Octopus Agile / Octopus Go Faster with 30 Amp Aga. How do you control appliances on Agile?

lohr500

Hi all.
We have a 30 Amp AGA which is basically a gigantic night storage heater. It has a 30 Amp power supply which powers banks of elements that heat up the core overnight using Economy 7. The 30 Amp feed is permanent live and there is a second 5 amp trigger circuit linked to the Eco 7 consumer unit fuse box. The AGA detects the presence of the Eco 7 signal and switches on the heating elements when Eco 7 is available. If the core falls below a certain temperature during the day due to heavy use, then the Aga controller will switch on the elements to use peak price electricity to raise the core to a minimum temperature. This is lower than the overnight temperature so as to only use the minimum amount of peak electricity.  
Looking at my energy monitor through April and May, the Aga has typically taken between 6 and 7 hours continuous draw at around 5.8kW to fully heat up overnight. The kitchen has no other heating so it will probably take longer in the depths of winter and less in Summer due to the difference in ambient temperature in the kitchen.

I have been looking at the Octopus Go Faster tariff with an 00:30 start and even though I would only get 5 hours at £0.05 per kWh, it would still be a big saving for us to switch due to the high overnight consumption from the Aga, even if the last hour or so of the heat storage charging was at the new Octopus peak rate. 
Depending on how they configure the smart meter that is due to be fitted today, I may need to replace the Eco 7 trigger signal with a timer based trigger for the Aga. That's not a problem.  

I have also been looking at Octopus Agile. My question here is how do you take advantage of the low price times and control when/how to switch on an appliance? I have seen an App called IFTTT which allows you to program events based on the rates, but what device would be needed to switch the trigger circuit on and off based on the program? Are there other switching devices/apps that can be used with Agile?
My other concern is that because the pricing is variable, there could be lots of switching on and off of the heating elements and the required Aga core temperature may not be achieved. 
My gut feel says Go Faster is the better option due to the certainty of the off peak timing and pricing, but if Agile could be made to work, it could be a better option if we see a return to the very low off peak pricing from last year.

How are people using Agile to maximise the demand when prices are low?

Thanks 

[Deleted User]

The bad news is that Agile isn’t that cheap at the moment. Electricity wholesale prices have been increasing since late last year. To use Agile, you either need the help of the manufacturer, or some knowledge of electricity and the ability to write your own software. Even making a standard immersion heater Agile compatible is a challenge. You cannot just plug it in to a smart plug. Thirty amps will require a programmed smart control device which is connected to an appropriately sized contactor. There are many knowledgable people on the Octopus Smart Forum when it comes to Agile control.

lohr500

Thanks for the info Dolor. It sounds very complicated, although I would only need to switch the low current 5 amp trigger circuit to the Aga so a smart plug would be OK if there was a simple way to activate it when prices were low. In fact the 5 amp trigger circuit draws even less as it is just an on/off voltage signal to the circuit board. The 30 Amp main circuit remains permanently live.
I think Go Faster will be the simpler and better option for now and then do some more research on Agile controllers whilst prices are high!!

[Deleted User]

lohr500 said:

Thanks for the info Dolor. It sounds very complicated, although I would only need to switch the low current 5 amp trigger circuit to the Aga so a smart plug would be OK if there was a simple way to activate it when prices were low. In fact the 5 amp trigger circuit draws even less as it is just an on/off voltage signal to the circuit board. The 30 Amp main circuit remains permanently live.
I think Go Faster will be the simpler and better option for now and then do some more research on Agile controllers whilst prices are high!!

The load is similar to that required to charge an EV. By the sound of it you already have a 30 amp main contactor controlled by the circuit board in the Aga. Is there a timer on this circuit board that you can control manually?  If so, then it is possible that this can be externally programmed. As far as I am aware there are no Agile controllers as such. Tariff information is provided via an API which Octopus makes available to its time-of-use tariff customers. The API cost information for Agile is updated at about 4pm each day.

