Disadvantage of bigger boiler
Discussion
Hi, we are replacing our conventional boiler with system Boiler. Builder has suggested Valliant 30kw boiler however offered an option for one size bigger with 35kw.
Its will be a 4 bed house with 2 bathrooms and 10 or 11 radiators. There is an off we may extend the house in ground floor in future. But irrespective of this is there any disadvantage of going with bigger boiler (cost difference is not significant). Boiler obviously consumes more gas but hopefully with a shorter running time relative to smaller boiler.
Modern boilers in general seem to have good modulation range so I am tempted to upgrade just in case!
Thanks for reading my post.
Its will be a 4 bed house with 2 bathrooms and 10 or 11 radiators. There is an off we may extend the house in ground floor in future. But irrespective of this is there any disadvantage of going with bigger boiler (cost difference is not significant). Boiler obviously consumes more gas but hopefully with a shorter running time relative to smaller boiler.
Modern boilers in general seem to have good modulation range so I am tempted to upgrade just in case!
Thanks for reading my post.
I'm in a 1960's 4 bed detached dormer bungalow, EPC E.
We recently switched from a 25 year old oil system boiler, rated at 15 kW. We now have a 6kW heat pump.
Heatloss calcs done before the heatpump install suggested we needed 5.7kW at minus 2 degrees.
The 6kW heatpump is actually too much. A 4kW unit would've coped on the coldest day so far (below zero degrees for more than 24 hours).
We recently switched from a 25 year old oil system boiler, rated at 15 kW. We now have a 6kW heat pump.
Heatloss calcs done before the heatpump install suggested we needed 5.7kW at minus 2 degrees.
The 6kW heatpump is actually too much. A 4kW unit would've coped on the coldest day so far (below zero degrees for more than 24 hours).
A 30kW boiler should be plenty.
It should be able to re-heat the HW tank faster than two showers can use the water.
Heating wise, the most I've ever managed to use is about 8kW continuous averaged over 3 extremely cold windy days when visiting aged inlaws wanted the place at 23 degrees.
30kW is over £50 of gas per day!
Is a lot of fair sized radiators too hot to touch.
It can be helpful to have a fast warm-up, but that carries a risk of temperatures over shooting.
30 and 35 kW are not very different. Do any other features or parameters make a difference?
It should be able to re-heat the HW tank faster than two showers can use the water.
Heating wise, the most I've ever managed to use is about 8kW continuous averaged over 3 extremely cold windy days when visiting aged inlaws wanted the place at 23 degrees.
30kW is over £50 of gas per day!
Is a lot of fair sized radiators too hot to touch.
It can be helpful to have a fast warm-up, but that carries a risk of temperatures over shooting.
30 and 35 kW are not very different. Do any other features or parameters make a difference?
xyz123 said:
Hi, we are replacing our conventional boiler with system Boiler. Builder has suggested Valliant 30kw boiler however offered an option for one size bigger with 35kw.
Its will be a 4 bed house with 2 bathrooms and 10 or 11 radiators. There is an off we may extend the house in ground floor in future. But irrespective of this is there any disadvantage of going with bigger boiler (cost difference is not significant). Boiler obviously consumes more gas but hopefully with a shorter running time relative to smaller boiler.
Modern boilers in general seem to have good modulation range so I am tempted to upgrade just in case!
Thanks for reading my post.
I get that if a boiler has a the same modulation range as a smaller one upsizing might not be a problem if you oversize the boiler and the CH circuit can't take move that much energy away from the boiler it's not going to be any advantage to oversize. In the warm up phase the boiler will just put in what it can so you are just spending money that isn't going to give any benefit.Its will be a 4 bed house with 2 bathrooms and 10 or 11 radiators. There is an off we may extend the house in ground floor in future. But irrespective of this is there any disadvantage of going with bigger boiler (cost difference is not significant). Boiler obviously consumes more gas but hopefully with a shorter running time relative to smaller boiler.
Modern boilers in general seem to have good modulation range so I am tempted to upgrade just in case!
Thanks for reading my post.
1980's 4 bed (extended) 13 rads - boiler is 16kW I only need 4 kWh absolute max at -2 Deg C (Heat loss said 4.7 kWh at -2.4 Deg C) I was going to get the 11kW version but that can't be range rated down like the 16kW one can
Other issue is 35 kW boiler may need a gas pipe upgrade from 15mm to 22mm where a 30kW can cope with 15mm gas feed (provided it's not a huge distance from the meter)
35 kw is way to big, hot water times will be rated by the cylinder coil not the boiler.
Back calculate your radiator sizes and then add some for your possible extension.
You will be able to alter the kw output of the boiler in its software.
Probably best advice I could give it to not let your builder have anything to do with your heating system.
Get a local independent heating company out that will service and maintain it long after the builder has gone
Ss
Back calculate your radiator sizes and then add some for your possible extension.
You will be able to alter the kw output of the boiler in its software.
Probably best advice I could give it to not let your builder have anything to do with your heating system.
Get a local independent heating company out that will service and maintain it long after the builder has gone
Ss
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