Powermax 155 - C/H but no H/W

[gcopland]

Boiler is a Powermax 155, central heating is working OK but no hot water, pressure to the Hot taps is also very poor. Boiler was serviced a year ago and the blending valve was changed, however, this has also been leaking again and I suspect may be part of the problem (although I can't see this causing the low pressure). My main thought is that the boiler is furred up and needs descaling, if anyone has any thoughts before I get somebody in it would be much appreciated, as I don't think the descaling is gonna be cheap.

 

[croydoncorgi]

Problem with any boiler of the Powermax type is that hot water (at least, a small quantity of it) is always present in the heat-exchanging coil inside the machine. The usual heatstore temperature is over 80C, so that's the temp inside the HX too. Problem is that this is higher than the 'critical temperature' for 'temporary hardness' in the water (calcium bicarbonate) which converts to carbonate with a lower solubility. Result is limescale deposits in the HX coil.
Usually, a Siliphos treatment gadget is on the boiler, which you are supposed to refill every year. Is it fitted? Did you refill it? If not, limescale is virtually certain. Alternatively, an electronic gadget may be fitted. Is it still working?

Descaling these beasts requires special kit.

 

[corgigazza]

check blending valve as this is the cheapest option some blending valves have filters also,to change the blending vave takes 30 mins

 

[gcopland]

Thanks for the advice guys. No filters are fitted near the boiler itself. The only filter that is fitted is a cannister type under the sink at the main inlet. I did suspect the boiler may be scaled up so it looks like I'll get somebody in to have a look. Did look into getting a new blending valve, £81.81 + VAT !!
Many thanks for the advice.

 

[croydoncorgi]

Siliphos system is NOT a filter. It's a chemical additive to the water that stops limescale downstream. On the Pwermax, it's usually mounted low down on the right side where the cold supply enters the casing. Later models (should) have an electronic system inside the boiler itself.

Can't think of a surefire test for you to rule out a blender valve problem.

 

[drboilerfix]

On the Powermax there is a filter and flow regulator, if the problem is just poor hot water flow it is most likely that the flow regulator is the problem. How old is the Powermax?
These are both fitted on the incoming cold water main in the appliance.

 

[a jeffries]

we can sell you a blender valve for 58.81 if your in our area we charge £145 total for a descale