central heating pump

Postby abrad38 » Sat Aug 16, 2008 2:24 pm

We noticed a couple of weeks ago that when we had our central heating on to heat some hot water the pipes started to bang, also when switching off the kitchen how water tap there again would be some banging from the pipes, I guessed at the time that we had air in the system, anyway last week we noticed a loud humming noise from the central heating pump even with the cental heating switched off, also the pump and the pipes either side were very very hot to touch.
Yesterday we switched on the heating to test the system and again there were some loud bangs and the boiler switched off, followed by bubbling sounds, and the pump continued to hum.
I have unscrewed the centre shaft and I can feel the impeller was moving freely.
Is this a case of a faulty pump or could it be low pressure in the system, the header tanks in the loft have plenty of water in them.

Many thanks
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Simply Build It

Postby htg engineer » Sat Aug 16, 2008 4:41 pm

There's different faults in your post, the banging when turning on/off the hot tap is water hammer, unclipped pipes, pipes need lagging or maybe as simple as closing stop tap slightly.

The noises from the heating system sound like - either air in the pump - air in the system or the pump is not runnning properly, it may seem like the impeller is turning freely when it actually isn't.

What's the make and model of the of boiler ?

htg engineer
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Postby abrad38 » Sat Aug 16, 2008 7:52 pm

Hi htg

Thanks for your reply, my boiler is a Baxi Solo 2PF, I have suspected there is air in my system but I am unsure how to vent the hot water system, the heating system I know to vent through the rads.
I have read it is possible to vent the pump, but I have checked and see no way of doing this as there is no bleed nipple.
I am still confused as to why my pump continues to hum and get very hot when all is switched off at the programmer.
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Postby htg engineer » Mon Aug 18, 2008 4:25 pm

Check the 3 port valev and actuator. Put into manual mode and see if you heating and hot water work and if the pump stops when turned off at the programmer.

Check near cylinder for any manual airvents,

You vent the pump by undoing the nut/screw in the middle of the pump (where you checked that the impeller was turning).

I bet the actuator on the 3 port valve is causing all your problems.

htg engineer
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Postby abrad38 » Mon Aug 18, 2008 6:30 pm

I put the actuator into manual mode and the pump stopped humming and did not get hot, at this point I thought great with your help I have found the root cause, but when I switched on the water and heating the pipes banged a few times and I did not hear the good old sound of the pump running as is normal, then the boiler turned off as it over heated, followed by the bubbling and gurgling sound.

I guess this is a simple case of a duff pump, or do I have two problems. The electric supply to the pump constant due to an actuator issue, and the pump simply not pumping.

Thanks very much for your help and responses.
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Postby htg engineer » Tue Aug 19, 2008 8:50 pm

Possible, I would start by changing the actuator. Venting the pump and trying to clear as much air from the system as possible.

If you can afford it, it may also be worth renewing the pump. Or at least removing the head and checking the impeller is still intact.

htg engineer
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Postby screech » Tue Sep 02, 2008 11:16 pm

is there enough wtaer in the syste? a simple thing often overlooked.

trying bleeding all the upstairs radiators, if they won't bleed there's not
enough water in the system, tank in loft full would say the cold feed to the system is blocked.
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Postby Rostdu » Fri Sep 19, 2008 8:15 am

I have a similar problem to this that I have noticed just this week. when I switch on the CH the system fires up but as soon as the pump starts ther is a loud ping (like a saftey spring firing) followed by a loud bang abd the system switches off. However, when the Hot Water is switched on and the CH is then activetaed the system workes fine. I am hoping to sort it out this week end, any advice would be welcome please.
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Postby Steve the gas » Sat Sep 20, 2008 5:13 am

Get a plumber/heating eng unless you definately feel able to do it
Steve the gas
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