RCD if required and what type, re-solar panel installation?

[EricMark]

I decided to get solar panels, the inverter instructions say one can use type AC, so the existing 14 x RCBO CU seems OK, may be a good idea to fit type A in the future, but if following what is says in wiring matters should have type F for my inverter drive washing machine, as if that will ever happen.

However two point with the solar install. One was the UPS system, to allow freezers and central heating to run when we have a power cut, earth rod fitted and the 4 sockets for freezers RCD protected, great not problem there, but the central heating has no RCD protection any more, not on a plug so maybe not required? But it is one item which is worked on live by plumbers, so would have expected RCD protection.

Second is the iboost+ it seems DC is fed to the immersion heater, is this a problem with a circuit protected with a type AC RCBO? I really don't know, can the DC get on the supply, or is it like the washing machine, and no one worries about the DC?

 

[pc1966]

I decided to get solar panels, the inverter instructions say one can use type AC, so the existing 14 x RCBO CU seems OK, may be a good idea to fit type A in the future, but if following what is says in wiring matters should have type F for my inverter drive washing machine, as if that will ever happen.

Generally type A should be used today for the obvious reason that most things have some degree of direct-off-mains electronics in them. Some type AC will be OK on pulsed DC, but that is not guaranteed by the design/manufacturer, so not so good to rely on. You could try testing yours on the type A setting of your MFT to see if they behave badly, or much as a type A would.

For Typical UK-style TN earthing stuff like washing machines don't worry me that much as in most fault scenarios they will clear on the OCPD anyway, and the combined risk of a partial fault causing much DC or HF noise, but not enough for the 13A fuse, etc, and someone touching the supply+earth at that time is small.

TT earthing would make me a bit more weary...

However two point with the solar install. One was the UPS system, to allow freezers and central heating to run when we have a power cut, earth rod fitted and the 4 sockets for freezers RCD protected, great not problem there, but the central

Check that your UPS links N-E when running off mains, and not leaving the lot as a floating IT supply. That can upset some boilers I believe due to flame detection or similar.

For example, the UPS we have at work (5kVA Riello things) measure a PFC of only around 100A when running off mains due, I think, to the EMC filters being very "RCD uplift" in behaviour, but if the incoming supply is off they measure about 2kA PFC due to the change to local N-E link. They wont actually deliver 2kA of course! That is just the electronic regulation making the supply look very "stiff" and low Z when the MFT switches the test current on/off to see the voltage change.

heating has no RCD protection any more, not on a plug so maybe not required? But it is one item which is worked on live by plumbers, so would have expected RCD protection.

Is it not off one of your 14 RCBOs?

Second is the iboost+ it seems DC is fed to the immersion heater, is this a problem with a circuit protected with a type AC RCBO? I really don't know, can the DC get on the supply, or is it like the washing machine, and no one worries about the DC?

If you can check your current type AC RCBO is well behaved or not, or simply replace it withy a type A, then that issues goes away.

 

[EricMark]

My son has my loop impedance tester, and RCD tester, should not need to test myself, should be able to read the results on the insulation certificate or minor works when they arrive, I have the compliance certificate, but nothing else as yet, so can't read the test results yet.

I will fit a RCD to the boiler supply, on my to do list. Already bought, but could not get a type A from CEF, so stuck with type AC, but should be OK for the old oil boiler.

I am not convinced that type A is much better than type AC without also fitting a RDC. Or even with a PWM controller as fitted to the immersion with a frequency of I will guess well over 50 Hz

I have looked for info on the iboost+ it says use shielded cables if over 3 meters to the immersion, so that does point to a high frequency.

 

[DPG]

My son has my loop impedance tester, and RCD tester, should not need to test myself, should be able to read the results on the insulation certificate or minor works when they arrive, I have the compliance certificate, but nothing else as yet, so can't read the test results yet.

I will fit a RCD to the boiler supply, on my to do list. Already bought, but could not get a type A from CEF, so stuck with type AC, but should be OK for the old oil boiler.

I am not convinced that type A is much better than type AC without also fitting a RDC. Or even with a PWM controller as fitted to the immersion with a frequency of I will guess well over 50 Hz

I have looked for info on the iboost+ it says use shielded cables if over 3 meters to the immersion, so that does point to a high frequency.

Is it not fed from one of the RCBOs? Where is it fed from?

 

[EricMark]

The FCU and two x double sockets are fed from the inverter, I tried fitting a RCD FCU but it tripped as soon as the boiler kicked in so was removed again, as yet not tested earth leakage, but never had a problem when fed from the RCBO so assume some thing to do with inverter supply, however turning off the supply to fit it seems to have upset the inverter and battery, inverter running again, but battery still not working, so now not going to touch again until an isolator is provided, clearly pressing a button on the battery and turning off the only AC isolator is not the way to isolate, even if told by installers it was.

I am not happy with a push button as an isolator, to my mind there should be a way to lock it off, and can't do that with a push button. And I feel there should be a single isolation point, should not need to turn off at two points.