First of all, I hope readers will understand the reasons for the length of this post. I am seeking advice from professional sparkies, being qualified and experienced in ways that I am not, so I feel it necessary to provide a minimum amount of information to allow any comments and advice provided to be relevant and properly informed.
This is the foundation for this post. I have come round to thinking that it would be sensible to look seriously at a backup generator supply for my home in case of a protracted power cut (I would regard anything more than six hours as protracted) or a sequence of rolling power cuts occurring on a repeated/regular basis. I do not regard the latter possibility as ridiculously far-fetched, at least if some of the more pessimistic forecasts of future electricity generation resources do materialise.
My objectives are (more or less in order of priority):
- maintain electrical supply to gas boilers (I have two matched boilers) for heating and domestic hot water. All DHW is provided by the boilers (no electric water heating). There are two circulation pumps, each ~50W, plus usual electrically operated valves;
- maintain minimum level of lighting in occupied rooms on ad hoc basis (all lighting is LED so a reasonably low aggregate load);
- maintain power supply via circuits for refrigeration appliances as follows: 1 x side by side fridge/freezer (dedicated circuit), 3 x under counter fridges, 1 x under counter freezer (all on ring main circuits);
- maintain power supply on ring main circuits for TVs (up to 2 at any time), laptop and phone chargers and similar, incidental, low-load items;
- facilitate controlled and selective use (i.e. not simultaneous) of large appliances as follows: washing machine, tumble dryer, dishwasher, microwave/combi oven, oven, induction hob, vacuum cleaner
- facilitate night-time use of EV charger (this is on a 7kW/40A supply but can be throttled back to anything between 5A and 24A);
In other words, I want to be able to use all of the electrically powered resources that I have, but in a controlled and, if necessary, tightly restricted way.
Clearly, if I had unlimited funds and space, I could buy a 10-20kW genset and install it with automatic changeover switching. However, I don't have that luxury in terms of finance or space. I am looking to arrange insurance against reasonably low probability events, but ones that could be extremely disruptive to my family’s lives and comfort, if they materialise. I don’t expect not to be inconvenienced by any loss of mains power, but I want to limit the disruption.
So, my thinking is to acquire a ~5kW diesel genset with minimum 12 hours fuel endurance. If the need to use it arises, I expect to have to move it from its usual storage location to a suitable operating location. An example genset I have seen online is 920x550x750 (LxWxH), wheeled, and weighs ~180kg, including fuel. I reckon this is reasonably manageable for one person.
I am willing to take the risk that a power cut could occur at a time when I am unable to effect a manual changeover from mains power to genset supply, so I don’t intend to install automatic changeover switchgear. My idea is to use a suitable length 32A cable and commando plug/socket to connect the genny to the house electrical network, via a manually operated ‘break before make’ changeover switch. The questions on which I seek advice from the learned, professional readers on this board are:
- Is there a desirable maximum cable length to connect genny to domestic electrical network (I have in mind a run of up to 25m)?
- Looking at the layout of installation in my meter cabinet, does the following wiring solution (word picture) make sense?
1. As seen in the pic, the supply from the meter is split at a (Henley) connector block. One P&N pair goes through the house wall (bottom of cabinet) to a 20 way CU (“DB1”) located on the inside of the same wall. The second pair goes to a switchfuse from which the SWA cable seen runs through the house foundations to a second CU (and sub-CU) (“DB2” and “DB3”) in the garage on the opposite side of the house. As I understand, a switchfuse was not required between the meter and DB1 because the separation is <1m.
2. Setting aside (for now) any question of physical space limitation, my idea is that the meter tails should be diverted to a ‘break before make’ changeover switch, which would have a corresponding feed from a genset source via a 32A male inlet socket mounted on the house wall outside the cabinet. a P&N pair from the changeover switch would then lead to the connector block. If the need to use the genset arises, I would wheel the genny to its operating location, connect a 32A cable between the genny outlet and the male inlet socket, then throw the changeover switch.
