Solic 200 mod - scheduled boost for off peak hot water

[RichardL]

The end game is probably a combined air source pump/cylinder.
In the interim, to get off oil, I'm going with solar excess immersion via a Solic 200 & off peak top up when there's no solar.

I've read the threads on expensive to install/cheap to run heat pump cylinders vs. cheap to install/expensive to run immersion - and on the latter for now. 

Shelley schedule
My first try is a Shelley module which has built in scripting, but in this case just needs the schedule to close dry contacts and hit the boost button.
Boost on a Solic turns on the immersion for 90 minutes - that should be plenty if timed on key days to top up the cylinder hot water.

Relatively simple, non destructive, mod to let the Shelley push the boost button - i.e. low voltage switching.

Bonus - the solic is a nice steel case - so relatively contained if there were any issue.

Programming
Merely a Shelly schedule to push its button and a timer on the same button to turn if off after 1 second.

Thinking
Keeping this super simple - i.e. if there was sun during the day the tank will already be hot and the immersion cut out, 
if no sun, or winter, then off peak will do most of the work.

Not perfect in terms of efficiency - but on the side of KISS for now.
No cloud - not even network required for it to work, other than NTP now and again to sync it's clock.


No questions - just sharing.

 

Before

Getting the board out needs the vice to spread the case sides - it won't just slide out.

 

Mods

 

 

After

[ProDave]

Have you got a spare thermostat pocket?  you could fit a temperature probe and read that, and then only activate the off peak boost if the tank was below a certain temperature.

[Marvin]

We run our immersion via a digital thermostat (which is a 2 channel relay but too weak to take 3kW) which signals another relay that can take the power for the immersion, supplied via our solic diverter.

 

We run the back up via our ASHP which uses a different digital thermostat.

 

The 2 probes fit 1 pocket in our tank.

 

The back up comes on when the tank temp is too low and is set just high enough to give us what we need. The diverter temperature is set at 75°C or more in the winter and 60°C in the summer and is easy to change because the controller is not on tank.

 

M

[RichardL]

3 hours ago, ProDave said:

Have you got a spare thermostat pocket?

Nope - just one, and for now while the oil boiler is off but not uninstalled - its not going away just yet.

When it does I may hook to the existing stat - thinking about it no reason I couldn't do that now for a temp reading with a simple mains detector on the output. Good line of thought - thank you.

Will see how relying on the immersion stat, and offering power on certain nights, goes in the short term.


Afterthought -  s*ds law the solic is by the consumer unit and nowhere near the tank - thats just the way it went in 12 months ago with the solar.

Taking both comments above into account - I could leave the solic mod alone for excess supply + scheduled boost then taking @Marvin's point on board - a simple local to the tank relay so the tank stat can make the final decision on supplying power to the immersion.


@Marvin Q -  Presumably, if I understand correctly,  you put your digital stat & relay after the solic -  
i.e.   mains->solic->stat relay->immersion
Does the solic mind?
 

Edited June 2, 2023 by RichardL

[Marvin]

3 hours ago, RichardL said:

Q -  Presumably, if I understand correctly,  you put your digital stat & relay after the solic -  
i.e.   mains->solic->stat relay->immersion
Does the solic mind?

Not quite that simple. Will elaborate later...

[JohnMo]

Just buy a Cool Energy diverter, does timed boosts out of the box and can drive two immersion heaters one after the other as well.

 

Way better than the Solic200 I had - which failed and the warranty was a nonsense.

[Marvin]

Hi @RichardL

 

Seems the above by @JohnMo is the latest thing:

 

https://cdn.shopify.com/s/files/1/2612/5402/files/Solar_Diverter_Data_Sheet_r-min_1.pdf?v=1669043972

Edited June 2, 2023 by Marvin

[RichardL]

Cheers @JohnMo @Marvin
Nothing wrong with that - personally I'm jury rigging the existing solic in the interim rather than a whole new investment.
The diverter solution has limited life for me.

