Hot water problem

[fixitflav]

the right choice in contacting an engineer

I think he'll be scratching his head, but let us know what happens, won't you?

 

[Madrab]

Run this test, set the programmer to off for both heating and hot water - does the boiler still fire up the same way when hot water is used?

 

[steviek]

Run this test, set the programmer to off for both heating and hot water - does the boiler still fire up the same way when hot water is used?

Yes it does - the central heating has been off since we moved in in July so the boiler is only firing up for the water.

 

[Madrab]

Got to be a wiring issue then as suggested in post #22, the stat on the cylinder must be bypassing the programmer and sending power (SL) directly to the boiler or there's a short in the programmer.

 

[Johntheo5]

Yes, but the HW is just on 24/7, the cylinderstat is working properly IMO since there is no sign of excessive HW temperature, IMO fixing the programmed time might only mask the real problem, whatever that is, its possible that up to 5LPM of HW is "escaping" somewhere, but if so, then the boiler would fire regularly even during the night with no HW demand.
Its easy to test the cylinderstat, next time it fires up just turn the stat down and the boiler should stop firing.

One last question, does the boiler fire for very long after drawing off a small volume of HW?>

 

[steviek]

Yes, but the HW is just on 24/7, the cylinderstat is working properly IMO since there is no sign of excessive HW temperature, IMO fixing the programmed time might only mask the real problem, whatever that is, its possible that up to 5LPM of HW is "escaping" somewhere, but if so, then the boiler would fire regularly even during the night with no HW demand.
Its easy to test the cylinderstat, next time it fires up just turn the stat down and the boiler should stop firing.

One last question, does the boiler fire for very long after drawing off a small volume of HW?>

Thank you - no it only fires up for a minute or two I believe.

 

[Mister Banks]

The OP has said that the HW is set to be permanently off on the programmer but the boiler still fires when there is a HW demand therefore the cylinder thermostat must somehow be bypassing the programmer or the programmer is faulty.

 

[Johntheo5]

Agreed, and we now know for certain that the cylinderstat is also working correctly anf if the boiler only comes on maybe once/twice (or never) during the night then there is no escape of HW and the excessive gas consumption has got nothing to do with the HW cylinder except that there are multiple long showers being taken.
Suggest turning the cylinderstat down to minimum before going to bed, and take a meter reading, then another one in the morning before restoring the stat to its original setting.

 

[RandomGrinch]

Sorry, probably a silly question, have you been keeping an eye on your water meter, for any unexplained usage?

 

[dilalio]

Random thought occurred to me...
Are one of your toilets piped up to the hot supply, in error?

Have seen this before.

 

[fixitflav]

Yes it does - the central heating has been off since we moved in in July so the boiler is only firing up for the water.

I think your measured gas flow 1.8m3/h is on the high side, my oldish 15kW boiler is ~ 1.6m3/h. Using 1.6, the boiler is firing for 413h to use 661m3. In 30 days that means it's firing 413/24/30 = 0.57 or 57% of the time. That can't be right for HW only.
Also Johntheo5 estimates 480l/day HW usage. You haven't said how many live there, but typical total usage (hot and cold) is 150 l/day, so there's something odd there.

Do you have a smart meter by any chance? That could be doing something funny.

Perhaps a gas leak is a possibility. You'd expect to smell it, but depending on where..........

 

[Johntheo5]

The monthly consumption was 60M3 or 661.3kwh = 22.04kwh/day, assuming a boiler efficiency of 80% = boiler running flat out for 71minutes/day.
Maybe turn the cylinderstat to minimum which should keep the boiler from firing on DHW and run the HW on the immersion for a day or two, might show up something.

 

[fixitflav]

The monthly consumption was 60M3 or 661.3kwh = 22.04kwh/day, assuming a boiler efficiency of 80% = boiler running flat out for 71minutes/day.
Maybe turn the cylinderstat to minimum which should keep the boiler from firing on DHW and run the HW on the immersion for a day or two, might show up something.

Yes you're right, I misread that. D'oh!

 

[Mister Banks]

Yes it does - the central heating has been off since we moved in in July so the boiler is only firing up for the water.

Have you checked the wiring to the programmer? What programmer do you have?

 

[steviek]

Have you checked the wiring to the programmer? What programmer do you have?

It's a Danfoss TP9000. I think I need to leave it to the experts as my DIY skills are not the best! Appreciate all the suggestions though.