Heating costing £150 per month - what's wrong?

[kentmonkey]

We've moved into a house recently and the heating bills are crippling us.

Last week we had some work done by a plumber as some of the rads weren't getting very hot and the heating was costing us a fortune to run. Our first bill was £170 for the month (Nov 18 - Dec 19) and then £110 (for Dec 20 - Jan 16) when we went colder and only had it on for four hours a day.

He powerflushed the system (although by his own admission nowhere near as much came out as he was expecting, very little in fact), fitted a new thermostat away from the cold outside wall, fitted one of those devices that collects sludge etc. and you can empty out by hand, increased the size of two radiators and rebalanced the system.

Since this the house has got a little warmer, the hallway rads now warm up and our bedroom is warmer, but the small bedroom is always freezing (despite the rad being warm) and one of the two radiators in the living room doesn't get very warm.

The main issue though is the cost. This evening it took 3.5 hours to get the house up from 12 degrees when I got in to 17 degrees, which is what the thermostat is set at. During this time, it took approx 60kwh of gas to do so. Hot water was on for half an hour during this time as well.

Our boiler is a 70kw Potterton, non-condensing. I think it's about 8-10 years old. We have 22mm pipework (and the plumber thought it should be 28mm for that size boiler, but said that it would cost a lot to replace all of the pipework and may not be an expense we want to incur).

We have 12 radiators, all double, and one towel rail. He calculated that they added up to 40,000 btu, if that sounds about accurate. We have a mix of 600x500 and 400x400 sizes mainly, depending on rooms, and he checked that they were all the right size (which is odd a the little room about 8 feet by 6 feet, but with half of the room reduced head height due to a dorma ceiling as it's a side extension, with a 300x300 rad).

I'm not sure if 70kw is too much and that is causing a problem (I've never even heard of 70kw boilers before to be honest, it sounds like a lot) and whether if we went for a lower kw boiler whether that may even improve things.

The house, as far as we are aware, doesn't have cavity wall insulation (it's a 1930's semi) and has only one layer of loft insulation. So that's obviously an issue, but not, I don't think, by any means the only one. And we're doing the loft in about four weeks to 270mm insulation and looking at having cavity wall insulation (although the horror stories I've heard with older houses and cavity wall insulation are frightening me). We have double glazing. Not very modern (early 90's) but still double glazing.

Any advice greatly appreciate as at £4.50 for each weekday heating and about £7 for each weekend day heating it's costing us a fortune, and is something we just can't afford long term.

 

[kentmonkey]

To add to that info:

Boiler is on for 1.5 hours in the morning and 5 hours in the evening.
Three bedrooms. Four downstairs rooms (inc kitchen) plus bathroom and hall. Thermostat set to 17 degrees.

Boiler has been recently serviced.

 

[swbjackson]

Are you sure the boiler is 70Kw, that's huge. With a boiler that big you should be able to dance round the house naked when it's -10 outside. I'd suggest you get someone else in to check the system over as something is very wrong if a 70Kw boiler can't heat a three bed semi.

 

[GasSafeTony]

What type of gas meter do you have?

 

[kentmonkey]

Yup, definitely 70kw, British Gas and plumber have confirmed that.

The gas meter is an old imperial style meter, although I get billed monthly so the two amounts provided are accurate and I've worked out the calculation to convert imperial to metric units so can work out now, to within about 2%, what it's costing me each night. I've become that anal about it.

Trying to get plumbers around at the moment is next to impossible. We phoned 11 to come round and give us a quote, three showed up, two quoted (both similar work, very different price) and one never even posted the quote.

 

[oph]

40,000 btus is the same approx as 12 kw. Your boiler is massively oversized fo a 3 bed 1930's semi. 15 kw or 50,000 btu approx in old moneys all you need in a property like this.
Ok, so how's the lagging under the ground floor?

Is the cylinder newer or older.

Insulation upstairs in the loft will help for sure

Also, what's your idea of heat comfort. Are you sitting in a tee shirt? You'd be surprised how many people do this. My b itches about how cold the house it but the daft hoe is walking round barefooted !!!!!

Really annoys me when does this

Have you tried splitting the load so that water and heating are not on together so that the boiler can put all power to the heating circuit without doing the cylinder at the same time.

