No hot water

November2

Before I contact BG again, can someone help me understand how my boiler works please.  Had a new Vailliant ecotec plus boiler fitted by BG, had them come out to it yesterday as each time the timer programme started the installation message came up on the boiler display, also hot water was so hot couldn't touch it, it was set to 45 on boiler.  Engineer fiddled with display and the message doesn't come up now - he said for some reason it had been set to combi boiler settings - we have a tank in loft and one in airing cupboard. He then replaced something on the tank in the airing cupboard to fix hot water issue setting the dial to 55, what is confusing me is he then said the boiler itself has no bearing on the hot water temperature at all and the hot water settings on the boiler are basically irrelevant.  Is that right?  Today hot water programme has been on but I have no hot water at all!  I had no problems at all with the hot water with my old boiler. 

TadleyBaggie

Almost certainly he replaced the thermostat on the hot water tank, which is the only way the boiler knows if the hot water is below the required temperature. Sounds like either the new thermostat is defective or it's not wired correctly.

I think the hot water temperature setting on the boiler is mostly redundant, although if set too low may not allow the water in the hot tank to ever get to temperature and be constantly calling for hot water.

Bendy_House

Hi Nov.

Just to pad out what TB said above, you can adjust the temp of the water being delivered by the boiler using the control panel. Once set, the water being delivered by the boiler shouldn't really go over that, although it will likely fluctuate to some degree as it controls itself. An internal (to the boiler) 'stat does this.

So, that's one side of what's going on.

If your boiler was running as a 'combi' type - ie one that delivers instantly heated water on demand, and doesn't use a hot cylinder in your cupboard like yours - then you'd be able to separately set the DHW temp (the 'tap' symbol) and the CH (the 'radiator' symbol) temp. Eg, you'd typically set the boiler to deliver 'tap' water at 60oC and 'rad' water at 75oC+.

However, from what I understand, your combi boiler has effectively been turned into a 'heat only' boiler, and no longer delivers 'instant' hot water on demand. The 'wee tap' side has therefore been disabled, and only the CH (radiator) side is still delivering the goods to BOTH your hot cylinder AND your rads. The boiler's 'CH' output will be diverted between the DHW and CH using valves (probably mounted beside your cylinder).

Since the rads will need >70oC in order to be hot enough for general use, and the DHW cylinder will also need to be ditto in order to heat up the cylinder quickly, then your boiler's ('rad') output temp must surely be set at over 70oC? NB - this output temp will be the 'CH' temp of the boiler, and not the DHW as that no longer exists.

If the 'tap' symbol still shows a temp, that will be irrelevant. It is no longer being used.

Ok, let's say the boiler delivers water heated to 75oC. That will be fine for your rads, but a bit hot for your tap water. So, your hot cylinder has its own 'stat fitted to its side to keep the DHW temp at what you want, which is around 60-65oC. That's 'ouch' hot but not 'scalding', tho' it would if you kept your hand in it. This cylinder 'stat is seemingly what the engineer replaced on your hot tank, and being set to 55oC is fine since it measure the temp waaay down the side, so the water above this - which is what comes out your tap - will be higher, probably 60oC+.

To sum up, your boiler delivers water at a likely 75+ degrees, and your cylinder stat keeps the cylinder at ~60oC. Your rads also get 75+ degrees, but your room stat shuts off the rads when the rooms are warm enough.

"Had a new Vailliant ecotec plus boiler fitted by BG, had them come out to it yesterday as each time the timer programme started the installation message came up on the boiler display, also (1) hot water was so hot couldn't touch it, it was set to 45 on boiler.  Engineer fiddled with display and the message doesn't come up now - (2) he said for some reason it had been set to combi boiler settings - we have a tank in loft and one in airing cupboard. (3) He then replaced something on the tank in the airing cupboard to fix hot water issue setting the dial to 55, what is confusing me is (4) he then said the boiler itself has no bearing on the hot water temperature at all and the hot water settings on the boiler are basically irrelevant."

1) That 'too hot' water was from your hot cylinder, whereas I suspect the '45o' set on your boiler was the combi 'tap' setting which is not used on your boiler as it isn't a 'combi' type any more. So that 45o reading was irrelevant, and had now't to do with how the boiler was running in your home. Your hot cylinder is being supplied by the CH ('radiator') side.

