RCD type with an iBoost+

[ericmark]

The instructions are here nothing about RCD protection which does seem strange.

The Output of the Solar iBoost+ is a specially modulated DC output which must never be connected to the normal AC circuit. The Solar iBoost+ output must be the only supply to the immersion heaters and connected through a good quality, working mechanical thermostat.

It can supply up to 3 kW so clearly a 6 mA DC is a bit pointless, I assume the problems are only after the unit, and supply side standard RCBO is fine. And since it only supplies the iboost+ if DC did bind it, in my case not a problem as don't really need the RCD protection on that circuit anyway. But surprised nothing in the instructions about RCD type.

 

[SpecialK]

Can you set an export offset on these? If not ideally you want these wired in between your CT and meter if you have a battery otherwise it can cause battery drain issues.

 

[JohnD]

Can you set an export offset on these? If not ideally you want these wired in between your CT and meter if you have a battery otherwise it can cause battery drain issues.

No, it is a device intended to divert power to a single appliance with a resistive load.

 

[SpecialK]

Yes but....It will drain the battery if the inverter can see it as a load. Hence you need an export offset? Doesn't look like it has one...

 

[JohnD]

Yes but....It will drain the battery if the inverter can see it as a load. Hence you need an export offset? Doesn't look like it has one...

No, it doesn't work like that.

It detects power being exported from your solar panels to the grid, and regulates the power to the appliance to be just under that.

 

[SpecialK]

No, it doesn't work like that.

It detects power being exported from your solar panels to the grid, and regulates the power to the appliance to be just under that.

When it takes the export the hybrid will see it as a load if its on the load side of the CT. Hence you need an export offset on the diverter with a hybrid inverter or wire its supply in between the CT and meter so it is not seen as a load.

There will be no issues with a non hybrid inverter.

 

[ericmark]

It has a series of off sets so one can insure last but export on list of usage. 100 watt is default setting, think I set mine to 200 watt, as when set the two CT coils were too close together.

It can put far less that 3 kW into the water, seen here with just 320 watts. The problem is my immersion heater is too short, so it only heats top bit of the tank, so looking at display all too often we get and still next day cold water until sun comes out, but heat with oil and it will stay hot 3 days. It can work with two immersion heaters, but we only have one.

 

[JohnW2]

.... It can supply up to 3 kW so clearly a 6 mA DC is a bit pointless,

Does the "6mA DC" not refer to an RCD which can detect an L-N imbalance of 6mA DC, rather than the L/N DC current in normal operation? ... or have I got it all wrong?

Kind Regards, John

 

[Murdochcat]

Does it actually need a RCD ?

 

[ericmark]

Does it actually need a RCD ?

Possibly not, and my thoughts are with RCBO's if any thing does stop a RCBO tripping it is a least limited to one circuit, so in real terms not some much of a problem. I was surprised reading the installation instructions for the solar panel inverter to see it stipulates type AC. And the boiler has been taken off RCBO protection when solar panels were fitted and I have the compliance certificate.

However to my mind the immersion heater is one of the appliances which is likely to as the element gets older to trip on earth leakage before over load should the elements be corroded away. So it would seem prudent to have RDC protection.

I need to get the immersion renewed as it does not heat up enough DHW, so want a longer one fitted, so it should then be good for many years. However to hear peoples opinion on if type AC is appropriate? I was reading another thread, and was about to say needed type A, then thought about it, and had second thoughts, one thing I keep on considering is if type A is only good for 6 mA is there really any point unless some system to detect and auto disconnect if 6 mA is exceeded.

 

[JohnW2]

I need to get the immersion renewed as it does not heat up enough DHW, so want a longer one fitted, so it should then be good for many years. However to hear peoples opinion on if type AC is appropriate?

There may be other issues in terms of the bigger picture of your installation as a whole, but if we were just talking about a circuit fed with sinusoidal AC and supplying only an immersion heater, there would presumably be no need for anything other than a Type AC RCD would there?

Kind Regards, John

 

[ericmark]

There may be other issues in terms of the bigger picture of your installation as a whole, but if we were just talking about a circuit fed with sinusoidal AC and supplying only an immersion heater, there would presumably be no need for anything other than a Type AC RCD would there?

Kind Regards, John

The iboost+ supplies the immersion heater with DC according to it's instructions.

 

[JohnW2]

The iboost+ supplies the immersion heater with DC according to it's instructions.

Ah yes, sorry, I'd forgotten that.

My understanding is that the only type of RCD that can detect smooth DC residual currents is the Type B, and that they achieve that by having completely separate technology for that purpose.

Do I take it that the output of the iboost is earth-referenced (i.e. one side is connected to earth)? If not (i.e. if it were ;'floating'), then no type of RCD would bee able to detect a 'leakage to earth. In fact, it would presumably be much 'safer' (and wouldn't need any sort of RCD) if it were not earth-referenced ?

, since the usual

 

[plugwash]

I would suspect that the output is referenced to the input.

 

[ericmark]

Do I take it that the output of the iboost is earth-referenced (i.e. one side is connected to earth)? If not (i.e. if it were ;'floating'), then no type of RCD would bee able to detect a 'leakage to earth. In fact, it would presumably be much 'safer' (and wouldn't need any sort of RCD) if it were not earth-referenced ?

This is the point I was making, I have no idea, and I would suspect most people fitting them have no idea. To my mind with a TN supply the RCD is extra protection, and should it not work, then we still have the same protection as before the RCD drive, so no big problem.

The problem is with TT supplies where use of plastic services has reduced the earth loop impedance to a point where we now rely on the RCD I still have type AC and since 14 circuits, I have no intension of changing them, it was only 4 years ago when I had no RCD protection in this house.

The inverter for the solar panels clearly states a type AC RCD can be used, I would have expected the iboost+ to also tell us what RCD can be used.