Advice needed on speccing a new system

13 Mar 2006
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United Kingdom
Would be really grateful for help here.

We live in a three-bed, three-storey house with one bathroom (and no possibility of more). We have one child (2 yo), so far... The bathroom has a bath and shower in it.

The house has (and needs) 10 rads.

We're looking to replace our current heating system (as we are moving the bathroom from one site to another in the house and therefore need to move the boiler). We currently have a gravity-fed system with a cold water tank in the loft, and hot water cylinder and boiler.

But ... we're getting conflicting advice from plumbers. We have been variously advised to:
1) Stick with the cold-water tank and replace boiler and hot-water tank and add an additional pump for the shower.
2) Stick with a condensing boiler but move to a pressurised system (without the cold-water tank in the loft). This would involve replacing some/all rads (which we intend to do).
3) Move to a combi.
4) Get 2) and a megaflo (or other non-vented cylinder). THe inlet to the house is 15mm, before you ask.

Our priorities in order are:
1) Efficiency
2) Keeping the noise down (the boiler will be sited above stairs with access from a bedroom - with a sound proofed access panel, hopefully)
3) Space - everyone likes the idea of losing a great big water tank.
4) Cost

EDIT: I'm adding anothe priority here. I want a shower that doesn't trickle. Mains pressure into the house is fine - indeed good.

I'd be really grateful for some help here. We're getting really bewildered by the conflicting advice.

Thanks everyone (again).
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Thanks for super-prompt reply. But would the person, um child, in the bedroom (near the combi boiler), be likely to constantly hear the combi firing up every time water/heating is demanded?

And would it be likely to present a problem that the combi boiler would be two floors away from the kitchen?

(I should say, that while it's great to save space, we do currently have a hw tank and a boiler and have room to accommodate a hw tank still.)
if you get the 937 vaillant you will have good hot water delivery and its one if not the quitest boilers around. wouldnt worry too much about kitchen, you probably would have similar senario with other system setups.bathroom is priority.
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p.s if your not going to use bath and shower at same time you could consider a smaller boiler.
THe shower will be in the bath so no, they won't be used at the same time...

Given the controversy that surrounds Combis vs Condensed, I'm surprised noone has yet shot down the combi idea...
It realy depends on what floats your boat this one. On what details you have given I would recommend an unvented unit, subject to water flow test. Downside is its more expensive than combi.
Vaillant 937. Just add water and radiators.

Quiet, long warranty (some installers have access to extended warranties), compact apart from the depth (595mm), easy filling loop.

It has the type of HW performance where bearing in mind most London water mains into properties are delivering under 22l/m, an unvented would give very little more for a whole lot more space and money.
THe shower will be in the bath so no, they won't be used at the same time...

Given the controversy that surrounds Combis vs Condensed, I'm surprised noone has yet shot down the combi idea...

This is where the public seem to get confused, all boilers are condensing, you will get a condensing combi and a condensing system boiler.
Whatever you do, get rid of the cold tank as this means only the cold kitchen tap is the only tap in the house that you can drink from.
Bit of a bummer when you have to go to the kitchen to brush your teeth.
Old fashioned cylinder is also number one source of legionella infection.
Both combi and unvented cylinder need upgraded mains water pipes.
Combi is about £1000 less expensive to install than heat only boiler with cylinder and slightly more economical to run.
Worcester cdi is whisper quiet. 37 kW version gives very impressive shower.
As mentioned before, all new boilers should be condensing.
Sorry to dredge this up again but we're still speccing this.

Given that we've got decent mains pressure, we're starting to lean towards a combi at this point.

An installer is recommending Worcester-Bosch - which I'm happy with. So it looks like being a greenstar.

I've rated the 10 rads needing around 20KW.

Any thoughts on which would suffice? My priorities would be to be able to run a decent bathhave a shower (thermostatic control) with an appliance (e.g. the washing machine) on. Is this possible? Should I just go for the highest flow rate I can?

Thanks again.

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