Aren't combi boilers meant to be efficient?

Joined
28 Mar 2013
Messages
5
Reaction score
0
Location
Bristol
Country
United Kingdom
I have a Vokera Linea Max condensing combi boiler which was already installed when we bought our house. It's my first experience with a combi boiler and I'm almost impressed. I say almost impressed because although it works fine it doesn't seem as economical as it should be. This is because when the pressure drops to a certain value the boiler turns on automatically, repressurises, and reheats the water. This is an infinite 24/7 constant cycle which it seems is burning gas unnecessarily. I haven't researched this fully but I'm guessing that this is normal operation. Naively I expected the boiler to remain dormant until there was a call for hot water from either a hot tap or the central heating. In an effort to save on gas bills am I OK to turn the boiler off at night and then tun it on again in the morning? The literature that comes with the boiler says that continual repressurising of the boiler will shorten its life. Could someone advise on this please? Thank you.
 
I think there is some confusion.

There is a pressure gauge on the front this is just for the central heating and should stay around 1bar hot or cold.

Some boilers have a preheat feature that they keep a small store of hot water ready to go. This is usually possible to turn off.
Turning it off is a good idea at night as it serves no purpose
and in the day time it only means a slightly longer wait for hot water.
 
It's the hot water preheat, which should come on about every three hours.

There is a small hot water tank inside the boiler which is kept hot by the preheat. The idea of this is reduce the waiting time before hot water gets to the tap. Unfortunately it can't be turned off.
 
There is a switch with three settings:

1.hot water
2.hot water and central heating
3.off/reset

I have turned the switch to off and this shuts the boiler down completely. Then I've waited for a few minutes, turned it back on and normal service is resumed. Am I ok to turn this switch to off for lengthy periods?
 
It's heating your hot water store, when that's up to temperature it will shut down. You could put it on a timer so it doesn't operate at night or when you're not home.

If your pressure gauge is rising and falling significantly, your expansion vessel needs attention
 
It's heating your hot water store, when that's up to temperature it will shut down. You could put it on a timer so it doesn't operate at night or when you're not home.

If your pressure gauge is rising and falling significantly, your expansion vessel needs attention

I think the pressure is ok, but my main worry was turning the boiler off completely for extended periods i.e. overnight.
From what you and others have said on various forums it seems ok to turn the boiler off overnight. I think the boiler is wired to a fused socket, but I could easily replace that with a standard socket and wire the cable to a timer plug that I used to use at my old house. Back there we had a cylinder so I used to shut the boiler down for the whole of the Summer and use the timer plug to heat the water in the cylinder using the immersion heater. Some days an hour's operation of the immersion heater and just one cylinder full of hot water was enough for a whole day. My gas bill during those periods was zero.
Mind you back then my kids weren't yet teenagers and didn't yet shower twice a day!
I think what I'll do is take a gas meter reading just before retiring for the night, and then first thing in the morning, and see what the difference and cost is over any given time period. Anyway thanks for your advice.
 
Whats this immersion heater? Have you a cylinder as well as the storage combi?

Tony
 
It's heating your hot water store, when that's up to temperature it will shut down. You could put it on a timer so it doesn't operate at night or when you're not home.

If your pressure gauge is rising and falling significantly, your expansion vessel needs attention
I used to shut the boiler down for the whole of the Summer and use the timer plug to heat the water in the cylinder using the immersion heater....My gas bill during those periods was zero.

...but your electricity bill was substantially more - did you know its approximately three times mote expensive to heat water with electricity than it is with gas?
 
It's heating your hot water store, when that's up to temperature it will shut down. You could put it on a timer so it doesn't operate at night or when you're not home.

If your pressure gauge is rising and falling significantly, your expansion vessel needs attention
I used to shut the boiler down for the whole of the Summer and use the timer plug to heat the water in the cylinder using the immersion heater....My gas bill during those periods was zero.

...but your electricity bill was substantially more - did you know its approximately three times mote expensive to heat water with electricity than it is with gas?

No it was fine, I had done all the sums and I was saving a lot of money. Trust me I don't do these things lightly.


No it was fine - I had done all the sums and I was saving a lot of money
 
The pre heat facility can be disabled on the Linea Max by moving a jumper on the PCB. I'd be wary about putting a time switch on the main feed to the boiler as if it regularly turns off when the boiler is heating the excess heat is not dissipated and it can distort the heat exchanger.
 
This is a storage combi so think turning off the preheat will be a bad idea. Turning off the boiler at night will be a worst idea especially in the winter as boiler will not operate for frost protection

Get you boiler serviced as described in the book (no LESS). An operation check will not be what you wnt but a proper service.

By the way boiler run has nothing to do with boiler pressure :roll:
 
This is a storage combi so think turning off the preheat will be a bad idea. Turning off the boiler at night will be a worst idea especially in the winter as boiler will not operate for frost protection

Get you boiler serviced as described in the book (no LESS). An operation check will not be what you wnt but a proper service.

By the way boiler run has nothing to do with boiler pressure :roll:

I've worked out that I use 0.2 units of gas per night by leaving the boiler on.
This equates to 2.2 kWh.
EON charge me £0.03475 per kWh.
Therefore the nightly cost for gas for the boiler is £0.08.
My current billing cycle means I will receive a bill after 82 days and a rate of £0.08 per night will mean an extra £6.56 on the bill.
Hardly worth faffing with really................
 
What is a unit of gas?

The 8p per night is not lost during the winter as it contributes towards heating the property.

It also ensures the store is all hot in the morning!

Very good value in my view! Far cheaper than your previous electric immersion heater tank.

Tony
 

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Back
Top