Efficiency of old boiler and cracked asbestos flue joint

[LordWest]

Hello,

I live in a conversion with 12 flats and we have communal heating and hot water. We have separate boilers for heating and hot water. The boiler for heating is a Potterton Dimplomat 225 (66Kw), and about 45 years old or more. If you were to take an educated guess, what kind of efficiency do you reckon this boiler would have now? I have attached a photo of the boiler.

Also, the boiler flue joint is made of cement asbestos (Chrysotile) and the joint seems to have some cracks. Woudl this itself be a reason to get rid of the boiler and put a different flue?

 

[Chuck]

Not 100% sure, but the Diplomat C225/66 BE, which I think is similar to the model you have, needed a natural gas input of 88kW to deliver 66kW, so 75% transfer. IIRC, that's not bad for boilers of that era.

Some of 25% 'lost' heat will be discharged into the room containing the boiler so the 'efficiency' could be slightly above 75% if this contributes useful heat inside the thermal envelope of the building.

I think that flue will need someone qualified to inspect it and advise whether repair is feasible.

 

[Gasmk1]

most of the parts are obsolete for these boier i dont think you can get the flue way seals they were a service item came indiviualy on a card sealed in with heat shrink, as said you need a gas safe engineer to check the flue and if repairabale he will know what to do, the flue needs sealing at the boiler hood also, but these boilers were old when i started as an apprentice in 1973 so its over 60 years old also no case fitted which makes it even more of a fire risk as anything can get blown into the burner. also is the ventilation up to standard. i am asssuming its in a school cellar or church hall or largish detatched house.

 

[centralheatking]

I consider you are near the end of the line with this old faithful. I assume the 12 properties are all shareholders in a limited company or is the freehold with a 3rd party. Most set ups like this have a
‘Sinking Fund’ topped up in various ways for maintenance and capital projects. I would start looking for a decent sized outfit to carry out all the remedial work, no domestic fellas. Dodd Group are nationwide and would gobble this up..especially if it can be specified late spring summer.
6kw per flat for what might be an elderly building is below standards. If you are a dir it might be a good way to put it to the others. Let us know how you get on. Def NO Combi boilers don’t not get railroaded by in experienced cowboys. Centralheatking

 

[LordWest]

Not 100% sure, but the Diplomat C225/66 BE, which I think is similar to the model you have, needed a natural gas input of 88kW to deliver 66kW, so 75% transfer. IIRC, that's not bad for boilers of that era.

Some of 25% 'lost' heat will be discharged into the room containing the boiler so the 'efficiency' could be slightly above 75% if this contributes useful heat inside the thermal envelope of the building.

I think that flue will need someone qualified to inspect it and advise whether repair is feasible.

Chuck, thanks for the reply. If a replacement boiler is classed 64KW, such as the Vaillant ecoTEC 64kW, is that input or output?
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most of the parts are obsolete for these boier i dont think you can get the flue way seals they were a service item came indiviualy on a card sealed in with heat shrink, as said you need a Registered Gas Engineer to check the flue and if repairabale he will know what to do, the flue needs sealing at the boiler hood also, but these boilers were old when i started as an apprentice in 1973 so its over 60 years old also no case fitted which makes it even more of a fire risk as anything can get blown into the burner. also is the ventilation up to standard. i am asssuming its in a school cellar or church hall or largish detatched house.

Gasmk1, thanks for he reply. We will look into the ventiliation. The boiler is for the communal heating of a residential block (two converted terrace houses) and services 12 flats.
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I consider you are near the end of the line with this old faithful. I assume the 12 properties are all shareholders in a limited company or is the freehold with a 3rd party. Most set ups like this have a
‘Sinking Fund’ topped up in various ways for maintenance and capital projects. I would start looking for a decent sized outfit to carry out all the remedial work, no domestic fellas. Dodd Group are nationwide and would gobble this up..especially if it can be specified late spring summer.
6kw per flat for what might be an elderly building is below standards. If you are a dir it might be a good way to put it to the others. Let us know how you get on. Def NO Combi boilers don’t not get railroaded by in experienced cowboys. Centralheatking

centralheatking thanks for the reply. Most of the leaseholders own the freehold, and I am one of the directors of the freehold. And, yes, we do have a reserve fund. I am sure that this project woudl be suitable for the Dood Group, but they mostly deal with very large properties, and most importantly their closest office to us is 1 1/2 hours away. Smaller local companies that deal with commercial boilers will be more flexible with pricing and servicing.

 

[Chuck]

Chuck, thanks for the reply. If a replacement boiler is classed 64KW, such as the Vaillant ecoTEC 64kW, is that input or output?

That's the maximum output. It does depend somewhat, however, on the installation and mode of operation as you can see from the specification sheet:

https://www.vaillant.co.uk/downloads/aproducts/ecotec-plus-48-64kw/ecotec-plus-tech-sheet-1-8-web-1205237.pdf

Your installer should do a proper energy loss calculation for the building and will be able to advise on the correct size of boiler(s). It might, for example make sense to have a pair of 32kW boilers (instead of a single 64kW one) and some clever controls to make sure that they are operate at maximum efficiency and reliability. This is why you want a commercial rather than domestic installer; you want someone used to considering the heating and HW requirements for the whole building as a complete system rather than a collection of individual parts.

 

[LordWest]

That's the maximum output. It does depend somewhat, however, on the installation and mode of operation as you can see from the specification sheet:

https://www.vaillant.co.uk/downloads/aproducts/ecotec-plus-48-64kw/ecotec-plus-tech-sheet-1-8-web-1205237.pdf

Your installer should do a proper energy loss calculation for the building and will be able to advise on the correct size of boiler(s). It might, for example make sense to have a pair of 32kW boilers (instead of a single 64kW one) and some clever controls to make sure that they are operate at maximum efficiency and reliability. This is why you want a commercial rather than domestic installer; you want someone used to considering the heating and HW requirements for the whole building as a complete system rather than a collection of individual parts.

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.

 

[king of pipes]

Like to see the service record for this one chaps long over due a upgrade i would say

 

[oz-plumber]

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.

 

[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
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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