Condensing Gas Boilers

[FB.]

Does anyone have anything nice to say about condensing gas boilers?

Most people seem to either complain that they freeze-up in cold weather (defeating the purpose of trying to heat a house with them!), or that they are quite costly to maintain/service and just don't seem to be built to last long enough to justify the thousands of pounds installation cost.

The reason I'm asking is that we have a 20+ year old Potterton boiler (75% nominal efficiency) which we know isn't going to last for more than a few more years, but building regulations apparently now make it a legal requirement to fit a condensing boiler.

We're not necessarily expecting an imminent failure of our old boiler, but you never know when it'll give up the ghost and not be repairable. So we're getting ahead of ourselves and trying to decide what to do when the boiler does fail.
We do have 11kW worth of assorted electric heaters and a 3kW immersion (we run them off solar for free, when the weather is bright), so we can "get by" for some time without our boiler if it does fail, since the boiler's nominal maximum output is about 15kW for heating the house and hot water (although it does have to work hard nowadays to manage to do everything - hence having several "backup" electric heaters; some of which came with us from our old house after the gas boiler there failed and we had to buy some electric heaters in a hurry).

Any experiences and thoughts on this subject would be appreciated.

Cheers,
F

[veggiechicken]

I have a gas condensing boiler - 7 years old. No problems so far - Touch wood
Can't tell you anything technical about it.

[chris]

We replaced a 15y/o boiler recently, umming and arring for a long time, we decided to go with a worcester/bosh - 42kW - really does belt the heat out, my rads are hot (though we replaced them too), where as before they were warm, tap water takes a few seconds to have hot water flowing through it... bar the tap furthest away, which takes a good minute (which is our en suite -- tad annoying as I use that a lot, to shave etc).

That one point is the annoying part - so deciding where to site it should be considered (we were going to change the location and put it in the loft, but our gas engineer advised against it, due to the run of pipes - and therefore time taken compared to the current location (old boiler location in our utility room)).

Mine only needs 5mm clearance on the sides, so will be building a cupboard around it, though it's not an ugly thing, I just want it to fit in with our new kitchen.

Added to that, we have a smart thermostat, which learns how fast and cold your house heats up, and on very cold days will come on earlier than it needs to, so the house will reach the temp set, depending on location. It can talk to the TRVs too, but I've not looked at that yet - and we've replaced some of them anyway so those ones wouldn't work now (10mm pipe + the adaptors - PITA!)

So really, thumbs up from me, ours cost 2.4k to install which included a new pipe run, as this boiler needed a 22mm feed, rather than the 15 that was in place. That included the smart meter, erm TRVs, moving the boiler location slightly (so pipework had to be altered (wanted it on a facing wall, rather than adjacent wall where it was awkward to fiddle with).

It's very efficient (98 or 99% I think), and comes with a 5yr guarantee which is nice too

Edit: oh and our shower now, off the boiler is like a power shower

[greenishfing]

I've had mine for about 6 years-touch wood- no problems even in the cold winter a couple of years ago. Instant hot water and the gas bill dropped quite a bit.

[FB.]

Hi Chris.

You said 42kW gas boiler - did you actually mean 42k BTU (42000 BTU) which is about 12kW?

My existing boiler is nominally about 14kW output, which in gas terms is about 50000 BTU (50k BTU).

[Potstubsdustbins]

F.B. No, Chris meant 42Kw his boiler is a condensing combi not a system boiler which is what you are talking about. Chris you will be pleased to know I chose Worcester too.

F.B. As yours is a system boiler and you also use electric to heat your water bear in mind that unless you have a full control system already installed this will have to be done at the same time as the new boiler is fitted.

Condensing boiler's, John Prescott legislation to meet Blairs eco targets on emissions, this should give you a clue. They are getting better but the technology is still fairly new.

When the time comes to change your boiler and it won't be long, dedicated spares tend to become unavailble after about 15 years.

Choose carefully, don't go for cheap and don't under any circumstances go for a new model on the market (let some other poor bu**er find out if its going to be a goodun).

At this time Worcester are about the best both in terms of efficiency and reliability. Ideal have just bought out a new model to try to regain their reputation after their last load of dung offering, but they need to be out another year before I would recommend/install one.

Do your research and tell the installer to quote using your spec, if I am still around I will try to help.

Choose your installer carefully Gas Register registration is not a domestic heating qualification and there is some real junk out there.

Colin

[FB.]

F.B. As yours is a system boiler and you also use electric to heat your water bear in mind that unless you have a full control system already installed this will have to be done at the same time as the new boiler is fitted.

Thanks for the reply, Colin.

What will need to be done regarding the "full control system" that you mention?

