I'm pulling cable for a future solar installation... I'm imagining we will connect up the immersion on hot water tank somehow..... What size cable would be needed? Thanks!
What size cable from solar panels / battery to immersion?
- Thread starter theflyingpig
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How many Watts is it?
2.75 - 3 kw
Without going into great detail about cable ratings and installation methods, just get 2.5mm² twin and earth for the fixed wiring and 2.5mm² heat resistant flex to the actual element.
The DIY places sell immersion flexible cable.
The DIY places sell immersion flexible cable.
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Edited.
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I would assume you are looking at iboost+ which uses the existing cables to your immersion heater and has a wireless connection to the CT coil which clips onto your incoming supply and is battery powered.
I have an iboost+ fitted, not sure if really worth the money, as only works in summer. As the central heating means cistern is too hot for the immersion heater to work in winter. The other problem is the immersion heater does not really go deep enough into the cistern, so it only heats the top bit of the tank. So where as with the hot coil and central heating heating water the tank will stay warm for 3 days, with the immersion by next day it is cold again.
So really do need a longer immersion heater fitted.
Today one needs to have a battery with solar to be able to use feed in, and the battery means you can use the solar for an extended time, mine allows me at the moment to go until around 9 pm before I am using power from grid. By also having an EV users tariff (I don't have an EV) it means from midnight to 8 am I have a reduced cost tariff, 31.31p day rate, 8.95p night rate, 59.14p standing charge and I clearly have to have a smart meter, so solar software is set to charge battery from grid from 0:30 to 7:30 so I start the day with a full battery, this time of year there is a dip
in the morning where the battery state of charge (SOC) drops, but this means I can run tumble drier, washing machine etc. early enough to ensure cycle completed before the point when sun is likely to reduce, so extending the time before the battery runs out.
With this in mind, it is likely a simple time switch would be enough to use immersion at a point in the day when likely there is solar and battery available. The point with the iboost+ is it does not use zero or 3 kW but can use just what is surplus. So here
it is showing just 1.55 kW being used, and here 
just 320 watt, where as the timer is simply on/off. The unit before needing batteries was essential, but does depend on battery fitted.
My battery is 3.2 kWh so not very big, just ticks the box that battery fitted, it can charge at 2 kW and discharge at 3 kW so when having a shower even with sun shining the 9 kW shower is still using 2.75 kW from the grid, the max from sun is 6 kW but 4.5 is more like normal up to date on a sunny day.
The charging of batteries over night also means they are available should we get a power cut. They only supply the freezers and central heating, but that is what I can't really do without for too long, I use re-chargeable torch which auto light with power cut for lighting, and can of course use candles, but CH and freezers we would be stuck without.
So rather than supply to immersion what you need to consider is emergency supplies, I have a SWA running around outside of house to supply freezers.
I have an iboost+ fitted, not sure if really worth the money, as only works in summer. As the central heating means cistern is too hot for the immersion heater to work in winter. The other problem is the immersion heater does not really go deep enough into the cistern, so it only heats the top bit of the tank. So where as with the hot coil and central heating heating water the tank will stay warm for 3 days, with the immersion by next day it is cold again.
So really do need a longer immersion heater fitted.
Today one needs to have a battery with solar to be able to use feed in, and the battery means you can use the solar for an extended time, mine allows me at the moment to go until around 9 pm before I am using power from grid. By also having an EV users tariff (I don't have an EV) it means from midnight to 8 am I have a reduced cost tariff, 31.31p day rate, 8.95p night rate, 59.14p standing charge and I clearly have to have a smart meter, so solar software is set to charge battery from grid from 0:30 to 7:30 so I start the day with a full battery, this time of year there is a dip
in the morning where the battery state of charge (SOC) drops, but this means I can run tumble drier, washing machine etc. early enough to ensure cycle completed before the point when sun is likely to reduce, so extending the time before the battery runs out.With this in mind, it is likely a simple time switch would be enough to use immersion at a point in the day when likely there is solar and battery available. The point with the iboost+ is it does not use zero or 3 kW but can use just what is surplus. So here
it is showing just 1.55 kW being used, and here just 320 watt, where as the timer is simply on/off. The unit before needing batteries was essential, but does depend on battery fitted.My battery is 3.2 kWh so not very big, just ticks the box that battery fitted, it can charge at 2 kW and discharge at 3 kW so when having a shower even with sun shining the 9 kW shower is still using 2.75 kW from the grid, the max from sun is 6 kW but 4.5 is more like normal up to date on a sunny day.
The charging of batteries over night also means they are available should we get a power cut. They only supply the freezers and central heating, but that is what I can't really do without for too long, I use re-chargeable torch which auto light with power cut for lighting, and can of course use candles, but CH and freezers we would be stuck without.
So rather than supply to immersion what you need to consider is emergency supplies, I have a SWA running around outside of house to supply freezers.
Last edited:
My iboost doesn't need any extra cables.
Immersion circuit goes from CU to airing cupboard FCU as usual. FCU feeds iboost which feeds immersion. A wireless current clamp on the tails tells the iboost when to turn on.
Immersion circuit goes from CU to airing cupboard FCU as usual. FCU feeds iboost which feeds immersion. A wireless current clamp on the tails tells the iboost when to turn on.
The op is ambiguous.
Cable from where to where?
Cable from where to where?
Apologies. From the battery location to the hot water cylinder
Thanks for this. Very interesting....
I've pulled a 2.5 t&e from cu location to hot water cylinder location already....
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I am still learning after solar panels fitted in Autumn. The inverters are not all the same, I had to have an earth rod installed for when the unit is island with not connection to grid, and the unit auto connects neutral to earth when that happens. And it states that type AC RCD's can be used. But that does not mean all are like that.
The main problem is the washing machine, tumble drier, and dish washer can have delay set, but with the washing machine we put a ball with the washing liquid in with the clothes, and if timer set, it every so often tumbles the clothes which means the soap ends up on the clothes neat until the cycle starts.
The draw would work with washing power, but not sure with washing liquid to if it would get onto clothes before it starts?
The main problem is the washing machine, tumble drier, and dish washer can have delay set, but with the washing machine we put a ball with the washing liquid in with the clothes, and if timer set, it every so often tumbles the clothes which means the soap ends up on the clothes neat until the cycle starts.
The draw would work with washing power, but not sure with washing liquid to if it would get onto clothes before it starts?
Suspect you’ve wasted your time. The feed for the hot water tank comes from your consumer unit and dependant on your set up will need 1 or 2 controllers
Who is fitting the PV system
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Thanks. What are the two differing controllers?
I'm not sure who will be fitting pv yet...
Rather depends if the immersion is on a dedicated circuit or not
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