Thorfun

thanks. the electricity is converted to AC by the PV inverter in the loft so I don't have to worry about that apart from the upsizing of the cables. the plant room for my electrics is pretty much a cupboard. it's about 1.7m x 1.4m and will also have my Loxone cabinet, CU and network/server rack in it. so that room will get warm but it has an MVHR extract in it and 3m high ceilings so I'm hoping that the warm air will rise to the ceiling and get extracted! plus it's underground so will be cooler than elsewhere in the house. then again, maybe the garage is the best place for it, just not in the cupboard. I've got loads of space there. ahh man....I just don't know and I've so many other things to think about as well. this self-building malarky is tricky when you're winging it! 😂

our meter is 25m from the plant room in an external cabinet on the boundary so I hope I don't have to run the CT back to the meter! will speak to the electrician about it next week when he's here.

thanks Nick. so I'll forget inefficiencies, that's one headache down. the garage is attached to the house and is timber frame whereas the basement is concrete. from a safety perspective would it be better in the basement rather than garage or am I ****** either way if they combust?

as the title says 'where do I put my battery storage?'. I have a few options and I want to ensure I choose the best place for safety, performance and expandability. I have a LuxPower Squirrel POD inverter and 2 x Greenlinx 3.2kWh batteries at the moment but plan to potentially add more batteries and another SQPOD in the future to expand the system. The batteries are LFP(LiFeP04) cell type (which I believe is the safer of the Lithium Ion battery chemistry) and are IP54 rated. the inverter is IP65 rated but the instructions say to not expose to direct sunlight, rain or snow. so basically if installed externally to keep it covered. Below is a plan of the ground floor of our house. I have marked up the location of the PV inverter in the loft and the CU in the plant room in the basement which is approx 20m cable run from the PV inverter. I was originally going to put the SQPOD and batteries in the Cup'd in the garage but was concerned about the loss of efficiency running all that way from the PV inverter and then back to the CU in the basement. Also it's quite a small cupboard and the MI instructions for the SQPOD states the following clearance requirements so it might be a bit tight: I could put it in the garage which has a lot more space but, again, surely some massive inefficiencies for running the cable that distance. so, now I'm thinking of putting it in the electrics/comms plant room in the basement so it's next to the CU. but I'm now worried about safety and the potential for Li-Ion fires. the basement is built from waterproof concrete and has B&B above which will, eventually, be covered in a 50mm liquid screed. Am I worrying about nothing and is that the best place for it? I could, I suppose, build a shed for it externally but that seems a little excessive and also how will the temperature fluctuations of the outside world affect the performance of the system? the basement should be a constant temperature and even in the recent heatwave it never got above 23°C and we haven't even finished the insulation/airtightness yet. any comments on this please?

yeah. cheers. plant room is in the basement so it's surrounded by concrete. I think I'll be ok with the cheapest option there. thanks for your help on this thread. it's really appreciated.

that all makes a lot of sense, thank you. yeah, our SWA is basically around 90% - 95% in the ground. 1m above ground in the cabinet and, at most, 2m in the plant room, then around 24m - 25m under ground.

if it was your place would you spec LSZH over PVC regardless of the cost?

and interestingly for the 5-core SWA the PVC is cheaper than the LSZH. it just makes no sense to me. 😭

I spoke to our electrician and he has done the voltage drop calculations and concluded that 25mm SWA will suffice which is great. he also said that although we officially only need a 16mm earth he’d just go 25mm because of the poor earth loop at source we have. he's suggesting 25mm 5-core SWA now so that I don't have to run a separate earth. still doesn't answer my question about LSZH vs PVC though! 😉

yeah, sorry. I know the PWs do work in a power cut (I believe you're referring to the Gateway) I was more asking about requiring DNO approval for 2 x PW2. as I thought that just some installer saying they will limit export wasn't enough for the DNO. which @Dan F has confirmed is required. again, sorry for my error. I know they don't export, that wasn't what I meant! I meant that even if you told the DNO that the PW2s were isolated they still need approval from DNO. I know that my proposed PW2 required to be part of our G99 application.

you can get 2 x PW2s installed for £16550! wow. that's a good price. I was quoted £9500 inc VAT for one. I'm definitely no expert but I would've thought that with the PWs having the ability to export the DNO wouldn't like that and does that also mean that you can't use them in a power cut? if not, have you considered DC batteries instead of the AC PW2?

https://www.ebay.co.uk/itm/333714806299 can't get much better than this stuff. £8.75 a can from this seller on eBay is where I got mine.

I think that you're favoured architect you have a good working relationship with using an external consultancy for the Passive House work is actually a good thing! I'd much rather a professional admit when they don't know something and get someone in that does than try and muddle through and wing it. knowing your limitations and when to ask for help is a great trait and I applaud the architects for taking that approach.

if you don't go the Tesla PW route you could get 2 x Squirrel Pods and 25.6kWh battery storage for approx £14k +VAT (parts only and approximated by doubling a quote I had for a 12.8kWh system). that will give you 7kW charge/discharge rate which is better and cheaper than 2 x PW2s. 😉

we have friends that did just this as they had a silver membrane outside the TF which would've been visible through the open cladding. they spoke to the manufacturer of the membranes who said it was ok to do. if you're going this route then speak to the relevant manufacturers to make sure their products are ok in this situation.

sorry, I can't answer the anticipated board load! I'm not that clever. But I have decided to go with this CU (again, bit of overkill but plenty of space for anything I want to throw at it and not much more than a smaller board) which is single phase. our electrician did think that we could be ok with 25mm but thought for the extra the 35mm will give us a lot of headroom should our loads ever require it in the future. I think I'd rather pay an extra £100 now than have to run a new cable further down the line! but, I guess that now I have prices on the cable I could ask him if we can go back to the 25mm cable. I understand what you're saying about the earth but it's what our sparky has suggested to do and as he will be installing it I feel I need to run the separate earth cable as he's requested. hope you understand. although, I, again, could simply have a chat with him about it! 🙂 I'm not very good with electrics and need to trust our electrician on all of these things. I've read pretty much every thread in the CU subforum on here so I've a bit of knowledge, but, as they say, a little knowledge is a dangerous thing.

