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Thread: Pond electrics help
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08-07-2020, 08:09 PM #1
Pond electrics help
Evening all, I’m still in the construction phase of my pond but I need some advise regarding the electrics. I’ve buried a 2.5mm three core armoured cable from the garage to the pond approx 25 metres away in the garden.
My original plan was to spur off the ring main circuit, but I can take it too the main circuit board if needed (get an electrician to install this bit obviously).
I’m lookin for it too run a
Draco solum 25 Drum
Two evolution aqua varipump 20,000l
Evo Aqua 55w uv
Evolution airtech 95lpm air pump
With the possible addition of a 8.5KW Air Source Heat Pump in the future. I feel like I should of used a bigger rated cable. But what does everyone else use?
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freddyboy Thanked / Liked this Post
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08-07-2020, 08:37 PM #2
On that length of run and the possibility of fitting an 8.5 kw ASHP on top of what you already have mentioned I would think you'd have to run a 6mm 3 core XLPE SWA.
It all depends on how and where you run the cable, as clipped direct to a wall or buried will give 2 different cable calculation results. Exact length of run will also dictate the minimum cable size required along with the maximum wattage you expect to need to run everything.
I'm guessing with the ASHP plus pumps, UVCs drum etc you'll need something like a 9 to 9.5 kw supply. That's about 40 to 45 amps.
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freddyboy Thanked / Liked this Post
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08-07-2020, 10:44 PM #3
Id agree mostly with what Frimley says above. The only point I would challenge is your indication of an 8.5kWh air source heat pump. Typically heat pumps list their power in output terms not consumption. Since one of the benefits of heat pumps is their electrical efficiently (denoted by CoP), they output more heat power for the consumed input power.
For example, I am currently looking at a "34Kw" air source heat pump, it's maximum input power is 7kW.
There are useful calculators for length of electrical cable / cable type and installation, I use the one on the TLC site here
https://www.tlc-direct.co.uk/Technic...ltageDrop.html
Assuming 3 core SWA XLPE installed underground, the calculator indicates a maximum draw of 26.6A (roughly 6kW) to be within acceptable voltage drop levels.
I would also recommend that the circuit is on it's own breaker and RCD protected as it is outdoors. Im not qualified, but I suspect this may be a requirement in the regs now too?
As for the other kit you listed, the two pumps will be the most power hungry, the Draco is light on power consumption, as are the air pumps, the UV is 55W as stated (maybe a touch more during start up). Basically you need to add up the maximum possible current draw and determine if it is within the limits of the cable you have. The cable should also be fused (ideally using the appropriate sized MCB or RCBO on the consumer unit) to a value slightly lower than the cable can handle. So in your case, probably a 20A RCBO would be best. Note that this will further limit your current draw to 20A, but does provide a bit of headroom in the cable capacity.
Which heat pump were you looking at if any at this stage?
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Nilsac Thanked / Liked this Post
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08-07-2020, 10:47 PM #4
I meant to add, the quoted power for heat pumps is usually its theoretical maximum, so be careful to check the specs and conditions required to achieve that. Low ambient temps significantly affect their performance. Since we tend to want to heat our ponds when it's cold, you will need to be very aware of this when sizing the pump.
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08-07-2020, 10:50 PM #5
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08-07-2020, 11:43 PM #6
Thermotec is at the top of my list, Duratech doesn't go bigger than 22 or 26kW as far as I know? Lots of useful data on it at Pool Heat Pumps, Largest Range to UK & Europe - HeatPumps4Pools too.
I'm hoping in the summer to control it so that it heats when I have excess solar generation, so ideally want to oversize so that it can make the best of the daylight when the light is in limited supply if that makes sense?
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09-07-2020, 06:57 AM #7
Seems the best bang for your buck all round. Just need to wait for stock to come in now...been waiting since April
Sent from my iPhone using Tapatalk
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09-07-2020, 08:12 AM #8
Yeah, I was just about to place my order for the 34kW 3 phase version which was the only thing left in stock (not many people will have 3 phase I suspect) and when I was ready to pull the trigger it had sold out.
I called and they said they were taking a call every 60 seconds during the mini heat waves we had and everything had gone! ETA is beginning of August now, so not too bad.
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09-07-2020, 12:40 PM #9
Brilliant thanks for the replies, at the moment I was looking at the ones on the quality nishikigoi website. But may well need to wait till I upgrade the cable and built a consumer unit in the shed to carry the added load.