2) What I would love to know is, why did they fit a combi boiler in a house that didn't need it?! You needed a 'heat only' or 'system' boiler. Combi boilers are (a) more expensive, (b) larger, (c) more complex and (d) over-sized. Why did they fit this?! Did you tell them that, perhaps 'one day' you'd like to change to a combi boiler so they future-proofed? If not, then surely to fit a combi and turn it into a 'heat only' is a mistake?

3) That's the cylinder 'stat, and a faulty one would explain why your DHW was too hot. 55oC is fine, tho' you don't want it any lower than this. Clearly the engineer did something else wrong, tho', as you no longer have hot water!

4) Largely correct. As long as the boiler is set to an output HIGHER than what's need by the hot cylinder, then it should work fine - your cylinder 'stat will shut it off when the required ~55oC is reached. (If the boiler was set to output only 55oC, tho', then your cylinder would take ages to heat up. If the boiler was set to below 55oC, then your hot cylinder would never get to 55oC. Usually you want the boiler delivering at least 75oC so that the cylinder can be reheated quickly enough.

Please ask them about their choice of boiler!

November2

Programme came on this morning for two hours alongside the heating and the water remained cold.  Just before programme ended I over-rode the control on the wall turning water off then back on again, ten minutes later heating programme ended with hot water programme remaining on, boiler wound down then fired up over and over for a minute with number on display going up and down. Is this normal?  It now has 58 with a flashing central heater radiator symbol on the display, radiators are off and cold.  Now after running the water programme for another hour I have warmish water.  As I had no problem with water before the new boiler fitted surely its something to do with this new boiler or something fitter did when in airing cupboard, that the new thermostat is defective is possible of course but seems a bit unlikely and surely something else is going on.  Engineer may not have even replaced thermostat, I'm sure if he'd said that I would remember, I think he said something like 'clip'.  

Bendy_House

The bottom line is - these guys need to come back to sort this!

If you like the investigation side, then if you post a photo of your hot cylinder and valves - I'm guessing they are in the same place? - then we can suggest things to try.

It does sound as tho' your programmer is telling the boiler to come on to heat up your hot cylinder, but the water isn't actually getting to your cylinder. That would suggest an issue with the valve that controls that flow, and it might be it isn't getting the 'signal' to open up as it should.

Photo please.

(As I said in my short post above, IF this 'combi' boiler has been set up to work as a 'heat only' boiler, then the DHW ('tap') side of it no longer performs any function. So, for BOTH the CH AND the DHW (your hot tank), only the CH 'radiator' side - and symbol - means anything.)

WHY did they fit a 'combi'? Did that decision have anything to do with you?

November2

Thank you for your reply, I'm not boiler savvy so have re-read it several times already!  On BG site I filled in a form choosing standard boiler not combi to replace a standard, a choice of boilers came up and I chose the mid price one Valliant Ecotec Plus (£2,400 fixed price).  Yesterday the water eventually did became hot when running the HW programme on its own after I'd turned the boiler CH programme off. Today its cold again running with the CH programme.  The boiler CH is set to 60, the cylinder tank to 55.  Radiators are very hot except the bathroom radiator which is only warmish.  I have no idea what the HW setting on the boiler is as I can no longer access it as the buttons will now only bring up the CH, guessing BG engineer did that when he came the other day. Too cold tonight to turn CH off to try water programme separately, but will try that again tomorrow. Will be phoning BG on Monday to come take a look. 

Bendy_House

November2 said:

Thank you for your reply, I'm not boiler savvy so have re-read it several times already!  On BG site I filled in a form choosing standard boiler not combi to replace a standard, a choice of boilers came up and I chose the mid price one Valliant Ecotec Plus (£2,400 fixed price).  Yesterday the water eventually did became hot when running the HW programme on its own after I'd turned the boiler CH programme off. Today its cold again running with the CH programme.  The boiler CH is set to 60, the cylinder tank to 55.  Radiators are very hot except the bathroom radiator which is only warmish.  I have no idea what the HW setting on the boiler is as I can no longer access it as the buttons will now only bring up the CH, guessing BG engineer did that when he came the other day. Too cold tonight to turn CH off to try water programme separately, but will try that again tomorrow. Will be phoning BG on Monday to come take a look. 

£2,400 was inclusive of fitting? Blimey, that's cheap for BG.

