ASHP via sub main

driverman · Sep 17, 2014

Hope OK to post here
New build project. Property having detached double garage with an all electric studio flat above. The garage will be wired via u/g SWA sub-main.
The AHSP for the house will be sited by the detached garage. At this point in time I'm proposing to wire the ASHP from the garage on it's own circuit.
The box of tricks (Apollo?) for controlling the heating etc will be sited within the house. My question is..Apart from the main circuit to the ASHP, do i need to wire any other cables between the ASHP and the box of tricks in order to control it? I take it normally the ASHP would be sited by the house with it's own dedicated circuit and as standard the detached garage via a sub-main. Does having both on the sub main make sense both electrically and viable?
I am in the process of getting more info via the owner from the manufacture but thought I'd like to ask here from experienced guys who install these on a regular basis.

thanks

jason121 · Sep 17, 2014

I am not familiar with Apollo, bot there is always wiring between control centers and Heat pumps and control centers to valves, flow switches, pumps, temperature sensors and immersion heaters. Normally all the controls are sited not far away from the heat pump. Depending upon heat pump, check size of cable for sub-main.

Rockingit · Sep 17, 2014

Yep - I'd think and tread very carefully here or you could end up with a whole heap of pain.

As already said, there will be control wiring between the two. You also then have the actual loading of the compressor to consider in your calcs for the sub main. But you may also find yourself needing to install a whole batch of relays or contactors if you've got two halves of the same system working across two different RCD's from separate supplies!

If it were me - 1) I'd get the full spec and wiring diagrams before going any further and 2) probably look to install a dedicated supply for the whole lot and run a separate feed to the compressor from it.

Rockingit · Sep 17, 2014

As a footnote to my post #3....... I saw a cracking cockup happen with this on a job earlier on in the year: First-time eco installer, didn't fully understand what was needed for the system he was spec'ing. Despite my every best effort and advice to the contrary, he/we ended up being 18 conductors short of a control system - having done the first fix weeks before! It was OK,though, as I'd already warned the customer!!!!

driverman · Sep 17, 2014

Rockingit said:
Yep - I'd think and tread very carefully here or you could end up with a whole heap of pain.

As already said, there will be control wiring between the two. You also then have the actual loading of the compressor to consider in your calcs for the sub main. But you may also find yourself needing to install a whole batch of relays or contactors if you've got two halves of the same system working across two different RCD's from separate supplies!

If it were me - 1) I'd get the full spec and wiring diagrams before going any further and 2) probably look to install a dedicated supply for the whole lot and run a separate feed to the compressor from it.

Yep. I'm leaning on the owner to get info so that i can have a good read and hopefully meet the ASHP installers on site to discuss their requirements. Appreciate comments re loading, I've read other threads on here on that subject.
I did plan to install a sub main to garage using min 16mm SWA (91amp) or max 25mm (125amp) from memory. 25mm over kill i think.

driverman · Sep 17, 2014

Rockingit said:
As a footnote to my post #3....... I saw a cracking cockup happen with this on a job earlier on in the year: First-time eco installer, didn't fully understand what was needed for the system he was spec'ing. Despite my every best effort and advice to the contrary, he/we ended up being 18 conductors short of a control system - having done the first fix weeks before! It was OK,though, as I'd already warned the customer!!!!

I'm on a learning curve with this one....The owner is a very good plumber (did I just say that) who is my partners son. Anyhow between us trying to do a good job as cheaply as possible. Not cutting any corners though. It's all touch pads for stats using cat 5 cable.

driverman · Sep 21, 2014

Bit of an update......2 x circuits are required from CU to cupboard which will house cylinder tank, all the valves and control box of tricks. Size cables to be confirmed later in week...but more than likely 2 x 6mm T&E or could be 1 x 6mm T&E and 1 x 10mm T&E.Both circuits to terminate into rotary isolation switches From box of tricks in cupboard a 4mm SWA cable required to ASHP. Hope that throws a bit more light.

Rockingit · Sep 21, 2014

Out of interest, what's the system being installed? Make and model?

driverman · Sep 22, 2014

Rockingit said:
Out of interest, what's the system being installed? Make and model?

Hopefully getting email with all spec later in week. The 4mm SWA from house cupboard to AHSP has to be 4 core (apparently the 4th core is for signalling)

driverman · Oct 4, 2014

Rockingit said:
Out of interest, what's the system being installed? Make and model?

[ElectriciansForums.net] ASHP via sub main

Hopefully this works. Info supplied

Rockingit · Oct 4, 2014

I hate pics like that! It's one designed for plumbers, and not sparks who understand schematics!! For starters, if you've got two rotary isolators in the same place, fed from the same place, then you might just as well install 1 x 63A supply to them and save on cable costs. Next, do you REALLY need a rotary isolator INDOORS on a domestic? Might a DP MCB be better and tidier (from the 63A, naturally...) and so on.

Worcester · Oct 5, 2014

In fact the only reason rotary isolators are installed is for maintenance purposes.... Sometimes it is far better to design them out.

p.s. What's a fuse box?

surely he's going to use MCB's not rewire-ables in this day and age...

driverman · Oct 6, 2014

Rockingit said:
I hate pics like that! It's one designed for plumbers, and not sparks who understand schematics!! For starters, if you've got two rotary isolators in the same place, fed from the same place, then you might just as well install 1 x 63A supply to them and save on cable costs. Next, do you REALLY need a rotary isolator INDOORS on a domestic? Might a DP MCB be better and tidier (from the 63A, naturally...) and so on.

Yes your comment does make sense. As I've said earlier, all new to me. I've requested MI info etc and this is what I've got. That's how they want it installed. If i do as they have requested I can't go wrong...............hopefully!

driverman · Oct 6, 2014

Rockingit said:
Out of interest, what's the system being installed? Make and model?

Does it make sense to you Rockingit? Why the 2 circuits?

Worcester · Oct 6, 2014

Two circuits common in heat pumps, all depends upon the exact internal configuration.

Typically one for the compressor and one for the controls and backup heater.

Make sure they are on Type C breakers, ideally also ensure they have a soft start, else the start up current can be surprisingly high.

ASHP via sub main

driverman

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jason121

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Rockingit

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Rockingit

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driverman

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driverman

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driverman

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Rockingit

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driverman

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driverman

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Rockingit

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Worcester

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driverman

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driverman

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Worcester

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