Solar. No longer heating water

ewor1958

I inherited Solar panels when I moved into this house last August. There is an Immersum diverting power to the hot water tank, which worked fine when we moved in, after a sunny day the hot water was hotter than when heated from the gas boiler.
One of the first things I had done after moving in was replace the water system with a pressurised unvented system with a 250ltr cylinder. But I've noticed that despite several sunny days lately the water is not getting hot.
Yesterday, for instance, the Immersum shows 4kwh of energy went into the hot water, the switch in the airing cupboard shows the orange light so power is getting to it, and an electrician checked the connection to the cylinder with a meter and that shows power, but last night there was no hot water in the tank.
Any ideas please?

Thanks

zeupater

ewor1958 wrote: »

I inherited Solar panels when I moved into this house last August. There is an Immersum diverting power to the hot water tank, which worked fine when we moved in, after a sunny day the hot water was hotter than when heated from the gas boiler.
One of the first things I had done after moving in was replace the water system with a pressurised unvented system with a 250ltr cylinder. But I've noticed that despite several sunny days lately the water is not getting hot.
Yesterday, for instance, the Immersum shows 4kwh of energy went into the hot water, the switch in the airing cupboard shows the orange light so power is getting to it, and an electrician checked the connection to the cylinder with a meter and that shows power, but last night there was no hot water in the tank.
Any ideas please?

Thanks

Hi

Some basic questions first ...

Was the previous cylinder also 250l ?
Is the immersion heater in the same position (ie top or bottom) ?

With the level of sunshine we've seen recently there's no way that a proportional diversion system would be contributing much to DHW ..... other than reducing the demand for gas usage for DHW heating that is always the case in mid-winter. As an example, around 4kWh of energy delivered at the bottom of a cold filled 250l cylinder would heat the water by less than 15C, lifting the temperature to somewhere around 25C at this time of year, which is still pretty cold according to MrsZ's shower scream test !

If there's no hot water it's more likely to be as a result of your main heating - have you switched the water heating off recently by mistake, or is there a problem with a motorised valve ?

As a side note, you mention that the immersion heats the water to a higher temperature than the GCH. With an unvented system it can be pretty dangerous to run the storage at too-high a temperature which could result in over-pressure issues, so make sure that your immersion is set to comply with the cylinder manufacturers' specifications/limits .... probably not an issue, but something to be aware of.

HTH
Z

ewor1958

Thanks for the reply Zeupater.
The previous cylinder was smaller, probably 150ltr, and immersion was in the top, new cylinder has the element at the bottom to heat the whole tank.
Are my expectations too high from Solar? 4Kwh seemed to be ample energy to heat the water in September when we first moved in, but I guess would have only been heating the top half of a smaller cylinder.
There's no problem with the gas boiler, I just don't put it on until 8pm on a sunny day as up to now there has been sufficient hot water for my washing up chores at 7pm!

Thanks

zeupater

ewor1958 wrote: »

Thanks for the reply Zeupater.
The previous cylinder was smaller, probably 150ltr, and immersion was in the top, new cylinder has the element at the bottom to heat the whole tank.
Are my expectations too high from Solar? 4Kwh seemed to be ample energy to heat the water in September when we first moved in, but I guess would have only been heating the top half of a smaller cylinder.
There's no problem with the gas boiler, I just don't put it on until 8pm on a sunny day as up to now there has been sufficient hot water for my washing up chores at 7pm!

Thanks

Hi

Your expectations are certainly high for winter, but you'll notice the difference as the year goes by ... hopefully from March onwards you'll need little/no additional DHW heating, but of course, that really depends on how many there are in the household and how much water you use.

We've had a pretty good day so far with our solar thermal, certainly the best for months, but it would take at least a couple more consecutive days of similar clear sky conditions combined with little draw-off to bring the cylinder up to full temperature ... in a month things will be completely different, as long as the sun shines!

HTH
Z

ewor1958

Ok, thanks for that. I'll tell my Plumber to stand down for a couple of months!

[Deleted User]

Yeah our solar pv diversion switch does nothing at this time of year. Generation is very low which is absorbed into the base load of the house never mind when the heat pump runs.

As said already I expect it to 'wake-up' properly come March and work through to late Oct

Cheers

pinnks

My immerSUN has really enjoyed the last couple of days but I do agree that you cannot survive on immerSUN alone for the darkest 4 or 5 months.

We need between 2 and 3kWh per day to satisfy the immerSUN (there are just two of us with a normal 100 or so litre tank). That needs about 5kWh or so to be generated to cover background use etc. and still send the magic 2.5kWh to the tank.

But today (and yesterday) we generated over 10kWh. Plenty for the immerSUN and 5kWh pumped to second immerSUN to take the chill off the living room.

Compare that with 3 days ago when we generated less than 1kWh and diverted nothing.

So, depending on your water use and how cold the tank gets between heating sessions you can expect hot water on a day like today. I suppose that with a 250l tank you would need to divert about 7kWh to achieve the same as my 2.5kWh achieves in my 100l tank...

ewor1958

We're not far from you Pinnks, in North Dorset and generated a similar amount today, 9.5kwh, with 4kwh going into the hot water, however the Plumber has been here fitting a new bathroom so drained the tank, any water that was heated was lost!