Carrerahill

I am struggling to work out what you are trying to do. When you say spur do you mean a spur leg of wiring or a fused spur? What you can do if you must create a spur with multiple sockets from a ring is fit a fused 13A spur then run a radial to as many sockets as you want, safe in the knowledge you cannot overload that cable. The reason you cannot spur off a spur is due to cable ratings, 32A ring main only works on 2.5mm cables because you have two of them, however if the circuit was a radial at 20A (which means the cable is then rated higher than the breaker) then you can actually create spurs from spurs because the whole thing is then only 20A.

I can speak from the electrical aspect here, although I can also comment fairly accurately on other utilities because I am fully aware of them and the hurdles they pose to developments. So the question you might first ask is, "Who applies for the utilities" well that would be, in most cases the M&E consultants. I probably do an application a month and for me the application is based off my proposed load assessment, sometimes this can be tough because the first question is gas or electric heating, if they go gas it makes life easier, as soon as they go ASHP or other electric then the can of worms is open and its never simple in the early stages. I would then fill out an application form to the relevant DNO (i.e. UKPN or SPEN etc.) and sometimes I also send them to some IDNO's (Energetics) and ask for X number of supplies at X rating. So in a block of 10 gas heated flats, I would ask for 10 x 2.5kVA single phase supplies and 1 no. 50kVA three phase supply for the Landlord (less if no lift) all fed from a single cable head into a main service board. The next step is I then get an email from the local connections manager who will say, yes that is fine, give me your site drawings, which we would have from the developer, architect etc. and they go and do a drawing and quote. Or they come back and say you will need a substation in which case they will quote you from the local HV network. Other variables are forms for solar. See below, red is 11kV and brown is LV ready to go directly into a house or office etc. If they have capacity on the LV they give you it, if not you have to put in your own sub. Developer pays for it. We did a hotel last year the sub was for 1 hotel and 1 restaurant, £150K. Water and gas are very similar actually, gas there is high pressure and low pressure networks, so a local tap can be had from wherever needed. Water may need upgraded or new run in. Openreach or Virgin media, fairly easy to be honest. This of course all assumes the plot is not 2 miles from anything. As with everything there are variables and exceptions. I have known HV lines to be brought in over a mile to a new development, subs are also sometimes considered at master planning stage. You may have a plot and they will say, no capacity, but actually there is, they just have it earmarked for a 5-10 year master plan and it might never get used, but it was put there as part of a bigger plan. The above site is a commercial estate. They put in a sub and allotted x amount to each plot, this way every plot will be able to get a connection. Oddly on this site there is also an Energetics sub, must have stacked up for them financially.

I think the installer is trying to make an arbitrary point that ASHP will work just fine on an older building. It also appears that only about 3-4 rooms are actually being heated with the ASHP. It proves very little. Just that you can heat 4 rooms with 4/5kW. I think he is being a typical installer, "Look it works fine, here I will install 100's of them for all you gullible sorts"

I think you have misunderstood me. I said the installation seems flawed, and you replied, "Yes but a rule of thumb that makes it "seem" flawed might not reflect reality. I gather that they were of the opinion that those rules of thumb weren't helping the industry, in the light of newer, more efficient HPs and better weather comp. So they did some calculations and used their office as a test to verify." My reaction was based on you making the comment "rule of thumb", you have assumed that I am basing my response on rule of thumb heating requirement, as a building services consultant I spend my life calculating things, I don't do things by rule of thumb. So for clarity, no rule of thumb, calculated area heating based on calculated heat loss. My reference to SAP calcs and LA requirements etc. was to point out that rule of thumb heating installations are not done anymore on new builds. Yes, there was a time when a plumber would look at a space, apply some typical figures and work out the heating requirements for a building and that was fine, it was just the done thing, energy was cheap and no one cared about CO2. Now steering this back round to the point I am making, this installation seems flawed and I cannot see how it stacks up, here is a brand new flat in London, insulated to the hilt, it still needs PV on the roof to offset CO2 to achieve the required DER: This is based on maintaining a room temp of 20°. Note the heat input required for this PIR air tight box...

Irony here is that an MK Logic white socket is sometimes more expensive than some of the "decorative" sockets from cheap manufacturers. But I see the point.

