06-01-2012, 12:06 PM
Hi David,
I'd forgotten that you worked for BG - apologies! I fully admit that I have no training in these matters, but have spent a lot of time researching and planning my installation, and have built up a fair amount of plumbing experience of the last few years. That said, I have a handful of minor plumbing queries that you might be able to help with - I'll start a new thread later on to save taking this too OT...
Sadly, however, I fear that British Gas are rather trading on their reputation. Many people still think of them as "the gas board", despite the fact they have been a commercial company (Centrica) for many years now. I'm no businessman, but I like to think that if I had the massive brand recognition and trust that came with British Gas, I wouldn't abuse it in quite the way BG seem to. A lot seems to depend on the contractor that turns up - many of them aren't BG employees, of course - apparently, if you get a good one, it's worth persuading them to work for you outside of BG. There is a fair amount of discontent out there - just search for "british gas powerflush" to uncover countless complaints about their Powerflush policy. I've never used their products or services, so have no particular axe to grind personally, but still feel cross about Mum's system. If I lived nearer to her, I'd hire the machine and buy the chemicals for around £100, then convert her system to sealed. She could have my old expansion vessel as it's only 3 years old, and the new boiler has its own. Of course, a magnetic filter is a good way to control the sludge: http://www.spirotrapmb2.co.uk/
You make a good point about the servicing, and I fully admit that I'm of a similar school of thought: if it's not broke, don't try to fix it. However, with condensing boilers, they absolutely must be cleaned every year - the aluminium hydroxide deposits clog up the heat exchanger and the channels for the condensate - not to mention the condensate syphon (if fitted). With my old Ideal, these deposits would build up in the bottom and eventually interfere with the ignition and flame-sensing electrodes - after about 13 months the boiler would reliably break down and require a service to get rid of these. New designs put the burner and electrodes in the top so the deposits are building up at the bottom away from the electrodes, but they still need hoovering up. Also, the large rubber O-ring that seals the combustion chamber on most modern boilers deteriorates and should be replaced at each service - when these fail, the consequences are really scary. And the electrodes need cleaning and realigning as they distort in the heat of the flame. I've read that this is important to avoid explosive ignition, and also to insure the ionisation flame-sensing electrode works correctly. In fact, my new boiler measures the ionisation current to determine and correct the fuel/air mixture, like an oxygen sensor in a modern car. I presume that the spacing between burner and electrode might be an important factor here...
I suppose some believe that responding promptly to a breakdown "seems" better to paying customers than preventative maintenance and no breakdowns (I once had a boss who felt the same), but I could never come to terms with this mentality. Apart from anything else, a failure to perform the manufacturers maintenance will invalidate the warranty.
I also agree that system choices are complicated, and while there used to be a time when you'd only ever see combi or open-vent systems in most domestic installations, the situation is much more complex today. With worries about water storage these days, there is a trend towards using smaller cylinders (and loft tanks) in "conventional" systems, allied with high-recovery cylinders and boilers that do DHW-priority. The smaller the cylinder, the more like a combi system you have! Indeed, Viessmann make a kit that I could add to my system boiler that converts my system boiler to a combi - it's just a plate heat exchanger and some switches/sensors - in other words the bits that would have been added to mine in the factory if I'd bought the combi version, but in an external box. While I doubt I'd want to do it, it's nice to know I can switch to combi operation without having to throw away the existing boiler...
Larger combi boilers have water storage built in, constantly kept up to temperature so that there's no waiting for hot water when the tap is first turned on. I think of these as using a very small water cylinder with a high-recovery coil rather than a plate heat exchanger (in simple terms - I've never investigated further). Of course, unvented cylinders and thermal store options are very interesting, and when I need to replace my cylinder, I might consider the latter (mains pressure hot water without the compromises of combi operation). A thermal store can be heated via solar or heat pumps, with the gas boiler providing the final input.
Mike, paying the best part of £4k to British Gas for so little in return is shocking! The final insult is when they convince you the parts are no longer available for your boiler (which actually means they don't stock them in their central warehouse), then quote you over £3k for a really simple boiler swap. This might be OK if the replacement was something like a Viessmann with new radiators and a replacement stainless steel DHW cylinder, but for a mid-range model (rebadged Worcester-Bosch) that's simply criminal. I would strongly urge people to listen to David's advice about finding a local installer - not always easy, but via word of mouth it should be possible. The chap that helped me was recommended by friends, and his wife works in our local butcher, so my wife knows her well...
