Big, cold, expensive house!

dunstonh

EssexHebridean said:

Apologies if this has already been mentioned - your home presumably would originally have been heated using open fires - does it still have its chimneys in place to make using that form or heating viable as a backdrop to the GSH? Particularly if the chimneys are in the centre of the building this can be a great way of heating the fabric of the building.

I would agree.   We have three burners in place each in three of the original chimneys.    Two of them heat the room they are in and don't provide any heat elsewhere but the hallway burner in the middle of thouse spreads a lot of heat around the house.  A burner in the right location can keep the middle of the house warm and spread some ambient heat taking the strain off the boiler.

InvertedVee

Moneysavingdoc said:

Is it normal for the boiler to run continuously at maximum output for > 1hr without pausing/cycling? Its the £4/hr thats racking up the energy bills...Seems pointless switching off lights etc when the gas bills are dwarfing the electricity!

No, it's not the optimum way. The ideal approach to warming is to go 'low and slow', moving the room temperature up and down by a couple of degrees over a 24h period. Trickling in the heat like this is most efficient but in a poorly-insulated home your heat losses probably won't let you do that.

First question: What kind of room thermostat/programmer do you have?

Not all smart thermostats offer modulating outputs and even those which do are not always connected properly. (I bought a new home last year and the thermostat was connected in on/off mode). You've got a good boiler but if it's connected to an on/off thermostat it won't know how much heat is needed, so it will give its full output or nothing.

In a well-insulated home you would be able to set a low flow temperature. I have a much smaller and newer home than you and I set my boiler flow temperature to just 48C in the coldest weather. Although it takes a couple of hours to shift the room temperatures by 1C, it lets me keep the home between 18.5C and 20C throughout the night and day. My boiler runs for very long periods but only at a low output, sipping around 30kWh (£2.60) per day at the moment. (It's a bit like driving on the motorway with your foot gently and constantly pressing the accelerator, rather than alternately jamming your foot to the floor then taking it off the pedal altogether. You can achieve a steady speed with both methods but the first is far more efficient and good for the car.)

Second question: are you up for doing an experiment?

Whichever thermostat you have, this cold snap is an ideal time for an experiment over a couple of days:

On the first morning

1. Take a gas meter reading
2. Set your flow temperature to 60C
3. Set your thermostat/programmer night and day temperatures to 2C apart
4. Keep all radiator valves (TRVs) on 4. 

You should start the second day with a nice warm home!

1. Take another gas meter reading
2. Turn the boiler flow rate down to 55C

Take another gas meter reading on the third morning.

If your home stayed warm on day 2, you could try dropping the boiler flow rate down another couple of degrees for a third day's experiment. Hopefully, you'll find the lowest flow temperature that will allow the system to heat your home satisfactorily while keeping the boiler running most efficiently (the 'low and slow' method).

At the worst, you'll discover how much heat your home actually loses in the coldest weather over a 24 hour period by learning how much gas is needed to maintain a stable temperature. This figure will be crucial for future assessments of improvements that you might consider. And you'll have an accurate idea about how costly this is and what kind of investments might be justified.

At the best, you'll find that you will be able to afford to keep your whole home warmed at the optimum boiler efficiency. But I can't promise! Good luck!

Moneysavingdoc

That is very helpful thanks. There are 2 old on/off thermostats. First in the entrance hall reception, second in the smallest bedroom (with probably an oversized radiator which doesn't help...). They connect to a basic Drayton lifestyle control. Could this be part of the problem?

RelievedSheff

Moneysavingdoc said:

That is very helpful thanks. There are 2 old on/off thermostats. First in the entrance hall reception, second in the smallest bedroom (with probably an oversized radiator which doesn't help...). They connect to a basic Drayton lifestyle control. Could this be part of the problem?

I think the problem is you are letting your house get too cold and it can never catch up again.

InvertedVee

Moneysavingdoc said:

That is very helpful thanks. There are 2 old on/off thermostats. First in the entrance hall reception, second in the smallest bedroom (with probably an oversized radiator which doesn't help...). They connect to a basic Drayton lifestyle control. Could this be part of the problem?

