Help diagnosing (& hopefully fixing!) a hot water supply issue

BeeTheGoddess

Hi, my household is having an issue with hot water supply which I'd like to understand better and hopefully fix without having to call my landlord, as we're a bit concerned about raising any issues in the current rental climate. I'm also worried it might just be us being a bit thick! Would appreciate any help or insight from people here. 

The basic issue is that we have no hot water. The problem seems to be that the system is not responding to the programmer, as nothing 'fires up' during the times that the hot water is set to be on throughout the day, or if we just set the programmer to 'on' for the hot water. 

We do not have a combi boiler. The boiler is in a cupboard in the bathroom, and it is a Worcester Bosch Greenstar 15Ri condensing boiler. We then have a hot water tank, an immersion heater, the programmer, and a bunch of pipes and valves in the airing cupboard. 

The boiler was installed shortly before we moved in (July 2022), but we were told the rest of the system is older. Due to being unfamiliar with anything other than a combi-boiler, we didn't quite get the point of an immersion heater, and we had that switched on, as well as the boiler programmer for both central heating and hot water. I understand now that the immersion heater is only supposed to be a backup for if the boiler fails. The immersion heater then broke last month, and we were told to keep it switched off and use the boiler for hot water, and the immersion heater will be replaced in the autumn. 

We thought that was fine until we switched off the central heating as the warmer weather started. Within a couple of days we weren't getting any hot water. I did some experiments, and we get hot water just fine when the central heating is on. There is still no response when we switch the hot water to 'on' on the programmer, but if we switch the central heating to 'on', everything fires up and we have hot water in less than an hour. 

However, we obviously don't want to have the central heating on now, and have to get too hot every time we want hot water. 

I'm hoping this issue is a consequence of not fully understanding how the system works, or has a simple fix. Some googling suggested a diverter valve issue, but I don't quite understand what that means. I can see the valve, however, and have noticed it is hot to the touch even when the system isn't firing and the pipes aren't hot. 

I don't know if it matters but we also have a Honeywell thermostat. As far as I can tell it only controls the heating not the hot water. 

Thanks very much for any insights or help. 

BarelySentientAI

It does sound quite a lot like the motorised valve head is playing up - a relatively common issue.

I'm not going to try and explain how to diagnose, because I've seen other posts on here explain it very well and I'll wait for one of those forumites to arrive!

ThisIsWeird

BeeTheGoddess said:

Hi, my household is having an issue with hot water supply which I'd like to understand better and hopefully fix without having to call my landlord, as we're a bit concerned about raising any issues in the current rental climate. I'm also worried it might just be us being a bit thick! Would appreciate any help or insight from people here. 

The basic issue is that we have no hot water. The problem seems to be that the system is not responding to the programmer, as nothing 'fires up' during the times that the hot water is set to be on throughout the day, or if we just set the programmer to 'on' for the hot water. 

We do not have a combi boiler. The boiler is in a cupboard in the bathroom, and it is a Worcester Bosch Greenstar 15Ri condensing boiler. We then have a hot water tank, an immersion heater, the programmer, and a bunch of pipes and valves in the airing cupboard. 

The boiler was installed shortly before we moved in (July 2022), but we were told the rest of the system is older. Due to being unfamiliar with anything other than a combi-boiler, we didn't quite get the point of an immersion heater, and we had that switched on, as well as the boiler programmer for both central heating and hot water. I understand now that the immersion heater is only supposed to be a backup for if the boiler fails. The immersion heater then broke last month, and we were told to keep it switched off and use the boiler for hot water, and the immersion heater will be replaced in the autumn. 

We thought that was fine until we switched off the central heating as the warmer weather started. Within a couple of days we weren't getting any hot water. I did some experiments, and we get hot water just fine when the central heating is on. There is still no response when we switch the hot water to 'on' on the programmer, but if we switch the central heating to 'on', everything fires up and we have hot water in less than an hour. 

However, we obviously don't want to have the central heating on now, and have to get too hot every time we want hot water. 

I'm hoping this issue is a consequence of not fully understanding how the system works, or has a simple fix. Some googling suggested a diverter valve issue, but I don't quite understand what that means. I can see the valve, however, and have noticed it is hot to the touch even when the system isn't firing and the pipes aren't hot. 

I don't know if it matters but we also have a Honeywell thermostat. As far as I can tell it only controls the heating not the hot water. 

Thanks very much for any insights or help. 

As you realise, you shouldn't have to have the CH on to get DHW. As BSA1 suggests, the most likely culprit is the motorised valve.
Could you take a photo of the hot cylinder, please, showing all the pipes and bits surrounding it? Close ups of the 'bits' if it ain't clear. One of them will hopefully be this valve, and we can then guide you through testing it.
When it's fixed, you'll find that getting your DHW from the boiler will cost around a third of what it did from your electric immersion heater :-)

danrv

Is it a Honeywell motorised valve? They have been known to play up. Tend to get hot due to lack of ventilation.
Maybe try resetting the programmer but it sounds like the MV microswitch isn't waking up the boiler as it should.

anniecave

Do you have a thermostat on the central heating? If so, if you switch the central heating to on (at the programmer) but then turn the central heating thermostat right down (so the heating system is active but not actually coming on) does the hot water still work? Or not?

BeeTheGoddess

ThisIsWeird said:

BeeTheGoddess said:

Hi, my household is having an issue with hot water supply which I'd like to understand better and hopefully fix without having to call my landlord, as we're a bit concerned about raising any issues in the current rental climate. I'm also worried it might just be us being a bit thick! Would appreciate any help or insight from people here. 