By way of example, this is what MyEnergi has done for its Zappi2 EVSE and EDDI solar diverter customers

https://myenergi.com/time-of-use-tariffs/

lohr500

30 amp breaker fuse on the main consumer unit which supplies a permanent live to the Aga.  
This 30 amp supply powers the Aga internal circuit board, a thermostatically controlled internal fan which transfers heat from the core to the ovens and a manually controlled extractor fan that vents the top oven to outside via a small flue. So the 30 amp supply needs to be continuous for the oven to work.
The same 30 amp supply is also used to feed the heating elements via a 30 amp control relay on the internal circuit board which switches the heating elements based on the controller logic on the circuit board.
Then there is a separate 5 amp fused supply from the Eco 7 consumer unit who's sole purpose is to act as a trigger voltage to tell the Aga circuit board when off-peak Eco 7 electricity is available. There is minimal load on this circuit.
If I move to Octopus Go Faster, I will need more than the 5 hours of off-peak electricity available on the tariff to fully heat up the Aga core. So my thinking is to replace the Eco 7 5 amp trigger circuit from the Eco 7 consumer unit with a digital timer based trigger signal fuse spurred off a permanent live feed. The timer would be set from 00:30 to 07:30 to give the required 6 to 7 hours of maximum charge time. The first 5 hours being on the £.05 per kWH Octopus Go tariff, and the last 2 hours (if needed) on the peak rate. 
I could limit the core charging to 5 hours and then let the controller decide if a peak rate top up is needed later in the day. But the problem is that when on peak rate the oven and hob temperatures drop to an unacceptably low level before the controller calls for a peak rate core top up. 
 

[Deleted User]

Bear in mind that Go and Go Faster have peak rates below what you would pay on a standard Octopus fixed tariff. My peak rate is 14.6p/kWh. This is what Agile would have cost me for the early part of today:


 

Setting a two tier t-o-u tariff is a lot easier than one where all 48 half hour periods change every 24 hours.

lohr500

Think Go Faster is the best bet then as there is some certainty over the price and as you say Dolor the fixed time for the off peak hours will make it easier to program the timer.
The discussion may well be academic though if they can't get a smart meter to work today. Just had a call to say they have been delayed but will be with us in around 15 minutes. When they tried last year they couldn't get a radio signal for the meter but I understand Arqiva have since put in a local radio mast so fingers crossed. 

niktheguru

Definitely go with go faster for your use case presently. Agile is pretty expensive at the moment and it would probably be havoc intermittently heating your aga when the prices dive low. Go faster at 5.5p for 5 hrs would be a better bet and so much simpler.

lohr500

The smart meter install went well and apparently it has a strong signal so that's a relief. They were able to fit a 5 wire unit as a direct replacement to the old dumb meter so no need for a separate Economy 7 contactor. The installer didn't explain anything about the meter (Itron EM425-UK2 5T) or the IHD (Chameleon 3). I'll check early tomorrow morning to make sure the meter has switched on the Eco 7 circuit and is recording usage on the 2nd register. 
If I understand things correctly it can take a few days for the readings to start appearing on my online EDF account.
Once I am happy its all working as it should, I'll do one final review of the Octopus Go Faster tariff and then initiate the switch.
Thanks to everyone who has provided answers to my question.

niktheguru

lohr500 said:

The smart meter install went well and apparently it has a strong signal so that's a relief. They were able to fit a 5 wire unit as a direct replacement to the old dumb meter so no need for a separate Economy 7 contactor. The installer didn't explain anything about the meter (Itron EM425-UK2 5T) or the IHD (Chameleon 3). I'll check early tomorrow morning to make sure the meter has switched on the Eco 7 circuit and is recording usage on the 2nd register. 
If I understand things correctly it can take a few days for the readings to start appearing on my online EDF account.
Once I am happy its all working as it should, I'll do one final review of the Octopus Go Faster tariff and then initiate the switch.
Thanks to everyone who has provided answers to my question.

You'll have to switch to go first, then to go faster but it only takes days. The peak rate on go and go faster has recently just gone up (like within the last two weeks, approx 2p higher than before)

lohr500

I spotted the increase but it still makes sense as we use so much off-peak. The the 5.0p is a bargain and even the new peak rate of 15.18p gives a good saving for us overall. We get through 22,000 kWh a year, so the savings can really add up, even with a small cost differential.