nav[aria-label="Primary Navigation"] { padding: 0; & ul { list-style: none; width: 100%; display: flex; flex-direction: row; justify-content: start; align-items: start; gap: 30px; padding: 0; & li { margin: 0; } & ul li { list-style: none; } } }

Child Item

Which type of 300 litre hot water cylinder works best with solar PV?

Bif

Hi. I am changing my old hot water cylinder to a 300 litre model. I want to be able to heat with my kerosene boiler but I mainly use the immersion via a MyEnergi Eddi diverter for electricity from my solar PV. Which model should I look for? I was considering a Joule stainless steel version. It is an a vented heating system. All suggestions welcome. Thanks.

Find more posts tagged with

Quick Links

Comments

graememk

https://www.boards.ie/discussion/comment/121982647#Comment_121982647

The eddi can have the relay board that can trigger the pump.

Pump doesn't need to run for very long to mix up the tank, immersion reaches max temp, pump kicks in for 5 minutes, and then waits for max temp again

A motorised valve would prevent bypass if your only access is the flow in and out.

Big Lar

https://www.boards.ie/discussion/comment/121978793#Comment_121978793

I don't think it would be that simple at all. Have to be a brass pump for a start, the circulating pump is 1" so that's a mighty flow of water, I was looking for a handy half inch one but cant find one.

I wonder if one was to put a pipe straight up a meter or so from the outlet of the tank an then down back into the bottom would the water naturally circulate. Perhaps an automatic valve on that so that the water only naturally circulates when the immersion is on.

[Deleted User]

I have a kingspan stainless steel tank for the same purpose. The immersion is down at the bottom of the tank. It is designed for a closed system but works fine in my open system.

Haven't yet added the solar but it works fantastically off the kerosine boiler.

graememk

https://www.boards.ie/discussion/comment/121980671#Comment_121980671

A normal circulation pump should be fine, out the top and in the bottom.

Big Lar

My element is also 2/3rds the way up the tank and I would really like to put more solar into it if I could, I had considered a wilis but my HW system is pressurized and by all accounts the willis will not work, has anyone ever come up with a cheap pump idea that could circulate water inside the tank ?

bullit_dodger

https://www.boards.ie/discussion/comment/121977876#Comment_121977876

Vertical. that's why I'm somewhat at the mercy of what the specs say. It's apparently a 36 inch element, which means that my sensor is about 6 inches underneath where the bottom of the coil is, if I read the tape measure right :-)

It's more a curiosity to me to be fair - I like to understand these things.

Jonathan

https://www.boards.ie/discussion/comment/121977339#Comment_121977339

Is your immersion vertical or horizontal though?

bullit_dodger

I do get a bit of heating (not much) below the bottom of the electric coil.

Before someone says it, the temperatures aren't correct. I know. They are not "proper" probes touching the tank but Govee sensors like.

https://www.amazon.co.uk/Govee-Thermometer-Hygrometer-Temperature-Greenhouse/dp/B08Y8XHNL8/ref%3Dsr_1_3_sspa?crid=QT6LEIAG8KGS&dib=eyJ2IjoiMSJ9.dQVgsIW_AQEVVSzs72dQKGG1mImKbHR5E97Uc-ULMtg4s2nOehhIrjpFiOGdnxZNFKApSZg9OnNE4679U8tr7xc26AbQopAqKzLdhArk6HiKp4k08MNaXKomosmOgAYmmc38FHMrbBbvAx3NWlONkrGPtSkDTiAjdd78A9avHFKGaDSA0wzs4CJM62MmCM214QZswdBhu7I-qNUuorGf0y1Vb2EVGSyftlnMzIrDZ1FltVksjjUm2AjWp9l6oLMMiJ60i0xZ88--3mfKJKxq48lHC_B50qgM2HVD7V0eenU.BWOHFUCaHFbvMUUqb2WNR1cgwFFSe_jYqgk-GgsRfyA&dib_tag=se&keywords=govee+temperature+sensor&qid=1712267626&sprefix=govee+temp%2Caps%2C92&sr=8-3-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1

45C is on the upper one is when the water is actually 60C. I could recalibrate the sensors, but decided to leave it. The main thing above is that I get a small amount of heating on the bottom one. The sensor is about 6 inches below where the coil stops (assuming it's actually 36 inches which the spec says). I estimate a temp loss of about 0.5C/hr - or there abouts.

