SYSTEMATE 2000 Intermittent Hot Water

Great forum and I think I've established most of the information needed to identify what the fault is with my system.

Moved into a new house last month (about six years old) and no problems with heating water or radiators.

Last week the thermostatic shower started playing up. Temperature went cool whilst in the shower and on coming down stairs found that the pressure for the boiler (Glow Worm Micron) had dropped to zero. Radiators no longer heated up.

Water pressure refilled and boiler reset resulted in radiators working again and hot water at the taps/shower. However hot water is intermittent and keeps fluctuating from hot to warm to cold and back again (takes about thirty seconds).

Boiler temperature is set to maximum.

The horizontal bar 3 (HW) on the digital readout switches on and off as the water temperature from the tap changes. Logic would suggest a faulty sensor. Is this correct? If so which one?

Store _T1 is 74
PHE_T2 is 99
PHW_T3 is H60

T1 on is 74
T2 off is 77

One thing of note (I think) is that the heated towel rail in the en suite does not heat up. All other rads work fine and towel rail has been bled correctly.

Any help or advice will be appreciated. Dave

Could be a sensor problem or DHW pump.
The towel rail is taken off from where as in pipe connections?
Mike
MGC/H2O
Norfolk

HI

The readings that you have posted are self evident. The problem you have is with sensor T2.
T1 is the temperature of the main water store, and this water is used to heat the water that comes from your taps via the heat exchanger. T2 is the temperature of the store water AFTER it has given off some of it's heat to heat your hot water.
Unless the laws of thermodynamics have changed in the last few days, the water can't be hotter AFTER it has given off some of it's energy than it was BEFORE it gave off the energy!

Please be aware, changing sensor T2 will require the unit to be drained. Not a DIY job.

Thanks for that I will get someone in to fix it. Is the towel rail connected to this fault or is there some other reason for it not heating up?

Just a thought - if the sensor is faulty shouldn't there be an error reading on the circuit board?

Not necessarily, there will always be an error reading if the sensor fails totally, however, yours hasn't failed completely as it has the ability to read something, even though it's an incorrect reading.
Fault finding isn't always about finding an error code, but interpreting the information that is available.

Thanks, thought the 99 readings were false. Any idea what it will cost to have the sensor replaced?

It really depends where you are in the country (London will generally cost more as a rule).
As a general rule of thumb for a PHE sensor on a Systemate 2000 we would normally charge around £145.00 + vat including the part, but it would depend on how far we had to travel.

This should give you some guidance.