Boilermate 2000 DHW too hot

[NormH]

Our problem seems to be the opposite of other threads I've seen as the hot water from our taps is extremely hot (over 45C). I've replaced the thermostat but it makes no difference. Cycling through the SW1/SW2 fault finding the DHW T3 reads 47/48C with a hot tap running. BGas solution is to reduce the temperature of the thermal store, which works but leaves the boiler pump running continually and the boiler continually turning on and off.
I cannot see how the required DHW temperature is set, is it pre-configured and fixed on the ACB? Is ACB replacement the only solution?

 

[MeldrewsMate]

Firstly a caveat - I cannot comment on your specific model of thermal store, my advice is general.

There should be a mixing valve on the hot water outlet which blends the hot with cold to give an acceptable outgoing temperature. If this has stuck, due to scale, debris, or other cause it can be cleaned, freed-off, or replaced. Try turning the adjuster from hot to cold to hot repeatedly. Is there a light resistance, slightly more when turning to cold from hot?
Is the outgoing temperature stable? Does it vary with flowrate?

I think BG may have turned down the boiler's flow temperature setting rather than the thermal store's temperature, hence the cycling.
Maybe a call to Gledhill's tech help would solve the mystery of the thermal store's temperature setting. They are designed to run at high temperatures, but I would imagine there is a temperature adjustment somewhere - perhaps a pot on the control board?

MM

 

[Ihavenojob]

Have you taken a reading of the temperature at the tap ? Does this have a back up (SWITCH) on the boilermate control? If so, make sure it is off.

 

[NormH]

As you surmised, reduction in the thermal store temperature was achieved by lowering the boiler temperature. It's now been increased but the boiler temperature still isn't set to MAX as the manual suggests but it's high enough (around 67C) to satisfy the Boilermate and stop the boiler from constantly cycling. The Boilermate 2000 doesn't have a mixing valve, it heats the incoming mains water via a plate heat exchanger which appears to be heating the water too much, resulting in the temperature of 45C at the taps. I should add the DHW pump to the heat exchanger has been replaced so should be running correctly.
A scaled up heat exchanger is a common problem, resulting in reduced flow but flow at the hot water tap is almost full mains pressure. The control on our model has a 3-position backup switch for emergency electrical heating but it is set to NORMAL BOILER OPERATION.

 

[cross thread]

From what I remember as I have not worked on one for several years the hot water pump is a special modulating model is the replacement the correct one

 

[Ihavenojob]

If the water at the tap is over 55° C , then it could be the sensor, below that and it is normal.

 

[ianmcd]

your Gas heating boiler MUST be set at maximum for the boilermate to work correctly, the BG so called engineer hasnt a clue how they work, the HW draw off is set at 55 C and is not adjustable if you want it lower than that you will need to install a blending valve