New house: cold rads & wrong thermostat settings?

[welshtom]

Hi all,

Having read through the highly useful FAQs & some previous posts I think I have diagnosed that I have insufficient pressure in the expansion tank of my sealed central heating system - this is resulting in cold rads on the second floor (modern townhouse). Initially tried to bleed the rads (as they are warm at the very bottom) but only get a momentary release of air and then nothing.

This is the hot water cylinder / controls / expansion tank:

So this was the pressure reading just now with the system running and at full temp, am I right in thinking this should be 1 bar with the system off and higher again with the system running?

To top it up / re-pressurise I believe I need to open the two black valves shown in this photo:

Is this correct?

Also the tank thermostat looks like it is set too low to me? I have read it should be ideally at 60^C - but if this is the case why produce a thermostat that has a scale of 25 - 65?

Any help or advice is much appreciated.

Regards,
Tom

 

[Dan Robinson]

Yes, btu I would have the pressure at 1.5. Remember to top up after each rad is bled.

The stat on the tank is fine where it is if your water is hot enough.

Don't worry about the scale. Life is too short and these stats are generic and used for other things.

 

[Gas1976]

Every time you bleed a radiator you are going to have to top the pressure up using the filling loop,should be about 1.5bar when system is cold/not in use (on the red needle)the pressure will rise when the boiler is running but shouldn't go near 3bar.set your thermostat to 60deg for your hot water

 

[welshtom]

Many thanks for the responses - reassuring to know I hadn't got it all arse about face!

@Dan: The hot water is actually uncomfortably hot with the tank stat as set in the pic above - could I turn it down a little without risk of excessive scale? Might borrow a thermometer from work to measure the temp. of the water incase the tank stat is not that well calibrated (I hope that is what you meant from your post).

Thanks again,
Tom

 

[Dan Robinson]

You are supposed to have the water stored at about 60. Scale forms around 62/63. So a lower temperature will reduce the chances of scale. However the top of the cylinder will end up hotter than the thermostat setting.

Turn it down as low as you like. But you open yourself more to the risk of legionellas taking hold.

The cylinder should be raised to above 60 once a week for a couple of hours.

 

[welshtom]

Thanks Dan - all clear now, was getting my 'scales' mixed up!

Legionellas + young children not a great mix - will leave it where it is I think.

Cheers

 

[Dan Robinson]

Depends on the kids -