All the best,
Mark
I'd forgotten that you worked for BG - apologies! I fully admit that I have no training in these matters, but have spent a lot of time researching and planning my installation, and have built up a fair amount of plumbing experience of the last few years. That said, I have a handful of minor plumbing queries that you might be able to help with - I'll start a new thread later on to save taking this too OT...
Sadly, however, I fear that British Gas are rather trading on their reputation. Many people still think of them as "the gas board", despite the fact they have been a commercial company (Centrica) for many years now. I'm no businessman, but I like to think that if I had the massive brand recognition and trust that came with British Gas, I wouldn't abuse it in quite the way BG seem to. A lot seems to depend on the contractor that turns up - many of them aren't BG employees, of course - apparently, if you get a good one, it's worth persuading them to work for you outside of BG. There is a fair amount of discontent out there - just search for "british gas powerflush" to uncover countless complaints about their Powerflush policy. I've never used their products or services, so have no particular axe to grind personally, but still feel cross about Mum's system. If I lived nearer to her, I'd hire the machine and buy the chemicals for around £100, then convert her system to sealed. She could have my old expansion vessel as it's only 3 years old, and the new boiler has its own. Of course, a magnetic filter is a good way to control the sludge: http://www.spirotrapmb2.co.uk/
You make a good point about the servicing, and I fully admit that I'm of a similar school of thought: if it's not broke, don't try to fix it. However, with condensing boilers, they absolutely must be cleaned every year - the aluminium hydroxide deposits clog up the heat exchanger and the channels for the condensate - not to mention the condensate syphon (if fitted). With my old Ideal, these deposits would build up in the bottom and eventually interfere with the ignition and flame-sensing electrodes - after about 13 months the boiler would reliably break down and require a service to get rid of these. New designs put the burner and electrodes in the top so the deposits are building up at the bottom away from the electrodes, but they still need hoovering up. Also, the large rubber O-ring that seals the combustion chamber on most modern boilers deteriorates and should be replaced at each service - when these fail, the consequences are really scary. And the electrodes need cleaning and realigning as they distort in the heat of the flame. I've read that this is important to avoid explosive ignition, and also to insure the ionisation flame-sensing electrode works correctly. In fact, my new boiler measures the ionisation current to determine and correct the fuel/air mixture, like an oxygen sensor in a modern car. I presume that the spacing between burner and electrode might be an important factor here...
I suppose some believe that responding promptly to a breakdown "seems" better to paying customers than preventative maintenance and no breakdowns (I once had a boss who felt the same), but I could never come to terms with this mentality. Apart from anything else, a failure to perform the manufacturers maintenance will invalidate the warranty.
I also agree that system choices are complicated, and while there used to be a time when you'd only ever see combi or open-vent systems in most domestic installations, the situation is much more complex today. With worries about water storage these days, there is a trend towards using smaller cylinders (and loft tanks) in "conventional" systems, allied with high-recovery cylinders and boilers that do DHW-priority. The smaller the cylinder, the more like a combi system you have! Indeed, Viessmann make a kit that I could add to my system boiler that converts my system boiler to a combi - it's just a plate heat exchanger and some switches/sensors - in other words the bits that would have been added to mine in the factory if I'd bought the combi version, but in an external box. While I doubt I'd want to do it, it's nice to know I can switch to combi operation without having to throw away the existing boiler...
Larger combi boilers have water storage built in, constantly kept up to temperature so that there's no waiting for hot water when the tap is first turned on. I think of these as using a very small water cylinder with a high-recovery coil rather than a plate heat exchanger (in simple terms - I've never investigated further). Of course, unvented cylinders and thermal store options are very interesting, and when I need to replace my cylinder, I might consider the latter (mains pressure hot water without the compromises of combi operation). A thermal store can be heated via solar or heat pumps, with the gas boiler providing the final input.
Mike, paying the best part of £4k to British Gas for so little in return is shocking! The final insult is when they convince you the parts are no longer available for your boiler (which actually means they don't stock them in their central warehouse), then quote you over £3k for a really simple boiler swap. This might be OK if the replacement was something like a Viessmann with new radiators and a replacement stainless steel DHW cylinder, but for a mid-range model (rebadged Worcester-Bosch) that's simply criminal. I would strongly urge people to listen to David's advice about finding a local installer - not always easy, but via word of mouth it should be possible. The chap that helped me was recommended by friends, and his wife works in our local butcher, so my wife knows her well...
All the best,
Mark
