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PV to hot water and heat storage controls


Marvin

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PV to hot water and heat storage controls schematic:

 

113787222_Hotwaterandheatstorage.thumb.jpg.e274d3436e41e0ada82c1deb6d94f362.jpg

 

 

This system only uses the excess PV power (unless the Solic 200 button to use any power is pressed, and then it will allow any power for 90 minutes).

 

There are three output choices. Firstly to the hot water tank immersion until the tank reaches the temperature set point, then to one of the two storage heaters as chosen.

 

Although some people have mentioned that the Solic 200 (other types I cannot comment about) will limit the power through it, this design is limited to one output at a time which is a maximum of 3kW.

 

When the hot water tank has reached its target temperature the controls automatically offer the excess power to the MK 3 way switch( K8).  This part of the system is designed for our home.

 

The choices are power to the hallway day storage heater or power to the timer which switches between the hallway and living room one.

 

Today we stored about 2.8kWh for overnight heating.

 

Any questions, let me know.

 

Marvin

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It seems a little over complicated.  In winter you won't get more PV than the cylinder will store, and in summer when you might, the last thing you want to be doing is heating a storage heater.

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15 hours ago, ProDave said:

In winter you won't get more PV than the cylinder will store, and in summer when you might, the last thing you want to be doing is heating a storage heater.

And during the other times of the year, charging storage heaters should pay dividends.

If I had PV, I would let the DHW take priority.  I am happy to let the house float around 19°C at the moment, which is 1°C lower than in the past.

Curing the old leaky door where I work has helped a lot.  Colder mean temperature, but more comfortable overall, and I use the fan heater less than I did. Not used it this year at all, but it has been mild.

So I think that any kWh pumped into a storage heater, is a kWh not brought in.

Can't comment on the complication of your system, I can't follow the sketch.

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10 minutes ago, SteamyTea said:

And during the other times of the year, charging storage heaters should pay dividends.

But the controls don't need to be so complicated.

 

Simple changeover relay that is energised by a tank thermostat to swap the PV diverter output to something else (the storage heater) if the tank reaches maximum temperature.

 

But I wager there will be very few times this happens except in summer when you won't want it.

 

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15 hours ago, ProDave said:

It seems a little over complicated.  In winter you won't get more PV than the cylinder will store, and in summer when you might, the last thing you want to be doing is heating a storage heater.

It depends on how you use your HW though. Early morning showers at any time of year will require the import of power and in the winter this may leave the cylinder close to full. It's just not easily predicted. If there is any spare PV, a cascade priority system such as this makes perfect sense to me.

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26 minutes ago, Radian said:

Early morning showers at any time of year will require the import of power

I can probably get 4 short showers out of my 200lt cylinder that is at about 45⁰ C. The last one may be a bit tepid, but would be fine for getting the work fat off.

 

I may try and experiment with timings on my DHW. Day just top heating, followed by day of just night heating. Not sure if it will make much difference as it is really about lowering losses, not using less water, at a colder temperature.

But in the summer, when I hear just the top of the cylinder, I save about 1.5 kWh/day.

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23 hours ago, ProDave said:

It seems a little over complicated.  In winter you won't get more PV than the cylinder will store, and in summer when you might, the last thing you want to be doing is heating a storage heater.

Hi @ProDaveYes very complicated.

 

 

Your quite right, I forgot to show the heater control switches.20230109_164807.thumb.jpg.a140bdd9dfc62b503a00b6080eeffd53.jpg

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8 hours ago, SteamyTea said:

Can't comment on the complication of your system, I can't follow the sketch.

Yes I have trouble..  

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8 hours ago, ProDave said:

But the controls don't need to be so complicated.

 

Simple changeover relay that is energised by a tank thermostat to swap the PV diverter output to something else (the storage heater) if the tank reaches maximum temperature.

 

But I wager there will be very few times this happens except in summer when you won't want it.

 

The design is to protect the relays from over amperage.

 

Actually today the tank was heated and some went in a storage heater.

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7 hours ago, SteamyTea said:

I can probably get 4 short showers out of my 200lt cylinder that is at about 45⁰ C. The last one may be a bit tepid, but would be fine for getting the work fat off.

 

I may try and experiment with timings on my DHW. Day just top heating, followed by day of just night heating. Not sure if it will make much difference as it is really about lowering losses, not using less water, at a colder temperature.

But in the summer, when I hear just the top of the cylinder, I save about 1.5 kWh/day.

The aim with the hot water tank is to over heat it enough with otherwise unused energy so it lasts a few days. At present the PV runs at a good day (for winter) then 3 poor days, or about average day after day, or a mix of the 2.

 

Yes we have to adjust things depending on the temperature etc, to achieve the best performance....

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2 minutes ago, Marvin said:

 

Yes we have to adjust things depending on the temperature etc, to achieve the best performance

I think this is half the battle.

I knew I was out all day yesterday, so turned the storage heaters input down.

Meant the house was about 17⁰C when I got in, but probably saved me 4 kWh.

Just went to bed early.

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52 minutes ago, Marvin said:

 

Your quite right, I forgot to show the heater control switches.20230109_164807.thumb.jpg.a140bdd9dfc62b503a00b6080eeffd53.jpg


Excellent user interface - passes the family test, i.e. not being funny just doesn't need a manual to work it out, and reduces any complexity on the backend systems to a simple timeclock and function on/off switches.

I guess no wifi/internet/cloud dependency - I love tech but making my heating system dependent on an external plethora of servers etc seems a bad direction to go in.

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1 hour ago, RichardL said:


Excellent user interface - passes the family test, i.e. not being funny just doesn't need a manual to work it out, and reduces any complexity on the backend systems to a simple timeclock and function on/off switches.

I guess no wifi/internet/cloud dependency - I love tech but making my heating system dependent on an external plethora of servers etc seems a bad direction to go in.

Hi @RichardL  Yes. SWMBO needs to be able to use it when I'm away.

 

There's two camps on the choices of controls. Some new wave, some old school.

 

You'll have to guess which camp we're in!

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