Central heating problem

[Smac]

Hi everyone I change 2no motorised valves as they have become faulty today the heating system is fed via f&e tank with combined vent and cold feed filled the heating system up fired oil boiler up got rads and water heating up eventually the cust rang back this evening saying that heating would not work called back flow was very hot at boiler but return pipe was cold with some adjustment got heating goin there was a strange noise at the circulating pump as if like a vibrating sound now I know that there could be still air in system any tips on how to get rid of this thanks

 

[Resolute]

Did you bleed the pump? Sounds like air or a blockage.

 

[Dannypipe]

You need to bleed the pump....if its still noisy. Isolate it, and remove the head. Check the spindle isn't broken away from the impeller. Clean the can, reasemble it and re-bleed it. Then try again. If its still noisy. Cut the power to it. Take a resistance reading with your electrical tester (isolate the power first!).

Check live to earth for open circuit. Check L to N and expect a reading in the hundreds, 150/200. If its wildly different, you might have a burnt out pump. Only perform these tests if you have the experience.

 

[Smac]

Thanks dannypipe yes did bleed the pump on several occasions the flow seems to be getting hot into the zone valves on the flow side approx about 6m from oil boiler but the return back to boiler is cold I have checked cold feed forblockage it seems to be ok any help thanks

 

[Dannypipe]

Did you drain the system? You might have an air lock.

 

[PowerFlushAssoc]

Most likely:
The down feed branch is blocked or restricted - systems sometimes have problems filling because of this build-up in the down feed.

Other possibilities:
- there is sludge / debris in the pump or pump connectors blocking the flow.
- pump connectors are shut / almost shut
- pump is weak, not pumping to full capacity
- air in pump, sometimes you have to bleed it more than once depending on system layout

 

[diamondgas]

Smac - Try turning the boiler off and see how quickly the flow cools off. That'll give you an indication too how fast the circulation is through the boiler and system. What position is the pump fitted in? Vertical, horizontal, pumping up and away or down and away? Makes for quite a difference when trying to give best advice

 

[Smac]

Pump is fitted vertical on flow pipe leaving the boiler with a by pass valve fitted have tried switching the boiler off a few times but flow remains hot return pipe at boiler cold have lifted a few rads off and flush out pipework to try realise of air to no avail

 

[diamondgas]

If it's vertical and pumping up from the boiler then I'd go with Dannypipe in thinking the impellar has become loose and would be checking that out if it's possible...