Have we been a little bit duped with our new central heating?

[Midlandsmum]

We recently decided to have all of our central heating replaced - pipes, radiators, boiler, everything. We have a 6 bedroom house with 1 bathroom, 1 shower room and a WC. The house has stone floors downstairs, and is old. We have 15 radiators total.

We were quoted for a 32kw Worcester or equivalent boiler. We've got a 25kw Grant boiler

The heating doesn't seem great, and we have 4 radiators still to fit. There seems to be a lot of air in certain ones. Is our boiler just too small?

 

[Ric2013]

Without knowing the heat losses of the house (you'd need to do quite a complex calculation, though there are some 'rule of thumb' online calculators), it's hard to say if 25kW will be enough or not. I'd agree 'or equivalent' doesn't apply to a boiler that is 7kW short of the original specification, but bigger is certainly not always better when sizing a boiler and it's possible the installer decided 25kW was ample for your house. Unfortunately 'old' doesn't tell us much - I've recently seen an EPC for a 50-year old flat with an F rating whereas my own house is a D, and yet it's 150 years' old. Stone ground floors wouldn't normally be a major factor in heat losses as they'd be no worse than uninsulated concrete and the heat losses for concrete tend to vary with the size and shape of the building, with long and narrow buildings being the least insulative. Draughtiness will, however, factor greatly.

Air in radiators needs to be removed as otherwise the radiators won't heat properly (nothing to do with the size of the boiler and often there will be air if the system has only just been installed).

After which, if the radiators aren't getting hot enough to warm the rooms and this isn't due to a boiler setting or balancing issue, then you can say the boiler is undersized. If the radiators get hot but the rooms don't then it may be the radiators themselves are too small. Obviously if a third of your radiators haven't been fitted, then the rooms that are heated will be affected by the heat losses into the unheated rooms.

 

[Deleted member 120897]

I’m guessing the 32Kw was based for hot water delivery, as majority of heating systems dont need that much. As Ric says, a heat loss calculation and u-values would need to be known. If youve been “quoted” for and accepted a quote for a Worcester 32Kw then that’s what I’d be expecting, so imo, you’ve been mis-sold. Get back onto them.

 

[Ric2013]

I’m guessing the 32Kw was based for hot water delivery, as majority of heating systems dont need that much. As Ric says, a heat loss calculation and u-values would need to be known. If youve been “quoted” for and accepted a quote for a Worcester 32Kw then that’s what I’d be expecting, so imo, you’ve been mis-sold. Get back onto them.

Bear in mind it's a 6 bed 2 bath. It could be quite a big detached house. We simply don't know. Good point on the hot water - if it's a combi boiler then the hot water output will most likely be not as good as a 32kW combi boiler.

 

[exedon2]

Grant don't do a 25kw boiler I assume you mean a 21/26?
Which model?
All Grant boilers arrive set up mid range have a look at the commissioning data it will tell you how boiler is set up.
If your radiators aren't getting warm I would measure up all your rads then look at a radiator size list (lots on line) add up outputs see what you get to in kw.

 

[Midlandsmum]

Thank you so much for taking the time to reply to this. These answers have given me a lot of insight.

When I say old, the house is 240 years old. It's semi detached. I don't imagine the EPC would be great for it, there isn't room for insulation between the floors. It's got a first floor and then loft rooms

The boiler is a 26kw grant vortex combi.

The water does take a long time to heat up, and the shower goes cold if someone washes up at the same time downstairs. I think overall I'm just feeling a bit bummed by replacing the whole thing and it not being perfect, but maybe I'm just expecting too much

 

[exedon2]

Decent boiler but I would suspect too small.
I for one would not consider fitting a 26kw combi in a property of your size in fact probably not a combi full stop.
You do realise that all combi's are hot water priority? So ever time you run hot water you have no heating for several minutes afterwards.
The largest combi Grant make is 36kw at the very least that would have been more suitable.
Have you checked to see the boiler has been set up at 26kw?
You do need to check what heat output you need to run the radiators you have.

