New boiler?

pensionpawn

km1500 said:

Don't forget to factor in that you will need it serviced every year without fail (or obvs. according to manufacturer requirements) in order to preserve the warranty - no skipping servicing!

Also factor in the cost of flushing etc your radiators.

A system clean should be included in the cost of a new boiler, however justmake sure that they do it.... Yes, servicing is mandatory during the warranty period otherwise the warranty lapses, just like cars etc....

[Deleted User]

Prior to the introduction of condensing boilers, central heating systems when set up for a 80C flow and 68C return: that is, a 12C temperature differential. Condensing boilers should be set up for a 20C flow to return differential. It is important therefore to consider the size of the radiators. To put it another way, your existing radiator area may be too small for a condensing boiler.

Why does this matter? If the new boiler is just bolted onto the existing system and a flow temperature of, say, 70C is set, then the temperature of the returning water may be above the condensing temperature of 56C negating one of the key benefits of a condensing boiler. The lower of return temperature the greater the efficiency of a condensing boiler.

pensionpawn

Dolor said:

Prior to the introduction of condensing boilers, central heating systems when set up for a 80C flow and 68C return: that is, a 12C temperature differential. Condensing boilers should be set up for a 20C flow to return differential. It is important therefore to consider the size of the radiators. To put it another way, your existing radiator area may be too small for a condensing boiler.

Why does this matter? If the new boiler is just bolted onto the existing system and a flow temperature of, say, 70C is set, then the temperature of the returning water may be above the condensing temperature of 56C negating one of the key benefits of a condensing boiler. The lower of return temperature the greater the efficiency of a condensing boiler.

I had a new Viessmann 100W (19kW internal pump) installed (4 bed detached) last October and it was left at 82c by the installers. They did a competent physical job however their knowledge of "optimising" a condensing system, along with a brand new Nest system to replace the old mechanical thermostat, left a lot to be desired. The radiators were dangerously hot. So by using this energy thread (and your graph above) to improve my knowledge of modern heating systems I explored the functionality of my new boiler (and Nest) steadily reducing the flow temperature and observing the effects (with Nest effectively re profiling each time) etc before eventually setting on a flow of 62c for Legionella purposes (water and heating share temperature control). Now my Viessmann can report operational data to their app on my phone via Wifi and although when it starts up the flow / flew temperature can be 10c-15c difference, by the time it settles at 62c the flew is reporting around 53c-55c. It also modulates down to 10% This is already significantly reducing my gas usage as since install the c/h has been set to 21c, 7 days a week (12c 11pm - 06:30am), as my wife retired last August and is home all the time now, and we're experiencing no increase in gas consumption and occasionally seeing a small reduction.

So what I am building up to is the how to get the flew (return) temperature further into the condensing zone. Now I get what you're saying about radiator sizing (and other discussion threads about the radiator size / flow temperature combination being insufficient to warm the room(s) resulting in the boiler chasing its tail) however there is an economic balance to be struct between the cost of replacing old radiators to achieve a few extra percent efficiency. Have you done the analysis of the gas consumption reduction returns against the capital cost of new radiators, and the length of consumption required to see a RoI? Are there any other tweaks that can be done without incurring further cost? I have (very old TRVs) however as all rooms are used daily I see no reason to replace them, at least until Nest release an equivalent system to Tado etc, which may prove worth while. Thanks.

inspectorperez

pensionpawn said:

Dolor said:

Prior to the introduction of condensing boilers, central heating systems when set up for a 80C flow and 68C return: that is, a 12C temperature differential. Condensing boilers should be set up for a 20C flow to return differential. It is important therefore to consider the size of the radiators. To put it another way, your existing radiator area may be too small for a condensing boiler.

Why does this matter? If the new boiler is just bolted onto the existing system and a flow temperature of, say, 70C is set, then the temperature of the returning water may be above the condensing temperature of 56C negating one of the key benefits of a condensing boiler. The lower of return temperature the greater the efficiency of a condensing boiler.