I’d appreciate any and all comments and observations on the above. TIA.
This is the foundation for this post. I have come round to thinking that it would be sensible to look seriously at a backup generator supply for my home in case of a protracted power cut (I would regard anything more than six hours as protracted) or a sequence of rolling power cuts occurring on a repeated/regular basis. I do not regard the latter possibility as ridiculously far-fetched, at least if some of the more pessimistic forecasts of future electricity generation resources do materialise.
My objectives are (more or less in order of priority):
- maintain electrical supply to gas boilers (I have two matched boilers) for heating and domestic hot water. All DHW is provided by the boilers (no electric water heating). There are two circulation pumps, each ~50W, plus usual electrically operated valves;
- maintain minimum level of lighting in occupied rooms on ad hoc basis (all lighting is LED so a reasonably low aggregate load);
- maintain power supply via circuits for refrigeration appliances as follows: 1 x side by side fridge/freezer (dedicated circuit), 3 x under counter fridges, 1 x under counter freezer (all on ring main circuits);
- maintain power supply on ring main circuits for TVs (up to 2 at any time), laptop and phone chargers and similar, incidental, low-load items;
- facilitate controlled and selective use (i.e. not simultaneous) of large appliances as follows: washing machine, tumble dryer, dishwasher, microwave/combi oven, oven, induction hob, vacuum cleaner
- facilitate night-time use of EV charger (this is on a 7kW/40A supply but can be throttled back to anything between 5A and 24A);
In other words, I want to be able to use all of the electrically powered resources that I have, but in a controlled and, if necessary, tightly restricted way.
Clearly, if I had unlimited funds and space, I could buy a 10-20kW genset and install it with automatic changeover switching. However, I don't have that luxury in terms of finance or space. I am looking to arrange insurance against reasonably low probability events, but ones that could be extremely disruptive to my family’s lives and comfort, if they materialise. I don’t expect not to be inconvenienced by any loss of mains power, but I want to limit the disruption.
So, my thinking is to acquire a ~5kW diesel genset with minimum 12 hours fuel endurance. If the need to use it arises, I expect to have to move it from its usual storage location to a suitable operating location. An example genset I have seen online is 920x550x750 (LxWxH), wheeled, and weighs ~180kg, including fuel. I reckon this is reasonably manageable for one person.
I am willing to take the risk that a power cut could occur at a time when I am unable to effect a manual changeover from mains power to genset supply, so I don’t intend to install automatic changeover switchgear. My idea is to use a suitable length 32A cable and commando plug/socket to connect the genny to the house electrical network, via a manually operated ‘break before make’ changeover switch. The questions on which I seek advice from the learned, professional readers on this board are:
- Is there a desirable maximum cable length to connect genny to domestic electrical network (I have in mind a run of up to 25m)?
- Looking at the layout of installation in my meter cabinet, does the following wiring solution (word picture) make sense?
1. As seen in the pic, the supply from the meter is split at a (Henley) connector block. One P&N pair goes through the house wall (bottom of cabinet) to a 20 way CU (“DB1”) located on the inside of the same wall. The second pair goes to a switchfuse from which the SWA cable seen runs through the house foundations to a second CU (and sub-CU) (“DB2” and “DB3”) in the garage on the opposite side of the house. As I understand, a switchfuse was not required between the meter and DB1 because the separation is <1m.
2. Setting aside (for now) any question of physical space limitation, my idea is that the meter tails should be diverted to a ‘break before make’ changeover switch, which would have a corresponding feed from a genset source via a 32A male inlet socket mounted on the house wall outside the cabinet. a P&N pair from the changeover switch would then lead to the connector block. If the need to use the genset arises, I would wheel the genny to its operating location, connect a 32A cable between the genny outlet and the male inlet socket, then throw the changeover switch.
I’d appreciate any and all comments and observations on the above. TIA.
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