Hi,
After a bit of a saga with my plumber, I need to chose boiler size as soon as possible, the plumber is not going to do any heat loss calculations or do anything to work out accurately so I am on my own. Appreciate this is not what should be doing but after some level of finger in the air guidance. The plumber had said he thinks the baxi 824 (24kw) system boiler is fine for property, annoyingly they don't do a 28 in that range. Could go for a 28kw baxi megaflow but an older boiler with less of a guarantee. There is a Baxi platinum but that only comes in a 32kw model. My preference is for the 824 24kw boiler if can cater for the house (there will be no further additions once renovation is complete).
Here is summary of the house:
1955 detached house with cavity wall insulation, it is 4 bedroom two of which added to new building regs so well insulated. House is not particularly cold in that there is only one room where radiator is on full in winter.
At the end we will have 13 radiators, many of them quite small, have done some calcs and KW of them all seems to add up to on 12kw - seems low as guidance seems to be 1.5kw per rad but a few of them are towel rails and small radiators. Worse case guess would be 16kw.
We will also have 2 zones of under floor heating first zone 1 is 13m squared and second zone 2 is 24m squared using 16mm pipe.
We have 3 showers but 2 electric so only one will be running off tank, did consider combi but would be long way from where water needed and decided on the system approach with unvented tank in centre of house.
We will be going for a 210 litre indirect unvented tank from gledhill - StainlessLite System Ready Indirect | Gledhill - https://www.gledhill.net/products/unvented-cylinders/stainlesslite-system-ready-indirect/, the manual lists the 210 tank having a primary coil rating of 20.5 kw - not sure if reading that correctly as cylinder calculations normally allow 3-5kw.
Another thing that has been mentioned is that the 824 has an integral expansion vessel of 7L - is that enough for 13 radiators of varying sizes (6 are doubles) and the approx 37m squared under floor heating with 16mm pipe ? Seems a lot of people mention fitting a separate expansion vessel but never come across that before with friends systems. The 28 kw and upwards boiler comes with a 10L integral tank.
Any thoughts greatly appreciated.....
Lawrence
After a bit of a saga with my plumber, I need to chose boiler size as soon as possible, the plumber is not going to do any heat loss calculations or do anything to work out accurately so I am on my own. Appreciate this is not what should be doing but after some level of finger in the air guidance. The plumber had said he thinks the baxi 824 (24kw) system boiler is fine for property, annoyingly they don't do a 28 in that range. Could go for a 28kw baxi megaflow but an older boiler with less of a guarantee. There is a Baxi platinum but that only comes in a 32kw model. My preference is for the 824 24kw boiler if can cater for the house (there will be no further additions once renovation is complete).
Here is summary of the house:
1955 detached house with cavity wall insulation, it is 4 bedroom two of which added to new building regs so well insulated. House is not particularly cold in that there is only one room where radiator is on full in winter.
At the end we will have 13 radiators, many of them quite small, have done some calcs and KW of them all seems to add up to on 12kw - seems low as guidance seems to be 1.5kw per rad but a few of them are towel rails and small radiators. Worse case guess would be 16kw.
We will also have 2 zones of under floor heating first zone 1 is 13m squared and second zone 2 is 24m squared using 16mm pipe.
We have 3 showers but 2 electric so only one will be running off tank, did consider combi but would be long way from where water needed and decided on the system approach with unvented tank in centre of house.
We will be going for a 210 litre indirect unvented tank from gledhill - StainlessLite System Ready Indirect | Gledhill - https://www.gledhill.net/products/unvented-cylinders/stainlesslite-system-ready-indirect/, the manual lists the 210 tank having a primary coil rating of 20.5 kw - not sure if reading that correctly as cylinder calculations normally allow 3-5kw.
Another thing that has been mentioned is that the 824 has an integral expansion vessel of 7L - is that enough for 13 radiators of varying sizes (6 are doubles) and the approx 37m squared under floor heating with 16mm pipe ? Seems a lot of people mention fitting a separate expansion vessel but never come across that before with friends systems. The 28 kw and upwards boiler comes with a 10L integral tank.
Any thoughts greatly appreciated.....
Lawrence