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09-07-2020, 02:12 PM #10
As a qualified electrician myself, I would go with a minimum of 6mm 3 core XLPE SWA and protect it with a 32 amp RCBO which will give you enough spare capacity to upgrade later on without having to pay out again. I would put a 4 way or 6 way consumer unit in the shed. The ASHP could then go on its own circuit, lights for your shed on another circuit, sockets for your pumps etc on a third circuit and at least 1 spare circuit for additional stuff later on. Depending on what the shed is made of you may have to fit AFDDs. An SPD may also be required unless a risk assessment is carried out to prove that it isn't but the cost of doing a proper risk assessment is possible going to be the same cost difference between buying an 18th Edition consumer unit with an SPD already fitted and buying the same consumer unit without an SPD already fitted. As for AFDDs unless the regs have changed this year for the ammendment 1 then they are currently only a recommendation but the customer should still be informed in writing so that they can decide whether to go for them or not.
The way it was explained to me last year when I had my Part P assessment was if you decide not to fit an SPD and something happens and then insurance companies get involved they would question why an SPD wasn't fitted and could use that as a reason for not paying out.
So I just fit them now as part of a consumer unit change or if I am running a supply to a garage or shed etc. Just stops any future issues.
I've currently not had too many dealings with ASHPs so just erred on the side of caution with my previous reply and worked on the quoted KW figures. It's always better to go bigger and not try to run cables at maximum figures.
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09-07-2020, 06:39 PM #11
So first things first, you defer to Frim rather than me as he is qualified.
secondly, completely agree with everything you say Frim in terms of your proposal. I always plan for additions later on and oversize and therefore would do the same as you’ve stated.
i used the 20a breaker scenario to utilise the cable thats already there on the grounds that it *may* be enough depending on Ashp choice, although remaining circuits would be limited. Depends how much effort is required to re-run the cable I guess.
i didn’t mean to suggest that you got the ashp details wrong, as you can only go on what the OP stated, just reflecting on my recent ashp research.
Out of interest what is an AFDD? I assume SPD is surge protection device as I have one of those installed in my outbuilding. I wondered why the electricians fitted it, but your post has clarified that, thanks.
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Frimley Koi keeper, freddyboy Thanked / Liked this Post
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09-07-2020, 06:51 PM #12
Sorry AFDD is Ark Fault Detection Device.
Bloody expensive at the moment unfortunately. I think they are currently about £200 each and you need one per circuit so if you have to fit them for a consumer unit change you'd need a mortgage to be able to do it
Yes SPD is Surge Protection Device.
I agree that 20 amps on the current 2.5mm cable would be the way to go.
You obviously know a lot more about ASHP than I do Baz so I will agree with what you say about how they are rated and your explanation makes sense otherwise why would they be so energy efficient and are becoming a more popular choice for new houses etc
Thanks for your understanding reply BTW
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GadgetBazza, freddyboy Thanked / Liked this Post
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09-07-2020, 06:59 PM #13
AFDDs are a bit of a strange thing as they pick up on series faults which are things like bad connections but how it differentiates between a bad connection starting to break down and a heater element switching on via a thermostat etc? Then they also pick up parallel ark faults which is where 2 cables start to short out.
It's difficult to keep up with all the regs changes sometimes unless you are constantly checking out the right websites. Unfortunately youporn is one of them
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freddyboy Thanked / Liked this Post
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09-07-2020, 07:19 PM #14
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Frimley Koi keeper, freddyboy Thanked / Liked this Post
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09-07-2020, 07:31 PM #15
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GadgetBazza Thanked / Liked this Post
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09-07-2020, 07:32 PM #16
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09-07-2020, 07:42 PM #17
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Frimley Koi keeper Thanked / Liked this Post
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09-07-2020, 07:49 PM #18
Ooh er missus, titter yee not
Lol open goal and all that lol
For once I'll refrain from making the obvious knob comment.
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GadgetBazza Thanked / Liked this Post
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09-07-2020, 08:13 PM #19
On your first reply Baz I originally missed the bit where you said you weren't qualified and nearly gave up on the thread thinking I was arguing with another electrician going by the various comments you made about cable sizing etc
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09-07-2020, 09:00 PM #20
Definitely not qualified! But I used to have a keen interest in electronics and have a logical approach to most things. I love a project too so researching and planning is a bit of a passion of mine I guess?!
Im still planning out my auto charging and battery operated circuits for my pond build as I want the pond to be free to run as much as possible using daytime solar stored in 12v batteries. So I’ll be putting my electronics to the test and probably worrying the crap out of my electrician!
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Frimley Koi keeper, freddyboy Thanked / Liked this Post
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