I changed three rads in a rented house today. Crap circulation . So if the rads are too old and too far gone so that they can't be cleaned out.

I left the house today with happy tenants .

First time for that I guess

 

[kentmonkey]

Currently sitting in jeans, t-shirt, jumper and slippers. Living room is warm, walk out into hall way and very cold. Dining room cold.

Bedroom involves getting undressed in about 0.2 light seconds into pyjamas and then diving into bed, only to feel that the bed is beyond freezing and it feels wet because it's so cold.

Wake up in morning, put on cold clothes (although room, to be fair in the morning, isn't quite so cold as the heating has now been on about half an hour so it's taken the chill off) and moan like buggery that it's still cold and cost a fortune.

Rads are getting warm, all bar one, so hot you can't actually touch two of them, with the 'not-warm' one still 'warm' I guess. Just not hot.

Cylinder I think is quite old, although it has the green foam around the outside.

Floors aren't insulated I don't think. They feel quite drafty. Not sure how you insulate a floor though (other than underlay and carpet, which we have).

 

[kentmonkey]

I know this is a stupid question but I'm going to ask it anyway...does it cost more to run a 70kw boiler than it does, say, a 25kw boiler?

Most of me thinks 'of course it does, you tool'. The other part of me thinks 'but if it's just heating up to a certain temperature, surely they're all the same'.

 

[oph]

It will burn more cubic feet or cubic meters per hour for sure. More gas burned equals a bigger bill .

I know you said that he's added up the outputs of your rads but has he just got that figure from what rad sizes you already have? It may pay to work out your actual heating requirement per room. If your rads arn sized big enough then the rooms won't be heated up o their design temp thus the room stat will never be satisfied and switch off

 

[oph]

It will burn more cubic feet or cubic meters per hour for sure. More gas burned equals a bigger bill .

I know you said that he's added up the outputs of your rads but has he just got that figure from what rad sizes you already have? It may pay to work out your actual heating requirement per room. If your rads arn sized big enough then the rooms won't be heated up o their design temp thus the room stat will never be satisfied and switch off

Excuse my ****e typing.

iPad is overrated IMO

 

[kentmonkey]

He did it both ways. Worked out what the room needed by the size and windows in the room. But then later on, when doing the work, he told me I had about 38,000 BTU's by measuring the rads in the room as I asked the question.

Wondering whether it was 38000 BTU's though, isn't that a bit low for 13 double rads? Perhaps not.

 

[gasbanni]

You're saying two rads are that hot you cant touch them and others are warm ( they should be hot surely) so turn the hot ones off temporarily and see if any of the others get hot.

Before you go in to heat inputs etc etc and cost the heating system needs to be working first !

Heat input of boiler and gas pressures needs checking and that you havent got a major gas leak ....That could be causing you big bills !!

 

[dcawkwell]

About £100 a month for a house now isn't too unusual.


Since you have a semi detach I suggest a quick trip around to
the neighbours to find out what boiler they have.

A small leak under the house that the header tank is topping up
all the time would mean an inflated gas bill.
Try stopping the header tank ball valve and see if the level drops
away over a days or so.
If the rooms aren't getting scorching hot radiators need to be increased
in size. Doubles with double convectors. Wickes have a handy radiator sizing chart online.
Faulty cylinder thermostats will keep a boiler cycling using more gas.

 

[gaswizzard]

Kentmonkey , what boiler do you have? , 70kw doesn't sound right to me or others on here (240,000 btus) , how are you working out your gas consumption bearing in mind you have an imperial meter with a 1cu/ft test dial? , is the meter a U6?

The last of the four digits (far right) represent 100 -900 cu/ft of gas used , 70 kw/hr would use gas at £2.80 hour. (4 pence/kw)

1000 cu/ft = 28.32 cu/m

70kw = 232.27 cu/ft hour.

Deffo a mistake here , 22mm on a 70kw boiler noooooooo wayyyyyy , check it again.

My guess is the 60 kw/h used in 3.5 hours is more likely to be an 18 kw boiler. , does 70.000 BTU ring any bells?

 

[lightning]

+1 was thinking the same 70,000 btu and if 70 kw on 22mm what size is the gas pipe to boiler 15mm