The spreadsheet database was available here:

https://www.energynetworks.org/links

When completing the form, I think I specified a Maximum Demand of 74A, but in reality if everything is turned on at once we'd exceed that. The heat pump could conceivably draw a combined 41A in DHW mode with the immersion on too for a legionella cycle, then hop in the 40A electric shower at the same time Sunday roast is cooking in the 13A cooker and someone turns on the 13A kettle, and we are well over 100A

After a few emails to octopus they have supposedly sent a revised application for a heat pump to the DNO today.

We don't used the 9kw shower in main bathroom, only use the en suite one,  so will be removing that for a normal bar type one saving about 40A which will be within total 80A limit. 

Hopefully get things moving with the install before cold weather creeps in.

Hi Mars,

Very interesting read. 

An 100A fuse would have made my life much easier.

I just applied to the DNO for a fuse upgrade as octopus after their heat pump survey said I needed one. 

Getting in contact with the DNO was easy and fuse upgraded within days for free but stated their policy will only allow up to 80A fuse.

As I've already mentioned they removed neighbours 100A fuse and replaced it with an 80A