Garage CU,house mains CU can I use same cable for inverter upload to main house

[minimuk]

Hello,

we live in a special time, my predictions for 2021 there will be man made powercuts lasting more then 1 hour up to weeks even. I have decided to have a small battery bank as a back up power system to be able to supply basic power for essential use in the main house, fridge, freezer,boiler, pump, led's, alarm,and a few other bits.

 

to power the battery bank I will have 2x300W solar panels, 2.4kW hybrid inverter/charger and 2x 100Ah AGM Batteries. I have a garage 15 meters from the main house. the power supply for the garage is from a MCB in the CU, cbaled up to a CU in the garage, which has 4 MCB's. My idea is to attach the inverter/charger underneath the Garage CU .

Question is, can I use the same cable from the house CU to the garage, sending battery bank power via the inverter/charger back to the house CU. If that is so will the Garage MCB on the house CU divert its power to the circuits which are 'ON' on the house CU.

 

thank you in advance

 

 

Edited December 17, 2020 by minimuk
spelling

[joth]

2 hours ago, minimuk said:

basic power for essential use in the main house, fridge, freezer,boiler, pump, led's, alarm,and a few other bits.

 

to power the battery bank I will have 2x300W solar panels, 2.4kW hybrid inverter/charger and 2x 100Ah AGM Batteries.

I'm afraid you're going to be very disappointed with the this setup. The batteries are about 2.4kWh. the  fridge + freezer will empty that in well under a day on their own.

The 600W panels might charge those batteries on a really clear summer's day, but I take it you're in the UK so if prepping, I wouldn't plan on relying on the sun being around for survival. A generator is probably a better bet, ideally coupled with a humvee and shotgun to help secure the gasoline supply in the case of civil disturbance (literally, as seen on a USA data center tour)

 

To the question, the single cable cannot safely serve both purposes as you need a transfer switch (break before make, to ensure only one source is feeding the domestic mains at a time) and that requires both sources to arrive in the same location. 

Edited December 18, 2020 by joth

[ProDave]

No way to use the single cable.

 

You need a dedicated "high priority" circuit in the house to just feed the essential stuff, and THAT needs to be fed from the batteries via a changeover relay.

 

So you will need a separate feed from the back up supply in the garage, into the house, and some controls to make it change over when the main power goes off.

 

And I think it's performance will be poor.  In winter (i.e. now) the output from your panels will be disappointing,

 

P.S. What makes you think 2021 will be the year of power cuts?

[minimuk]

8 hours ago, joth said:

I'm afraid you're going to be very disappointed with the this setup. The batteries are about 2.4kWh. the  fridge + freezer will empty that in well under a day on their own.

The 600W panels might charge those batteries on a really clear summer's day, but I take it you're in the UK so if prepping, I wouldn't plan on relying on the sun being around for survival. A generator is probably a better bet, ideally coupled with a humvee and shotgun to help secure the gasoline supply in the case of civil disturbance (literally, as seen on a USA data center tour)

 

To the question, the single cable cannot safely serve both purposes as you need a transfer switch (break before make, to ensure only one source is feeding the domestic mains at a time) and that requires both sources to arrive in the same location. 

Thank you JOTH

The set up is mainly for powering the essentials for max 4 hours a day, there are double connectors next to the mains feed to the house and only one of +/- each in use, I take it a transfer switch can be placed there. Could a Grid tie Unit be an answer?

[minimuk]

1 hour ago, ProDave said:

No way to use the single cable.

 

You need a dedicated "high priority" circuit in the house to just feed the essential stuff, and THAT needs to be fed from the batteries via a changeover relay.

 

So you will need a separate feed from the back up supply in the garage, into the house, and some controls to make it change over when the main power goes off.

 

And I think it's performance will be poor.  In winter (i.e. now) the output from your panels will be disappointing,

 

P.S. What makes you think 2021 will be the year of power cuts?

Thank you ProDave

Understood clearly the switch over relay, and seperate feed, what controls would I need  to make this high priority circuit?

understand poor preformance in this season, but once it is charged up 1-5 days it is a unsefull back up for now