Radiators still cold after power flushing

Postby Kidz » Mon Feb 18, 2008 11:08 pm

SOS!! I have just power flushed my heating system, but all the radiators are still cold. I can't even hear the water flowing into the radiators. I tried bleeding all the rads all i get is the hissing sound and no water coming out.

I have just had a new circulation pump fitted before doing the power flushing and i can hear the pump running, and the boiler was also inspected and given a clean bill of health. The water level in the header tank is also not changing and i don't think the inhibitor that i have put in there has been circulated through-out the system which also seem to explain why i can't seem to completely fill the rads with water. ANY HELP will be greatly apreciated on this issue(s), the house is freezing cold.
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Joined: Mon Feb 18, 2008 10:53 pm


Simply Build It

Postby Kenj » Thu Feb 21, 2008 6:59 pm

The radiators should have been bled before switching on the pump. Do this with the system off. Manually open any motorised valves, and bleed the radiators and the H/W cylinder if you have one. Then vent air from the pump.
This will ensure that the pipe work and rads are full of water. Only then should you switch the pump on. The pump cannot move trapped air, only water.
The new pump should have instructions with it saying how to vent it.
For a Grundfos pump proceed as follows :-
1. Place a container or towel under the pump to catch any spilled water
2. Remove the large central chromium screw (vent plug)
3. Make sure isolating valves either side of pump are open
4. Using a small screwdriver rotate the exposed shaft several times
5. Turn the pump on and verify that the shaft rotates in the direction shown
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Postby Kidz » Mon Feb 25, 2008 9:00 pm

Thanks for your response, i have followed all the steps you have prescribed below, there was no water coming out from the vent plug opening. I even tried to run the pump with and could see that the pump was rotating freely when i turn on the Heating/hot water. I also opened the H/W cylinder vent and nothing came out of it. I'm running out of ideas now, don't know anything else to try.
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Joined: Mon Feb 18, 2008 10:53 pm

Postby Kenj » Fri Feb 29, 2008 10:40 am

You appear to have little or no water in the system. The most likely causes are a blockage or a stop cock, gate valve, or issolator valve not open.
The blockage would need to be near the header tank to prevent water getting to the pump, and H/W cylinder, assuming these are both in the airing cupboard.
The way to proceed is to loosen the compression joints around these valves to determine if water has got this far.
Starting from the headed tank, there should be a stop cock or gate valve in the flow from the header tank to the pump. There will probably be issolator valves each side of the pump (these may be ball valves). Then you will have one or two motorised valves.
My guess from what you have said would be the pump. If it has ball type issolator valves, the screw heads should align with the pipe run. If the screw heads are at right angles to the pipe run then they are closed.
Good luck, let me know how you get on.
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Joined: Mon Jan 28, 2008 8:30 pm

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