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

orrery

I'm using a small electric radiator for heating my study when there is ample solar generation, but there is a danger that it may end up costing me more if I leave it turned on. So....

I've worked out a way of making sure that it shuts down after a period of time. I don't doubt that there are timers that will do this (but I haven't seen one). However,it can be accomplished with a standard plug-in timer and one of those leakage-sensing contact breakers (earth leakage trip or RCB/RCCB trip) providing that the trip is one that is 'non-latching' (i.e. one where the trip drops-out if you turn off the power to it). I've set the timer to turn on for each 2 hour segment and only be off for 1 minute before the next. The trip is then plugged in to the timer and heater plugged in to that.

The resulting operation is that, at the end of each 2 hour segment the timer drops the power and the trip drops out disconnecting the heater. To turn the power on again (if there is adequate generation) the trip has to be re-set. So, the heater can't be left on for more than 2 hours.

It does mean that you need to make sure that the trip is the non-latching type! Added: Just bought the Masterplug one, which is fine for the job.

Fruit_and_Nut_Case

orrery wrote: »

I'm using a small electric radiator for heating my study when there is ample solar generation, but there is a danger that it may end up costing me more if I leave it turned on. So....

I've worked out a way of making sure that it shuts down after a period of time. I don't doubt that there are timers that will do this (but I haven't seen one). However,it can be accomplished with a standard plug-in timer and one of those leakage-sensing contact breakers (earth leakage trip or RCB/RCCB trip) providing that the trip is one that is 'latching' (i.e. one where the trip drops-out if you turn off the power to it). I've set the timer to turn on for each 2 hour segment and only be off for 1 minute before the next. The trip is then plugged in to the timer and heater plugged in to that.

The resulting operation is that, at the end of each 2 hour segment the timer drops the power and the trip drops out disconnecting the heater. To turn the power on again (if there is adequate generation) the trip has to be re-set. So, the heater can't be left on for more than 2 hours.

It does mean that you need to make sure that the trip is the latching type!

This seems quite complicated. Can't you trust your butler to take care of that sort of thing?

orrery

Fruit_and_Nut_Case wrote: »

This seems quite complicated. Can't you trust your butler to take care of that sort of thing?

Nope - He's up on the roof with a torch.

DATMAN_2

orrery wrote: »

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!

Hi Orrey

Have you got yours up and running?

May answer my question re Megaflow and running this with Solar Immersion I have posted elsewhere today!

As I have a 3kw heater in the Megaflow - what will happen if this is feed 750w. Will it work and heat the water up or will it need the full 3kw before kicking in and turning on?

cheers

orrery

DATMAN wrote: »

Hi Orrey

Have you got yours up and running? ...

I'm using the 110V transformer with a 500W radiator. I'm afraid solar availability for room heating is far too variable to be of much use, so I can't recommend it - but more use for water heating in summer, I'm sure. I have a wiring issue with my immersion - I had an immersion put in (but never used), but I've since found that the wiring to the immersion isn't capable of 3kW - some previous owner has changed things so the feed is being used for loft lighting instead.

I have no knowledge of a Megaflow, but it should be fine for a standard 3kW immersion heater.

silverwhistle

Sorry for bumping this thread but it seemed the best place.. My mind was drifting from lesson planning to my return to the UK this summer and all the budgeting and planning, and I wanted to avoid thinking about the local bureaucracy...

Does anyone have their freezer on a timeswitch so that they tend only to use their PV production? Locally they advertise freezers (normally the chest ones) with 36 hour autonomy, but that may reflect a local need based on the OH lines and unreliability of the supply in rural areas.

How does the use of fast-freeze impact consumption? I was thinking of filling up spaces with plastic bottles of saline solution to help overnight cold retention; is that a reasonable approach?

kfsimpson

sly_dog_jonah wrote: »

No probs. Do you know how much of that consumption is attributable to the ASHP?

Even on a dull day like today our Immersun has still managed to divert 2kWh (out 6kWh generation) into the immersion at a trickle, electricity which we'd have struggled to use without importing some power.

I'm looking at having an Immersun fitted, especially now the price has come down to £550 fitted. How have you found it after a year? Will it allow me to turn the boiler off completely for four months or more? I reckon it looks viable now ...
2.6KW system, gen records since April 1st this year show only twelve days with total gen under 6 KWh, 120 litre HW tank.

legoman62

kfsimpson wrote: »

I'm looking at having an Immersun fitted, especially now the price has come down to £550 fitted. How have you found it after a year? Will it allow me to turn the boiler off completely for four months or more? I reckon it looks viable now ...
2.6KW system, gen records since April 1st this year show only twelve days with total gen under 6 KWh, 120 litre HW tank.

Have a good look round before you buy!
There are many products on the market, that will do what you want....possibly at a lower price.

I believe there is a new Immersun due any day now.
Some people say the old model causes lights(yours and your nieghbours to flicker)
Also I think you could get a better price than £550.00

Have you had a word with your PV installer?:D

kfsimpson

Thanks, really helpful. That's exactly why I wanted to ask what experiences others have. Two local installers have both recommended an Immersun - trying to get shot of the old model?

What alternatives would you suggest I look at? I have waited while the system has two summers to give me an idea of performance, and it is now clear that there is significant excess for five or six months. Hot water seems to be the best way of using this, and having looked at DIY solutions, I prefer to go for a manufactured solution which requires no daily monitoring.

sly_dog_jonah

Since installation on 20th September 2012 the ImmerSUN has used 1149kWh of our generation to heat water into our 210litre tank via a 3kW immersion element. We are quite high users of hot water as we have 4 people in the house including two toddlers who love a bath as part of their bedtime routine. My wife has also been on maternity leave so that has meant hot water and electricity usage has been higher.

Average per day is 4kWh or 107kWh per month but there is huge variation from winter to summer: 33kWh for Jan 197kWh for May (our best month up to that point) and just over 180kWh for June & July. Gas usage has dropped to:

May: 499kWh (767kWh 2012)
June: 150kWh (410kWh)
July: 80kWh (373kWh)
August: 31kWh (333kWh)

...although those figures are extrapolated from readings taken 5th April, 11th May, 26th May, 14th July, 21st July and just now. The hot water program has been off for months now and only occasionally do we have to boost it for an hour. I've only listed months above when the (gas) central heating has been off as well. We cook with electric so the usage above is purely for hot water.