Immersion hot water system, what schedule is most optimal?

Bendy_House

Apodemus said:

I think we are getting somewhere!  Time to pause and review the evidence.

You have unexpectedly high energy usage.  You have a hot water system controlled by a motorised valve that switches off properly, but doesn't seem to switch on when instructed to do so (but can be opened manually).

Occam's razor (WHAT?!!) might suggest that these two pieces of information point to the immersion being on, the water in the cylinder being hot and the tank thermostat giving a message that the motorised valve should remain shut.

So first job is to hunt down the switch that controls the two immersion heaters in the tank.  Once these are off, and with the hot water in the tank used up, then see if the Hive controls will send a message to the motorised valve to open it. 

If you can't find a switch for the immersion heaters, then look at your fuse board/consumer unit as it is most likely that the immersion heaters will be on a separate fuse.  If you know what you are doing, you could make sure that the immersions are off, by switching off at the fuse box.  (It's also not unheard of for the immersion switch to be adjacent to the consumer unit, but I'd be surprised if this was the case on a modern system like yours). 

"but doesn't seem to switch on when instructed to do so (but can be opened manually)" - I think, from Arfa's description, it is working ok.

They described how, with the CH 'off', the valve's lever was firm against the default end, but could be pushed against firm spring pressure towards opening the valve, and would spring back when released. That's good. And then, when they turned the CH 'on', this lever became loose - which is also correct as the valve will have been 'motorised' open by the controls, therefore taking the pressure off this lever - and this was followed by the pipe becoming hot. It would all appear to be working fine, I think.

I agree - Arfa should investigate the immersion controls, and get that turned off if it's currently being used to heat the tank. Unless they also have cheap-rate leccy, in which case they should compare energy sums - off-peak leccy vs gas.

Section62

Le_Kirk said:

The pipe stat would (probably) be used in conjunction with the frost stat.  The frost stat says (to use Bendy phrases) "Oooh, I'm cold, turn on the boiler" and the pipe stat says "OK, I've warmed up nicely, you can turn off the boiler".  I thought over-run stats and overheat stats would be internal to the boiler.

Yes, unless you install a radiator in the garage (not recommended), having the boiler running won't increase the ambient temperature in the garage by much, so the frost stat isn't going to switch off by itself.

The pipe stat should do the switching off when the water in the system is warm enough, and back on (if necessary) as the system cools if the frost conditions persist.

Bendy_House

Drawn a bit of a blank as to why you still have a powered-up BG WR1. This is a ONE-channel unit, usually used to control ONLY the CH, say when using a combi boiler. It looks identical to a Drayton unit from that time (it's getting on now), and is usually paired with a digital wireless room 'stat:

But, Arfa has a new, 2-channel (DHW & CH), Hive controller, so why the WR1 is still there, I have no idea.

It could have something to do with the frost stat, possibly? BUT, that Potterton Controls Frost Stat is pretty clearly a 'wired' fellow, so surely can't be?

And then there's the Pipe Stat above the boiler, but - again - there's a cable coming from that.

Could someone, therefore, have simply left it powered up - but not connected to the boiler - when they installed the HIve?! If so, they are very naughty indeed.

Arfa, that WR1 currently has a STEADY red light showing? I'm guessing that is 'alarm', which likely means no-one is talking to it. Does that ever change? Any other lights come on? Does that one flash?!

Your HIVE - when you manually override (buttons on the very top of the unit) the DHW and the CH in turn, do the BOTTOM lights in your Hive receiver come on in response? And does the boiler respond too? (NB, when you 'manually' turn a Hive on and off like this, it won't go 'off' right away, as it wants to protect the boiler from fast switching. So, when you turn it on, and then off quickly, it'll carry on being 'on' for 20-odd seconds before going off. I think the display flashes on the control unit during this.)

Homework:

1) As Apode says, find out how to operate the immersion heaters - and ideally turn them off.

2) Tell us if you have cheap-rate leccy at any time.

3) Test your Hive to ensure it DOES control your CH and DHW as it should.

4) Search for the WR1's partner in crime - it could look like the left-hand jobbie in the pic above. If there isn't one, then don't worry (as long as your system works ok with the Hive), but make a note to tell your GasSafe at the next service to remove the bar steward.

5) That upper grey box on the side of the cylinder, does it have a cable going to it? If so, where does it lead to?! Is there anything written on that box? (I'm hoping it's the cylinder 'stat)

6) Do you have a Hive 'HUB'? If not, please seriously consider getting one - you can buy the latest Nano 2.5 on eBay for £37 - a bargain (unless all sold...). This WILL make your life easier - the control, programming, and operation via the phone or PC App is superb.

Arfa__

Bendy_House said:

Drawn a bit of a blank as to why you still have a powered-up BG WR1.

...

But, Arfa has a new, 2-channel (DHW & CH), Hive controller, so why the WR1 is still there, I have no idea.

..

Arfa, that WR1 currently has a STEADY red light showing? I'm guessing that is 'alarm', which likely means no-one is talking to it. Does that ever change? Any other lights come on? Does that one flash?!

Always a steady red light. Doesn't change as I turn on CH or DHW.

The boiler was replaced in 2014, could this be some vestige from a prior boiler installation that should have been disconnected?

