how many people are in this situation with installations not carried out to the book.
I've been responding to Heat Pump 'complaints' online for about 5 years, starting with a group of 250 households who were part of a government-funded trial in SE England.
I've read the customer's descriptions accompanied by photos for about 300 sites, and seen three which appeared to satisfy Building Regulations. All three were on this forum.
you should charge for a video inspection for my future installations
I'm looking at the wider picture. The latest Government target was announced in July'24. They want to see 600,000 installations occurring per year by 2028.
Individual video inspections aren't going to make a dent on that quantity of potential failures which will need correcting.
We need to prevent the poor installations occurring in the first place... ... and one cause of the problem is that customers don't know enough to spot what's going wrong. So they pay the balance of the invoice to the installer and wave goodbye.
They only begin to realise there's a problem when they look at the next few electricity bills.
Even so, a fuse is not a DC Breaker, which is what the SunSynk manual states should be used. I use both a fuse (on one of the wires) and a double-pole breaker. And I have a high-current relay on each battery supply too.
If I need to manually isolate any one of my three inverters, then I use the breaker.
My system is designed/configured for 100A maximum charge/discharge per battery or inverter. That means I can use 125A DC-rated MCBs for the breakers.
125A is the highest current-rating possible for a DIN-rail mounted MCB. Above that capacity you require an MCCB, which gets screwed onto a backboard.
This post was modified 7 months ago 4 times by Transparent
when I bought the batteries I was wanted to ensure they had back up
Let me slightly 'tighten up' that wording.
I assume we're talking about a 240v AC supply which remains live when there is a grid outage.
Your SunSynk inverter offers this by default.
You wouldn't loop that back into your existing 3ph consumer unit.
For safety reasons, I'd recommend a separate consumer unit to feed circuits you want to be supplied from the 'always on' output from the inverter.
I have some circuits which can be switched over from one supply to the other. But when you wire a house like this it's important to label everything very clearly.
This post was modified 7 months ago 2 times by Transparent
@transparent looking at that consumer unit you are running battery in that example with grid isolated. I understand that a device needs fitted to mine which will automatically switch off grid to battery during an outage, presumably back on later. Why is yours not configured that way. Also I’m a bit confused regarding the fuses, mines is an 80amp mains supply and was 100amp. Are you describing DC here.
@david999 - regarding 'off-grid' use, I was specifically answering the points made by @bretix who has a SunSynk inverter
I can't remember which inverter you have, nor how it might be adapted to supply in-home devices during an outage whilst still complying with G98. 🤔
The majority of my house is running off-grid (from the storage batteries) continuously. The EV-charger is an obvious exception!
My connections to consumer units reflect that mode of operation. My inverters connected to the storage batteries here do not, and cannot, export back to the grid. That's a design choice I made after being a trial-site for a grid-tied battery for 2 years.
I've gleaned practical experience with both approaches.
Yes, the fuses I was referring to are those which @bretix has on the wall between the 10kWh SunSynk inverter and the two GSL storage batteries.
We still don't yet know what those fuses are, nor why the installer didn't fit the 2-pole breaker in the installation manual's diagram. There may yet turn out to be a good reason.
You are referring to the Service Fuse at the DNO incomer to your house. That's quite a different subject, but we can discuss why it's been de-rated to 80A if you'd like to.
This post was modified 7 months ago 2 times by Transparent
@transparent I think my fuse was derated because I was looped, could be something to do with the new 3 phase cable but I run single phase.
could you clarify a point please. What figure am I looking at when purchasing panels and not wanting to overload my inverter. Voltage, amperage, short circuit voltage etc. I can’t see what’s on the rear of my existing panels and I don’t want to rely on what my installer detailed in the docs, any way to work it out.
@transparent I think my fuse was derated because I was looped, could be something to do with the new 3 phase cable but I run single phase.
could you clarify a point please. What figure am I looking at when purchasing panels and not wanting to overload my inverter. Voltage, amperage, short circuit voltage etc. I can’t see what’s on the rear of my existing panels and I don’t want to rely on what my installer detailed in the docs, any way to work it out.
a lot of detail on that tab, could you break it down for me
PV panels that you're likely to consider for rooftops have three electrical parameters which we need to take note of.
Voltage, open-circuit (abbreviated to Voc)
Voltage, maximum or peak when the inverter is operating in MPPT mode (V-MPP or Vmax)
Current, maximum (Imax) when first connecting, as if it's open-circuit
MPPT is the mechanism by which an inverter draws the maximum available power from a PV panel. It stands for Maximum Power Point Tracking.
If the inverter were to take too much current, then the voltage falls; And if it doesn't allow the voltage to drop far enough from Voc then it will be taking too little current.
Here's a graph which shows how the algorithm works, but you really don't need to understand it in any great depth. Just note that there's an optimal 'sweet spot' in the curve, which is referred to as 'the knee'.
Now let's turn to the inverter. Here's the three relevant parameters we need to look at:
Max PV voltage: If we add together the Voc from a series string of panels, then it mustn't exceed this figure
PV voltage range: the sum of Vmax for the string of panels must lie between these figures
Max input current: I-MP mustn't be more than this. Usually not a problem until you want to put panels in parallel
At present almost all silicon solar panels will have Vmax around 36v and I-MP around 12 Amps.
There are a few high-quality panels which have high-voltage, around 70v, and low-current, around 6A. You're only likely to buy those if there's another feature of interest to you, such as a particularly long lifetime. I have some of those (from Panasonic) on the highest arrays on my roof, positioned above the sloping glass section.
Now let's perform a typical selection for your SPH-3600 inverter, which has two independent solar inputs.
First we need to choose a panel where the current won't rise above the maximum 13.5A specified on the label. Here's some PV panel specifications which I've found on the Midsummer website:
These are all 425w panels, and from Longi, Trina and Perlight.
Longi must be ruled out. The 13.9A current is too much for your inverter.
Trina is a better choice. The current is well inside the specification. But the higher voltage means that we'll reach the maximum possible 550v of your inverter with fewer panels.
Perlight is a more expensive panel, but a better match for the maximum current rating on your inverter.
Connecting these panels together in a series string you'd be able to have 10 Trina panels or 13 Perlight before hitting the 550v maximum of the inverter. So, whilst you'd pay more for the higher quality Perlight brand, you'd have 3 x 425w (1275v) more power available.
That's the basics for choosing the electrical characteristics.
You might find an even better match by checking a panel with a slightly higher power-rating.
There are other factors to think about. On an ethical point, the MOD won't purchase Trina products due to doubts about the use of slave labour. Do your own homework!
This post was modified 7 months ago 6 times by Transparent
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