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central heating system question

km79

i am trying to establish if i have a sealed system and if i do so how do i top up the water(if i need to)
basically 2 rads upstairs are only warm at bottom. i have bled them . lot of air came out of one but no water followed???
i have attched pictures to help ye figure out my system and whether the water needs to be topped up.
the pressure remains at 1.2 when heating is on and off
TIA

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youtheman

Looks like a pressurised (sealed) system to me. The shot of the presure gauge shows two needles, the fixed needle is the set point (i.e. the pressure it shoould be). The other needle is the actual pressure, and it's at zero. So under normal conditions you want both needles together.

There is another picture of a small red vessel beside your cylinder, this is an accumulator, another sign that it is a pressurised system.

In a pressurised system, if you bleed a radiator, then you quickly pressure and will have to top the system back up because you have no header tank to re-fill the system (though the aforementioned accumulator will allow you draw off a small volume of water before you drop the pressure).

Not sure how to do it as my system is vented. I know it's not rocket science, and I'm sure someone else here will advise.

km79

thanks for the reply. a little more info when i switched off the downstairs heating ( there is thermostat both upstairs and downstairs) i heard water leaving either the attack tank or cylinder in hot press? i then closed all rads upstairs except the ones affected. i heard water entering them but they still only got warm at bottom

km79

just realised this should really be in plumbing & heating section:cool: can one of the mods move it please?

crosstownk

It looks like a sealed system alright.

As your gauge is currently reading close to zero, you will need to repressurise the system by refilling it. To do this you will need to locate the filling loop/valve.

In your 3rd photo above, is the pipe the gauge is attached to connected to that red tap? If so then this may be your filling valve. Open it and see if the pressure increases. If it does increase then fill to between 1.0 to 1.5bar and all should be well. Be sure to close the tap after refilling!

km79

so on the pressure gauge there are 2 needles one red one black. the red one constantly sits around 1.2 and black one around 0.2. i had always assumed the red one was reading the pressure and black one was kind of a fail safe that switched system off if pressure dropped too low? but its actually the black one i should be reading???

crosstownk

The red one is manually adjustable - you can twist it yourself. It's a reference marker. The black needle indicates actual system pressure. This is the one that will increase as you add more water which will consequently increase the system pressure. The black needle will also rise as the water in the system heats up - the hotter the water in the (primary) system gets, the more the pressure will increase.

km79

oh dear very low pressure so :eek: ill try the red valve so i think its from mains? and let pressure go how high

crosstownk

Let pressure get to 1.0/1.5 bar. Turn on your boiler and see if all rads heat.

km79

the red valve will only turn once anticlockwise. i am reluctant to force it but dont think it will twist further anyway. no increase in pressure

crosstownk

Maybe it's not the fill valve but as you can turn it anti clockwise then it is off normally. If it's on the same pipe as the gauge then I'd be inclined to think that is the filler. Maybe the valve is stuck.

km79

it was stuck! got it to open fully but still no change . how long should i leave it open ?should i have boiler on/off

crosstownk

Hmmmm. Maybe it's not the filler. Any other taps on that pipe run?

km79

thanks for your help so far.
the utility sink is to the right of it but it does not lokk to be connected to that pipe.
should water rush in immediately once fully opened?

crosstownk

Yes. Pressure should rise once filler is fully opened - assuming mains pressure is greater than that in the system

km79

got it sorted last night. opened the red valve fully and then the black knob just under and to the right of pressure gauge:D have bled them all now and topped up to 1 bar now to balance them!!!
thanks for all the help