Oil Fired Hot Water.. Explain?

Bexm

Hi

We have just moved into a new house that has oil fired heating and water and there's no chance of connecting to gas.
We've never had oil before and I'm not sure if this is standard or a different type of boiler but I can't work out when we need to put the water on.

According to the previous owners the boiler (which is almost the size of a washing machine) has an inbuilt 40(?) ltr tank - not one in the airing cupboard- but the hot water is instant and you just need to leave it "on", although it has got a timer setting.
From previous experience of gas, instant hot water meant you turn a tap on, the boiler fired, you got hot water.
This boiler seems to fire when you turn the water on, but also randomly to probably heat this 40ltrs. This seems a total waste of money but I don't know what to set the timer for as I only have 3 settings.
Currently I just have it coming on about 6:30 and going off about 11pm when we go to bed but this seems uneconomical as obviously we don't need hot water all the time, but then how do I choose 3 periods of the day that I need hot water? Especially as we work random hours and some times need it to do lunch time washing up and sometimes don't..

Am I being totally stupid? How does everyone else do it?

Thanks for any advice!

Bex

suki1964

No idea on your system but my oil heats the water for an hour in the morning and an hour in the evening. Enough for showers morning and night and hot water during the day. If it runs out I either save the dishes for later or boil the kettle

Smiley_Dan

Sounds like a pre heat combi boiler: http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5115

40L is not a lot. By my reckoning it will use just over 1kWh to heat from cold at this time of year to 40C, so that's about 5p at today's oil prices.

But it's still a bit of a waste yes. I think they do it to cope with oil boilers being slower to heat up.

I prefer inline modulating electrical heaters pre-heated by some other source (solar or heat pump to low temp).

macman

Make and model of your boiler would help...but I'd agree, sounds like a combi with a pre-heat function. Your previous gas boilers were combi's, so you've never had a conventional system with stored hot water.

Maelwys

Bexm wrote: »

Am I being totally stupid? How does everyone else do it?

That Boiler setup there does sound a little odd.

Mine is an ANCIENT (circa 1980s) boiler which is literally just a big metal furnace box with feed line from the Oil tank, an exhaust flume and a few water pipes running through it. It has a plastic thermostat dial (which isn't actually attached properly to the knob underneath, but a pair of pliers will let you set it anything from 55-85 degrees). It's far from efficient, but the maintenance costs are precisely zero so I'm just planning to run it until it breaks and then buy a replacement.

For Hot Water, the water being pumped through my boiler passes through a heat exchanger in a insulated Hot Water Tank in an upstairs Airing Cupboard. There's also an electric "immersion heater" attached to this Hot Water tank which I can turn on and off directly via a separate boost switch/timer.

Usually my Hot water tank will warm up a little bit when the heating comes on in the morning, then the Immersion will top it up as/when I need it. I also have a back boiler attached to my Fireplace which can heat the pipes inline with my Oil Boiler (and comes in very handy in the winter!)

Cardew

Agree with posts #3 and #4 that it sounds like a combi with a pre-heat function.


Heating the internal 40 litre tank is not a great cost, particularly in the winter when any heat lost warms the fabric of the house anyway. However the noise of the boiler randomly firing up in the middle of the night can be annoying.


I think most boilers have the facility to turn off this pre-heat function - the setting is 'economy' on a combi I have in an annex. The penalty is a longer wait for the warm water to reach the taps.

Bexm

Thanks for all the replies.
We are mains water.. just middle of rural wales where gas hasn't reached yet.
Yes it is a combi..
Our gas boiler in the old house had a pre-heat thing, but only heated 5 ltrs and seemed pointless so we switched it off. Running 40 ltrs away seems too much though especially now our waters metered for the first time!

Cardew

Bexm wrote: »

Running 40 ltrs away seems too much though especially now our waters metered for the first time!

Switching off the heating for that 40 litre internal tank does not mean you have to 'run off' the 40 litres before you get hot water. If that were the case you would be running off 40 litres every time a hot tap was turned on - potentially hundreds of litres a day.


When that pre-heat function is switched off the combi acts as a 'normal' combi and does not draw any water from that tank. It starts heating water straight away, albeit it takes time to get up to temperature and deliver hot water.

matelodave

Have a look to see if it's got an Eco setting and see if it performs OK. It's probably a good idea to have it come on before you get up in the morning to give you quicker hot water when you are all getting abluted but then switch it to Eco mode for the rest of the day and if you really need, it have it on for a while in the evening.

Work out when you use most hot water - is it for morning showers or night time baths. Don't forget having shorter showers and shallower baths will save water and the energy required to heat it.

In the end its trail and error, there's no advantage in keeping it hot all the time especially when you are out or asleep so time it for when it's needed.

Get into the habit of washing your hands or rinsing stuff with cold water - running several gallons off to get hot water wastes the water and the hot water that sits in the pipes gets cold and wastes the energy that was used to heat it.

Smiley_Dan

Agreed, one reason I like modulating inline heaters near point of use. But sometimes hot water just isn't required.

mikegparker

Does anybody know how to disable the combi side of an oil boiler which is now used to heat a cylinder that is also heated from a log burner, combi side no longer needed, do i just disconnect the hot water thermostat?