Help with central heating/hot water please

[AR74]

Hello. New to the forum but I have seen members have been able to help people with their heating problems and I was hoping someone might be able to help me out similarly. I am a complete novice when it comes to plumbing/central heating so might be missing something really obvious but I will try to explain what the issue is as best I can and hopefully someone might be able to offer some advice.

The system I have is:

Boiler: Remeha Avanta Plus 30S

Timer/controller: Drayton LP522

Hot water thermostat: Potterton PTT2

Central heating thermostat: Potterton PRT2

All of the system was already installed when we bought the house (about a year ago) and it was all working fine until a few months back.

The timer/controller appears to work correctly (i.e. the display shows the time correctly and the little green lights showing whether the hot water or heating is on illuminate according to the programmed timings or when the unit is manually set to “on”) but it does not seem to trigger the thermostats, and therefore the boiler, correctly.

If I want the central heating to come on I need to ensure that the central heating light on the timer/controller is illuminated (i.e. controls are either “on” or set to “timed” and the programme is timed to be on) but the light on the central heating thermostat does not illuminate until I cycle the hot water settings through to “off”. Once I do this, the light on the central heating thermostat comes on and, if the room temperature is below the thermostat setting, the boiler kicks into life.

The reverse is also true (i.e. I cannot get the hot water to come on without manually cycling the central heating settings through to “off”).

I do not have to leave the setting at "off" but can cycle back to "timed" or "on" without then affecting whichever thermostat has kicked in to life.

It is not possible to have both the hot water and central heating on at the same time.

I found the manual for the boiler and then followed the instructions to check whether it was set to be able to heat hot water and central heating simultaneously and it was.

I cannot see anything obvious in the instructions for the Drayton LP522 that indicate that I might have entered a mode where it will only heat hot water or central heating but not both.

I have tried turning off the mains power to see if this would reset things but after everything powered back on the situation is unchanged.

I put up with the situation for the last few months as I didn’t really need the central heating and manually heating the water was not too much of a chore but now that the temperatures outside are dropping I would like to get this sorted so my family don’t freeze in the mornings.

Any suggestions would be very gratefully received!

 

[dilalio]

Do you have an S or Y plan system?

Sounds like a 3-port valve problem.

Look in airing cupboard, near cylinder and see if you have 1 or 2 square boxes mounted on to pipework at that location.

If one "box" with 3 pipes to it, then google mid-port valve problems.

 

[AR74]

Thanks for the reply Dilalio.

Do you have an S or Y plan system?

I am afraid I don't know but...

Sounds like a 3-port valve problem.

Look in airing cupboard, near cylinder and see if you have 1 or 2 square boxes mounted on to pipework at that location.

If one "box" with 3 pipes to it, then google mid-port valve problems.

There is a smallish metal box attached to the pipework in the airing cupboard. The label on it says that it is a Honeywell F-5 and also says "Sundial Y Plan 3 Position Diverter Valve". I assume this means I have a "Y plan" system?

I will Google mid-port valve problems as per your suggestions and see what I can find. Thanks again for taking the time to reply.

 

[jackthom]

I'm wondering about the programmer in this case. The room thermostat should heve power available to it whenever the CH is switched on at the programmer. The state of the 3 port valve, or whether DHW is ON or OFF shouldn't be able to affect that.

I would want to get a multimeter on the appropriate points in the wiring centre to be sure.

 

[D_Hailsham]

Remove the programmer from the backplate (screws underneath) and check that the switch on the back is set to P.

 

[AR74]

Thanks for your replies. I googled the 3 port valve thing but the symptoms seem slightly different to the issue I am having, although that obviously does not rule it out as the cause.

My initial thoughts were that it was a problem with the programmer but unfortunately this poses a few additional issues as it has been tiled around, with very thick tiles, and the screws on the underside of the unit are not accessible. I can try to scrape the grouting out but I am not convinced this will create enough space to unscrew them due to the thickness of the tiles

I think I might need to get a professional in and see what my options are. Maybe install a second programmer somewhere else and bypass the current one? Or break the front off the existing one and hope I can somehow fix a replacement on?

 

[jackthom]

You need to get someone who can test the voltages being produced by the programmer in the wiring centre, then you'll know for sure. TBH if the programmer is at fault it won't be such a terrible job encouraging it to come off the wall and the new one can then be fitted with it's backplate flush with the tiles.

 

[Agile]

It always amazes me at the lack of intelligence shown by those who tile around things like that!

 

[jackthom]

It always amazes me at the lack of intelligence shown by those who tile around things like that!

The daft thing is it's usually much easier to remove that sort of thing than try to cut tiles around it.