It will be part of the problem as your Vaillant boiler isn't being controlled as effectively as it should. Vaillant have their own video about using modulating thermostats with their clever boilers. A modulating thermostat will certainly help to get the best out of the gas you're burning. But it sounds like your biggest issue is the heat loss from a poorly-insulated large home.

chris1973

Moneysavingdoc said:

Is it normal for the boiler to run continuously at maximum output for > 1hr without pausing/cycling? Its the £4/hr thats racking up the energy bills...Seems pointless switching off lights etc when the gas bills are dwarfing the electricity!

Yes, the water in the radiators and pipes is stone cold and the boiler has to run at maximum power to heat all of the water in the radiators to the desired temperature, after which most modern boilers will modulate the burner which varies the Gas consumption, when this happens and how many hours  it takes largely depends on how much water is in the system - i.e how many radiators it has to heat.

Todays Gas costs the same as yesterdays Electricity or close to, at least 2 years ago I was paying about 10.8p per KWH for Electricity, and Gas currently is costing around the same on a variable tariff. If you had come onto the forum back then and said you were plugging in 24kw worth of convector heaters to heat your home, people would have pitched a fit telling you how expensive it was, and not to do it and how expensive 10.8p per KWH was to heat with- however running a 24kw boiler with Gas costing the same is now accepted as the norm by society in silent contentment. Strange times!.

BUFF

Moneysavingdoc said:

That is very helpful thanks. There are 2 old on/off thermostats. First in the entrance hall reception, second in the smallest bedroom (with probably an oversized radiator which doesn't help...). They connect to a basic Drayton lifestyle control. Could this be part of the problem?

Part of it but not all of it. Modern controls should pay for themselves from energy savings over the life of a boiler (~15 years) but quite possibly in much less than that especially on a large/high use system.
There is a very good chance that swapping to a Drayton Wiser system would be an easy upgrade (just make sure that you get the right kit to start with if you need zoned+hot water) from your existing Drayton Lifestyle - they may well use a common backplate.

Oversized radiators can actually be a good thing - certainly better than undersized!

Cautiouslyoptimistic

We've got a 1960's reasonably sized 4 bed detached that isn't fantastically insulated with a 20-year-old Bosch 28 Cdi boiler that is a bit like Triggers Broom as it's been maintained/rebuilt several times by British Gas over its lifetime. 

Unfortunately, there's no pain free solution to heating a big, poorly insulated property in my experience.  This year we've changed our strategy to heating the living room only with a 5 kw log burner and wood plus smokeless coal, so we have a warm room in the house where we can all congregate and feel comfortable.

I have 4 small dehumidifiers going in the bedrooms 24/7 which cost about £1.30 each a week to run to try and counter moisture and reduce the likelihood for mould.  I also have a dozen disposable box dehumidifiers placed strategically in wardrobes and other spaces.

It's not the same as last year, we used over 20,000 kwh over 6 months heating the house through the colder months but I'm just not paying what it would cost to repeat that this year so the kids can jump in their beds with a thick duvet and get warm after a night sat in front of the log burner.   Working for us so far, although I must admit this cold snap is a real challenge.    

EssexHebridean

I'd consider checking on those dehumidifiers costs if I were you - I have mine running on a tapo plug and that tells me that 7 hours running last night = 1.2kWh. If I were to have it running 24/7 it would be costing me in the region of £1.36 a day if I were n a single rate tariff. Now it might be that yours are very small indeed - but still, that cost per week seems optimistic for something that would actually be effective. 

theoretica

Stopping drafts is usually cheaper for the difference it makes to temperature than most other added insulation.  If you have unused chimneys is heat going up them?  What about the skirtingboard and floors?  Doors - do they need draft excluders?  Heavy curtains over doors, unused windows, bottom of the stairs (if they are enclosed) will help.  Any leak at all around window frames?  You don't want an air tight house, but chances are you are a long way from that!