Gravity Fed HW Problems

13 Aug 2006
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United Kingdom
I am having problems with my HW/CH system. The boiler is a Glow Worm Spacesaver MKII (GC No 41-313-54). The HW is gravity fed and the CH is pumped. I have not been able to find any port valve or actuators so assume each system is stand alone, also there are 4 pipes going to the boiler itself. There is a F&E Tanks in the loft so guess the system is an open vented system

With the programmer switched to HW only it takes some time (approx 2 hours) before the water gets hot. I have also noted that the radiator in the bathroom gets warm at the bottom.

With the programmer switched to HW & CH, the rads get hot pretty quick, but once again the HW appears to be slow in getting hot.

Once the room stat switches the CH off the rads begin to cool; all except the rad in the bathroom as this remains hot.

Also if the HW is heated via the immersion heater the rad in the bathroom gets warm at the bottom.

Can anyone help identify my problem and assist with me fixing it – thanks in advance

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Sounds like air or no water in your heating system at the flow to the cylinder.

Have you checked there is water in the F&E tank? Or,if there is water there could be a blockage on the cold feed.

Make sure the ball valve in the F&E tank is not jammed by moving it about.

Other than that the primaries to the cylinder could be blocked.
I have checked the system for air and it is clear. There is also water feed to the cylinder ok. I still need to confirm in the primary circuit is blocked or not. I have read somewhere a gravity check valve is required on the heating flow pipe, but I am unable to locate one. Is there a difference between a gravity check valve and a non-return valve and should I have one fitted.

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