Boiler sizing

[invalid unparseable]

Hi, we have been offered a free central heating system (via the local authority) and as I've never had a house with central heating (only night storage heaters) I'm wondering how I make sure that the contractor sizes the boiler correctly.

It's a mid- terraced house, one bathroom, five bedrooms, two living rooms on three levels.

The deal is that they will only instal radiators in the 'lived in' rooms, that is not in the bathroom, hall, landing nor the kitchen. Without those rooms that would mean, I reckon seven radiators.

Thet mentioned that a Worcester combi boiler Greenstar 2000 would do the job.

I would porbably want to add further radiators later, in the bathroom and kitchen in particular and possibly in the downstairs hall.

Your advice gratefully received.

- Mike looking forward to having a warm house this Winter.

[Andy Burns]

Tell them to piss off, you'll only accept a free heat pump :-P

[Dave Plowman (News]

A guess from here would be no different to a guess from anywhere. There are online calculators for sizing things for your particular house - as regards heat loss etc. And I'd be most surprised if a free system allowed for expansion in the future. It is stupid not to fit heating in a bathroom - the very room where you're often naked. Equally stupid not to heat the hallway etc.

[Clive Arthur]

One data point...

That's about the size of our house, which is also mid-terrace. Our boiler is 32kW and it copes - on very cold days I'd turn the water temperature up.

The Greenstar 2000 appears to be available in 25kW and 30kW, so I'd go for the bigger one - I'm guessing it's not too much more expensive, especially if it's free. Mine dew, our house is old and poorly insulated, though of course being mid-terrace doesn't have sides to lose heat.

[Roger Mills]

If it's a combi boiler, the size is largely determined by how fast you want to heat 'instant' hot water. If it's *not*, the size is determined by the house's heat loss plus a reasonable allowance for heating stored hot water.

If you currently have stored hot water, you won't want to lose it - particularly if you like baths rather than showers. Try to avoid combi boilers! The cost - to whoever is providing it free - probably won't be any higher for a system boiler and indirect cylinder because you're less likely to have to upgrade the gas supply.

[The Natural Philosopher]

What counts is floor wall and roof insulation levels. And whether or not you have a hot water tank.And double glazing

Its possible to have a stab at a quick and dirty ball park heatloss calculation of you list the area and construction type of every surface leading to the outside

On a well insulated house with hot water storage, 15kW might be enough. Or if you need hot showers off a combi, 45Kw+

You might want to put some more in yourself

Fucking combi crap one person one piddling shower and heaven forfend anyone else in the house opens a hot tap while they are having it

Still at one bathroom you MIGHT be ok

Pay for a mains pressure hot water tank and, if in a hard water area , a water softener.

Then a 25kW boiler will probably be OK.

Its almost certainly enough to heat the house, just not the hot water

[The Natural Philosopher]

And a reasonable allowance to get the house up to warm from cold. Its less how much it takes to keep it all warm, than how much it takes to make it warm to start with

Couldn't agree more. Gold standard is water softener to protect the plumbing, plus mains pressure hot water tank, plus reasonably oversized system boiler...

[Andrew]

:-) Where is this 'free' money coming from ?.

[Andrew]

The OP hasn't actually confirmed that there *is* gas to his property. Free insulation would be a far better use of other peoples money.

[John Rumm]

It sounds like you are not getting much say in the matter since the greenstar 2000 is their "budget" combi, and only available in 25kW and

30kW models.

Generally installers are unlikely to want to tit about using the combi to provide stored domestic hot water (DHW) in addition to its "instant" DHW[1], so you want the more powerful one if possible to get better DHW flow rates. Both models output a maximum of 20kW to the heating, which ought to be adequate for the property you describe.

You could do your own heat loss calcs to prove it to yourself if you want:

(however I would not bother - since I have a 24kW boiler for property that is likely far more leaky than yours, and it's plenty adequate)

[1] Something you can do with a combi, but most installers never seem to think of doing it. If you already have a hot water cylinder with an immersion, then setting it up as a C-plan or w-plan system would not be much extra effort for the installer.

Chapter and verse on all the various plans:

[Tim+]

Only if he wants higher heating bills though?

Tim

[Roger Mills]

Chances are that current cylinder is direct - so he's going to need a new indirect cylinder.

[John Rumm]

Yup fair point - no need for it to be indirect unless there is a back boiler or something similar.

[Brian Gaff (Sofa]

Oh never look a gift horse in the mouth is what I say, I got storage heaters under a similar scheme many years back and they have been very good and I've not been cold, I only needed three, two big uns and a small one, but then my house is your bog standard 2.5 bedroom terraced property. Brian

[Max Demian]

I wonder how economical storage heaters will be in the future. I had them from 1998-2015; at the end off-peak was half price of peak rates; I

*think* they were third price at the start.

With lots more people having them in the future (as an alternative to gas boilers) and people charging their electric cars at night, I expect there'll be very little difference between peak and off-peak rates eventually.

[The Natural Philosopher]

Well the intention of the Climate Zealots is to flatten the demand curve: one way of doing that is to recharge heatbanks overnight as well as charging electric cars.

More than one country doesn't have central heating boilers. Sweden IIRC a family house being UFH done with electric wires. Same in France.

Both countries have hydro and nuclear power

In the end we will, assuredly if civilisation survives, be a predominantly nuclear electric society.

Heat is the one thing it is very easy to store. Building heat retentive mass - concrete or water - into a house is not hard to do.

Storage heaters - not so easy.

Put all that together and you wont see the return of storage heaters BUT a massive UFH heated concrete floor over a foot of insulation is far far better.

And direct heating or heat pumps.

The problems are large, but not insurmoutable

- electricity requirements of the house. Only well insulated modern houses can be heated on less than 10kW, which is mostly the limit for domestic supplies that have for example electric showers as well. But mains pressure stored hot water is becoming te norm in these houses.

- overall grid requirements must be upgraded

- ditto power generation. But only nuclear power is able to really supply what is needed.

That's the way it will probably go. Nukes, bigger grid, heatpumps, more efficient UFH equipped houses.

Wont happen by 2050 tho

[invalid unparseable]

Hi all, many thanks for you contributions.

It's part of the Portsmouth City Council initiative, see:

We will be removing all but one of our storage heaters (the one in the hallway) because the difference in price between off-peak and domestic electricty is very small now. They will take them away for free.

I agree; The terms and conditions of the free offer don't allow any add-ons, such as a radiator in the bathroom. We might add one at a later date, though. Finding space for it will be a challenge, though.

We will be retaining our existing electric shower, which works very well. We haven't taken a bath for decades.

The house is insulated. We got free loft insulation and free cavity wall insulation some years ago.

We have no hot nor cold water tanks anywhere in the house and will be keeping it like that.

We have gas to the house, it powers our hob and oven and the Chaffoteaux water heater (which will be removed). It used to power our living room gas fire but that packed up last year.

We cannot add anything to the offered installation at the time of installation.

Portsmouth water is medium hardness.

Cheers

- Mike looking forward to having a reasonably warm house this Winter.

[Andrew]

Just sign up for something like Octopus GO where you choose your own 4 or 5 hour overnight period where your leccy is much cheaper, like 5p (-ish). THis needs no alterations to the house. Needs a Smart meter though.

[Andrew]

To comply with Part L (does it still exist ?) then a new HWCyl` would be needed anyway, even it was an (old) indirect one.

[invalid unparseable]

A non starter for our storage radiators which require eight hours. Anyway I've had it with storage heaters; Had them for decades and I now want a system that I can control the heat more or less straight away straight away.

- Mike