Indeed, see my graph posted above, that is the fusing curve of a BS88 (what they fit in the fuse carrier of just about every fused supply in the land) 80A and 100A. To get a 100A BS88 to fuse within 1 second (which is slow) you would need nearly 800A. They will of course fuse within 0.1s at about 1000A which is basically instantaneous short circuit protection.

That isn't a rule of thumb, that is calculated room by room heat loss and a sized radiator, on new builds you cannot get by with rule of thumb anymore as you have SAP calcs and CO2 targets and council schemes and standards now. So this installation is systemically flawed.

A diversified load which demonstrates sustained current draw well over the 100A mark. When I do a load assessment, usually for a commercial/industrial development (residential, until now has generally just been taken as a 100A fuse) I take all the main plant loads, lighting loads, small power, lifts, water pumps, EVC, etc. and add them all onto a table. Small power for an office for example is based on office type and W per meter sq. So that gives an estimate of "uncontrolled loads" i.e. plugged in items. In your house you could work this out, by working out how many of you there are and what do you all do. Laptops, TV's, do you run washes a lot, cook a lot etc. etc. Lighting can be much more accurate as you spec the lighting and know the connected loads and switching arrangement so you can work out burn time. Then we apply diversity to the other loads. Lighting might be 80% if you assume stores, WC's etc. and occasional use rooms are not always lit, general power I usually take at 100% because I have already worked out estimated loads and I don't like to reduce it more if I am sure the estimate is good. Lifts in a busy office maybe 70-75%. Vent 90% Water pumps, 60% and so on. At the bottom of the speadsheet it spits out a amps per phase figure, then I add 30% for expansion. On this office I am doing just now the figure was 215A per phase before the spare 30%. So clearly this will be a 3 phase supply, but had that figure rolled up at 16A per phase and I knew that we could get single phase kit, I would propose a 25kVA single phase supply which is about 100A. If you PM me your email address I will send you the spreadsheet and you could tinker with it. I will leave it populated so you can see how it works.

Do it if they offer it, but I think you would cope. Say you have ASHP and EVC and also electric cooking (which is meant to be green - ha!). I would think so.

I am saying that the chances of all those electrical loads all simultaneously drawing full current is unlikely. Ovens and hobs modulate most of the time they are on, so they don't often pull that current for long periods of time. Even if you did go and load up your electrical system the chances are that the full load may only last 15minutes or so then start to fall off. You also need to consider normal use. In my house just now the WM is on a 40° wash, the oven is on too, this laptop and some lighting. Then there are the parasitic loads, so peak power draw right now is probably 25A. I could add an EV charger and ASHP and still only be at 80A, however, as said above, the oven and washer load will modulate, so might peak at 80A but realistically sit at 70A. For the record, a 100A fuse won't blow at 100A, see green curve below: Without going into the technical details of it all, basically even if you did pull 100A for say 10-15minutes it would be fine, not ideal but it would be fine, the actual BS88 fuse would take 100A for over 1 hour, seems odd you may think but incoming fuses are there to do multiple things, one is to protect downstream and upstream cabling. Yes, that fuse also protects the DNO's incoming cable before your fuse, because that cable will probably be jointed to a much bigger cable in the street which is on a 1250-5000A fuse at the other end, but that cable coming into your house sure isn't capable of carrying even 250A. Cable protection is based on time. A cable will not go 1A overcurrent then explode into flames, it will just warm up quicker than intended and may then tip over its maximum rated operating temp and at a point the cable will be damaged, twin and earth is rated at 70° - so if the cable goes overcurrent for say 30 minutes and got up to 50° it would be fine. It is quite common for submains distribution and switchgear to allow periods of time where the rating may exceed for example the cable rating, but it is controlled with MCCB's (big fancy, sometimes micrologic controlled breakers) or even a BS88 fuse like the DNO will fit. The weak point in your system might be the incoming isolation switch(s) therefore a board with a main isolator rated at 125A is a good idea. I personally always spec a higher mains isolator than the supply ought to deliver.

Doesn't work like that, you must apply diversity, if all supplies were calculated like this we would have colossal electrical networks and switchgear. Actual demand after maximum diversity, or ADMD is how the DNO's work out how many buildings they can actually supply, most class a 2 bed house with gas heating as 2.5kVA - which is basically 2500W at 230! They still fuse it at 60/80/100A depending on what/where etc. but they don't actually allow for all properties to use the max or the grid would fall over, which it will do soon enough with all the EV chargers.