My old cyclinder with 2x lagging jackets was losing about 1c/hr, so these new tanks are pretty good.

Latro

Stainless steel Joule Cyclone 300l. The temperature probe pocket is about 20cm from the top.

14 days:

And 1 day:

It loses about 0.33 degree per hour.

Ha Long Bay

I see the same here on Saturday I use the Eddi to heat the water as I have free electricity on the current tariff.

This is heating gas where the sensor is below the immersion.

Back to the original question I got a Joule 300L single coil single immersion cylinder installed last year and very happy with it especially the heat retention.

Jonathan

https://www.boards.ie/discussion/comment/121974167#Comment_121974167

I don't see any mixing below the element. I've got three sensors on the cylinder; two above the immersion element, and one below. There is no change registered on the bottom sensor when heating.

There is a slight issue with calibration of the top two sensors, they should be the same, but the middle one is out by about 1.5°C.

slave1

https://www.boards.ie/discussion/comment/121973945#Comment_121973945

Well two drawbacks if looking to lower immersion

It will only heat above itself so maybe 2/3 of a tank, the bottom immersion is annoyingly not at the bottom but I guess my coils occupy that space
You cannot heat as much as the Willis, mine is at 85degrees in the tank and temp sensors will peak at 85top and 54bottom (where the sensors are placed)

bullit_dodger

https://www.boards.ie/discussion/comment/121974039#Comment_121974039

Generally I'd agree with that, but what happens in my experience is that the hotter water circulating up through the center of the tank from the immersion coil creates circulatory flows and hot water does go down "a little" beneath where the coil is. The reason I bring this up is sort of a heads up to people who might be thinking of swapping out their tank and going for a larger one is that you won't necessarily get all that water.

I went from (circa) 120L tank last year to 200L, but in real terms my hot water probably went from 80-90L to 120-130L - when I'm comparing heating with electrics. Just something to be aware of if your thinking that say 300L will solve all your water shortages.

Jonathan

https://www.boards.ie/discussion/comment/121973945#Comment_121973945

For horizontal immersions, you heat from that point to the top of the cylinder. So work out the ratio of the heights and you'll have reasonably good approximate.

Source: my cylinder has a horizontal immersion.

bullit_dodger

Yeah, I looked at getting one of those Willis heaters installed too (Graememk tipped me off on it). Decided since it was only me in the house to not go that road as it wasn't justifiable, but I like the concept of it.

So when you heat via the lower immersion, how much of your 300L do you reckon you get? Out of curiosity….

slave1

I got the Joule stainless steel 300L last year with twin coil as I have oil and stove also.

As GMK said, my "top" immersion is a Willis (heats from the top down) and my bottom immersion is the usual fixed at the side immersion, I rarely use it as the Willis operates on a syphon principle so eventually heats the whole tank (much hotter at the top obviously), I get a bit of hot/cold mixing but not at a level I'm so concerned to fit a destratification

bullit_dodger

That's a fair point that Graememk makes above. The location of the immersion in the tank really affects the amount of hot water you get. The lower down it is helps heat a larger amount. The draw back is that unless you have 2x immersions in there, it's difficult them with a low immersion location to only heat a "sink" amount of water.

My 200L tank gives 200L of hot water nearly when heating via the domestic hot water, but I estimate I only get about 120-130L of hot water from the electric immersion coil because the coil internally only goes about half way down into the tank.

graememk

Parking the " it will be cheaper to heat via kero and export the solar"

What you are looking for is the immersion as low as possible and/or an external Willis style immersion fitted.

Also with the thermostatic mixing valve on the output, so you can store the water at a higher temperature and it gets mixed down with the cold to a safe level.

Or a destratification pump to equal out the tank

darraghsherwin

I have been looking into changing my cylinder too, I think the Joule TCEMVI-0300NFC looks like a good fit