faulty potterton boiler?

tom o

i have a potterton suprima boiler with a control unit that i've set up to timer the HW and CH. however, sometimes the CH doesn't come on at all.both come on twice a day at the same time. Have i set the thermostate on the unit too high/low, run out of hot water? etc. the boiler is only 7 years old. any help would be great

mark_56

The pottertons I've worked on had a DHW prority relay. That means that making hot water takes priority over making heat. When it is done making hot water it should then switch to making heat. If your water is hot, but not quite hot enough to satisfy the limit it will keep trying to make hot water. Turn DHW limit down, and/or boiler limit up. Check for air in DHW circuit and/or heating circuit. If DHW priority is achieved by using a 3-way zone valve make sure that it is operating correctly and not siezing up, and that it is installed to fail in the heating mode (if heat is more important than hot water- if you live where it gets pretty darn cold).
And finally you will need to check that your aquastat, thermostat, boiler limits, and relays are working properly. Any one of these not opening or closing when they should will cause this problem.

Andy Byrnes

Have you tried the room stat. Turn it up and down and make sure it is clicking.

I am assuming you are in the UK ( with it been a Suprima. )
and you have a cylider with a stat strapped to it and a pump and diverter valve some where near the cylinder.

If this is so the sequence of operation should be some thing like this. On a demand from the clock power is sent to the room stat, if this is calling power is sent to the diverter valve to open for central Heating.

You may have 2 zone valves one for Heating and one for Hot water and if so one of the zone valves could be faulty.

Andy B.