mah
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Post by mah on Jan 13, 2024 21:10:39 GMT
Could people suggest what changes to the pipework would be needed to replace a conventional boiler (gravity fed with hot + cold water tanks + expansion tank) with a combi boiler ? I guess
a) 2 more pipes needed for the Boiler - inlet / outlet for the (instant) hot water ? Do they need to be of different sizes ? b) If different sizes, do all the pipes feeding the hot water taps / showers need changing ? c) Do any cold water pipes feeding taps / showers / cisterns need changing ?
d) The closed circuit heating pipes remain as they are with the diverter valve (hot water - heating), hot / cold / expansion tanks becoming redundant ?
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markyg61
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Post by markyg61 on Jan 14, 2024 8:09:36 GMT
When our boiler was changed I had to have the gas supply changed from 15mm to 22mm - insufficient pressure.
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Post by crabbyoldgit on Jan 14, 2024 8:18:53 GMT
Correct but will need condensate pipe to soak away in garden .Also be aware heating engineers don't like doing pipe calculations so will probably want a bigger gas feed pipe from the meter to the boiler. It is easy for them compared to doing all that's maths to see if the existing pipe is big enough and a good easy earner to. Pipe work on hot domestic hot water will be ok the output flow rate from a combi is much lower than that of a tank store system. So get a good paper to read while waiting for the bath to fill. Cold feed will be ok. Should not be a problem but if the radiators are to small do not try and up the space heating water temp high to the radiators to compensate. If you do the boiler will lose it's condensing function and become up to 30% less efficient. Ps getting the existing heating pipe work properly cleaned and radiators flushed is worth very penny but expensive for the work involved , another easy good earner.
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Post by moonraker on Jan 14, 2024 12:24:29 GMT
Nothing like the pipework changes (and costs) that will be necessary for a heat pump
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keitha
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Post by keitha on Jan 16, 2024 13:43:56 GMT
Correct but will need condensate pipe to soak away in garden .Also be aware heating engineers don't like doing pipe calculations so will probably want a bigger gas feed pipe from the meter to the boiler. It is easy for them compared to doing all that's maths to see if the existing pipe is big enough and a good easy earner to. Pipe work on hot domestic hot water will be ok the output flow rate from a combi is much lower than that of a tank store system. So get a good paper to read while waiting for the bath to fill. Cold feed will be ok. Should not be a problem but if the radiators are to small do not try and up the space heating water temp high to the radiators to compensate. If you do the boiler will lose it's condensing function and become up to 30% less efficient. Ps getting the existing heating pipe work properly cleaned and radiators flushed is worth very penny but expensive for the work involved , another easy good earner. interestingly, my condensate pipe feeds into the waste water drain under the sink the plumber who replaced my boiler thought it was a great idea as it reduces the chance of the condensate pipe freezing and locking the boiler out. mah if you are keeping the cold water tank then no change needed but otherwise to plumb the cold water supply to the taps.
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adrianc
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Post by adrianc on Jan 16, 2024 17:15:42 GMT
interestingly, my condensate pipe feeds into the waste water drain under the sink As does mine. But, for some bizarre reason, it's blocked at the mo. We've not long had a new kitchen, and I'm waiting for the plumber to come back from skiing... It's astonishing just how much condensate I'm emptying out of the boiler daily - about 4-5 litres.
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michaelc
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Post by michaelc on Jan 16, 2024 17:21:33 GMT
When I last looked into it, my 25 year old non-condensing boiler seemed only 10% less efficient than a new condensing type. Problem is the new ones are a lot more complex, go wrong regularly, have lots of plastic parts and only last 7 or 8 years. My boiler rarely goes wrong and when it does its one of 5 things that are easily fixed.
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adrianc
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Post by adrianc on Jan 16, 2024 17:29:18 GMT
When I last looked into it, my 25 year old non-condensing boiler seemed only 10% less efficient than a new condensing type. Problem is the new ones are a lot more complex, go wrong regularly, have lots of plastic parts and only last 7 or 8 years. My boiler rarely goes wrong and when it does its one of 5 things that are easily fixed. Ours is 18yo. It had some work last year - the rubber flap in the flue had gone sticky in the more corrosive LPG exhaust.
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adrianc
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Post by adrianc on Jan 28, 2024 11:27:06 GMT
interestingly, my condensate pipe feeds into the waste water drain under the sink As does mine. But, for some bizarre reason, it's blocked at the mo. We've not long had a new kitchen, and I'm waiting for the plumber to come back from skiing... It's astonishing just how much condensate I'm emptying out of the boiler daily - about 4-5 litres. As the weather's become less humid, the amount has massively reduced, less than a litre a day at the mo.
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mah
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Post by mah on Jan 28, 2024 11:38:20 GMT
When I last looked into it, my 25 year old non-condensing boiler seemed only 10% less efficient than a new condensing type. Problem is the new ones are a lot more complex, go wrong regularly, have lots of plastic parts and only last 7 or 8 years. My boiler rarely goes wrong and when it does its one of 5 things that are easily fixed. I agree that the old Boilers are much more reliable - 20 to 30 years of life is normal and if they go wrong, they can easily be fixed. Mine must be 20+ years as the house was built around 2000. In the last 13 years, I have had to change the Diverter Valve and the Pump (also the Programmer, which I replaced myself) - the most common ones that usually go. So, am expecting it to last a few more years now. Hence I'm reluctant to replace it, particularly due to the pipework changes, and the associated wall damages. Given the slight increase in efficiency, as experienced by you, I don't think I'll go ahead now.
