So now I have a solar PV system how do I make the most of it???

grahamc2003

Been mentioned before about driving a 3kW immersion with 110v from a site transformer, making the power around 750W. Possibly useful for my small 1.75kW system.

My question to any electrical bods is how possible it is to have a dual wired immersion - i.e. 230v as now, plus a couple of more wires from the transformer at 110v (wired to the ring main)? Would any simple circuit make this safe? Obviously, the idea is to have the flexibility to use 3kW at night (on economy 7), (or when the kids want sequential baths), and 750W when I have that spare from my panels during the day, and also be safe whatever combination of 'on' and 'off' the two switches are.

KevinG

Doc_N wrote: »

Sorry, right thread: "So now I have a solar PV system how do I make the most of it???"

It's a discussion of how best to use 'surplus' solar energy, and one of the ways is to heat hot water via a relatively low wattage immersion heater.

Erm, I put my post in the wrong thread so changed it to "Sorry, wrong thread". I hadn't even read your post at the time! I won't make that mistake again.

EricMears

grahamc2003 wrote: »

Been mentioned before about driving a 3kW immersion with 110v from a site transformer, making the power around 750W. Possibly useful for my small 1.75kW system.

My question to any electrical bods is how possible it is to have a dual wired immersion - i.e. 230v as now, plus a couple of more wires from the transformer at 110v (wired to the ring main)? Would any simple circuit make this safe? Obviously, the idea is to have the flexibility to use 3kW at night (on economy 7), (or when the kids want sequential baths), and 750W when I have that spare from my panels during the day, and also be safe whatever combination of 'on' and 'off' the two switches are.

What I've done with mine is to have the immersion feed wire fitted with a 110v plug which is normally fitted into the transformer. Should I wish to run immersion on 230v, I have an adaptor lead with a 13A plug one end and a 110v socket the other. Note however that lead has to be very carefully labelled and not left where some halfwit might think it's a (very compact !) 230 - 110 transformer. As it happens I already have some E7 sockets but anyone else might need to wire in a new one.

John_Pierpoint

What is an E7 socket?
[I've got several En sockets for small strange heads in my tool box ]

I've got it we are talking about full voltage Economy 7 through a socket?

grahamc2003

EricMears wrote: »

What I've done with mine is to have the immersion feed wire fitted with a 110v plug which is normally fitted into the transformer. Should I wish to run immersion on 230v, I have an adaptor lead with a 13A plug one end and a 110v socket the other. Note however that lead has to be very carefully labelled and not left where some halfwit might think it's a (very compact !) 230 - 110 transformer. As it happens I already have some E7 sockets but anyone else might need to wire in a new one.

That's quite a good solution, albeit probably against a mountain of regs (which wouldn't worry me unduly, however, not sure 110v hardware is perfectly safe with 240v through it).

In my case, I have a mechanical timeswitch to control the immersion, which complicates things a little. Also my tank is old and pooly lagged. Atm, it's all automatic (on between 06:30 and 08:30) (at least it has been up until today when it didn't heat the water - the 3 month old ebay timeswitch seems to have failed!, and even the little manual override switch doesn't work). Ideally, I'd just like to keep what I have (once it's working again), i.e. 3kw during a couple of e7 hours, then additionally another switch to turn on the 110v manually (usually it would be off).

John_Pierpoint

My Economy 7 is simply wired through a "Smiths" time switch with two rings of holes (outer ring is "off"). These are turned into switches by pushing little silver aluminium pins into the holes. It also has a small red indicator for "on or off" that can be flicked manually.

It has been like that since the 1970s and I now have to make a decision each day at about 06:30.

John.

PS it was originally fitted with a dual element vertical immersion. The small one for those occasions when the hot ran out before the end of the day.
But with only the two of us living here now, such an expensive design of immersion is not needed,

EricMears

grahamc2003 wrote: »

not sure 110v hardware is perfectly safe with 240v through it

110v plugs & sockets are virtually the same as 230v 'caravan' plugs & sockets. Both (and 'standard' 3 pin plugs etc) are tested at much higher voltages than 230v.

JP wrote:

What is an E7 socket?

Just shorthand for an 'ordinary' socket wired from an off-peak consumer unit.

Cardew

John_Pierpoint wrote: »

What is an E7 socket?
[I've got several En sockets for small strange heads in my tool box ]

I've got it we are talking about full voltage Economy 7 through a socket?

I am assuming that EricMears has his House wired so he only gets economy 7 cheap rate to storage heaters and immersion; rather than the more normal situation of all electricity in the house at cheap rate for 7 hours.

Graham 2003
That's quite a good solution, albeit probably against a mountain of regs (which wouldn't worry me unduly, however, not sure 110v hardware is perfectly safe with 240v through it.

By 'hardware' you mean the 110v plug and 110v socket? To a 240v 3kW immersion heater it will be low current! Although I am certain with electrical regulations preventing you changing a bulb these days(almost;)) you are doubtless correct that it is a Capital offence!

EricMears

Cardew wrote: »

I am assuming that EricMears has his House wired so he only gets economy 7 cheap rate to storage heaters and immersion; rather than the more normal situation of all electricity in the house at cheap rate for 7 hours.

No, it's a perfectly normal E7 contract where all off-peak units are charged at the lower rate.

However, I do have several sockets wired up so that they're only live during the E7 period. That's much easier than running washing machine, tumble drier, greenhouse heater, dishwasher and anything else that seems appropriate via a bank of separate timers. It is possible to use the immersion heater thus though I seldom do.

orrery

Just a cautionary note:
I've taken delivery of a 110V site transformer today, with a view to running an immersion heater through it.

A quick first test reveals that the no-load current is already over 1 amp! So, just over 250VA without connecting anything else to it (although it only shows as about 50W). :mad:

It will be interesting to see what the figures are when connected to my 3kW immersion!