Combi versus unvented cylinder

[Ackoman]

Hello all,

Looking to upgrade my hot water system - currently have a system boiler, which heats a vented hot water cylinder which also has an immersion heater fitted.

The house has got 16 photovoltaic panels.

I like the idea of an unvented hot water cylinder fitted with an immersion, as that way I get the benefit from the free electricity when the sun is shining. But the installation will require quite a bit of upheaval.

The alternative and easier installation is a combi boiler. The advantage there of course is that you only heat the water that you need. But, economically, does that outweigh the benefit of having a cylinder with an immersion heater and PV panels?

Any advice would be much appreciated!

Ackoman

 

[ianmcd]

all depends on your HW requirements, how many bathrooms shower rooms etc

 

[Agile]

The easiest solution is to replace with another heat only boiler. I usually fit those for about £1800.

To convert to a combi needs a lot more work and is often about £2200.

With a cylinder to use PV generated electricity you appear to need a unit to power the immersion when you have enough power.

But a simple DIY solution is possible simply using a light operated switch to turn on the immersion when there is a lot of sunlight. That could cost about £30 or so compared with the sold units at about £376. That's a lot of capital to spend for questionable savings compared with a timeswitch to just heat the water during the daylight hours.

Furthermore a cylinder gives up to twice the flow rate than a combi.

Tony

 

[picasso]

So much for no advertising on this site, not quite sure why agile wants to change the boiler just install an unvented cylinder, not sure about the solar connected to an immersion heater on an unvented cylinder, maybe something to look a bit further into.

 

[Agile]

Not quite sure why agile wants to change the boiler just install an unvented cylinder, not sure about the solar connected to an immersion heater on an unvented cylinder, maybe something to look a bit further into.

The OP has implied that he thinks the existing boiler needs replacing but erroneously suggested a combi which would be more expensive to use as a replacement.

The existing open vented cylinder can also be used to be heated using the PV output. It done not need to be replaced!

Just needs a little DIY gadget to switch on immersion when there is bright sunlight outside.

Or the official expensive option of an expensive dedicated unit like the Inmersun or similar. But that is an expensive option in my view when it costs £376!

Tony

 

[Agile]

Just found Immersun on sale for £265. But that does not alter the gist of what I said.

But more worrying is that the makers are apparently closing down:-

It is with great sadness that we must announce the impending closure of 4eco Limited and consequent immediate cease of trading.

The solar industry has had many highs and lows over the years, with the most recent claiming many businesses.

There is still a chance that this may not be the end of the road for the immerSUN and other products that were in various stages of development. We are still working towards securing the future and also continued support for existing immerSUN owners.

We would like to thank all of you for your loyalty and support over the last few years and remain positive that a solution can be resolved in the interests of all.

Insolvency practitioner contact details:

DIP Insolvency Practitioners
Suite 2, Stable Court,
Hesslewood Country Business Park, Ferriby Road,
Hessle, East Yorkshire
HU13 0LH
Tel: +44(0)1482 212077
Fax: +44(0)1482 642326
Email:[email protected]
If you have an issue with your existing immerSUN, please provide details by clicking here and completing the form. Although support may not be forthcoming, there is a possibility that the brand is acquired and support provided by another company.
Manufactured by 4eco Ltd - the UK's leading designer and manufacturer of microgen energy saving devices

Of course there are other makers but Immersun was probably by far the best known in the UK.

Its design was also good as instead of triac power control it used inverter control with pure sinewave output.

I was looking at a simple linear solution to reducing the power input to an immersion element but have not come up with anything better than a series capacitor but that would need to be about 100 uF.

A easier solution could be to use a failed battery inverter which can be bought for less than £10 and use that.

Tony

 

[ajstoneservices]

I saw that and that another company had been set up with the same directors selling the same kit.

 

[Ackoman]

Not quite sure why agile wants to change the boiler just install an unvented cylinder, not sure about the solar connected to an immersion heater on an unvented cylinder, maybe something to look a bit further into.

The OP has implied that he thinks the existing boiler needs replacing but erroneously suggested a combi which would be more expensive to use as a replacement.

The existing open vented cylinder can also be used to be heated using the PV output. It done not need to be replaced!

Just needs a little DIY gadget to switch on immersion when there is bright sunlight outside.

Or the official expensive option of an expensive dedicated unit like the Inmersun or similar. But that is an expensive option in my view when it costs £376!

Tony

To clarify - the reason why I want to upgrade the system is because the water pressure is terrible, given that the hot and cold taps are all gravity fed (other than the kitchen tap). There is a shower pump which works well but is so loud it wakes the kids up.

I want to have decent pressure in all taps, and to do away with the shower pump, and the two solutions which have been suggested to me are to have an unvented cylinder or a combi boiler.

Thanks,
Ackoman

 

[Ackoman]

all depends on your HW requirements, how many bathrooms shower rooms etc

Two bathrooms, at present only one has a shower fitted but we are looking to put a shower in the other one at some point.

 

[JohnD]

Just found Immersun on sale for £265.

Having looked at my Summer gas bill (almost entirely used for heating the cylinder, a little hob cooking), in June I used 28m3, costing £6.59 plus VAT (313kWh). Standing charge is unaffected by usage.

There are only about 5 months of the year with worthwhile Solar PV generation, and even then it is only about 2/3rd of the days, and up to about 7 hours a day.

Let's be generous, and suppose that I was able to halve my Summer gas bill with an immersion heater and Immersun or similar. That's about £3.50 a month x 5 months. A saving of £17.50 a year.

It is not a paying proposition to buy an Immersun.

 

[flameport]

a combi boiler. The advantage there of course is that you only heat the water that you need.

It's not really an advantage - the energy savings by not having a cylinder of hot water are next to nothing.

 

[Agile]

There is the other problem that a combi cannot supply two bathooms at the same time!

Solar PV is not an economic technology because the panels are only up to 20% efficiency. But they have been promoted with subsidised feed in tariffs.

Solar thermal in contrast absorb up to 80 % of the incident heat. But the heat gained is only used within the property unlike the solar PV which is exported to the grid and used elsewhere.

But an unvented cylinder needs an adequate water supply. Ideally a minimum of 22 li/min @ 1.0 bar Little point in thinking further until that has been measured.

Tony

 

[PullerGas]

Without knowing all the details; If you're not going to upgrade your incoming mains water supply, fit a large vented indirect cylinder, with immersion heaters & an Intergas boiler on your open vented central heating.

Pointless considering any kind of upgrade with a poor water mains supply.

 

[DP]

So much for no advertising on this site, not quite sure why agile wants to change the boiler just install an unvented cylinder, not sure about the solar connected to an immersion heater on an unvented cylinder, maybe something to look a bit further into.

How does specifying a price help anybody. It in fact makes it more difficult for would be installer as he is then having to justify/ explain the difference in his price and Tony Agile price.

Tony, care to discuss how you would set up the 30 bob circuit to switch power to immersion heater? If it is a serious answer, I am sure you will respond else like the 'Hot water problem' thread, you will quietly depart from posting an answer

 

[Agile]

Danny, I am sure that you are equally capable of making up a simple circuit to turn on the immersion heater when the sunlight reaches the level which will generate 3 kW.

A simple way would to buy a light operated switch on Ebay and use it to operate a 20 A contactor. Both can be bought for less than £20.

Giving typical prices of different options enables those who have less experience of costs to get an idea of what is involved.

They are usually people who will do installations far cheaper than I will. I don't set out to do cheap work or undercut others as I don't need to.

Tony