Hot water boiler Santon Premier - cheaper always on or not? PigletJohn?

(10 Posts)
webminx Mon 22-Sep-14 16:10:44

We live in a newbuild and have a large hot water tank upstairs (santon premier plus unvented) with a control downstairs (Channelplus h27xl) to turn it (and the heating) on/off. The builder told us it's cheapest to leave it on all the time, but I'm not convinced - it seems to heat the water up to a very high temperature (which keeps upstairs really hot, even in summer) and we don't need boiling hot water, nor do we need hundreds of litres every day. We turned it off just to see how it would go on Fri, and as of Monday afternoon, we still have enough hot water. Any advice? Is it energy efficient to just turn on when needed? Or use the boost function ahead of planned use (i.e. baths/showers?) TIA for any advice!

PigletJohn Mon 22-Sep-14 23:25:25

Is this a round white cylinder, or square?

It will be insulated to a very high standard, so heat losses will be very small, therefore it will not lose much even if you keep it on all day.

If you have no gas boiler then I suppose you are heating it electrically. In which case it would be cheaper to fully heat it at overnight cheap rate economy 7 or similar, and to keep the upper, full-price, top-up element switched off unless you run out of hot water during the day. Unvented cylinders are usually very big so it would probably fill two baths plus a day's washing-up.

I expect the thermostat has been adjusted to about 60C which many plumbers like as it kills legionella bacteria very quickly. However an unvented cylinder is unlikely to get infected with legionella, and lower temperatures above 45C also kill it, but more slowly.

webminx Tue 23-Sep-14 11:39:58

Hi Pigletjohn,
thanks for answering! it's a tall white round cylinder - 300L. It seems to be very hot when on all day but I do think we have a gas boiler - it's downstairs and is connected to that programmable control. The boiler is a potterton promax xl. we don't have instructions or manuals for any of these things! Thanks for the info re the temperature - did not even think of that?! Do you know how we can adjust the temperature?

Also, when we left it on all the time, it would kick in at night and one of the kids is a light sleeper so would always somehow be woken by it. We still haven't turned it back on and we both had showers this morning that were still hot so it really must be very well insulated.

We really only need it for two quick showers, a small bath and random handwashing during the day as we have a dishwasher and washing machine that heats water as it needs it from the mains.

Is there a way to programme it to just come on in the morning for 1 hour and in the early evening for one hour without it being on all the time do you know? Thanks again for your advice!

PigletJohn Tue 23-Sep-14 11:48:22

if you have a gas boiler, you should not use the electric heaters that are (probably) fitted to the cylinder. You only need them when the boiler is out of action. Energy from electricity costs about three times as much as energy from gas.

Unless you have electricity from solar panels, when it makes sense to use it when the sun is shining (but you need controls to do that).

If, as is likely (and sensible), the cylinder is heated by the gas boiler, set the HW timings on the boiler programmer for an hour a day, starting before you start to get up. That will be long enough to heat the cylinder and, as you have seen, 300l will easily last all day. Modern gas boilers are more efficient when they run for a period and are then turned off. If it keeps running for multiple short periods to top up the cylinder every time someone runs a hot tap, it is less efficient.

If you look at your gas meter frequently, you will probably find you use about half a metre to a metre of gas a day in summer like that, which will cost you in the region of 25p to 50p.

You can usually download instructions from the makers website.

PigletJohn Tue 23-Sep-14 11:52:25

the programmer probably looks something like one of these

Honeywell is a very popular make.

PigletJohn Tue 23-Sep-14 12:03:45

here you are

email Horstmann if you can't find the instructions on their website.

The cylinder will also have a thermostat, but I don't know what it will look like. Probably a round knob on the side or front. It will control the hot water temperature when it is heated by the boiler.

Immersion heaters have their own thermostats inside the round cap (you must isolate the electricity supply before opening the round cap). They are unaffected by the cylinder thermostat.

webminx Tue 23-Sep-14 15:03:13

Thanks SO MUCH pigletjohn - that's brilliant. I'll set the control as you suggest! Thanks again

Hanabal62 Sat 23-Jan-16 11:02:58

I have a Santon premier plus cylinder that gives off a very bad smell. It's a bit like damp card board is the only way to discribe it. Santon have said it's possible a heating element which is breaking down. It is only three years old and as done this for at least two of these years. I live in a new build, the builders have checked it several times but never found any fault with it.

PigletJohn Sat 23-Jan-16 11:14:56

I'd suspect a water leak. The smell might be the chipboard floor getting damp. It is more likely outside or around the cylinder itself (they are very well made) in some other pipe connection. Ask around for a reputable plumber to look for signs of a leak (he will probably not be qualified to repair the cylinder itself) or at extra cost you could get a Santon approved repairer to look at the cylinder, I think they maintain a register of trained local agents. I don't think Santon will help if it turns out to be something else, but they will charge for the visit.

If you drape wet washing around it could be related to condensation.

PigletJohn Sat 23-Jan-16 11:16:35


They do have a very long guarantee.

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