Boiler - combi, system or electric?

beachmat

Hi there

I've moved into a 2 up 2 down house recently with an old style gravity hot water system and a 11 year old Baxi boiler which I was thinking about replacing with a combi in order to reclaim the space being used by the hot water cylinder which is in a corner of the living room. I'm a little reluctant though when the boiler is still working and is not the most inefficient. Having said that the current setup doesn't seem to work that well as the water isn't always that hot. But I've been a bit put off by talk of the unreliability and maintenance expense of combis. Is that valid or are they getting better now? I was also told I would get mains pressure (which is pretty good) on the hot water with a combi - is that correct?

I understand an alternative is to have a mains-fed hot water cylinder in the loft, and a cold tank would not be needed in that case. Would I then need a system boiler? Or could I keep my existing one? How would this solution compare to a combi?

I had also been thinking about solar panels. If I did that would an electric boiler make more sense than a gas one?

thanks

macman

An electric boiler only makes sense if you are happy to pay about 300% more per kWh than on mains gas.
Assuming you are referring to solar hot water, not solar PV, you need a stored hot water system-i.e not a combi.
Combi's have been around for years and are no more or less reliable than conventional boilers. Whether a combi is even suitable for your property can only be determined by your chosen RGI doing a flow and pressure test at the property.
So firstly you need to decide about the solar hot water.
Or you could keep the Baxi and install a tank in the loft?

beachmat

Thanks - sorry I meant solar PV. I was thinking they might make it possible to run an electric boiler cheaply but from what I've seen they wouldn't contribute a great deal to the running costs.

So my existing boiler (open-vent presumably?) could work with a mains-fed cylinder in the loft? My understanding was that I'd need a system boiler for that. Any idea of the expense of installing a cylinder in the loft compared to installing a combi?

Robwiz

Hi beachmat

You're asking 'how long is a piece of string?' type questions. There are so many variables that influence the cost that it's hard to give a sensible figure. But for a new boiler, with the 'gassafe premium' you would be looking at £2k plus for a new boiler and converting your system to unvented.

You could run solar PV to an immersion heater but it would take a good few years before your investment paid back.

Before you do anything to your heating system why not look at measures to keep more heat in your house? Your bills will go down, your house will heat up faster and you won't need to run your heating on as many days in the year. When you upgrade it you will be able to specify smaller/fewer radiators.

If you're determined to go ahead with your heating, ask around for recommendations of local RGIs (or look up Checkatrade or Which? Local) and get two or three round and ask them to price up a replacement for you.

beachmat

Right, it's storing the power from solar pv that's the issue isn't it. If someone sorted that then maybe we wouldn't have to buy Russian gas any more...

Robwiz

You'll find more about solar PV on the Green and Ethical forum here.

It would be feasible to re-wire all a house's lighting with a 12V circuit, powering LEDs and operating it from a caravan leisure battery which is recharged from solar PV during the day. Otherwise, many people find using proportional diverters with solar PV is an effective way of using as much of their own generated electricity as they can.

macman

Think about it. Your solar panels might produce 3kWp on a good day. They will produce zero at night or on a dull winter's day-which is when you need to produce the heat. During a peak summer's day output, all you would need to power from them would be hot water-the CH will be off.
Standard solar PV installs use the power generated directly, or feed it back into the grid. It's not practical to store it.

beachmat

Had a look at solar thermal and again the benefits don't seem that significant and the time to recoup investment long. Oh well, nice thought.

Can anyone clarify the issue of needing to replace the boiler or not when moving the hot water cylinder into the loft?

macman

Theoretically, it's perfectly possible, but in practice only a proper site inspection by your RGI can determine that. And whether it's economic to do so.
Are you sure it's gravity-fed? CH Pumps have been around rather longer than the 11 years since your Baxi was installed, so I would have expected it to be converted to fully pumped back in 2003?

beachmat

I will have it looked at again, thanks.

Pincher

Do some research on hot water cylinders.

You can get horizontal ones that fit in the loft.

You can get a tiny cylinder, mount it high up in the existing closet, and use the space lower down for storage.

I was in a studio apartment recently, where the hot water cylinder was about 40 litres or so, hidden in the space above the bathroom (lower ceiling). It was heated by a 3kW electric element. Provided you start with a hot tankful in the beginning, and the 3kW element keep heating while I showered, I had plenty for a satisfying shower. Ideally, the shower should have a thermostatic mixer, to cope with the cooling supply as you shower.