We recently had a 4 hour power outage due to a blown street joint and found out I could hardly lift my existing generator, so it was time for a rethink.
My previous blog covers the internal transfer switch enabling my consumer unit to be safely switched from utility power to local generation, that bit of the system has not been altered.
This blog covers the Honda EU22i generator, house inlet and circuit protection.
Generator
I gave some thought to the replacement of my old open frame generator, and the following points were key for me (in no order):
- Reliability
- Manageable weight
- Low running noise
- 100% Sine Wave
- Min 1800w output
- Machine history
- Cost
- Serviceability
Although expensive, the EU22i met my requirements and was purchased from a local Honda approved dealer which increases my confidence in aftercare.
In case of extended running being required, I bought from eBay an additional external petrol tank and petrol lines for this reason.
Build
Construction was very straightforward, I start by making a dimensioned drawing using Visio of the enclosure and all parts to be used, this allows me to play about with the layout and finally print the front label which I use as a cutting template for the any holes required.
The parts were relatively inexpensive apart from the hour meter which functionally wasn’t required but is a ‘nice to have’ to monitor the generators onload usage to the house.
House Connection
The original connection from the generator to the transfer switch has been removed and replaced with one containing a voltage and current protector, a 30mA RCCD and an hour meter to monitor time off grid.
The above image shows the standby generator inlet powered externally from the EU22i without any load, the voltage and current protector GPS8-02), is displaying the actual generator voltage of 244v AC, the voltage and current protectors internal contactor will disconnect if any of the follow occur:
- Voltage out of 210v – 252v range
- Current over 7.5A
The Red LED indicator illuminates when the generator is running with the RCCD ON and controllers output is within the set parameters.
Image of power transfer switch below the consumer unit in the garage, below is an image of the consumer unit RCBO descriptive labels which are either Red or Green, if RED, then they must be turned OFF in advance of the generator power being switched over with only the GREEN left ON.
Electrical Connection
First thing to note is that the generator is separated from the Utility power system by a ‘break before make’ switch, specifically designed for the purpose of external network protection, with this arrangement it is not possible to ‘back feed’ into the network and possibly cause injury to downstream workers.
The house supply is TN-C-S or PME, I had previously installed an Earth Rod for two reasons, the first was to remove reliance on the DNO protective conductor being the single point of failure and the second was to ‘Ground’ the otherwise ‘floating neutral’ of the legacy open frame generator.
NOTE: Earthing is the biggest area of debate regarding home generators, please do your own research on this complex area.
The above is the wiring schematic of the Honda EU22i with the addition of voltage measurements I have taken and a guide image inlay of a split load transformer.
I wanted to establish if the generators chassis ground screw was connected to anything other than the chassis, ideally I was looking to see if the neutral and chassis were directly connected, this would give me a fixed reference voltage and replicate my existing incoming electrical supply configuration.
Results:
- Socket earth pin to chassis ground screw – Continuity and 0v AC
- Socket live pin to chassis ground screw – 120 v AC
- Socket neutral pin to chassis ground screw – 120v AC
- Socket live to neutral – 244v AC
Conclusion:
The generators inverter output is split phase, effectively two live conductors when measured to the chassis, therefore, bonding the neutral to the chassis would cause a direct short circuit of one half of the inverters output and I’m assuming ‘magic smoke’ would soon follow.
In light of this, I have made no modifications to the generators output (no N-E plugs etc) and instead opted to earth the generator to the house earth via the plug and add a global 30mA RCCD on the generators output.
The consumer unit does have RCBO’s, but I’m not bothered by selectivity of device operation in an outage, overcurrent again will be globally managed by the GPS8-02.
12v DC
I don’t envisage using the generators 12v DC output, however, I did measure the voltage and though I’d share the results:
- Eco Mode – no load voltage = 16v DC
- Eco Mode – across 21w load = 11.2v DC
- Non Eco Mode – no load voltage = 33v DC
- Non Eco Mode – across 21w load = 16.7v DC
Just one to note!