I had a new Viessmann 100W (19kW internal pump) installed (4 bed detached) last October and it was left at 82c by the installers. They did a competent physical job however their knowledge of "optimising" a condensing system, along with a brand new Nest system to replace the old mechanical thermostat, left a lot to be desired. The radiators were dangerously hot. So by using this energy thread (and your graph above) to improve my knowledge of modern heating systems I explored the functionality of my new boiler (and Nest) steadily reducing the flow temperature and observing the effects (with Nest effectively re profiling each time) etc before eventually setting on a flow of 62c for Legionella purposes (water and heating share temperature control). Now my Viessmann can report operational data to their app on my phone via Wifi and although when it starts up the flow / flew temperature can be 10c-15c difference, by the time it settles at 62c the flew is reporting around 53c-55c. It also modulates down to 10% This is already significantly reducing my gas usage as since install the c/h has been set to 21c, 7 days a week (12c 11pm - 06:30am), as my wife retired last August and is home all the time now, and we're experiencing no increase in gas consumption and occasionally seeing a small reduction.

So what I am building up to is the how to get the flew (return) temperature further into the condensing zone. Now I get what you're saying about radiator sizing (and other discussion threads about the radiator size / flow temperature combination being insufficient to warm the room(s) resulting in the boiler chasing its tail) however there is an economic balance to be struct between the cost of replacing old radiators to achieve a few extra percent efficiency. Have you done the analysis of the gas consumption reduction returns against the capital cost of new radiators, and the length of consumption required to see a RoI? Are there any other tweaks that can be done without incurring further cost? I have (very old TRVs) however as all rooms are used daily I see no reason to replace them, at least until Nest release an equivalent system to Tado etc, which may prove worth while. Thanks.

Hope you don't mind me butting in on this very interesting thread.

My Potterton Apollo Myson boiler is now 35 years old and still going strong. New thermocouple every so often and annual service is all that it ever seems to need! I appreciate that this cannot go on forever and have seen a number of people recommend the Viessmann boiler in terms of good design and reliability. From my own research however it does seem that the number of installers is limited inasmuch as they are all affiliated to Viessmann in some way presumably by means of authorisation having trained on that particular product.

This suggests that the installation cost and subsequent servicing might be more of an issue particularly if the provider is located some distance from where you live? I know our own independent gas engineer would probably charge in the region of £1500 to £2000 for say a Baxi or WB boiler

My other thought is that based on an annual typical gas consumption of 16,000KW, I wonder what the equivalent would be using a new modern Viessmann product?

Would appreciate any observations that might guide me in this deliberation.

FreeBear

inspectorperez said: My Potterton Apollo Myson boiler is now 35 years old and still going strong.

My other thought is that based on an annual typical gas consumption of 16,000KW, I wonder what the equivalent would be using a new modern Viessmann product?

I'm assuming the Potterton has a pilot light on 24/7  If that is the case, there is a significant saving to be had by replacing the old boiler with a modern one. Doing away with the pilot light will save ~1500KWh over the course of a year on its own. A condensing boiler could save another 25-40% depending on how it is set up. You may well want to fit larger radiators so that you can run at a lower flow temperature (more cost though).

inspectorperez

FreeBear said:

inspectorperez said: My Potterton Apollo Myson boiler is now 35 years old and still going strong.

My other thought is that based on an annual typical gas consumption of 16,000KW, I wonder what the equivalent would be using a new modern Viessmann product?

I'm assuming the Potterton has a pilot light on 24/7  If that is the case, there is a significant saving to be had by replacing the old boiler with a modern one. Doing away with the pilot light will save ~1500KWh over the course of a year on its own. A condensing boiler could save another 25-40% depending on how it is set up. You may well want to fit larger radiators so that you can run at a lower flow temperature (more cost though).

WOW!

I literally had no idea. Never use the boiler between April and October using solar and electric combination for hot water, so that is a no brainer to turn off the gas for those months.

pensionpawn

inspectorperez said:

pensionpawn said:

Dolor said:

Prior to the introduction of condensing boilers, central heating systems when set up for a 80C flow and 68C return: that is, a 12C temperature differential. Condensing boilers should be set up for a 20C flow to return differential. It is important therefore to consider the size of the radiators. To put it another way, your existing radiator area may be too small for a condensing boiler.