I'm in a sort of start where I am/what I have rather than from scratch.

Long term
Subject to change, my end game is a hot water heat pump/cylinder - in which case one of its dry contact enable inputs will be driven by something like a Shelley talking to my hybrid inverter making decisions on schedule, solar, battery etc.

My inverter will already share live data on grid import/export etc at the end of a simple RPC (JSON over HTML) call - i.e. no need for more CVs if you can just ask the inverter.

If/when that scenario happens the solar diverter will be redundant anyway.

[Radian]

Having personally gone to great lengths to build a diverter basically for free, I'm still undecided about the economics of using it. If it required an outlay of several hundred quid it would definitely not be cost effective given that (in theory) you can be paid 15p/kWh for the export instead.

[dpmiller]

so given that anyone can at any time add a diverter and start making savings, how does one start- at any time- to receive payment for export with a self-installed non-MCS PV system?

[Luc500]

Hello @RichardL,
Great post and information provided.

I have tried to contact the 'Solic' guys but got nowhere in relation to their available products or any assistance for the off peak tariff.
Your solution seems to be as simple and effective as it can be.

I am planning to purchase one of the Shelly products and set this up in the same way as you presented.
However, I have a questions to you:

Would you be able to provide/share some details (commands you executed) from your 'Shelly' configuration, please?
Many thanks in advance.
  

[Wil]

I went even simpler than this and wired the Shelly in parallel to the water heater instead of messing about with the wiring. Same 16A feed to both, same output to immersion. Then set a schedule on the Shelly for 1hr at 5am (or whenever you want to schedule).

 

This way I could switch the immersion on whenever I wanted and leave the Solic standard and free to feed the excess whenever the PV was out.

 

Separate Shelly 1 with add on temp probes to give me tank temp but I never linked the two operations as an hour of 3kW immersion was plenty for my tank.

 

Edit:

Since getting batteries, I removed the solic altogether and just switch the immersion on when the batteries hit 95% and the PV is over 500W (to ensure the immersion isn’t on at night when the batteries charge off cheap rate) and turn it off when the batteries go below 88%. Rinse and repeat as the batteries fill back up with solar.

Edited September 7, 2023 by Wil

[Luc500]

Hello @Wil,
this would my preferred option. However, in my case I don't have additional wiring (main) to support this case.
The only option I have is the one presented by @RichardL.

Cheers.

[Wil]

It uses the same wiring as the existing Solic. There’s a fixed load (3kW immersion) on the end and the same 16A breaker at the beginning of the circuit. Then a solic and a Shelly in parallel. Effectively two switches between the same load and supply. If they’re both on at the same time, it’s no issue as both fed from the same place and protected by the same breaker.

 

If the Shelly is on the whole 3kW boost is active for as long as you programme the Shelly. If the Solic is on then it trickles whatever is left. I left the solic in all the time and just used the Shelly as a timed (or remote manual) boost.

 

If you did have a different feed to each and on to the immersion, you’d have to be more careful about paralleling.

 

Edited September 13, 2023 by Wil

[RichardL]

On 07/09/2023 at 15:48, Wil said:

ince getting batteries, I removed the solic altogether and just switch the immersion on when the batteries hit 95% and the PV is over 500W (to ensure the immersion isn’t on at night when the batteries charge off cheap rate) and turn it off when the batteries go below 88%. Rinse and repeat as the batteries fill back up with solar.

TBH - I reverted to even simpler than this a few months ago now,  just use the immersion. 210l tank - its about £200 / year to heat from off peak 9p / kWh electric. Just a simple timeclock now 02:30-04:30 - pulls 3kW until the stat turns it off.

Mixergy iHP looked interesting - they quoted me best part of £3k   ...   which although fun doesn't make any sense until off peak electric goes away - I'm guess that will happen when electric cars are mandated.


Only planned update - When the oil boiler goes next year I'll use the tank thermostat for water temp instead of the immersion built in mechanical one.