Vaillant 824 and big house

[hightower]

We're in the proess of buying a 3 storey house which has a combination of heating sources including a gas aga, wood burner, economy 7 storage heaters and an 824 turbomax combi boiler. Presently, the boiler looks after the hot water and roughly 7 rads split across the 3 floors. There are approx 5 other rooms on the 1st floor (one on the 2nd floor actually) which have economy 7 in, which I want to replace with extra rads. The big question is, is the boiler going to be up to the job? Is there a guideline to how many rads a sealed unit will support, or is it subject to too many variables to give a useful answer? All advice very much appreciated.

Thanks

Rich

[Doctor Evil]

Calculate the total heat loss of the house. Then compare the boiler "output" to your needs. I would find it odd that it does not cope, but maybe your house is very big and hence the two systems. If it falls short, consider extra insulation, double glazing, etc, to reduce heat loss. How many bathrooms, showers, etc?

As the house is big, consider another combi. One doing one zone, maybe the ground floor and the other combi the other floors. Each combi has a Honeywell CM67 programmer/stat with optimisation, so the two are totally independent of each other. In winter the upstairs can be off for most of the day making it far cheaper to run. One combi does one shower, one the other, so one shower does not influence the other. Combine the hot water outlets for only the bath using non-return valves. This is probably the best and most cost effective solution for you, giving you far more than what you have now for little outlay. You will also have backup in case one combi drops out.

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[Ed Sirett]

The radiators would have to be very large on average for the boiler not to support 12 radiators. The boiler has about 24kW output which should be sufficient for a substantially larger than average house.

However I would suggest that for more than 8 radiators you consider having an additional expansion vessel added (see the SealedCH faq).

[hightower]

Ed,

Thanks for the response. As a man in the know, any idea how much I should expect to pay for a trade professional to fit an extra expansion vessel and the extra rads, should I decide not to do it myself?

Cheers

Rich

Ed Sirett wrote:

[hightower]

Doctor Evil (nice name by the way),

I think the existing setup is more to do with the piecemeal installation over a period of time than anything else. The economy 7 was the original heating system, and the combi got added when an extension was built on to the house. I guess they decided to only put rads in the new rooms and leave the storage heaters as they were.

[Doctor Evil]

The combi may well be big enough to heat the whole house. What heat the hot water? Do you have a cylinder? Where does the combi come in? The DHW will need sorting too.

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[hightower]

No cylinder. Mains pressure. Combi currently looks after all 7 rads and all hot water for the house. Basically just wanting to add another 5 rads to it.

Cheers

Rich

[Ed Sirett]

Well the materials using standard modest rads, TRVs of course,pipe, fittings and sundries, would likely be 300-500.

The Labour is in all honesty a bit likely asking how long is a piece of string. House construction. How much making good. How accessible the things are. Where are you? London and SE might be +50% or more on some areas? Layout of the rooms. Where you want the rads. How (in)convenient the existing pipework is. Does the existing have a good 'backbone' in 22 which you can T off or extend. Or will a big section need upgrading to 22mm?

I think the absolute bottom would be 2 days but it could `be quite a pig perhaps 5 days or maybe more in the worst case.

Then there's those storage heater to remove -seriously heavy work plus a skip.