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

(26 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.

Jefriwa Sat 25-Mar-17 22:22:27

I have a wanton water solar boiler and have a pipe with a connection on it which you can see into. There is water constantly running through and I was wondering if this is normal.
Hope you can help

PigletJohn Sat 25-Mar-17 23:03:57

show us a photo

Jefriwa Sun 26-Mar-17 18:19:27

It is down the right of the tank. Photo attached

PigletJohn Sun 26-Mar-17 18:32:45

it appears to be venting into the tundish, which suggests that it is overpressured.

You need to get it serviced by a heating engineer who is qualified to work on unvented cylinders (not all are).

Jefriwa Mon 27-Mar-17 06:32:59

Thankyou. Probably an expensive job then . I shall get some quotes

PigletJohn Mon 27-Mar-17 12:14:51

I think a fairly common repair. It may be a matter of adjusting or replacing a pressure regulator.

Unvented cylinders should be inspected regularly, it can often be included during the annual boiler service, provided the engineer is qualified both on boilers and unvented cylinders.

Jefriwa Mon 27-Mar-17 18:24:06

Do you have anyone you can recommend for a service in the southend Essex area ?

PigletJohn Mon 27-Mar-17 18:49:41

no, sorry

Dibble1452 Tue 04-Apr-17 18:56:26

I live in a new build (well it was in 2007) which has a Santon Premier plus unvented hot water system with an unvented indirect cyclinder. I love the system, and in the winter I have the heating constantly turned 'on', but vary the thermostat. I have the hot water to come on twice a day, that way I always have hot water to wash up/shower with. A former work colleague who used to work for the Gas Board as an engineer, told me once that in the winter it is cheaper to have your heating on all the time (just turn the thermostat down low at night), as everything from the walls of your house to the furniture absorbs the heat, but if you have it go completely off and the house (and furniture) go cold, then the system has to work harder and it costs more, for the house (and furniture) to come back up to the temperature it was before it went off. Plus that way its unlikely the system will freeze up or fail, when it fires up.

mano2415 Tue 21-Nov-17 20:57:45

Hi, I have Promax SL condensing central heating boiler with santon premier plus unvented cylinder.
The boiler is set to turn on by Honeywell temperature control at 6am till 8pm but the problem is boiler turns on at 6am, heats up the water in cylinder but doesn’t turn back again once the water is cold even though the boiler is at on position till 8pm.

PigletJohn Tue 21-Nov-17 23:56:10

that's curious.

please post photos of your timer and any other controls. I expect you have separate time settings for the Central Heating and the Hot Water. I don't know what a "Honeywell temperature control" is.

When did you last have it inspected or serviced?

I'm surprised you can use all the hot water in a single day.

mano2415 Wed 22-Nov-17 16:32:27

Thank you very much for reply. I was trying upload the pics of controls but could not do it on this thread. I can try to explain the controls . I have two controls one is to ST9420C controls and the other one is DT92E.
There is time set for hot water on from 6 am to 8pm on ST9420C and it is on once position. The boiler only comes on at 6am to hot the water which stores in santon premier plus unvented storage cylinder.
Onnce we use the hot water in the morning for 1 or two baths then water turns cold and the boiler does not light up to hot the water even though the ST9420 is set on between 6am till 8pm. Boiler turns back on the next morning 6am for short time and turns off automatically, never turns back again until the next morning 6am.
Mean while the heating side of ST 9420C is on off position. But if we run out the hot water we need to turn on the heating, which boost the boiler to turn on and warm the water. The DT92E is room temperature display and heating temperature controler.
Please send me an email to so I can send you the pics directly.

PigletJohn Wed 22-Nov-17 18:29:43

sounds to me like a wiring error. Did it ever work correctly? Some older boilers are not fully pumped, but it looks like you have a modern system, so unlikely to be that.

I think you have one of these kits

If you set the timer on the ST9420C to HW on, CH on, but turn down the temperature on the ST9420C, what happens?

I am not keen on the wireless controls as they sometimes stop working for no apparent reason, and are more work to fault-find.

PigletJohn Wed 22-Nov-17 18:34:14

turn down the temperature on the DT92E, I meant.

PigletJohn Wed 22-Nov-17 18:41:28


sometimes odd faults occur when the batteries need changing, so an easy fix is to try new ones all round.

Duracell are a slightly different shape, and sometimes don't fit well

Energizer, Aldi and Lidl AA batteries came out well in Which.

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