Correct sizing for a conventional gas boiler

JaseH

Hi All,

Apologies if this is posted in the wrong area. I'm new to posting into the forum but have been a reader for some time now.

Me and the other half finally got ourselves onto the property ladder in December and so far it hasn't been the best buy, still enjoying not giving our money away to a landlord though so there are pluses. We are currently staying at my parents house as we have had a leak of Kerosene oil in the kitchen, the insurance contractors have dug the whole kitchen out to the foundations. Anyway, to the point...

After this bad experience with oil, we have arranged for national grid to lay us a pipe to the mains gas (We had planned to do this anyway, just not so soon after moving in) to avoid this happening again and to benefit from the cheaper heating costs. I'm looking for confirmation of what size boiler to buy, I have used the IDHEE.org.uk website and that comes back with 12.71kw which seems really low to me. The house is a reasonable sized 1980's 4 bed detached with cavity walls which aren't filled, decent insulation in the loft. We have just replaced all the windows and doors so everything is A rated. I think we have 12 radiators of varying sizes and an old tank in the attic for the hot water (something which I'm unsure about replacing, looking at the newer unvented tanks but am not to sure about the pressure through the pipework becoming an issue. This won't be done until at least the summer though).

I have been looking at a Vaillant EcoTEC Plus 418 Regular Boiler, would this do the job or is it, as the IDHEE suggest, oversized? Also, will it be capable of filling the hot water tank and possibly handle the upgrade to the tank.

Finally, is the market worth my while trying to sell the redundant oil boiler. I have been told that it is fairly new and working at a very good efficiency for a non-condenser. Possibly a Firebird?

Many Thanks in advance for any helpful replies!!!!

Canucklehead

JaseH wrote: »

Hi All,

Apologies if this is posted in the wrong area. I'm new to posting into the forum but have been a reader for some time now.

Me and the other half finally got ourselves onto the property ladder in December and so far it hasn't been the best buy, still enjoying not giving our money away to a landlord though so there are pluses. We are currently staying at my parents house as we have had a leak of Kerosene oil in the kitchen, the insurance contractors have dug the whole kitchen out to the foundations. Anyway, to the point...

After this bad experience with oil, we have arranged for national grid to lay us a pipe to the mains gas (We had planned to do this anyway, just not so soon after moving in) to avoid this happening again and to benefit from the cheaper heating costs. I'm looking for confirmation of what size boiler to buy, I have used the IDHEE.org.uk website and that comes back with 12.71kw which seems really low to me. The house is a reasonable sized 1980's 4 bed detached with cavity walls which aren't filled, decent insulation in the loft. We have just replaced all the windows and doors so everything is A rated. I think we have 12 radiators of varying sizes and an old tank in the attic for the hot water (something which I'm unsure about replacing, looking at the newer unvented tanks but am not to sure about the pressure through the pipework becoming an issue. This won't be done until at least the summer though).

I have been looking at a Vaillant EcoTEC Plus 418 Regular Boiler, would this do the job or is it, as the IDHEE suggest, oversized? Also, will it be capable of filling the hot water tank and possibly handle the upgrade to the tank.

Finally, is the market worth my while trying to sell the redundant oil boiler. I have been told that it is fairly new and working at a very good efficiency for a non-condenser. Possibly a Firebird?

Many Thanks in advance for any helpful replies!!!!

Hi: get in a RGI recommended to you by a source you trust to conduct a site survey, discuss your requirements and quote on the job. Alternatively, try the Vaillant search facility here.

I would recommend the Vaillant 600 series (system boiler) over the 400 series and if you have sufficient mains water pressure/flow, a Vaillant Unistor unvented cylinder.

More advice available here.

Let us know how you get on.

Canucklehead

JaseH

Canucklehead wrote: »

Hi: get in a RGI recommended to you by a source you trust to conduct a site survey, discuss your requirements and quote on the job. Alternatively, try the Vaillant search facility

I would recommend the Vaillant 600 series (system boiler) over the 400 series and if you have sufficient mains water pressure/flow, a Vaillant Unistor unvented cylinder.

Let us know how you get on.

Canucklehead

Thank you for the advice, I will check out the links tonight. I was originally interested in getting the 600 system boiler but some of the stuff I've read has made me cautious with introducing pressure to 30+ year old pipework.

I'm taking advantage of the current situation with my current boiler being removed by the contractors. They have kindly agreed to do the installation as part of the insurance works, as a boiler has to go back in. Would a system boiler require much more work than a like for like swap of a conventional boiler?

This also makes it more difficult for me to get a proper site survey done as I will only be wasting someone's time, knowing full well that the work will be carried out by someone else. Unfortunately, the heating engineer who disconnected my oil boiler will only be returning to install the new boiler which will have to be waiting for him as travelling some distance to do the work.

Canucklehead

JaseH wrote: »

Thank you for the advice, I will check out the links tonight. I was originally interested in getting the 600 system boiler but some of the stuff I've read has made me cautious with introducing pressure to 30+ year old pipework.

I'm taking advantage of the current situation with my current boiler being removed by the contractors. They have kindly agreed to do the installation as part of the insurance works, as a boiler has to go back in. Would a system boiler require much more work than a like for like swap of a conventional boiler?