Why does this matter? If the new boiler is just bolted onto the existing system and a flow temperature of, say, 70C is set, then the temperature of the returning water may be above the condensing temperature of 56C negating one of the key benefits of a condensing boiler. The lower of return temperature the greater the efficiency of a condensing boiler.

I had a new Viessmann 100W (19kW internal pump) installed (4 bed detached) last October and it was left at 82c by the installers. They did a competent physical job however their knowledge of "optimising" a condensing system, along with a brand new Nest system to replace the old mechanical thermostat, left a lot to be desired. The radiators were dangerously hot. So by using this energy thread (and your graph above) to improve my knowledge of modern heating systems I explored the functionality of my new boiler (and Nest) steadily reducing the flow temperature and observing the effects (with Nest effectively re profiling each time) etc before eventually setting on a flow of 62c for Legionella purposes (water and heating share temperature control). Now my Viessmann can report operational data to their app on my phone via Wifi and although when it starts up the flow / flew temperature can be 10c-15c difference, by the time it settles at 62c the flew is reporting around 53c-55c. It also modulates down to 10% This is already significantly reducing my gas usage as since install the c/h has been set to 21c, 7 days a week (12c 11pm - 06:30am), as my wife retired last August and is home all the time now, and we're experiencing no increase in gas consumption and occasionally seeing a small reduction.

So what I am building up to is the how to get the flew (return) temperature further into the condensing zone. Now I get what you're saying about radiator sizing (and other discussion threads about the radiator size / flow temperature combination being insufficient to warm the room(s) resulting in the boiler chasing its tail) however there is an economic balance to be struct between the cost of replacing old radiators to achieve a few extra percent efficiency. Have you done the analysis of the gas consumption reduction returns against the capital cost of new radiators, and the length of consumption required to see a RoI? Are there any other tweaks that can be done without incurring further cost? I have (very old TRVs) however as all rooms are used daily I see no reason to replace them, at least until Nest release an equivalent system to Tado etc, which may prove worth while. Thanks.

Hope you don't mind me butting in on this very interesting thread.

My Potterton Apollo Myson boiler is now 35 years old and still going strong. New thermocouple every so often and annual service is all that it ever seems to need! I appreciate that this cannot go on forever and have seen a number of people recommend the Viessmann boiler in terms of good design and reliability. From my own research however it does seem that the number of installers is limited inasmuch as they are all affiliated to Viessmann in some way presumably by means of authorisation having trained on that particular product.

This suggests that the installation cost and subsequent servicing might be more of an issue particularly if the provider is located some distance from where you live? I know our own independent gas engineer would probably charge in the region of £1500 to £2000 for say a Baxi or WB boiler

My other thought is that based on an annual typical gas consumption of 16,000KW, I wonder what the equivalent would be using a new modern Viessmann product?

Would appreciate any observations that might guide me in this deliberation.

A new condensing boiler should halve the consumption of a 35 year old boiler, under the same conditions. Given that gas is at an all time high, it could pay for itself, at your current consumption, in 5 years give or take a couple of years. The cost should be in the range £3k - £3k5 if it's a quality brand model, like for like location etc.

macman

inspectorperez said:

FreeBear said:

inspectorperez said: My Potterton Apollo Myson boiler is now 35 years old and still going strong.

My other thought is that based on an annual typical gas consumption of 16,000KW, I wonder what the equivalent would be using a new modern Viessmann product?

I'm assuming the Potterton has a pilot light on 24/7  If that is the case, there is a significant saving to be had by replacing the old boiler with a modern one. Doing away with the pilot light will save ~1500KWh over the course of a year on its own. A condensing boiler could save another 25-40% depending on how it is set up. You may well want to fit larger radiators so that you can run at a lower flow temperature (more cost though).

WOW!

I literally had no idea. Never use the boiler between April and October using solar and electric combination for hot water, so that is a no brainer to turn off the gas for those months.

