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How does central heating work with an unvented cylinder systemm - PigletJohn???

(8 Posts)
RandomMess Wed 13-Jan-16 21:16:46

So have my lovely all singing all dance mains pressure wonderful showers etc. and very happy with PJs recommendations.

Question is should I set the HW to come on before the heating does or is that irrelevant.

I mean does it use hot water out of the storage tank to heat the rads?

PigletJohn Wed 13-Jan-16 21:50:06


But it is quite usual, in the heating season, to set the timer for hw to start half an hour before the radiators start, so the boiler does not have to heat both of them from cold at the same time. The boiler will be more noisy if it is running at max output.

Modern cylinders are very well insulated.

It is a bit more economical to heat the cylinder a couple of times a day rather than every time you use a bit of water, so set the hw timer to be on before and during morning and evening showers and baths. Once a day may be enough as unvented cylinders are usually quite large.

RandomMess Wed 13-Jan-16 22:22:29

Yes I had the HW set for when showers etc were being used but need the heating to come on before that hence wasn't sure what to do!!!! Noise isn't an issue as boiler/tank etc. are all downstairs, the cats are far louder in their demands for us to get up...

From cold for just HW how long do you reckon it takes to heat up the tank?? We don't have the smallest size but the next one. Basically what you told me we needed for 6 people in a small 5 bed house!

Whatdoiknow31 Wed 13-Jan-16 22:43:55

We have an unvented cylinder run off a system oil fired boiler which is also supplying two heating zones (one underfloor and one radiator circuit)

Now if I remember this right we have the hot water coming on at 5am for half an hour. Then at 5.30 the two heating zones come on (underfloor might come on at 5am as well, can't remember not up at that time ;-) )

Our unvented is 150l and easily does 3 power showers a day plus all our hot water needs for the day on 30min heat up (all appliances are cold feed).

That's what we do anyway.

Whatdoiknow31 Wed 13-Jan-16 22:47:38

To answer your question about heat up from cold. If we ever run out of hot water (when teenage step daughters are here) we put timer on for extra hour. Does not take an hour to heat up, have never timed it, but that's the only setting on programmer I.e no choice for extra 30mins etc

RandomMess Wed 13-Jan-16 22:58:20

Hmmm I wonder if I ought to shorten the HW cycles then...

PigletJohn Wed 13-Jan-16 23:20:43

No need, as soon as the cylinder reaches target temperature, its thermostat will stop drawing heat from the boiler. In summer, when the radiators are off, you may notice the boiler stops firing.

RandomMess Thu 14-Jan-16 12:41:32

Isn't technology such a fab thing (when it' working!!!)

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