Efficiency of old boiler and cracked asbestos flue joint

[LordWest]

For peace of mind, what ever you replace that boiler with will have a lifespan of @ 10 years.
So it might be worth increasing the 'slush fund' after the new boiler is installed.

Put some heat shrink around the flue joints and put a couple of coats of paint on the flue and the boiler will probably still be there in 30 years.

The existing boiler (which is used only for the communal heating of 12 flats) may last another 30 years, but it will cost us dearly in gas bills. The input of this 66kW boiler is 286K BTU and output is 225K BTU, meaning that when new is has an efficiency of 78%. Given that this is a 50-year old boiler, my guess is that it would have lost another 10% in efficiencies, though I would be interested in getting some feedback on this. In addition, unlike modern boilers, this one does not have any modulation controls, and thus we are losing some efficiencies there as well. All in all, I think that with a high quality boiler (such as the Worcester GB162 65kW or Vaillant ecoTEC 64kW, either about £2.5K incl VAT) we will use about 30% less gas than before. Given that this boiler costs about £6K a year in gas, we should be able to roughly save £2K per year with a new boiler. Even if we were to replace the new boiler in 10 years, we would have saved at least £10K, and this is after incoporating the costs of new boiler, instalations and improvements, etc. Does this make sense?

 

[Gasmk1]

to be honest a new boiler/boilers is the way to go but i would keep the two systems separate that is the new boilers have there own loop through a plate heat exchanger make that side sealed and the heating side can be kept as open vent thus not putting any undue stress on the old system by make it sealed and pressurised. using one of these Plate Heat Exchangers - https://www.systemlink.ie/plate-heat-exchangers.html

 

[centralheatking]

The existing boiler (which is used only for the communal heating of 12 flats) may last another 30 years, but it will cost us dearly in gas bills. The input of this 66kW boiler is 286K BTU and output is 225K BTU, meaning that when new is has an efficiency of 78%. Given that this is a 50-year old boiler, my guess is that it would have lost another 10% in efficiencies, though I would be interested in getting some feedback on this. In addition, unlike modern boilers, this one does not have any modulation controls, and thus we are losing some efficiencies there as well. All in all, I think that with a high quality boiler (such as the Worcester GB162 65kW or Vaillant ecoTEC 64kW, either about £2.5K incl VAT) we will use about 30% less gas than before. Given that this boiler costs about £6K a year in gas, we should be able to roughly save £2K per year with a new boiler. Even if we were to replace the new boiler in 10 years, we would have saved at least £10K, and this is after incoporating the costs of new boiler, instalations and improvements, etc. Does this make sense?

Your logic is fine, against the old girl you will get your money back finestyle. Chk
[automerge]1581345096[/automerge]

ok thanks. This boiler is only for heating. We have a different boiler for hot water. We recently replaced the hot water boiler with a Worcester Bosch Greenstar 30kW boiler.

Put up which area you are in there are outfits on here quite capable of this ...just stick a post code up
We don’t fit anymore just design stuff for high volume plumbing and heating sales ...but I know and like your project CHK

 

[LordWest]

Your logic is fine, against the old girl you will get your money back finestyle. Chk
[automerge]1581345096[/automerge]

Put up which area you are in there are outfits on here quite capable of this ...just stick a post code up
We don’t fit anymore just design stuff for high volume plumbing and heating sales ...but I know and like your project CHK

Sure, area is Paddington, London