Correct sizing for a conventional gas boiler

southcoastrgi

just wondered why he is putting it in the loft ? you will need a frost stat in combination with a low limit pipe stat, a proper light in the loft & it will need to be boarded from the loft hatch to the boiler, because if you haven't & you have a prob under warrentee the service engineer won't even get in the loft to sort it plus if it needs re-setting or you want to alter the boiler stat do you really want to be messing about getting in the loft at 10-30 pm on a freezing cold december eve, just my view of course.

gas4you

A 624 is rather overkill if you rad calcs only came out at around 13 kw.

The 615 or even 618 should suffice and save you money.

Mr_Ted

Probably a bit late for this OP but doesn't anyone actually know the regulation about boiler sizing and the fact that a whole of house calculation is now the way it should be done?
If you do the course you get the knowledge, methodology and the FORMS required!

JaseH

keithgillyon wrote: »

just wondered why he is putting it in the loft ? you will need a frost stat in combination with a low limit pipe stat, a proper light in the loft & it will need to be boarded from the loft hatch to the boiler, because if you haven't & you have a prob under warrentee the service engineer won't even get in the loft to sort it plus if it needs re-setting or you want to alter the boiler stat do you really want to be messing about getting in the loft at 10-30 pm on a freezing cold december eve, just my view of course.

I have already installed a light and boarded it out plus put a loft ladder in, so no trouble at all with access to where the boiler will be. The benefit of having it in the loft is it being out of the way and not being an eyesore on the kitchen wall. It was my choice having it up there and don't all modern boilers have frost protection anyway???

JaseH

gas4you wrote: »

A 624 is rather overkill if you rad calcs only came out at around 13 kw.

The 615 or even 618 should suffice and save you money.

I completely agree, that is the advice I was originally asking for. Unfortunately I got advice from the wrong source

The plumber who is installing the boiler has said that it is oversized. However, because it modulates, will not use any more gas than a smaller sized boiler and won't actually cost any more to run. From that, it would seem I've only lost the extra money it cost to buy the bigger boiler.

gas4you

The installer should range rate the boiler to 15kw.

Then it will only ever go to this at maximum.

The only problem being that Vaillant's run at 75% of maximum output for the first few minutes when they first come on, so you may have problems where it is going to dump the heat

southcoastrgi

JaseH wrote: »

don't all modern boilers have frost protection anyway???

yes you are correct most modern boilers do have frost protection but that is only to protect the boiler it won't protect any of your pipework & if the winters carry on like we have been having then the boiler will be working throughout the night to protect itself wasting your gas even if the heating is switched off, i only pointed out the other things as if you hadn't of done them then you may have been slightly upset when the engineer walked out leaving you freezing cold