I'm unable and unwilling to have to choose the loads I want for battery back up. I want the whole house to have battery backup should I require it. hence running the whole house on a single phase. not to mention that running a house on 3-phase, afaik, needs to split each phase by at least per floor for safety reasons due to the arcing potential. and so all battery backup loads would need to be on a single floor. (note. I am not an electrician and am only going on what I remember reading regarding 3-phase and arcing. but what I remember reading filled me with worry about potential dangers and so I want to avoid it)

underground in a 110mm twin-wall duct from the cabinet to plant room in the basement.

ahh....(firstly I must apologise for not giving all the facts)....even though we have a 3-phase supply trying to get a 3-phase meter is next to impossible so I haven't bothered yet. again, as the whole house is being run off a single phase we are having a single phase smart meter installed in a couple of weeks (hence getting the cabinet and CU in ready for that to happen) and then, in the future, we can upgrade to a 3P meter when they become available again and if we deem it necessary. but I want the SWA cable in place from the cabinet to the CU to be able to handle 3P if/when it happens. yes, we could potentially fit more PV but I've pretty much run out of roof space! so the 10.5kWp is enough for us for now I think. and we already have a single phase inverter here and paid for as I've always only ever wanted to run the house off a single phase. I wanted to avoid the complication of running a house across 3 phases, having a battery that spans 3 phases or 3 battery storage systems (one for each phase) and wanted to avoid any risk of arcing across the phases no matter how small that risk might be.

our house is 420m2-ish in total. our M&E consultants wanted to give us 2 x units but I fought against it as didn't want double the running costs, double the maintenance etc. in the end they designed a system that worked with a single Q600 and 90mm semi-rigid ducting. it's not commissioned yet though but they promise me the flow rates will work.

Hi Peter. I fail to see how it's irrelevant. my PV inverter is on a single phase and so feeds back to my CU on that single phase. the electricity generated by the PV can only be utilised on that phase so if our ASHP is on another phase then how can the PV generated electricity power it? afaik the only way is to ensure that net metering is in place so that any power drawn by the ASHP on a second phase will be cancelled out by the exported electricity on the first phase. unless I'm completely misunderstanding this whole thing!

could you fit external blinds or shading to reduce the solar gain whilst allowing you to keep the large windows and views? might alleviate the need for active cooling. although, we're having AC and also have external blinds so if you want it go for it.

we do have a big cabinet (https://ccf-fibreglass.co.uk/products/electric-kiosk-housing-meter-box-cabinets-enclosure-grp) so the size of the TP&N isn't an issue. the reason for running everything off a single phase is our Solar PV inverter is single phase and batteries will be on the single phase and so I didn't want to complicate matters by having different phases in the house/garage. we have a room above the garage as well so that is part of the house really. and the garage is attached to the house. our electrician said, as our cabinet is about 25m from the CU we're on the cusp of 25mm and suggested going up to 35mm which I'm fine with, just in case. we have an 11kW ASHP (Mitsubishi Ecodan) which, again, I will want to power from our single phase PV array. in theory, I don't yet need to run cables/isolators etc for 3-phase but I'd rather do it now than running for a single phase and then needing/wanting to utilise the 3-phase later down the line and having to run more cables/install more isolators then. hope that makes sense! it does in my mind. 😉

DNO installed 3 x 100A head. our electrician has sized 35mm 4-core SWA with a separate 35mm earth. our system is a TT earthing system so I will be hammering an earthing rod in to the ground in the not too distant future! we're planning on running the house off a single phase but I am planning on utilising 3-phase in the future for EV charging, mostly. so am running the cable for future proofing. I also need a TP&N switch fused isolator which isn't cheap.

I need approx 30m of 4 core 35mm SWA cable for the connection from the cabinet to the CU in the plant room (damn that stuff is expensive!). I've been doing my research and have found on superlecdirect.com their LSZH SWA cable is £1.01+VAT cheaper per meter (https://www.superlecdirect.com/cables/steel-wire-armoured-cables-bs6724-lszh/bs6724-35mm-4core-xlpe-swa-lszh-cable-harmonised-black/) compared to the PVC version (https://www.superlecdirect.com/cables/steel-wire-armoured-cables-bs5467-pvc/6944x-35mm-4core-bs5467-xlpe-swa-pvc-cable-harmonised-black/). My electrician said that he's previously used LSF cable and it's a pig to strip and as my SWA is going in a duct in the ground he said just get the PVC stuff. But LSF is different to LSZH, right? so is the LSZH cable also a pig to strip? And if the LSZH cable is cheaper than the PVC why wouldn't you buy it? it's better, right? am I missing something here? I have a LOT of cable to buy and will be agonising over the whole LSZH/LSOH vs PVC argument lots in the near future. can someone also please tell me if it's worth using the LSZH stuff even if it's more expensive than PVC? I would've thought that in a domestic environment by the time the cable catches fire, i.e. has gone through the plasterboard, I've got bigger issues than the PVC burning, right? is LSZH more for commercial buildings when you have to evacuate a multi-storey office block or high-rise buildings like apartment blocks etc Can someone please help to clear up this whole issue for me? 🙂