Choice of intelligent switches ?

EricMears

orrery wrote: »

The clip-on detectors don't work well at low levels

My Wattson generation clip-on never quite agrees with the inverter's figures - it tends to differ by one or two kWh (either way) most days. I also see some rather silly peaks which can't possibly be right - e.g. @09:45 today Wattson tells me I was generating 5.3kW ; common sense tells me it was unlikely to have been more than 4kW and probably not even 3; inverter was saying 1.9. On one occasion (that I can't easily find again) Wattson assured me I was generating well over 10 kW !

Also get similar, unexpected peaks in usage figures. On the whole, I tend to believe most of the nett figures but will always take them with a pinch of salt.

danesol

EricMears wrote: »

My Wattson generation clip-on never quite agrees with the inverter's figures - it tends to differ by one or two kWh (either way) most days. I also see some rather silly peaks which can't possibly be right - e.g. @09:45 today Wattson tells me I was generating 5.3kW ; common sense tells me it was unlikely to have been more than 4kW and probably not even 3; inverter was saying 1.9. On one occasion (that I can't easily find again) Wattson assured me I was generating well over 10 kW !

Also get similar, unexpected peaks in usage figures. On the whole, I tend to believe most of the nett figures but will always take them with a pinch of salt.

Have you always had rogue values given on the odd occasion ??

(and/or) Do you have any kind of recently fitted immersion proportional control device fitted as they can mess with readings ??

EricMears

danesol wrote: »

(a)Have you always had rogue values given on the odd occasion ??

(and/or)
(b)Do you have any kind of recently fitted immersion proportional control device fitted as they can mess with readings ??

(a) Not really sure. I've had the Wattson a couple of years but couldn't get on with the earlier versions of Holmes so have only been able to see a graphical output for a few months.

(b) No proportional control device - just a couple of Optiplugs which switch on (completely) a 750W immersion heater & a 600W kettle respectively.

Martyn1981

sly_dog_jonah wrote: »

Of course some days the spare power will be only be enough to part-heat the tank and we'll need to top up with gas heating, even if only a little. The question is how many such days will there be, and how much gas would that require? Only time will tell, but I think the Immersun will probably save us 20% of our gas hot water usage in Nov-Jan, 50% in Oct & Feb and 80% for the rest of the year (even that is conservative I think), or an average of 60% per month. That would be equate to 3060kWh of gas each year, which will save us £113 a year (based on EDF Blue Price promise prices inc VAT).

I realise of course that the gas kWh savings is much greater than the electricity we currently export, but I think that is down to the inefficiencies of the boiler rather than a flaw in my calculation. I welcome any pulling apart of the above logic though!

Hiya SDJ, just wondering how the first year has gone. Do you know how many kWh's you managed to divert?

Also wonder if anyone on here has managed to divert around 2MWh's which would roughly equate with the suggested/hoped for target of £100 savings (against gas assuming approx 4p and 80% efficient (more with tier 1 savings)).

Mart.

danesol

Martyn1981 wrote: »

Hiya SDJ, just wondering how the first year has gone. Do you know how many kWh's you managed to divert?

Also wonder if anyone on here has managed to divert around 2MWh's which would roughly equate with the suggested/hoped for target of £100 savings (against gas assuming approx 4p and 80% efficient (more with tier 1 savings)).

Mart.

Martyn1981, I think you have your sums wrong fella - 2,000 kw divert, £100 saving - i dont think so!

EricMears

danesol wrote: »

Mart i think you have your sums wrong fella - 2,000 kw divert, £100 saving - i dont think so!

Depends how you do your sums.

If you bought it at daytime rates, 2,000 kwh would cost you around £200 (perhaps a little more).

However, if you're lucky enough to have a gas supply (or even postponed same heating till E7 hours) it would indeed only cost you around £100

danesol

Here are my calculations extracted from other thread...........

Composed:- 20.6.2013

"Today, was a bad day for solar generation for us, any power been generated was used internally by the dishwaster etc etc, however some was avail to the solar immersion device, but very little, so my wife had to turn on the Gas Boiler ( 3yr old Valiant Condenser boiler ) at 6pm'sh to ensure she had hot water for her bath, so I found it was time to see just how much it costs to heat semi hot water via the gas boiler - here are my findings, even though the water had been preheated now and then by the immersion device.

Reading after boiler shut off ( Both reading and pic taken after 50mins ) - 2949 [28] 2
Reading before ( picture taken of meter prior to boiler been switched on ) - 2949 [16] 3

Total gas used = 0.12 units
Convert to kwh via multiplying by 31.5

= 3.78kwh

Cost of that gas 3.78 @ 3.45p per kwh = 13p ( ignoring std charge for this exercise ! )


Therefore rounding up to 30p for 2 heats per day - to allow for a colder fill and still an estimate as winter mths would cost alot more, over 365 days a year that would cost 30p x 365 = £ 109.50

Even using my exact reading for one heatup from been preheated - still would cost £ 94.90 p/a

So my previous estimation of £ 80 saving using my Solar Immersion Device could be well under and the saving even for GCH users could be more than you think ....... food for thought

Please check my calculations and comment away....................."

zeupater

danesol wrote: »

Mart i think you have your sums wrong fella - 2,000 kw divert, £100 saving - i dont think so!

Hi

Maths is correct for those assumptions (2000kWh/year, Gas@£0.04/kWh, 80% efficiency on gas boiler) ...

((2000x0.04)/0.8) = 100

... looks like nothing wrong to me ....

HTH
Z

danesol

and the other calculations ............

"Based on a calculation on another thread for June's Gas bill - it appears that £ 8.00 a mth to heat a hot water cylinder twice a day for 2 hourly periods is more or less correct for my particular setting, therefore I recon' in the good PV mths you will be saving roughly and on average between 7-12pounds per mth if you have one of these immersion switches fitted !

The more energy you have surplus and the more water you heat, the better the saving IMO !"

danesol

zeupater wrote: »

Hi

Maths is correct for those assumptions (2000kWh/year, Gas@£0.04/kWh, 80% efficiency on gas boiler) ...

((2000x0.04)/0.8) = 100

... looks like nothing wrong to me ....

HTH
Z

But i've come from the other angle and worked out how much it costs to heat the water using GAS and therefore what you actually SAVE when you switch your GAS completely OFF which we have done for the past quarter, the calculations although different give more or less the same resultant answer.

besides, 2,000 kwhr is a tall order as most small generators ( <3kw systems ) - dont even make 2,000kwh or possibly just over like me at 2.3mwh .... and would also assume ZERO export to the grid - most ppl are incapable of that, especially when you are at the mercy of the British Weather and dont use the energy as generated !