Could we ask for some advice from those with combi boilers please

TanDiy

We have a 4 bed detached 70s house with a single bathroom and a downstairs cloakroom. We are looking to replace our warm air system with a wet system but our brains have been fried with conflicting information on the best system to go for - even the british gas engineer and his boss stood and argued in front of us, one suggesting a combi and the other advising us to keep a hot water cylinder. The combi sounds really good as we could make space by ripping out the water cylinder, etc. - so, could we ask a couple of questions from people with these systems please...

(1) Does a combi really take a long time to fill a bath - is the flow to the hot taps really low?

(2) In summer when the combi boiler is not being used for heating, does it take a long time for the hot water to start coming through.

(3) Is the combi boiler reliable or does it break down all the time.

(4) One company recommended a pressurised system - they say we have a water cylinder but no cold water tank. However BG then said these are trouble and we should stick to a traditional arrangement with water tank and header tank - does anybody have one of these systems?

Thank you very much indeed.

macman

The flow rate will depend entirely on the combi you select, but generally won't match a conventional system filled from a hot tank.
Combi are not inherently unreliable, it depends more on the brand of boiler you choose. Perfectly suitable for a larger property with only one bathroom.
The first thing I'd do is get a local independent RGI in to give you a quote-with BG you will pay around 40% more.

TanDiy

Thanks macman - yes we have already had a couple of independent heating installers in - one recommending combi (vailant ecotech plus) the other recommending a pressurised system where we still have a hot water cylinder with expansion tank rather than big water tank in loft (advised this needs to be carefully serviced to ensure safety?) - so conflicting information all the time. However, both a little cheaper than the £10K quoted by BG!

macman

What on earth were BG offering you for £10K!?
Unvented cylinders require specialist installers and servicing because of the potential dangers-not all RGI's can work on them.
Some of the newer combis have a small reserve tank which holds about 15 litres of stored hot water.

TanDiy

BG were quoting a traditional system - boiler, new water cylinder, header tank, 12 radiators, valves, controls, fitting, etc. Said it would be about £1500 cheaper for combi. Independent quoting around £7-7.5K. I was initially budgeting 6K.

ziggyman99

macman wrote: »

The flow rate will depend entirely on the combi you select

Incorrect. If the flow rate into the house is rubbish it doesn't matter what combi you select it isn't going to get any better. You can't make a silk purse out of a sow's ear. That's not strictly true because it is possible to boost the pressure and flow rate but not by boiler choice.
The first thing you need to find out is how many litres per minute are available at the kitchen or outside tap. You will also need to know what kind of water pressure you have at that tap.
Once you have these figures you can then make a decision on what system is suitable.
£10k! Wow! That is a lot. Where do you live? I'll do it for that.;)

TanDiy

Hi, two people have checked the flow rate at the cold water tap in the kitchen - one said 15l/min and the other said 12l/min. They both said that the pressure was very high. However, one thing that concerns me is that the water supply is out of our control - if say they build a new estate around the corner then I guess the flow/pressure could change.

It's all a bit of a pain because the current warm air system has never gone wrong in 15 years and does not have any water to leak. However, it does not evenly heat the rooms and is now getting rather noisy. We would like to install a nice modern system with the least amount of hassle and things to go wrong.

Thank you very much for your help.

sanders78

Hi.

I can't answer all of these questions as I'm no boiler expert.. but we have a three yr old gloworm combi boiler in a similar size house (3 bed) and it shas always been very good at providing constant hot water.

we've had it serviced a couple of times and so far no problems!! best of luck. Simon.

gas4you

TanDiy wrote: »

(1) Does a combi really take a long time to fill a bath - is the flow to the hot taps really low?

Only in mid winter if you have the smallest 24Kw fitted

(2) In summer when the combi boiler is not being used for heating, does it take a long time for the hot water to start coming through.

No more than an extra 10-20 seconds

(3) Is the combi boiler reliable or does it break down all the time.

Fitted and commissioned properly on a clean system they are just as reliable as any other type of boiler these days. Intergas and Atmos are more reliable as they have less parts in them than other combi's

(4) One company recommended a pressurised system - they say we have a water cylinder but no cold water tank. However BG then said these are trouble and we should stick to a traditional arrangement with water tank and header tank - does anybody have one of these systems?

These are not any trouble, but you need at least 3.5 bar pressure and 20 l/min to get your monies worth out of this expensive outlay.

With your stated flow rate I would advise a 28/30/31 kw size of combi for your hot water use.

TanDiy

Many thanks for the advice. We still struggling whether to change to combi - sounds excellent but just that little niggle that we should keep a water cylinder. Need to sleep on it again - thanks again for all the information.

st999

Did you not look into replacing your warm air unit with a new one?

The new ones are seemingly more efficient.