Overload risk?

[NSS]

Quick question. Wife wants a Mini electric. We're already on Octopus Go and use the four-hour cheap rate period to run the 8kW ASHP to heat the domestic water. Would charging the car at 7kWh at the same time have any unwanted consequences?

[Carrerahill]

9 minutes ago, NSS said:

Quick question. Wife wants a Mini electric. We're already on Octopus Go and use the four-hour cheap rate period to run the 8kW ASHP to heat the domestic water. Would charging the car at 7kWh at the same time have any unwanted consequences?

Is that 8kW output or input?

 

Lets assume worst case and that is input, then I doubt it will pull full current all the time.

 

Worst case is the two will therefore pull 65A solid. I would assume you're on an 80A or 100A BS88 cut out fuse - so leaves 15A spare at night. BS88 will not blow at rated current would be over 2.7hours, so even if you did peak 90/100A sometimes, on a 80A you would be fine. 

 

You can get EVC's which have CT clamps on the main tails and monitor load, if it peaks over a pre-set (you can per-set) value, it drops output to the EVC until it fixes.

 

In my personal & professional opinion, I think you are fine. 

 

See if you can workout what size fuse you are on - only real way to know is to kill everything and pull it, means you need to cut the seal and you are not meant to, but if I have £1 for every time it was done I would be a millionaire. 

 

 

Edited August 15, 2022 by Carrerahill

[Carrerahill]

Note breaking curve for 80 & 100A BS88's - you can put nearly 25% more through them for 100 seconds. The 1250A BS88 is just a potential upstream protection device.

[NSS]

Thanks @Carrerahill but most of that's flown straight over my head. Heat pump is rated 8kW output so I assume input is between 2 and 3. Main fuse is 100A so from what I think you're saying I guess I should be safe?

[Carrerahill]

3 minutes ago, NSS said:

Thanks @Carrerahill but most of that's flown straight over my head. Heat pump is rated 8kW output so I assume input is between 2 and 3. Main fuse is 100A so from what I think you're saying I guess I should be safe?

Absolutely. So your full draw at full chat for ASHP & EVC together would be 43A. Lots of spare.

 

Make sure the consumer unit and all associated wiring for these circuits is good, even just checking terminals have not become loose, 43A continuous through the night would soon turn a loose terminal into a arcing burning mess. 

 

 

 

 

[NSS]

1 hour ago, Carrerahill said:

Absolutely. So your full draw at full chat for ASHP & EVC together would be 43A. Lots of spare.

 

Make sure the consumer unit and all associated wiring for these circuits is good, even just checking terminals have not become loose, 43A continuous through the night would soon turn a loose terminal into a arcing burning mess. 

 

 

 

 

Thanks for that. Much appreciated 👍🏼

[NSS]

Right, Mini electric on order. Next question, any recommendations as to which home charger to go for? Mini partner with Pod Point but thought I'd se what others would choose before committing. 

[NSS]

6 hours ago, NSS said:

Right, Mini electric on order. Next question, any recommendations as to which home charger to go for? Mini partner with Pod Point but thought I'd se what others would choose before committing. 

Probably not the best (or most obvious) place to post that question so I'll start a new thread.