The basic issue is that we have no hot water. The problem seems to be that the system is not responding to the programmer, as nothing 'fires up' during the times that the hot water is set to be on throughout the day, or if we just set the programmer to 'on' for the hot water. 

We do not have a combi boiler. The boiler is in a cupboard in the bathroom, and it is a Worcester Bosch Greenstar 15Ri condensing boiler. We then have a hot water tank, an immersion heater, the programmer, and a bunch of pipes and valves in the airing cupboard. 

The boiler was installed shortly before we moved in (July 2022), but we were told the rest of the system is older. Due to being unfamiliar with anything other than a combi-boiler, we didn't quite get the point of an immersion heater, and we had that switched on, as well as the boiler programmer for both central heating and hot water. I understand now that the immersion heater is only supposed to be a backup for if the boiler fails. The immersion heater then broke last month, and we were told to keep it switched off and use the boiler for hot water, and the immersion heater will be replaced in the autumn. 

We thought that was fine until we switched off the central heating as the warmer weather started. Within a couple of days we weren't getting any hot water. I did some experiments, and we get hot water just fine when the central heating is on. There is still no response when we switch the hot water to 'on' on the programmer, but if we switch the central heating to 'on', everything fires up and we have hot water in less than an hour. 

However, we obviously don't want to have the central heating on now, and have to get too hot every time we want hot water. 

I'm hoping this issue is a consequence of not fully understanding how the system works, or has a simple fix. Some googling suggested a diverter valve issue, but I don't quite understand what that means. I can see the valve, however, and have noticed it is hot to the touch even when the system isn't firing and the pipes aren't hot. 

I don't know if it matters but we also have a Honeywell thermostat. As far as I can tell it only controls the heating not the hot water. 

Thanks very much for any insights or help. 

As you realise, you shouldn't have to have the CH on to get DHW. As BSA1 suggests, the most likely culprit is the motorised valve.
Could you take a photo of the hot cylinder, please, showing all the pipes and bits surrounding it? Close ups of the 'bits' if it ain't clear. One of them will hopefully be this valve, and we can then guide you through testing it.
When it's fixed, you'll find that getting your DHW from the boiler will cost around a third of what it did from your electric immersion heater :-)

Thank you so much! I've attached two pics of the whole setup + close ups of all the bits. Really appreciate & thanks for the heads up about the saving! It's not quite clear on the valve photo but in the bottom right is a small metal lever that flips between Auto and Man. I've tried flipping it and nothing happens - still no boiler response. 

BeeTheGoddess

danrv said:

Is it a Honeywell motorised valve? They have been known to play up. Tend to get hot due to lack of ventilation.
Maybe try resetting the programmer but it sounds like the MV microswitch isn't waking up the boiler as it should.

No it's a Danfoss valve.....if I reset the programmer does that just mean I have to reprogram all the timings again? What's an MV microswitch?

Sorry for all the questions - I want to actually git gud at this stuff lol. 

vacheron

Looks like you have a 3 position valve setup with a tank thermostat. 

There are therefore 2 likely problems if the hot water works when the CH is on. 

1: The tank thermostat (the one with the rotary dial cut into the foam of the tank) is set far too low, or isn't working. This turns off the hot water when the tank reaches temperature.  From the picure, if the indication is at 6 o'clock, the dial may be set to turn off at about 20C so the HW will never come on. Turn this up to about 60C if this is the case. 

2: The three position valve (second last pic with the two black arrows on) is faulty . These can be pushed into position manually to test them, but they regularly fail These also call the boiler to heat, these are pushed one way by a motor and retun using a spring, so if it cannot move (valve is stiff/seized) or the internal motor drive or one of the internal microswitches are faulty, it cannot call the boiler to fire.  

 

BeeTheGoddess

vacheron said:

Looks like you have a 3 position valve setup with a tank thermostat. 

There are therefore 2 likely problems if the hot water works when the CH is on. 

1: The tank thermostat (the one with the rotary dial cut into the foam of the tank) is set far too low, or isn't working. This turns off the hot water when the tank reaches temperature.  From the picure, if the indication is at 6 o'clock, the dial may be set to turn off at about 20C so the HW will never come on. Turn this up to about 60C if this is the case. 

2: The three position valve (second last pic with the two black arrows on) is faulty . These can be pushed into position manually to test them, but they regularly fail These also call the boiler to heat, these are pushed one way by a motor and retun using a spring, so if it cannot move (valve is stiff/seized) or the internal motor drive or one of the internal microswitches are faulty, it cannot call the boiler to fire.  

 

OH MY GOD I THINK YOU FIXED IT YOU ABSOLUTE SAINT!! I thought the indication was 12 o'clock where the 60c is currently. Made 60c at 6 o'clock, turned the hot water on and the boiler responded!!!!! Just waiting to see if hot water actually appears, but now feel really draft for not spotting that hehe. 

Albermarle

1: The tank thermostat (the one with the rotary dial cut into the foam of the tank) is set far too low, or isn't working. This turns off the hot water when the tank reaches temperature.  From the picure, if the indication is at 6 o'clock, the dial may be set to turn off at about 20C so the HW will never come on. Turn this up to about 60C if this is the case. 

Although it looks like this has maybe solved the problem, then there is something  I do not understand.

If the hot water thermostat was set too low, then the hot water should not have worked when the CH came on or when the Immersion heater was on? 

Rodders53

Albermarle said:

If the hot water thermostat was set too low, then the hot water should not have worked when the CH came on or when the Immersion heater was on? 

Immersion will have its own thermostat under the metal cover!  Completely separate from the tank strap on stat.

Valve could be letting-by when in CH position to still give some flow through the tank heating coil?