Hot water cylinder not getting to temperature

[xr4x4]

Untitled

• starfire
• 5 Sep 2014
• 1

That's red tap at the middle bottom looks like your balancing valve.

 

[xr4x4]

Waking up this thread, thanks to all the previous help which partially sorted the issue but in the end I moved my tank thermostat down to 55C so the boiler and pump eventually stop.

Can I ask, I find whenever the system has been drained and then refilled it seems to get completely full of air and this problem reoccurs, as its an open vented system shouldn't the air just dissipate up the vent pipe ?

Pictures here //www.diynot.com/network/starfire/albums/

Thanks

You need to bleed, rads, pump and bleed valve after a drain down.

 

[leakydave]

Is it a Primatic Cylinder, or do you have two header tanks?

 

[MeldrewsMate]

I find whenever the system has been drained and then refilled it seems to get completely full of air and this problem reoccurs, as its an open vented system shouldn't the air just dissipate up the vent pipe ?

Pictures here //www.diynot.com/network/starfire/albums/

Thanks

Some systems are badly designed and trap air in many places, worse they pump over into the header tank and/or suck air in via the open vent pipe.

It looks like your hot water cylinder balancing valve is only 15mm size, in this case you will probably benefit from having the valve almost fully open. As you have a thermometer I suggest the following.

1. Take the thermostat off the cylinder's surface, so that it calls for heat constantly.
2. Attach the temperature sensor to the boiler's flow pipe (flow out of the boiler) and wrap the sensor with some insulation (dry cardboard is as good as anything else for this test). Run the HW program only. Compare the peak temperature recorded on the Multimeter and the boiler over several boiler cycles to assetain repeatability.
2. Move the sensor to the boiler return pipe, and repeat. Continue opening the cylinder balancing valve until there is about 15C temperature difference between Flow and return.
As you open the valve you should see that the boiler will run for longer periods as the flow rate increases. If not then you may have a partial blockage in the primary system pipework. You may end up with the 15mm gate valve fully open on your configuration.
There is also the possibility that the rubber ball inside the 3 port valve has come adrift - unusual with a new valve, and unlikely as the CH flow seems improved, but possible.
If you're sure that the powerflush was done properly then beyond this you may have to investigate further blockages.

 

[starfire]

Untitled

• starfire
• 5 Sep 2014
• 1

That's red tap at the middle bottom looks like your balancing valve.

Yes that's the balancing valve, I have it fully open.

 

[starfire]

Is it a Primatic Cylinder, or do you have two header tanks?

The other pipework you can see is for a power shower and can be ignored, there is just one header tank and a normal hot water tank.

 

[starfire]

I find whenever the system has been drained and then refilled it seems to get completely full of air and this problem reoccurs, as its an open vented system shouldn't the air just dissipate up the vent pipe ?

Pictures here //www.diynot.com/network/starfire/albums/

Thanks

Some systems are badly designed and trap air in many places, worse they pump over into the header tank and/or suck air in via the open vent pipe.

It looks like your hot water cylinder balancing valve is only 15mm size, in this case you will probably benefit from having the valve almost fully open. As you have a thermometer I suggest the following.

1. Take the thermostat off the cylinder's surface, so that it calls for heat constantly.
2. Attach the temperature sensor to the boiler's flow pipe (flow out of the boiler) and wrap the sensor with some insulation (dry cardboard is as good as anything else for this test). Run the HW program only. Compare the peak temperature recorded on the Multimeter and the boiler over several boiler cycles to assetain repeatability.
2. Move the sensor to the boiler return pipe, and repeat. Continue opening the cylinder balancing valve until there is about 15C temperature difference between Flow and return.
As you open the valve you should see that the boiler will run for longer periods as the flow rate increases. If not then you may have a partial blockage in the primary system pipework. You may end up with the 15mm gate valve fully open on your configuration.
There is also the possibility that the rubber ball inside the 3 port valve has come adrift - unusual with a new valve, and unlikely as the CH flow seems improved, but possible.
If you're sure that the powerflush was done properly then beyond this you may have to investigate further blockages.

OK, I will try this thanks.

First call is to try and get rid of all the air I can hear swooshing around.

From what I understand with a vented system like this an Automatic Air Valve shouldn't really be needed, even in place of the existing manual one you can see in the picture at the top of the pipe feeding the cylinder?