Heating Water with Solar Panels

noelfitz

Recently I got solar panels and want to know the best way to heat water. In the past I set the timer to heat water using gas at 7 am for an hour daily. With solar panels should I use boost for an hour every morning or is there a better way to heat water?

I include the system I have for gas and electricity. Please let me know if my discussion is in the correct place and I would very much appreciate support.

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PV System (Solar Panels System) supplied by Ecoplex

12 Jinko panels (0.430 x 12 = 5.16kW)

12 Optimisers (as trees near the house)

Solis hybrid inverter (single phase, 3.6kW)

Myenergi hot water diverter (eddi, model 16A1P01H, single phase smart solar diverter)

Shunt

Ber testing and report

On my phone I have myenergi app.

Electric Heaters

4 electric heaters, one is a Dimplex, model ECR20, 1.85- 2.00kW, which is a 2kW oil free column radiator. The others are also Dimplex heaters.

Gas System

Viessmann vitodens 100 - Gas condensing boiler

EPH Controls which independently regulate hot water and central heating.

Energy Suppliers

Electricity, Yuno, contract ends 19 Sept 2025.

Gas, Flogas, contract ends 16 Nov 2024.

bullit_dodger

Assuming your on Day/Night rate, then (at the moment) night time rate is from midnight to 9am. When the hour goes back, this also moves back to 11pm→ 8am.

Since Night rate is generally cheaper than what you get paid via FIT (feed-in-tarrif), your best logic is to set your Eddi to heat the water at 7:30am for 1.5 hrs, or however long it takes to heat your immersion tank….and then export the electricity you generate from solar during the day.

Just don't forget to change your schedule in the Eddi when the clocks move back end of Oct by an hour. Basically you want to also heat the water on night rate.

If you are not on D/N rate, then the strategy is different.

Cypher_sounds

Also if you have the EV rate at night 2/5am, it would be more frugal to boost the cylinder via the Eddi then I'd imagine.

noelfitz

Thanks for reply.

I do not have a battery, what I have is shown below. So perhaps I am OK now about heating water.

My next concern is heating the house, but I will raise this in a separate discussion.

Thanks to all who have helped me.

*** *** ***

PV System (Solar Panels System) supplied by Ecoplex.

12 Jinko panels (0.430 x 12 = 5.16kW)

12 Optimisers (as trees near the house)

Solis hybrid inverter (single phase, 3.6kW)

Myenergi hot water diverter (eddi, model 16A1P01H, single phase smart solar diverter)

Shunt

Ber testing and report

On my phone I have myenergi app

Electric Heaters

4 electric heaters, one is a Dimplex, model ECR20, 1.85- 2.00kW, which is a 2kW oil free column radiator. The others are also Dimplex heaters.

Gas System

Viessmann vitodens 100 - Gas condensing boiler

EPH Controls which independently regulate hot water and central heating.

Energy Suppliers

Electricity, Yuno, contract ends 19 Sept 2025

Gas, Flogas, contract ends 16 Nov 2024. Plan Name: FixedDiscount 24H, Monthly Payment Day: 4

noelfitz

As suggested previously, with the help of participants here, I hope to reach certain objectives using solar panels and my present one is to achieve hot water relying on an eddi diverter instead of gas which I used in the past.

The first thing I did was to lower the water temperature in the tank to 50 °C using its thermostat.

In Heater Settings I set Heater 2 (Bottom) as Priority and in Boost Timer I selected the water heating to start at 7:30 every morning (Mon – Sun) and heat for one hour.

In this way will I have hot water all day? Will the eddi keep the water hot sending power from the panels (trickle) to the tanks (1 and 2) as water cools and to the grid if the tank is heated sufficiently, as I do not have a battery? Alternatively, if the panels are not generating electricity, will the grid electricity keep the tank water hot? Will the water be kept hot all day (24 hours) and if so do I need the boost every morning? Will I ever need to use a manual boost?

As you can see I am not sure about the best way to get hot water with my system and welcome corrections, modifications and improvements.

ian123

Hi a quick Google search shows that min hot water cylinder temp is between 60 and 65C, not 50 like you are planning on, based on minimum temp to kill bacteria

graememk

Eddi on boost is just using your electric - not on solar

What you could do if you really wanted to heat water with solar and not export it is set a base temperature with your gas, and have the eddi top it up.

As for temperature of HW. It's a big "it depends"

The more you use the lower you can go

https://youtu.be/oJeyc_cGIMU?si=sZOksMyjdB9I__mr

bullit_dodger

https://www.boards.ie/discussion/comment/122682322#Comment_122682322

You actually want to set the thermostat to 60C or above. 60C is the default for most tanks and I'd keep that. Problem when you go above 60C is that you really should have a thermostatic valve which controls the temp of the hot water coming from the tank, by mixing some cold water in there to avoid people accidentally scaling themselves as 65C-70C water can be dangerous. If you have one fitted, then I'd go to 65C or 70C (if it lets you)

Why 60C and not 50C? Well, this thermostat sets the temp of the water that the tank will no longer heat beyond - irrespective of if it's using the mains/grid or solar. So right now you have a hr "boost" at 7:30am and it will heat the water up to 50C and then stop. If you picture the scene though of a dark cloudy day with no solar excess, this 50C water will start losing heat as the day goes on, and by (say) noon it will be 45C, 3pm it might have dropped to 42C.

If you set it to 60C in the morning boost, then at noon it will have cooled to 55C and 3pm it might be 52C……so you can see setting it higher means that the hot water will last longer. Also when you are showering, you don't use the hot water direct from the tank. You mix it with cold water to achieve your desired result. If the hot water is hotter, you have to use less of it - so it will last longer.

aside: Unless you need hot water at 8:30am…..the night time electricity rate (at the moment) is from midnight to 9am. I'd have your boost of 1hr at 8am→9am. Don't forget that when the hour goes back end of October, you need to move your schedule to 7am→8am as that's when the night time rates end (in winter)

slave1

I've a 300l tank set to 85c with thermostatic valve fitted, lots of showers so constant demand from night rate heated tank, then export excess PV during the day

noelfitz

Thanks for all the comments and suggestions in this discussion. I now think that I have hot water as I want it.

My next issue is heating the house for which I will start a new discussion.