Although I understand that a combi can be used as a heat-only boiler (by simply not connecting up the DHW side to it, and possibly by changing its control settings), it is still a very strange choice to make, and I'd love to know why they did it. Is it because it simplifies their range of boilers - "stick in a combi and make it act like a heat-only"? As I said, there's lots of reasons to not do this (it's larger, more expensive, more complicated, often requires a larger gas pipe), and you clearly didn't choose a combi either! 

Anyhoo, it should be able to work as you now need it. ONLY the CH side of the boiler is now made operational; ie, all the boiler does now is to heat water and send it out one pipe. This heated water is then diverted to either the CH or the DHW or both using motorised valves.

I'd love to see a photo of your hot cylinder and accompanying pipework :-)

You say the CH is set at the boiler to 60oC? That's surprisingly low. Yes, that would be 'hot' to the touch, but rads at 60oC would hardly be described as being 'very hot'. How long can you keep your fingers on a rad?! But, if that heats your house fine, then it's a good temp to have.

It must surely be more problematical for heating your DHW cylinder, tho'? You will want your cylinder to be pretty much 60oC for it to be hot enough and to kill Legionnaires. Also, you'll ideally want to heat up that cylinder quickly. This won't happen if the supplying water is only at 60oC - there isn't enough of a temp difference to heat up the tank quickly.

It's all a bit strange.

You could email BG and ask about their choice of fitted boiler? :-)

November2

Hi, thank you again for replying. I have now worked out the water will get hot if running alone when CH is turned off.  Ran them together this morning - cold water, ran CH through day very hot radiators, then both again at teatime - cold water.  As an experiment I turned CH off this evening and turned HW on, after an hour water is boiling hot!  Getting back to BG tomorrow.  

Bendy_House

November2 said:

Hi, thank you again for replying. I have now worked out the water will get hot if running alone when CH is turned off.  Ran them together this morning - cold water, ran CH through day very hot radiators, then both again at teatime - cold water.  As an experiment I turned CH off this evening and turned HW on, after an hour water is boiling hot!  Getting back to BG tomorrow.  

That's very promising, Granny. Clearly, the essential setup works, but its control is very suspect! You obviously should be able to have both CH and DHW running at the same time.

It could even be that they've tweaked down the flow to the DHW cylinder so it won't pinch the boiler's supply when both are running (the DHW would usually have an easier path, so the water would find it easier to go this way at the expense of the CH. By restricting the flow to the DHW by using a partly-closed valve, this forces more water to the CH side. But if they close that valve too far, then the DHW will be starved). That's just guesswork, of course.

I'd still love to see a photo of your cylinder and fittings...

Anyhoo, please report back when they've been, and pleeeeeze ask them "Why a combi?!" :-)

November2

Well here's the update. Engineer came out and after over an hour of tests replaced a white box in the airing cupboard which he said must've been fitted in error as it was the wrong model number so switch wasn't moving from HW to CH.  It seemed to do the trick, only the hot water has still been very hot (engineer set boiler CH temp flow to 65 and 60 on tank).  Well tonight its not working again, HW did not go off on the programme timer so I manually turned it off on the wall, usually if I turn HW off manually boiler will clunk and the display goes blank but then comes on again because CH programme still running, (engineer said that's normal) however tonight the display stayed blank and boiler didn't come back on despite the CH programme still running, I then discovered radiators were only warm so CH must've gone off earlier even though it was still lit up as 'on' on the programmer. 
Is the boiler supposed to keep clunking on and off, its forever making loud clicking noises too. I have no paperwork saying electrics were checked when fitted, electrician only looked about 16 years old which struck me as odd at the time, I didn't see him check anything, neither did he turn electrics off at meter like I was told he would. 
Bendy-House, the model number is 415 and engineer said its a heat only boiler not combi (the display has tap symbol and settings but isn't used so maybe they just use same display unit for regular and combis) 

Bendy_House

We really could do with some photos, Nov. The boiler display & controls, the valves surrounding the hot tank, the 'white box', and all other external controls - room stat and stuff.
You say the water can be too hot? Have you ID'ed the cylinder thermostat wot's fitted to the side of the cylinder, and which has a temp scale on it? Well, when the water is 'too hot', try turning that scale up and down and noting the middle point where it goes 'click'. Return it to '60' when you've finished.