At the moment we can choose whether to heat our hot water by gas boiler or by electric.
There is a fairly basic mechanical-timer mechanism for the gas central heating or gas-heated-water in the airing cupboard on the landing which allows two on/off cycles per day, for each of the heating or the water, or it can be set to be constantly on or completely switched off.
The electric immersion is manual-operated switch.

We often use electric for the hot water because we can often do it cost-effectively with the solar making at least a partial (if not a full) contribution to the electric consumption of the immersion.
Using electric to heat our hot water whenever reasonably possible/cost-effective also means less effort for our boiler, which hopefully will keep it rumbling along that bit longer through less wear-and-tear.

Anyway....I've wandered a bit: what's the "full control system" thingy that you mentioned?

[veggiechicken]

Mine's a Worcester Greenstar HE - I've no idea what the output is - can't find the manual for it
My controllers are the same as yours FB but I don't use the immersion to heat the water.

[FB.]

My controllers are the same as yours FB but I don't use the immersion to heat the water.

Hi, VC.

Electric immersion is almost twice the cost as from a 90-95%-efficient condensing gas boiler, and about 1.5x the cost if I use my older 70-75%-efficient gas boiler.

It gets tipped towards electric, for me, because I have 3.75kW solar panels which even this morning in the lower-in-the-sky autumn sun were able to peak close to 3kW output and produce a total of about 9.5kWh for the day despite quite a lot of cloud at times.
My solar panels only need to be outputting about one-quarter of their maximum capacity to make the electric immersion competitive with using my gas boiler especially since the boiler uses a few hundred watts of electricity to run the fan and pumps in addition to its gas use.

[FB.]

Mine's a Worcester Greenstar HE - I've no idea what the output is - can't find the manual for it

Instead of "What kind of fruit tree is this?", you could take some pics and get the plumbers on the forum to show how good they are and answer "What model boiler is this?".

[Potstubsdustbins]

Building Regs Part L1 again via Mr Prescott.

First your system. Boilers used to be fitted using gravity hot water and pumped central heating. Easy to identify the boiler will have 4 water pipes leading away from it. 2 to the hot water cylinder and 2 to the central heating system. If your system is like this you will need a complete repipe to a fully pumped system (only 2 water pipes coming from the boiler.)

During the repipe you will have to install a control system comprising of a minimum of a 2 channel programmer, cylinder thermostat and room thermostat. This has to be wired so as to form a boiler interlock, simply explained the boiler shuts down completely when both stats are satisfied and does not cycle. Finally if your boiler requires a 'bypass' and most do this will have to be an automatic bypass valve not a manual set one.

There will need to be extra insulation of bare seen pipes near your cylinder and you may have to change your hot water cylinder.

Thermostatic radiator valves will have to be fitted to the bedroom radiators again as a minimum requirement.

The above is the reason most people now go for a combi boiler

Finally the system will have to comissioned by a 'competent person' as describe in the regulations or you will have to pay the local Building control body to certify the system for you.

Not good news I am afraid but the cost of fitting of a system boiler these days fars exceeds the cost of a combi if all the changes have to be made.

Colin

[Potstubsdustbins]

One more pleasing thought for you your Potterton was 75% nominal efficiency when it was new take it from me it won't be anywhere near that now.

Colin

[veggiechicken]

My life is complicated by having two homes, FB! One with gas central heating, the other with oil CH, solar PV and solar thermal. To make it even more confusing, the oil boiler was a combi but was converted to a system boiler when the solar thermal went in.
My gas boiler was a straight replacement for a much older Ideal Mexico. The big difference was that the Ideal boiler was on the floor and had a flue that went up an old chimney while the new one had to be wall mounted with an external flue knocked through the wall. It picked up the existing pipework and controls.
Bet you're as confused as I am now

[FB.]

One more pleasing thought for you your Potterton was 75% nominal efficiency when it was new take it from me it won't be anywhere near that now.
Colin

Yes, I used the word "nominal" intentionally - I suspect that its efficiency is closer to 65% nowadays, rather than the 75% when it was new.

Boilers used to be fitted using gravity hot water and pumped central heating. Easy to identify the boiler will have 4 water pipes leading away from it. 2 to the hot water cylinder and 2 to the central heating system.

From what I can see, there's an electromechanical bypass switch in the airing cupboard which changes (or allows the splitting of) the flow of hot water being pumped from the boiler. So the water can:
1. Go to the radiators.
- or -
2. Go through a coil inside the hot water tank.
- or -
3. Be split equally between the radiators and heating the hot water.

[FB.]

Bet you're as confused as I am now

I just want a simple, reliable boiler to replace the simple, reliable old Potterton.

Is that too much to ask?


Seriously, though, I had heard from others that Worcester-Bosch were virtually the only one worth considering, but even they have allegedly had their share of problems.