Love or Hate your Combi Boiler - advice appreciated

stan5001

Cardew wrote: »

Well you must have had a faulty boiler and a faulty or leaking Hot water system.

A tank of Hot water will stay hot for days. As I said above, with water at a very hot 65C a tank will only lose a tiny amount of heat in 24 hours.

A huge number of people heat their water on Economy 7; so it stops heating the tank very early in the morning and is still hot at night.

As for two hours to heat a tank - that is just not the case for normal systems. A gas boiler produces 30kW or more to heat hot water in a tank. In 30 minutes even from cold there is enough for a bath.

If 30kW from a combi is sufficient to run a bath, then 30kW supplying hot water to a tank will heat it quickly.

Well, it wasn't actually 2 hours, it was 20 minutes in the morning on timer for two showers for most of the time. Which worked.

But sometimes we wouldn't shower, or want to shower in the evening instead, or have a bath, and we found ourselves constantly fiddling with the timer and over-ride, unless you wanted an awful lot of wasted hot water.

Unless you use hot water both morning and evening 100% of the time, it's not worth it.

With a combi there is no waiting.

And yes, we only have the heating on December through to early March in London (with a break when we're up north at Christmas) , as it's expensive.

Cardew

stan5001 wrote: »

and we found ourselves constantly fiddling with the timer and over-ride, unless you wanted an awful lot of wasted hot water.

Unless you use hot water both morning and evening 100% of the time, it's not worth it.

It is this notion that there is 'an awful lot of wasted hot water' that is not correct for most people.

My HW comes on in the morning on a timer, if none is used until evening it will have lost heat equivalent to about 0.5kWh(say 2p).

I have been away for a week, with the boiler switched off, and the water in the tank is still warm when I return.

To repeat the statement above, modern insulated tanks lose between 1kWh and 2kWh over 24 hours with water at 65C. So in practice lose far less heat than the 1kWh.

Virtually everyone on Economy 7 heat their tanks overnight and use the water over the rest of the day.

stan5001

In the real world, with our modern and fully BS approved water tank, 20 minutes a day was enough for two showers within 10 or so hours.

The problem being that there then wasn only enough for one shower in the evening if you didn't shower that morning; and if you wanted a bath you'd have to switch it on and wait 30 minutes again. But not many people have a bath every day.

And if you didn't use any hot water, there wouldn't be enough 24 hours later. So that would be a waste, however you try and spin it with figures.

It felt like we wasted a lot of hot water if it came on but we didn't use it. Sure it stays "warm", but not hot enough to be of any use.

Idiophreak

Sure the techies on here will know what it's called, but I've a combi boiler that also feeds into a tank in the airing cupboard...Means that pressure's maintained when multiple people are showering, we can run baths nice and quick and we've an immersion heater in emergencies. By far the best arrangement I've lived with....

tm9

Thanks to everybody for the information and advice. We started this thread to get peoples views on combis as we were looking to change our warm air system which is not very efficient upstairs due to ceiling vents and only has a very small hot water cylinder (and not a lot of space to fit anything bigger).

After reading all the info and advice on these forums and having had quotes from three installers, we are now thinking that we might stay with what we have got.

The dilemma -

combi sounds brilliant but not sure of performance until it is installed, the external water pressure is then out of our control and could change at any time, if it fails we lose everything so probably have to keep electric shower over bath rather than running on the boiler, BG and one independent said they would not recommend them.

One independent has quoted a maxi flow tank downstairs next to boiler in utility room or loft. The other independent said these were dangerous and complicated (and looking at all the safety features listed I wonder if he is correct) and over the top for our water requirement - all sounds far too complicated.

Good old British Gas then suggested a straight boiler and water cylinder (have to be tall bullet type due to limited space ?) with water tank and header tank in loft.

So we have to wonder if we are better off sticking with what we have. It has never gone wrong in 14 years, we have backup water by way of the electric shower but it is just a bit noisy and inefficient upstairs.

Thanks again for all the feedback.

Owain_Moneysaver

tm9 wrote: »

One independent has quoted a maxi flow tank downstairs next to boiler in utility room or loft. The other independent said these were dangerous and complicated (and looking at all the safety features listed I wonder if he is correct) and over the top for our water requirement - all sounds far too complicated.

No, they're not, but they do have to be installed by someone with an Unvented Hot Water certificate. They should also have an annual safety check.

Quite possibly this 'independent' doesn't have that certificate and so can't do the job.