It's a no-brainer to use the gas boiler to provide the hot water all year round, at less than a third of the cost of electricity. This assumes that you can still dump solar-derived hot water into the cylinder anyway. 
Just use the immersion for an emergency back-up
Or is this is solar PV system, rather than solar hot water, wired to divert the surplus output into the immersion heater when necessary?

inspectorperez

macman said:

inspectorperez said:

FreeBear said:

inspectorperez said: My Potterton Apollo Myson boiler is now 35 years old and still going strong.

My other thought is that based on an annual typical gas consumption of 16,000KW, I wonder what the equivalent would be using a new modern Viessmann product?

I'm assuming the Potterton has a pilot light on 24/7  If that is the case, there is a significant saving to be had by replacing the old boiler with a modern one. Doing away with the pilot light will save ~1500KWh over the course of a year on its own. A condensing boiler could save another 25-40% depending on how it is set up. You may well want to fit larger radiators so that you can run at a lower flow temperature (more cost though).

WOW!

I literally had no idea. Never use the boiler between April and October using solar and electric combination for hot water, so that is a no brainer to turn off the gas for those months.

It's a no-brainer to use the gas boiler to provide the hot water all year round, at less than a third of the cost of electricity. This assumes that you can still dump solar-derived hot water into the cylinder anyway. 
Just use the immersion for an emergency back-up
Or is this is solar PV system, rather than solar hot water, wired to divert the surplus output into the immersion heater when necessary?

Yes, the latter.

Average solar harvest from our system is 14-16Kw per day with average electric consumption circa 10 Kw per day in summer months.

There is probably still an economic case to replace the boiler which is why I interrupted this thread as it related to the Veissmann model I am interested in, although still very surprised to learn how much gas a typical pilot light uses in a dinosaur boiler.

pensionpawn

inspectorperez said:

macman said:

inspectorperez said:

FreeBear said:

inspectorperez said: My Potterton Apollo Myson boiler is now 35 years old and still going strong.

My other thought is that based on an annual typical gas consumption of 16,000KW, I wonder what the equivalent would be using a new modern Viessmann product?

I'm assuming the Potterton has a pilot light on 24/7  If that is the case, there is a significant saving to be had by replacing the old boiler with a modern one. Doing away with the pilot light will save ~1500KWh over the course of a year on its own. A condensing boiler could save another 25-40% depending on how it is set up. You may well want to fit larger radiators so that you can run at a lower flow temperature (more cost though).

WOW!

I literally had no idea. Never use the boiler between April and October using solar and electric combination for hot water, so that is a no brainer to turn off the gas for those months.

It's a no-brainer to use the gas boiler to provide the hot water all year round, at less than a third of the cost of electricity. This assumes that you can still dump solar-derived hot water into the cylinder anyway. 
Just use the immersion for an emergency back-up
Or is this is solar PV system, rather than solar hot water, wired to divert the surplus output into the immersion heater when necessary?

Yes, the latter.

Average solar harvest from our system is 14-16Kw per day with average electric consumption circa 10 Kw per day in summer months.

There is probably still an economic case to replace the boiler which is why I interrupted this thread as it related to the Veissmann model I am interested in, although still very surprised to learn how much gas a typical pilot light uses in a dinosaur boiler.

Same here. No central heating required May - Oct inc (as we also have electric UFH across 2/3s of the ground floor) and (Immersun) solar divert heats the water for washing, showers etc. Gas only required November - April inc for central heating and heating water to 60c with solar divert increasing water to 80c. That said we still changed the boiler as with spending more time at home and increasing tariffs, we'll recuperate the capital cost in minimal time. Looking next to increase the size of the HW tank to store more (free, most of the year) hot water and also use this as a thermal store to minimise gas for C/H in Oct - Nov and Feb - April. Out of interest today I diverted 6.5 kWhrs into the H/W tank / under floor heating. The main reason for choosing a Viessmann was because its stainless steel boiler works with water softeners, however being H2 ready and modulating down to 10% were also major factors.