 

[DrMaybe]

Grant don't do a 25kw boiler I assume you mean a 21/26?
Which model?
All Grant boilers arrive set up mid range have a look at the commissioning data it will tell you how boiler is set up.
If your radiators aren't getting warm I would measure up all your rads then look at a radiator size list (lots on line) add up outputs see what you get to in kw

Decent boiler but I would suspect too small.
I for one would not consider fitting a 26kw combi in a property of your size in fact probably not a combi full stop.
You do realise that all combi's are hot water priority? So ever time you run hot water you have no heating for several minutes afterwards.
The largest combi Grant make is 36kw at the very least that would have been more suitable.
Have you checked to see the boiler has been set up at 26kw?
You do need to check what heat output you need to run the radiators you have.

.

Grant don't do a 25kw boiler I assume you mean a 21/26?
Which model?
All Grant boilers arrive set up mid range have a look at the commissioning data it will tell you how boiler is set up.
If your radiators aren't getting warm I would measure up all your rads then look at a radiator size list (lots on line) add up outputs see what you get to in kw.

I’m sure the combi are fixed heat output; it is the utility boilers that can be adjusted.

Did the installer leave a filled out CD11 form?

Did the installer leave you with a user manual?

Is the boiler thermostat wound down to minimum? Note this only adjusts the heating temp not the hot water (set to max by default)

 

[SimonG]

I’m sure the combi are fixed heat output; it is the utility boilers that can be adjusted.

Did the installer leave a filled out CD11 form?

Did the installer leave you with a user manual?

Is the boiler thermostat wound down to minimum? Note this only adjusts the heating temp not the hot water (set to max by default)

Combi can be adjusted same as all oil boilers.

In this instance, just like most, a combi, especially oil is not suitable.

 

[Ric2013]

Combis certainly have their place in small houses with one bathroom, but once you start adding competition for hot water there can be issues.

It's a bit of compromise as maximum hot water flow is never as good as a cylinder, but if you aren't actually using much hot water, then you can find they save on gas/oil, and if 12 people want to have a shower one after the other, a combi will accommodate this whereas a cylinder needs time to re-heat.

 

[DrMaybe]

Combi can be adjusted same as all oil boilers.

In this instance, just like most, a combi, especially oil is not suitable.

Grant Combi’s are not adjustable

 

[SimonG]

Grant Combi’s are not adjustable

Oh yes they are, why do you think they sell a 21/26.

I've had a look and although the handbooks dont say they are adjustable, a different nozzle with the necessary adjustments to the combustion settings can give you more kw or less as required.

 

[Midlandsmum]

Thank you very much for all of the information and experience - lots to be thinking about, and I have so much more knowledge now, so I really appreciate it

 

[DrMaybe]

Oh yes they are, why do you think they sell a 21/26.

I've had a look and although the handbooks dont say they are adjustable, a different nozzle with the necessary adjustments to the combustion settings can give you more kw or less as required.

Yes you can adjust System boilers but not a combi, so I’m currently fitting a Grant Vortex Pro System 26/36 and can make it 26kW, 31kW (factory set) or 36kW dependent on nozzle settings. I don’t think this helps the OP though

 

[SimonG]

Yes you can adjust System boilers but not a combi, so I’m currently fitting a Grant Vortex Pro System 26/36 and can make it 26kW, 31kW (factory set) or 36kW dependent on nozzle settings. I don’t think this helps the OP though

You know what, I'm full of cold and cant be chewed to argue the toss.

If I needed to I have the experience and knowledge to change the output on a combi.

 

[gpbeck]

If you have space it would still be possible to add a hot water cylinder, heated by your existing boiler with new controls. You just need to ensure you have adequate mains water pressure and flow.

 

[exedon2]

Yes you can adjust System boilers but not a combi, so I’m currently fitting a Grant Vortex Pro System 26/36 and can make it 26kW, 31kW (factory set) or 36kW dependent on nozzle settings. I don’t think this helps the OP though

Like SimonG I can't be bothered to argue with someone who obviously thinks they know more than me.
Out of interest how many grant boilers do you fit/maintain a year?