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angrysaveruk
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Post by angrysaveruk on Jan 28, 2024 12:04:02 GMT
Could people suggest what changes to the pipework would be needed to replace a conventional boiler (gravity fed with hot + cold water tanks + expansion tank) with a combi boiler ? I guess
a) 2 more pipes needed for the Boiler - inlet / outlet for the (instant) hot water ? Do they need to be of different sizes ? b) If different sizes, do all the pipes feeding the hot water taps / showers need changing ? c) Do any cold water pipes feeding taps / showers / cisterns need changing ?
d) The closed circuit heating pipes remain as they are with the diverter valve (hot water - heating), hot / cold / expansion tanks becoming redundant ?
Your existing hot water pipes may need to be changed, but this is not because of the pipe size you can probably adapt the existing piping. Basically a gravity fed hot water system is not operating at mains pressure. A combi boiler hot water system will be operating at mains pressure - ie could start to leak if you start putting mains pressure through them leading to damage to the property. You could try to see if the existing hot water pipes are ok under mains pressure if it is a real hassle to change it. If it is easy to do I would get the hot water pipes replaced.
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angrysaveruk
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Post by angrysaveruk on Jan 28, 2024 12:11:09 GMT
When I last looked into it, my 25 year old non-condensing boiler seemed only 10% less efficient than a new condensing type. Problem is the new ones are a lot more complex, go wrong regularly, have lots of plastic parts and only last 7 or 8 years. My boiler rarely goes wrong and when it does its one of 5 things that are easily fixed. I agree that the old Boilers are much more reliable - 20 to 30 years of life is normal and if they go wrong, they can easily be fixed. Mine must be 20+ years as the house was built around 2000. In the last 13 years, I have had to change the Diverter Valve and the Pump (also the Programmer, which I replaced myself) - the most common ones that usually go. So, am expecting it to last a few more years now. Hence I'm reluctant to replace it, particularly due to the pipework changes, and the associated wall damages. Given the slight increase in efficiency, as experienced by you, I don't think I'll go ahead now.
I actually had to fix our Combi Boiler in the Pandemic - had to replace the pump. Was not exactly rocket science however I was later told by the Bosch engineer that because this is a gas appliance I am not legally meant to do some DIY on it. From what I understand it can invalidate your household insurance etc and lead to problems if you try to sell the property etc. Got him to redo the job to avoid problems. * * - if I had not told him the chances of it ever being noticed is 0% - assuming I installed it correctly and there was not a fire or explosion that was later investigated.
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adrianc
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Post by adrianc on Jan 28, 2024 12:22:37 GMT
I actually had to fix our Combi Boiler in the Pandemic - had to replace the pump. Was not exactly rocket science however I was later told by the Bosch engineer that because this is a gas appliance I am not legally meant to do some DIY on it. From what I understand it can invalidate your household insurance etc and lead to problems if you try to sell the property etc. Got him to redo the job to avoid problems. * * - if I had not told him the chances of it ever being noticed is 0% - assuming I installed it correctly and there was not a fire or explosion that was later investigated. It's not. It's perfectly legal for you to DIY gas work in your own home, so long as you are "competent". It's illegal for you to do it for anybody else, even your own next door neighbour or family, even without charging. Anyway, I presume this was the water pump within the boiler? You weren't working on the gas side at all? Then it's perfectly legal, no caveats.
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spiral
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Post by spiral on Jan 28, 2024 12:31:46 GMT
* - if I had not told him the chances of it ever being noticed is 0% - assuming I installed it correctly and there was not a fire or explosion that was later investigated. Some years ago we had a new kitchen installed. The installation failed its gas pressure decay and after much head scratching from the installers, it turned out the fault was pre existing. It was a gas pipe under the upstairs floorboards that had a 0.5 inch scratch that had been soldered up and installed face down so was not visible. The house was about 15 years old at this point and at some point during that 15 years, the solder had failed and was letting a small amount of gas escape. Not enough to smell but enough to fail the safety test. Presumably the pipework had been installed by a reputable engineer but rather than replace the damaged pipe, they bodged it and installed it in a way that it couldn't be seen.
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angrysaveruk
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Post by angrysaveruk on Jan 28, 2024 13:21:12 GMT
I actually had to fix our Combi Boiler in the Pandemic - had to replace the pump. Was not exactly rocket science however I was later told by the Bosch engineer that because this is a gas appliance I am not legally meant to do some DIY on it. From what I understand it can invalidate your household insurance etc and lead to problems if you try to sell the property etc. Got him to redo the job to avoid problems. * * - if I had not told him the chances of it ever being noticed is 0% - assuming I installed it correctly and there was not a fire or explosion that was later investigated. It's not. It's perfectly legal for you to DIY gas work in your own home, so long as you are "competent". It's illegal for you to do it for anybody else, even your own next door neighbour or family, even without charging. Anyway, I presume this was the water pump within the boiler? You weren't working on the gas side at all? Then it's perfectly legal, no caveats. I looked into it at the time and concluded it was a bit of a minefield. You say it is perfectly legal I would say you could easily fall foul of "The Gas Safety (Installation and Use) Regulations 1998" especially if there is a fire/explosion and he insurer tries to get out of it after inspecting the boiler. Some points from the Regulation: "If you’re not a gas professional or a Gas Safe engineer, then servicing your own boiler is illegal under The Gas Safety (Installation and Use) Regulations 1998." This includes: "Maintaining, servicing, permanently adjusting, disconnecting, repairing, altering, renewing fittings or purging them of gas or air" is prohibited. I would say changing the pump of a gas combi boiler probably comes under repairing the unit. I would not want to have to call you in as an expert witness to argue it in court if my house had been burnt down and the insurer had found out I had been dismantling the Combi Boiler to repair it.
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