Hi All
We're about to get our old back boiler replaced with a system boiler, Ive found an RGI who's been recommended to me by family and he's given us an estimate we're happy with, but although he's made a suggestion, he's left it to me to ultimately decide on the make and size of boiler.
Regarding output, his recommendation is to over-size so there's always enough power at full demand, saying that it will modulate when there's less demand so there's no real problem with it being too big. I can understand this logic but I'm still worried the recommendation is overkill, even taking this into account and Im worried it may not modulate low enough to maintain maximum efficiency if its grossly oversize.
We have an 8m x 8m 3 bed semi with recently built 5m x 2.5m single storey extension, we've got partial cavity wall insulation (couldnt do it all due to tiles on the 1st floor front/rear walls), well insulated loft and ~20 year old UPVC double glazing. We have 9 radiators (all fairly large for the room size) and one indirect hot water cylinder.
Using the whole house calculator with slightly conservative inputs such as saying no cavity wall insulation at all, it gives me a figure of 11Kw output, yet I'm being recommended to go for a 24Kw or 28Kw boiler, over double what the sedbuk website suggests. For comparison I think our existing boiler is 45,000BTU (13Kw?) and it seems to heat the house OK, so I was thinking more like an Ecotec 618 so it could modulate down to around 7kw if needed?
Your thoughts and comments on the technical aspects and the suitability of each of the options would be most appreciated, thanks in advance.
We're about to get our old back boiler replaced with a system boiler, Ive found an RGI who's been recommended to me by family and he's given us an estimate we're happy with, but although he's made a suggestion, he's left it to me to ultimately decide on the make and size of boiler.
Regarding output, his recommendation is to over-size so there's always enough power at full demand, saying that it will modulate when there's less demand so there's no real problem with it being too big. I can understand this logic but I'm still worried the recommendation is overkill, even taking this into account and Im worried it may not modulate low enough to maintain maximum efficiency if its grossly oversize.
We have an 8m x 8m 3 bed semi with recently built 5m x 2.5m single storey extension, we've got partial cavity wall insulation (couldnt do it all due to tiles on the 1st floor front/rear walls), well insulated loft and ~20 year old UPVC double glazing. We have 9 radiators (all fairly large for the room size) and one indirect hot water cylinder.
Using the whole house calculator with slightly conservative inputs such as saying no cavity wall insulation at all, it gives me a figure of 11Kw output, yet I'm being recommended to go for a 24Kw or 28Kw boiler, over double what the sedbuk website suggests. For comparison I think our existing boiler is 45,000BTU (13Kw?) and it seems to heat the house OK, so I was thinking more like an Ecotec 618 so it could modulate down to around 7kw if needed?
Your thoughts and comments on the technical aspects and the suitability of each of the options would be most appreciated, thanks in advance.