New hot water cylinder if I'm getting solar

Comer1

I have a small copper hotwater cylinder, 36" I think. Its not insulated but I have a lagging jacket and duvet covering it and it holds the heat very well. Problem is that it's small and the hot water generated from the previous night's central heating, or nigh rate electricity, doesn't last past the morning. I assume if I go ahead with solar, I'll need something bigger and also better at holding the heat. Also, I have my own well which apparently is to be considered when installing a cylinder.

Any recommendations on what I should be looking at. We have four to six adults in the house. Thanks

graememk

If your getting pv, you dont need to fit a hot water diverter (eddi) and just export the excess power.

Can you heat your hot water independently from your central heating (ie nothing to the rads, just the tank?)

If you can do that and let the export credit offset the cost of the oil/gas?

Although if you are finding you are running out of hot water, and not able to heat it fast enough to keep up with demand a bigger tank would be useful.

I wouldn't be changing the tank just because you are getting pv, Change the tank for other reasons.

Comer1

https://www.boards.ie/discussion/comment/121298184#Comment_121298184

Thanks for the reply. I have read some posts here saying that eddi isn't worth it, just sell back to the grid. I currently have an immersion heater in the summer to heat water during the day. It just seems a bit mad to me if I'm going to have solar panels and not have hot water all day during the summer, but that's probably because my understanding of how it all works is off. Can you leave the immersion on in the summer to take excess generated from the panels, or is that a stupid suggestion?

graememk

The first wave of solar was solar thermal, which are very good at heating water, I suppose that's why the solar = hot water

Before the feed in tariff, we got nothing for export, so if you don't use it, you lose it. So immersion diverters used it and could control the power the immersion used to match the excess of solar, to minimise export.

Now, the export rates are 20-27c depending on your supplier,

You didn't say if you were on oil or gas but generally the cost to heat water is 10-15c/kWh.

So for heating hot water, it's prudent to just export at 20 c and use gas at 10c. And not spend €500 on an eddi. If your hot water cost is 10c/kWh you'd have to put 5000kwh through the eddi just to pay for it, and if you just exported that 5000kwh you would have made €1000, and if you needed that hot water would have spent €500, and you would still have €500 left over!

So spend €500 for "free" hot water.. or just export, and be €500 up.

slave1

But hot water throughout the day convenience factor...OP will need big new tank to have water throughout the day for 4-6 adults. I have 4 and 300l tank needs reheating during day rates to satisfy later part of day showers

Comer1

That makes perfect sense. I have a Stanley oil stove so using it in really hot weather isn't ideal as the kitchen gets too hot. I can control all the rads as I have smart valves on each rad so can close them all on the phone in seconds.

Telling me that I don't need to change the cylinder is music to my ears🙂

graememk

https://www.boards.ie/discussion/comment/121298871#Comment_121298871

My parents have an eddi for the summer because they heat the HW from turf, so in the summer they don't have to put on a fire just to have hot water. Convenience wins there.

Does the oil Stanley ever turn off or just keep ticking over 24/7?

Do you currently use the immersion to keep the tank hot? Does it satisfy your requirements now?

Could you re-jig the plumbing so you don't even have to turn off the trvs to heat the hot water (would recommend that even if you are replacing the tank)

There is reasons to change, but for solar isn't a reason.

cobham

How old is your present tank? A new one would be stainless steel and fitted with layer of insulation so neat. Maybe a larger capacity is what you need for your household? We have an Eddi and it is second in the Q for taking energy after the house needs are satisfied. Then the excess goes to the grid. The hot water tank considered a way of storing energy (like the battery) when paid very little for the excess but things have changed. If you have a decent night rate that water tank could be charged up at a lower night rate.

Comer1

My current cylinder is about 18 years old. The house is 27 years old and that is the third cylinder in that time. I'm thinking that the well water may be causing an issue withbthe cylinders so maybe just wait and if I need to replace the current one in the not too distant future, put in a larger, better insulated one then.

The stove fires up when needed as it is controlled by a thermostat on the water and is very efficient to heat water with all the rads turned off.

What I'm getting from the opinions on this thread is that the cost and inconvenience of changing the cylinder, plus the cost of a diverter vs immersion and oil is not worth it. My wife loves heat, so actually puts on the stove for a lot of the year anyway, except for very hot days in the height of the summer.

Thanks

con747

https://www.boards.ie/discussion/comment/121299255#Comment_121299255

You know you can get a grant every 7 years to upgrade the well treatment system and other works as well. I had mine replaced 2 years ago with a cost to me of about €1000. If a new well is required it's covered under the grant scheme as well. Look at your Co Council website for information. My hot water tank was 1/3 full of sludge.