Help with Boiler issue

m_r_jackson90

I have a promax he plus combi boiler which has recently developed a fault where the heating and hot water stays on and even though the thermostat and timer are programmed to be off. This happened last week and turning off the boiler for a few hours rectified the problem however its happened again today and turning the boiler off hasn't solved it.

any ideas

matelodave

Not really sure what you are saying.

A combi tends to fire up when the hot tap is turned on irrespective of any timer and the heating is usually under the control of an external timer/thermostat (ideally a programmable stat rather tha a separate stat & timer)

so how is your actually configured and what exactly is happening - go through the sequence in a methodical manner to see if there's a bit of finger trouble somewhere.

m_r_jackson90

the boiler (heating/water) is on timer to come on morning and night. however it is still running when the timer program is not on. the radiators are red hot (when the timers off) and it is running even if no water is being used

CashStrapped

When was it last serviced?

Have you tried manually lowering the temperature for the radiators so they do not get too hot? at lest for the time being.

It could be a thermostat failure (hence the boiler thinks it is cold and is putting the heating on 24/7). Or it could be a PCB issue....

For more specific problem solving

try

https://www.diynot.com/diy/forums/plumbing/

It is a fantastic site with a lot of resident trades who give advice.

Ultimately however, unless not directly connected to the boiler i.e timer or thermostat replacement.

Anything that requires looking under the hood should be done by a Gas Safe registered plumber.

But use that forum to get an idea as to what it could be.

m_r_jackson90

thanks for your help

matelodave

It sounds like there could be a control board problem which is holding the boiler on when the timers shut it down. Most combis have overun controls which maintain the boiler fan and pump to allow it to shut down gracefully rather than just shutting off completely so you probably need to get it checked out by an engineer.
Have you checked the handbook to see if there's anything obvious or if theres a fault finding flow diagram which could help you diagnose it.

m_r_jackson90

ive checked the handbook and there are no error codes being displayed on the boiler. i have limited knowledge of diy so id struggle with anything else

matelodave

Has the boiler got a frost protection thermostat - if so it could be stuck closed thus causing the boiler to run coninuously as it's wired across the timer/room stat connections.

You really need to know what you are doing, be able to read a circuit diagram and use a multimeter to check out the controls.

If you can't then I'm afraid that you need to get hold of someone who does.

m_r_jackson90

thanks, i know i need a gas safe engineer to sort it i just didn't want to be fobbed off with "you need a new boiler"
:rotfl:

TinoMclaren

Boilers are fitted by gas safe engineers, wiring to the timer usually by electrician. Having a background in electrical engineering and having wired up a lot of boilers this could be caused by:
- Faulty Timer
- Solenoid water flow valve is sticky (most likely)

Unfortunately there is nothing you can do except keep turning your boiler off and on, this will cause a power up cycle which will include a solenoid test, this may free it up for a short while.

As has been said, you need a good gas safe engineer to take a look at it. I usually ask about my local area for recommendations (facebook etc...)

Good luck