I would use a 32A contactor, 25A would work too, but it's only just over 5A greater than max load, I like more spare as the contacts will be better sized. Second question depends on control hardware/software. Some heaters for PV work on a variable input, so if you have 500W it will take 500W, some however wasn't their full rated input all the time in which case you need to spare 4500W. I personally would have gone for a couple of smaller elements and banked them up as power was available, but you could use the variable input control perhaps and mitigate this issue.

£156 a month on electricity for heat alone at my price as of 1st April (so I will be submitting some high meter reads for this month and next). It is not terrible I suppose, but it is not good. Installation seems flawed, uninsulated house with those little radiators? In new build developments with all their insulation we are seeing little 3500BTU rads and that includes a percentage of space for the calculated space heat loss and was based on a delta of 60°. I just can't see how that stacks up.

So was asbestos back in the day!

It never ceased to amaze me that roofs were actually done like this down south. Being in Scotland I expect nothing less than sarking board, membrane then slate/tile. As for dancing tiles, there is not a lot you can do if they are already fully fixed.

I edited my own post to add the above line and seem to have deleted the original post, I shall post again below: Perhaps the OP @dnoble could start by answering the above and posting some photos then we can start to chase this down. Unless I am mistaken we still don't actually have a system breakdown, just snippets of information in insolation, and as a group we are going round in circles with the same thoughts and assumptions. The OP is looking for a specialist, I doubt he needs a specialist as the collective minds of this forum can almost certainly unravel the details here with the only exception being if we do decide there is an issue. OP states that the panels were self-installed, so all the details must be easy enough to list. I posted what I think is a good starting point and it appears to have fallen into the ether. I think it is fair to say that when people take their time to answer it is worth exploring said answer or at least acknowledge it. Rant over.

Can we get photos of the install?

How many panels have you got and do you have their make and model and peak output rating? Maybe you have a 6kW inverter not 6kW peak worth of panels. The "fuse" that trips, shall be a MCB, RCD or RCBO - the latter two trip if there is current leakage going somewhere it should not go and I think, given the conditions it trips under, that is your issue, caused maybe by water ingress. You need to confirm what trips. If it is an MCB then you may have a short somewhere that only faults when weather conditions impact it. This issue is probably AC side and an issue between your breaker and inverter or inverter itself. Unless you have a protective DC device? I think photos would help us help you. So lets work out what you have then that is that solved. Batteries, are you regularly exporting a lot of energy? At 2.8kW peak I cannot imagine you are, therefore more panels probably make more sense first.

Is it such a problem waiting a few seconds?

Smash & chuck.

Depends what your idea of a "nicer" design is. I might think your nicer design is pants. You must design what your client asks for, it doesn't mean it is right or wrong, but it is what the client wants and the client will not build your ideal or dream house.

The factor? Might be an "estate agent" business but does factoring too? Factor may be renewing building insurance, loads of reasons, I have never rented domestically but they used to send all sorts of surveyors round to our business premises, asbestos registrar (waste of money, building was built after asbestos was banned), insurance survey, delap survey as the landlords sold up, fire risk survey, including inspecting our own PAT testing records etc. - you name it, people wanted to survey the place - we just let them get on with it. Didn't really care apart from a a chap doing a fire risk assessment for the landlords buildings insurance, who started to lecture us about storing paper drawings, he was also a cheeky git so I threw him out and told him to write his report.

Even if they sell new landlord will likely leave tenants be, properties change hands all the time with little or no impact on tenants, yes sure not always but common enough. You could also simply ask the factor (estate agent) why.

Is it not just the paint/finishes etc. burning off? Very common for a new stove to need a burn in period. After the 2-3 small fires you are supposed to have (after materials have set/gone off etc.) you are meant to have a hot fire and burn off any metal oils, paint finishes etc. Our house had a haze of smoke in it on the first burn in night, opened all the windows, lit it, fired it hard and went upstairs. Second time it did it a little then nothing. Have witnessed this about 3-4 times in my puff now. Normal I'd say. Like using a brand new oven.

Tell me about it. We have 2 mature pines at the back of our garage, the 2 year old roof is totally green at that end with a layer of algae stuff and the gutters ended up having to be dropped into a sump gulley to catch all the needles and needs cleaning out twice a year.