Your HIVE - when you manually override (buttons on the very top of the unit) the DHW and the CH in turn, do the BOTTOM lights in your Hive receiver come on in response? Yes. And does the boiler respond too? (NB, when you 'manually' turn a Hive on and off like this, it won't go 'off' right away, as it wants to protect the boiler from fast switching. So, when you turn it on, and then off quickly, it'll carry on being 'on' for 20-odd seconds before going off. I think the display flashes on the control unit during this.) Yes, they come on when engaged and then flash for a bit after turning off (fast-switch protect as you suggest I guess).

Homework:

1) As Apode says, find out how to operate the immersion heaters - and ideally turn them off.

Have turned off immersion heaters at the wall switch near the tank. That was labelled 'water heaters'. Though light on the switch was out, will need to pursue that I guess. Also found a trip switches on the consumer unit for 'heating' and 'immersion'.

2) Tell us if you have cheap-rate leccy at any time.

I don't. On a standard fixed rate, no economy-7.

3) Test your Hive to ensure it DOES control your CH and DHW as it should.

Yes, it does appears to do so. Turning on/boosting causes it to kick in, schedules kick in as expected.

4) Search for the WR1's partner in crime - it could look like the left-hand jobbie in the pic above. If there isn't one, then don't worry (as long as your system works ok with the Hive), but make a note to tell your GasSafe at the next service to remove the bar steward. 

Right-o, will have a hunt around but not seen that RC1 unit anywhere yet.

5) That upper grey box on the side of the cylinder, does it have a cable going to it? If so, where does it lead to?! Is there anything written on that box? (I'm hoping it's the cylinder 'stat)

Nope, no cables going to it.

6) Do you have a Hive 'HUB'? If not, please seriously consider getting one - you can buy the latest Nano 2.5 on eBay for £37 - a bargain (unless all sold...). This WILL make your life easier - the control, programming, and operation via the phone or PC App is superb.

Yes. Had to buy a new one of course as old one couldn't be transferred, but that's another story...

Thanks again for the help!

Bendy_House

Fab, and 10/10 for doing your homework

I suspect it's as you say - that other receiver is a leftover from the previous boiler. It isn't hurting to have it there, but it should really have been removed.
I wonder if that pipe stat is also from that previous installation? Do you tend to have annual services? If so, I'd ask about these, and have them disconnected at the wiring centre. Hopefully your GasSafe is also clued-up electrically, or else they may need to send in their sparky.
Or, just ignore these parts - almost certainly they are not affecting the current system.

Ok, that upper grey box will likely be a location for a second immersion heater, then, or possibly a further pipe connection. In any case, it ain't doing nuffink, so don't worry about it.

The existing immersion near the bottom will almost certainly have a built temp stat under that cover, probably set to no more than 60oC. Since it's very close to the tank bottom, by the time it gets to the set temp way down there, it'll be a LOT hotter at the top of the tank - 80-odd, I'd guess, so hopefully the immersion stat isn't above 60!

The immersion switch light doesn't work. As you suspect, it's either a blown fuse (if it has one on the switch plate), or tripped at the CU. Or, the neon light has failed. Another thing for your sparky to check...

Cool, the main things - DHW and CH - appear to be working fine. Now just programme your Hive to the most efficient settings.

One concern - tho' I suspect it won't be - is the seeming lack of cylinder 'stat. Could you have a look all the way around the cylinder, and try and locate it please? It's usually just under half-way up.

If you cannot find one, could you unscrew that upper grey cover and photo what's underneath?

Le_Kirk

Bendy_House said:

Le_Kirk said:

The pipe stat would (probably) be used in conjunction with the frost stat.  The frost stat says (to use Bendy phrases) "Oooh, I'm cold, turn on the boiler" and the pipe stat says "OK, I've warmed up nicely, you can turn off the boiler".  I thought over-run stats and overheat stats would be internal to the boiler.

Thanks... I think...

I'd have thought the overrun would be integral too, but just can't think of any other purpose for that pipe stat.

Yep, just commenting on your style of prose - I enjoy reading your posts.

Bendy_House

Le_Kirk said:

Bendy_House said:

Le_Kirk said:

The pipe stat would (probably) be used in conjunction with the frost stat.  The frost stat says (to use Bendy phrases) "Oooh, I'm cold, turn on the boiler" and the pipe stat says "OK, I've warmed up nicely, you can turn off the boiler".  I thought over-run stats and overheat stats would be internal to the boiler.

Thanks... I think...

I'd have thought the overrun would be integral too, but just can't think of any other purpose for that pipe stat.

Yep, just commenting on your style of prose - I enjoy reading your posts.

OOooOOh! Thank you.

I'll make them twice as long in future

kipsterno1

I have a similar cylinder and the stat for it is under the bottom grey cover. Turn the power off before you remove it. On mine there isn't a dial just a small spigot.  If you cant see it I'll try and sort a photo.

Arfa__

Pic of what's behind the top grey cover on the tank:

Regarding the RC1 receiver, no sign anywhere of what connects to it. But in the big pile of manuals left to us by the previous owners, I found one for a T4RF thermostat which I suspect would have mated with that RC1. Also found a bunch of manuals for random other appliances not present in the house too! Including a Grundfos Home Booster pump...

Arfa__

Pic from behind the lower cover on the tank:

Would I be right in saying there is only one immersion heater fitted here and that the top cover just has a blanking plate?