Hi,
Hopefully someone can help? I have a system boiler ( Ideal mini S24 ) which forms part of the unvented system I have in our house.The boiler sits in the first floor of a three storey townhouse, right next to the unvented cyclinder. There are two valves, one for the unvenetd hot water cyclinder and one for the heating circuit. There are about 8 rads on the system. I have had the system power cleaned about a year ago and also the boiler heat exhcnager replaced about 2 yeras ago.
In order for the CH flow switch to make when the heating only is called for, the cold pressure needs to be at about 1.3 bar, as shown on the boiler pressure gauge. The issue is that as the house heats up, the pressure gauge on the boiler shows about 3 bar and water starts dripping into the tundish ( as designed to do ). So when the heating shuts off, the cold pressure is down to about 0.75 bar which is not enough to bring the CH flow switch in when CH is called for. I am relucatant to keep topping up the pressure from the filling loop as this will sludge up the system eventually ( I think this is what may have clogged the heatexchanger a couple of years ago.)
My thoughts are that the water in the CH circuit is heating up, expanding and that the boilers internal expansion vessel ( 6 Litres ) is not man enough to cater for the increase in pressure due to expansion ( hence dumping out the tundish ) of water in the CH circuit
We do have a 12 litre external expansion vessel which is appear to be connected to the hot water cylinder cold inlet, so I think that this caters for increased pressure in the hot water tank only.
We don't have an external expasnion vessel on the CH Hot Water circuit. Is it normal to have an additional expansion vessel on the CH cirucit to cater for increased pressure when on CH only?
This problem seems to have been teased out due to the addition of an additional rad.I have bled all air from the system completely. So I am thinking that we now have increased volume in the system and now need an external expansion vessel on CH circuit.
If anyone can offer advice, I would be most grateful!
Best Regards
Hopefully someone can help? I have a system boiler ( Ideal mini S24 ) which forms part of the unvented system I have in our house.The boiler sits in the first floor of a three storey townhouse, right next to the unvented cyclinder. There are two valves, one for the unvenetd hot water cyclinder and one for the heating circuit. There are about 8 rads on the system. I have had the system power cleaned about a year ago and also the boiler heat exhcnager replaced about 2 yeras ago.
In order for the CH flow switch to make when the heating only is called for, the cold pressure needs to be at about 1.3 bar, as shown on the boiler pressure gauge. The issue is that as the house heats up, the pressure gauge on the boiler shows about 3 bar and water starts dripping into the tundish ( as designed to do ). So when the heating shuts off, the cold pressure is down to about 0.75 bar which is not enough to bring the CH flow switch in when CH is called for. I am relucatant to keep topping up the pressure from the filling loop as this will sludge up the system eventually ( I think this is what may have clogged the heatexchanger a couple of years ago.)
My thoughts are that the water in the CH circuit is heating up, expanding and that the boilers internal expansion vessel ( 6 Litres ) is not man enough to cater for the increase in pressure due to expansion ( hence dumping out the tundish ) of water in the CH circuit
We do have a 12 litre external expansion vessel which is appear to be connected to the hot water cylinder cold inlet, so I think that this caters for increased pressure in the hot water tank only.
We don't have an external expasnion vessel on the CH Hot Water circuit. Is it normal to have an additional expansion vessel on the CH cirucit to cater for increased pressure when on CH only?
This problem seems to have been teased out due to the addition of an additional rad.I have bled all air from the system completely. So I am thinking that we now have increased volume in the system and now need an external expansion vessel on CH circuit.
If anyone can offer advice, I would be most grateful!
Best Regards