Cable size requirements for battery system

[JohnMo]

22 minutes ago, Russdl said:

C’est la vie, I’ll work on it. 

Sleep on it, something will pop into your head, when you are not thinking about it.

[ProDave]

1 hour ago, Russdl said:

The installer/sparky got the following response from Givenergy:

 

”Unfortunately, GE will only give approval for a singular 6mm cable to the AiO Battery.”

 

I suspect that means no warranty etc if it’s not installed as approved, I also suspect the sparky won’t install it unless it’s iaw the manufacturers now very specific guidance which is fair enough I suppose. I’ll run the points raised in this thread past him but it looks like it’s time to reassess. 
 

Thanks for all the input (despite me only understanding half of it!)

In the real world the 4mm cable or that in parallel with the 2.5 will be okay.

 

At both ends, join those to a short length of 6mm and connect that to the bits of kit.

 

In the event of a warranty claim, they are not going to pull your house apart on the suspicion it may not be 6mm all the way.  Just don't make the transition obvious at either end.

[Russdl]

@ProDave I like that plan, thanks. I think the “hive mind”agrees it won’t be an issue (?) because I don’t really want to burn the house down. I shall propose that to the installer, or maybe magic to bits of 6mm either end (I know he won’t fall for it but I’ll see how I get on 👍)

[Russdl]

I have an idea. Is this crackpot?

 

The cable needs to go from the loft, right where the MVHR is, to the utility room. Several MVHR ducts take that route already. 
 

How about I run my required cable inside an MVHR duct. I would obviously need to airtight seal where the cable enters and exits the duct. 
 

Madness? Has anyone done similar before? What are the pitfalls?

[Adrian Walker]

31 minutes ago, Russdl said:

I have an idea. Is this crackpot?

 

The cable needs to go from the loft, right where the MVHR is, to the utility room. Several MVHR ducts take that route already. 
 

How about I run my required cable inside an MVHR duct. I would obviously need to airtight seal where the cable enters and exits the duct. 
 

Madness? Has anyone done similar before? What are the pitfalls?

I suspect that it would/might move around, but the cable would be nice and cool with the airflow!

 

 

[Alan Ambrose]

>>> How about I run my required cable inside an MVHR duct.

 

You'll need to convince your spark as it's a bit unorthodox, but can't think of any real reason why not. Some fire reg detail maybe? SWA cable possibly?

[Russdl]

@Adrian Walker our flow rates  are generally low, circa 100m3/hr unless our CO2 monitor tells us to speed things up or we’re drying clothes in the utility room so I don’t think it’s going to be moving around - but who knows. 
 

5 hours ago, Alan Ambrose said:

You'll need to convince your spark as it's a bit unorthodox, but can't think of any real reason why not.

I may not tell him, I may just present him with some 6mm without explanation of the route the cable has taken. 

 

5 hours ago, Alan Ambrose said:

SWA cable possibly?

That may be a bit of a pig to drag round the numerous bends the duct takes. I expect the 6mm cable may be problematic enough. 
 

I think I’m leaning toward the cable inside the MVHR duct. It’ll be dead easy to do. Famous last words. 

[Russdl]

On 08/11/2023 at 11:32, Alan Ambrose said:

You'll need to convince your spark as it's a bit unorthodo

I decided to tell the the sparky my unorthodox plan. Delighted to say that he has no problem with it. 
 

Also delighted that he/his company came up with a price that seemed very reasonable considering previous quotes I’d received. 

[Russdl]

Phase one of operation ‘MVHR as Conduit’ has been a rip roaring success, next stage is to pull a length of rope back through and then attaching the new 6mm² cable and pulling that through the MVHR duct. 
 

Mk1 foam ball was a bit big

Smaller Mk2 foam ball.   

 

 

[Russdl]

Phase 2 complete. 
 

 

[Russdl]

Slight modifications to the plan and the MVHR duct and the 6mm² is in situ, exiting the duct in both rooms via a slot in a short piece of white duct I had left over and inserted into the main duct run. I’ll make the slots airtight once the battery is in situ and the cable doesn’t need to be moved any more.
 

The modification is easily reversible should the need arise by just removing the smaller sections of duct that I inserted into the run. 

I pulled a small torch through the duct to make highlight the correct one. 
 

 

Smalls sections prepped ready for inserting into the main duct run. 
 

I wish I’d had the foresight to make provision for getting cable etc from the utility room to the MVHR room, but I didn’t so out comes the Stanley knife. 
 

Utility room

MVHR room in the loft. 

 

Battery won’t arrive until early in the new year but I’m ready for it now. 
 

One bit of good news, the interior of the duct was as clean as the day it was fitted. 

[JohnMo]

Well done, plus good thinking out the box.

[Russdl]

The ‘All In One’ was finally commissioned a couple of days ago and the butchered MVHR duct has been patched up. 
 

 

 

The batteries sit up in the loft in a small room that contains the MVHR unit, since installation that room has gone from being perhaps the coolest to what is now the warmest in the house as the battery slowly releases heat whilst charging/discharging. 
 

 

It’s very difficult to tear yourself away from the app, especially when it’s chucking down outside and as others have seen there is pretty much always a small flow to/from the grid even when there theoretically shouldn’t be. 
 

When I did manage to tear myself away from the app I had a look at the MVHR and spotted something interesting. Since the battery was commissioned, the airflow supply temperature has increased by about 1 degree despite the outside temperature trending downwards. I’m assuming this is because the MVHR is in a room that is 2-3 degrees warmer than it was. Could that be so??

 

 

Edited February 22 by Russdl