This also makes it more difficult for me to get a proper site survey done as I will only be wasting someone's time, knowing full well that the work will be carried out by someone else. Unfortunately, the heating engineer who disconnected my oil boiler will only be returning to install the new boiler which will have to be waiting for him as travelling some distance to do the work.

Hmm...don't really follow
..you are getting a freebie install and supplying your own boiler...ask your installer...as said you don't want to be a time waster.

JaseH

Boiler issue resolved now, been in touch with a friend of a friend who has recommended the Vaillant 624 or a Worcester Greenstar 24i. Thank you Canucklehead for the same advice to go down the sealed system route. I've decided on the Vaillant as both are fairly similar price wise and Vaillant seem to be the better company.

Cheapest place I've found so far is PlumbNation but still searching for the best deal. Also buying the VR 65 control centre and VR 392f wireless programmable thermostat. I'm just hoping that the current cable which runs from the old timer (which was sited right next to the old boiler in the kitchen) to the 3 port valve in the airing cupboard will be ok for me to re-use as the link between the control centre (which will be sited in the airing cupboard) and the new boiler.

warmhands.coldheart

JaseH wrote: »

I've decided on the Vaillant as both are fairly similar price wise and Vaillant seem to be the better company.
.

I'm in the proces of changeing over to Gas and Everyone I've spoke to recon Worcester-Bosch are by far the best on the Market!

gas4you

Wouldn't go that far about Worcester.

croninsfc

JaseH wrote: »

Boiler issue resolved now, been in touch with a friend of a friend who has recommended the Vaillant 624 or a Worcester Greenstar 24i. Thank you Canucklehead for the same advice to go down the sealed system route. I've decided on the Vaillant as both are fairly similar price wise and Vaillant seem to be the better company.

Cheapest place I've found so far is PlumbNation but still searching for the best deal. Also buying the VR 65 control centre and VR 392f wireless programmable thermostat. I'm just hoping that the current cable which runs from the old timer (which was sited right next to the old boiler in the kitchen) to the 3 port valve in the airing cupboard will be ok for me to re-use as the link between the control centre (which will be sited in the airing cupboard) and the new boiler.

Hi JaseH
I have recently got a Vaillant 618 boiler and new sealed system HW tank for our property with the VR 65 and 392f controller. You won't need your old timer as the VR392f does everything - timing for both hot water and heating as well as being a room thermostat.
I also had the same concerns about going from vented to sealed regarding old pipework and radiators, but in my case it was no worries. I have not had to use the filling loop at all in nearly 2 months since commissioning as pressures at cold/hot operational has not dropped at all, not even by 0.1 bar.

JaseH

Finally getting somewhere with the works at my house. The removal of all the contaminated materials in the foundations has taken longer than expected.

I have a plumber coming on Monday who has quoted £1295 to install the Vaillant 624 which I have already bought. This includes:

- Installing the boiler in my attic
- A powerflush
- Installing new gas pipes to the attic and connecting to the feed
and return pipes in the airing cupboard
- Spirotech mb3 filter
- Sentinel inhibitor
- Installing heating/water controls (which I have supplied)

This all seemed fairly reasonable when compared to another quote I received who wanted to cut corners by not powerflushing. Also because the plumber I have chosen is recommended by Vaillant, he upgrades the warranty from 2 to 5 years. He even talked me out of having the sealed water tank, at least for the time being anyway, so that saved some money.

Canucklehead

JaseH wrote: »

Finally getting somewhere with the works at my house. The removal of all the contaminated materials in the foundations has taken longer than expected.

I have a plumber coming on Monday who has quoted £1295 to install the Vaillant 624 which I have already bought. This includes:

- Installing the boiler in my attic
- A powerflush
- Installing new gas pipes to the attic and connecting to the feed
and return pipes in the airing cupboard
- Spirotech mb3 filter
- Sentinel inhibitor
- Installing heating/water controls (which I have supplied)

This all seemed fairly reasonable when compared to another quote I received who wanted to cut corners by not powerflushing. Also because the plumber I have chosen is recommended by Vaillant, he upgrades the warranty from 2 to 5 years. He even talked me out of having the sealed water tank, at least for the time being anyway, so that saved some money.

Hi: always great to see an update.

Just curious..does your chosen RGI hold his G3 certification for unvented cylinders? What reasons did he give for not fitting an unvented cylinder other than cost to you? Are you not replacing the existing vented cylinder with a new Part L version? Have you considered the impact of the hot water supply on any bathroom works you might be considering?

Canucklehead

JaseH

Canucklehead, Yes he does hold the relevant qualifications and would happily fit an unvented cylinder. He ran one of the hot taps and said I have fairly decent pressure as it is, getting an unvented tank would definitely improve it but not considerably so, for the amount it would cost to install.

Taking this on board, I'm leaving the hot water as is. Biggest decider is the money situation with all the other stuff going on which I hadn't planned for. I will be getting an unvented cylinder in the near future though, as I do want some work doing on the bathrooms. A decent shower will be a massive gain!