House takes ages to heat up

[nebjamin]

Hi,

Just moved into a 1930s detached with solid walls (no cavity).

It has a Worcester Greenstar 37Cdi boiler (just a couple of years old I think), and a random selection of radiators around the house.

Last w/e the outside temp got down to 2 degrees and even with the CH on ALL day the downstairs rooms didn't reach the themostat temp (21).

The boiler is running at 72 degrees (displayed on the front panel) and when it's heated up to that temp it's not using much gas (I can see by looking at the meter). All the rads are boiling hot.

The downstairs rooms are (in m):
Dining: 3.8x4.4x2.5h
Radiator: 176x60 single panel with convector

Living: 5x3.8x2.5h
Radiator: 270x60 single panel without convector (curved!)

Kitchen: 5x3x2.5h
Radiator: 50x60 single panel with convector

Hall: 8x2x7h (open staircase). Also big old draughty door with leaded single glazing all around.
Radiator: 176 x 60 single panel without convector

--

Since the boiler is keeping the water nice and hot with minimum gas, it seems to me that the radiators aren't doing a great job of radiating their heat.

The radiators are probably from the original installation of the CH (no idea how old that is), so am thinking of upgrading them.

Does this sound like the right thing to do? (I am also sorting out insulation)

Ta

 

[45yearsagasman]

There are plenty of rad calculators on line, but you need to put in more info regarding your rooms, ie aspect, number of outside walls, windows etc.

 

[dcawkwell]

You probably have two panel radiators with no convectors.
I replaced my one in this room with double panel double convector.
Before couldn't get the room above
14 degrees. Now it's 20 degrees in an hour or two.

 

[ALEC1]

are all the valves fully open, and is the system properly balanced...

 

[nebjamin]

Everything seems to be balanced OK - the rads all get hot at about the same time. The rads are all toasty.

As dcawkell said the curved rad has no convector on it.

Hav considered a double here but it's curved and the best quote I've got for that is £910

 

[Agile]

The firt thing to do is to put proper insulation in the loft and then reduce the draughts.

That can cut heat loss by 20-30% and make the house much warmer.

Then consider where you need more heat and upfrade rads for finned or double panel types.

In the room with curved rad then consider adding another somewhere.

Tony

 

[ALEC1]

no doubt the system was designed with a flow temp of 82c...I don't know if the CDI will go to that temp though..

The other side of heating is of course insulation......


And how long are you allowing to heat up tne rooms... ?

 

[Agile]

The CDI will go to 82 C but the existing 70 C is what the replacement boiler will work most efficently.

Typically its expected a house will reach close to normal temperature in about 45 minutes when it has been heated within the last 12 hours.

Tony




PS I expected to see alex today at St Albans!

 

[nebjamin]

Yeah - insulation is high on the list of todos.... as is draught proofing.

The radiators pre-date the boiler by a long way.

Last w/e when we had a frost (on top of a hill here in South London) it was on from 7AM and didn't hit 21 until about 4PM!

As I said the boiler isn't using much gas once it gets to 72 deg, just keeps the water at that temp without much

I have used a rad calc on the living room and it reckons about 2.3kw. Don't think the existing panel is up to that.

 

[nebjamin]

Just seen Agile's response.

Loft insulation is on average 70mm, but a bit patchy in places.

House is also a bit draughty - particularly the front door and cupboard under the stairs where the meters are (and where there are holes in the floor for services.

Considering a porch for the front door and I'll get in the cupboard and cover with hardboard to stop the draughts from there.

 

[Agile]

Last w/e when we had a frost (on top of a hill here in South London) it was on from 7AM and didn't hit 21 until about 4PM!

Since when did London extend into Wiltshire???

Your loft insulation of 70 mm is way below the 350 mm + recommended now!

 

[nebjamin]

Wowzers.. it's 350 now? Last I read it was 270!

Thanks for spotting the error. Should be fixed up to say Surrey now.

 

[Agile]

It has been 270 mm for the last 9 years but thats the minimum thickness.

Its now considered wise to use more than that and its expected the recommended figure will soon be increased.

 

[nebjamin]

Thanks for the link.

Other thing we are considering is external wall insulation. There are large chunks of render that need replacing on the house anyway.

Gonna hold out to see what the green deal looks like when it's introduced in January.

 

[oldskoo1]

Are you sure it isn't using much gas? If my boiler was on that long my bills would easily be £180-£200 per month.

I'm using about £130 of gas at the moment (in this cold weather) just to maintain 18-20c then it goes off at 22:30

Takes about 40-50 mins to reach temp then just maintains it.