Combi boilers, CHEAPEST WAY TO USE.

Hadrian

My 'Combi' boiler provides hot water 'on demand'. Unless I turn the hot water on it simply sits there doing nothing.

ystalyfera

mech wrote: »

Personally I'm against the idea of "topping up" or manual override because it encourages breaking rules you try to put in place to reduce gas usage. Most people don't understand the relation between the controls and how much gas is burnt. "I can't believe how much gas I've burnt. I only turned it up for half an hour". Yes, but it probably charged the house up with extra heat for hours and hours to come afterwards. Also, turning a room thermostat or TRV up higher doesn't heat the room any faster, but many people think it does. So they turn it up to silly levels when they're cold and then later on the house is too hot. Only the thermostat on the boiler itself can make the house heat up any faster and many people don't even know that one is there. And with a condensing boiler, turning that up higher can hurt efficiency anyway.


That isn't unusual, but it's probably not relevant. It will take a similar amount of time to cool down too, so on a day-to-day basis it will never cool down entirely anyway.

The key issue here is that extreme followers of either method assume the house cools down to background levels as soon as you leave the house in the morning or go to bed at night. If you believe in timed heating then this is great as you lose no heat when you're not up and around. For believers in leaving the heating on constantly that's bad because they've measured how much gas they used when coming back from a winter holiday, noticed it's astronomical compared to day-to-day usage when on constant and again their view is reinforced.

In reality houses don't cool down or warm up in the timescales heating timers operate in, so the assumptions are naive in both cases. It isn't just laypeople making these assumptions. A professor of physics at Cambridge is just as capable of making this error in my experience.

A house heated constantly does NOT use four times the fuel it would use heated for 6 hours a day. Probably not even 1.2 times if the 6 hours is split between morning and evening. Therefore turning the thermostat down CAN offer similar savings. BUT turning the thermostat down AND using a timer still saves most. The issue then comes down to whether you can tolerate turning the thermostat down further with a more consistently heated house versus timed, and as that's so subjective and probably influenced by factors that vary a great deal from house to house/person to person, it turns out that it's just not possible to give that kind of advice.

That last point depends on the outlay. Most measures against heat loss require you buy stuff and do things to your house. In comparison, twiddling with controls is quick and costs nothing (and a landlord won't need to be involved either).

Personally I think human behaviour mustn't be ruled out of energy saving. If by wearing warmer clothing you can be comfortable with the thermostat 2 degrees C cooler, you can reduce your gas consumption by something like 20%. And that applies whether or not you have the heating on timed or constant. I'm not sure there is another single energy saving measure that saves as much yet costs so little to do. It should be at the top of any list.

:money:for these tips.I'm having one put in Monday.The back boiler i have at the moment is ancient so this system should be far better.One tip i read was to turn the tvr's 1/2 way and if its to hot turn it down or to cold turn it up a little more.

C_Mababejive

I am not being flippant but the cheapest way to use a combi boiler is to turn it off where possible and wear one of these as it is now officially winter. If you dont have lumps on your front,wear the male equivalent. You only buy a thermal vest once but you pay for gas all the time.

It isnt rocket science.

Boiler on>meter runs> you incur costs>you get a bill

The idea is that you FEEL warm..so wearing a vest gives the same feeling without the meter turning....simples!

smjxm09

For a combi boiler to be efficient it needs to condense. It will only condense if the water from the radiators is below 57C when it arrives back into the boiler. It is usually recommended that there is a 12C difference between the water entering the radiator and the temperature when it leaves it. This difference is controlled by the speed of the water passing through the radiator. Assuming that there is a 12C difference then the boiler should be set to no higher than 69C.


How to balance your radiators http://www.diydata.com/projects/centralheating/balancing/radiator_balancing.php

samtheman1k

DGJsaver wrote: »

Do you leave your kettle on all day ?

I do, yes, because I have a Quooker that produces instant boiling water. Standing electric usage is 10p/day, which works out less than boiling the 2 cups minimum required for most kettles, when I only need 1 cup (I drink a LOT of tea!).

samtheman1k

mech wrote: »

I'm quite happy to reply. The answer is nobody really knows.

Everyone can find out though, quite simply by doing each methods on different days, and seeing which one uses less gas! Simple really!

Pincher

samtheman1k wrote: »

I do, yes, because I have a Quooker that produces instant boiling water. Standing electric usage is 10p/day, which works out less than boiling the 2 cups minimum required for most kettles, when I only need 1 cup (I drink a LOT of tea!).

http://www.quookershop.co.uk/order

£830!?

I have an Insinkerator, for about £400, but it's only "near boiling". The tea doesn't quite brew properly. The cold mug probably brings it down to 90 degrees. So I usually nuke it for 15 seconds.

Must consider the cost and benefit of a wife/tea maker one of these days. Must be more than £830, but then I don't have to leave the sofa. What's the running cost?:)

grahamc2003

samtheman1k wrote: »

Everyone can find out though, quite simply by doing each methods on different days, and seeing which one uses less gas! Simple really!

Not that easy at all.For the results to be meaningiful, you have to keep all other factors constant each time, and that is hard to do in the real world. For example, setting your thermostat to 19 degrees may burn more gas than the day before when set to 20 degrees due to the ambient temperature being lower. If you suck it and see, then you have to be very careful to inetrpret the results correctly, and if you know how to interpret the results, then you know the theory behind heating and heat loss. And if you know the theory, then there's not much point in doing the experiment in the first place.

The theory is pretty clear - lowering the thermostat will have a dramatic effect of gas burnt (because radiative heat losses are proportional to the temperture difference to the power four). For the same reason, turning off the system (or turning it so low that it doesn't come on) when you are not there will burn less gas then keeping it at the same temperature as when you are there.

The view often stated that keeping the house heated when you're out is cheaper than letting it cool and heating it back to temperture when you get back is just nonsense. It may be more comfortable (in that it's warm when you return) but it certainly isn't cheaper or the same cost.

grahamc2003

samtheman1k wrote: »

I do, yes, because I have a Quooker that produces instant boiling water. Standing electric usage is 10p/day, which works out less than boiling the 2 cups minimum required for most kettles, when I only need 1 cup (I drink a LOT of tea!).

My 3kw kettle boils 1.5 litres in about 5 minutes, so costs 0.25kwh, or 2.5p.

So for your 10p/day usage per day, I can have 4 pots of tea, each serving 4 or 5 people.

I think your maths is out regarding how much it costs to boil two cups of water in a kettle - or were those the costs quoted in the sales blurb for your quooker?

ixwood

How can keeping a tank of water at near boiling 24/7 be cheaper than boiling the kettle a few times when you need it?

This comes up again and again on here. People just seem to want to believe that leaving heating on all the time is miraculously cheaper somehow.

Leaving the heating on when not required WILL cost more money. I can't actually understand how anyone could think that it wouldn't.

If you were away for 6 months, would you think it'd be cheaper to leave it on? Of course not.

The better insulated the house, the less extra it'll cost, but it will always cost more.