Boiler & Immersion vs Combi?

mee_2

Hi

I have just moved from a (modern) flat to a(n old) house, and can't understand the heating/water setup.

In the flat, we had a modern combi boiler, which heated water whenever you turned on a hot tap, and also ran the central heating (with a timer).

In the house, there is a boiler in the kitchen, which appears to run the heating, and in the bathroom there is an immersion unit. Both heating and hot water are controlled via a single timer, near the immersion.

I have tried to understand why one would have this setup rather than a combi boiler, and failed. Surely the immersion is more expensive to run, and means there is only hot water when the timer (and heating) is on.

Any ideas?
Thanks
-- Mike

andrew-b

It's more likely that you have a conventional open-vented heating system where an immersion heater would be included for the rare occassions that your boiler is out of order and so is unable to heat the hot water storage cylinder. In such a system the immersion heater would be left turned off. Should be a switch (probably with red neon light) in the bathroom airing cupboard connected upto the immersion heater..turn if off, set the timer so heating is off and hot water is on, run hot water for a while and see if the boiler lights (may take quite a while to kick in if it's a big cylinder) which will prove if the immersion heater is required for hot water.

Andy

mee_2

andrew-b wrote: »

It's more likely that you have a conventional open-vented heating system where an immersion heater would be included for the rare occassions that your boiler is out of order and so is unable to heat the hot water storage cylinder. In such a system the immersion heater would be left turned off. Should be a switch (probably with red neon light) in the bathroom airing cupboard connected upto the immersion heater..turn if off, set the timer so heating is off and hot water is on, run hot water for a while and see if the boiler lights (may take quite a while to kick in if it's a big cylinder) which will prove if the immersion heater is required for hot water.

Andy

I'm pretty sure it is not set up like this, firstly because it is really old, but secondly because last night, an hour after the heating had gone off, there was no hot water (hot water in the immersion had been emptied by Mrs_Mee having a bath just after the heating went off)

-- Mike

jennifernil

If you have pipes from the CH boiler going to and from your HW tank (not just the water pipes themselves), then you have a system as Andy described. If your timer has separate switches for heating and hot water , or some type of selector switch on it, then you can have the heating off but the water still on. There should also be a thermostat fitted to the HW tank to turn off the boiler when the water is hot enough.

Combi boilers are a relatively recent thing, so in an old house it is not unreasonable to have such a system.

If your boiler does not also heat the water then you will need to use the immersion heater, which runs off electricity. You can buy a separate timer for this so it does not need to be on all the time.

It would be pretty unusual for one time clock to control both a gas boiler and an electric immersion heater.

andrew-b

Perhaps a more simple way would be
to count the number of pipes going in/out the cylinder? If it's 2 then your immersion heater is likely to be the only heat source for hot water. If it's 4 then it'll be hooked upto the boiler pipework.

If it really is the case that hot water is heated only by the immersion heater then i'd get some quotes in to have the system upgraded or if it's what you really want then get a combi fitted instead.

Andy

p.s Jennifer beat me to it.. some cross-posting there!

HelzBelz

The immersion heater is usually just so you can heat water when the central heating isn't on, as it is more expensive than the water heated normally.

Is there a switch in the bathroom (probably in the airing cupboard) it usually has immersion heater written on it, but might just have a little light above the switch.

ormus

i doubt the immersion is controlled by the timer. its probably just a manual switch with a thermostat.
it may be best to scrap the HW cylinder, and just use the combi as per normal.
(baths will take ages to fill though).

jennifernil

But they haven't got a combi.

cajef

mee wrote: »

but secondly because last night, an hour after the heating had gone off, there was no hot water (hot water in the immersion had been emptied by Mrs_Mee having a bath just after the heating went off)

-- Mike

If Mrs_Mee ran all the hot water off for a bath after the heating went off, it stands to reason that the water would be cold until the heating came on again.

jennifernil

The problem is that the HW should be able to be on without the CH being on, after all......what about summer?

EliteHeat

Combi boilers are certainly not a panacea for all households and do not suit many.

A properly installed fully pumped indirect system will give excellent performance and reliability and in addition contains built-in hot water redundancy for those occasions when your boiler packs up.

I doubt if many heating engineers would choose to have a combi in their own home.