Noisy pump

[neiloneil]

Hi.
I’ve got a problem with my mum’s central heating. The pump is making a humming noise that is very annoying. All the radiators heat up fine so my mum won’t get an engineer in. I’m just worried that something may go wrong. It was happening last year but not as bad as now.
I have bled the radiators and I find that one particular (upstairs) radiator needs bleeding every so often, which I find strange, as there must be air in the system, which is moving around to this point. I have done this in the past with the heating switched on. I am led to believe this can introduce air into the pump, and that could be why it is labouring so much. I have removed the slot head screw from the front of the pump and a trickle of water comes out. Should I conclude then that the bearings are worn? The pump is set to its highest speed, any slower and it really struggles.
I was reading a thread on this forum where the person with the problem was asked the following questions that seem relevant to this situation (but they did not reply)
1. Does the highest radiator bleed differently to the others?
2. What colour is the liquid?
3. Is the pump higher or lower than the highest radiator?
My answers are
1. One radiator seems under higher pressure. Air, then water sprays out.
2. The liquid is clear at first then turns black.
3. The pump is slightly higher than the rads.
I have tested the f & e vent with a jar of water. The result was; when the heating was switched on about 1/3 of a cup of water was sucked up the vent then released 2-3 seconds later. When it was turned off air bubbles were forced out (about the same capacity).
Hopefully this information will mean something to somebody. Please let me know if you have any advice.

Details of system-----
10 or 12 years old
Ideal Classic LXFF & FF fanned flue gas boiler
Grundfos super selectric 15-60 pump
9 rads (5 up & 4 down) 30 years +

 

[Gas2Air]

The pump should cope on speed 2 with limited noise as oppose speed 3 on the size of your mums system. If as you say it struggles then it could be a configuration issue, has the noise always been there or just started/become more evident?

 

[John506]

When was your system last cleaned out?

If the water coming out of the system is clear then turns black, it means it is sludged up, and the sludge will not do the pump anygood.

Get some Sentinel X400 and introduce it into the system, pour it into the F&E system and drain at the lowest point so the water is taken into the system. If you can get someone to hold the arm up in the F&E while you are draining so only the water with the chemicals go into the system (but don't suck any air in).

Turn your heating on everyday for a few hours for a week, then drain down after a week and the water should be black, fill up again, turn the heating on again until hot then drain down again, then finally fill up and add Sentinel X100 to the system.

Don't forget to switch off boiler when draining down.

Your pump may now be alot quieter, or if not at least you have a clean system.

 

[neiloneil]

Thank you both very much for your advice. Its much appreciated.
The radiators haven't been cleaned out since the new boiler. The noise has been present for the last few years, but getting worse each year.
I'll get some X400 into the system and follow your advice, as it seems that sludge is the problem. Many many Thanks.

Neil

 

[neiloneil]

I put x400 in for a few weeks. Drained it out, not a great deal of sludge came out though. The pump does now run on speed setting 2, but still quite noisy.
I drained the system as simply as possible. That is, not flushing it with mains pressure, as I've heard its a tricky thing to do right. Would I shift a lot more sludge if I did this? If you think its worth doing ' could you talk me through the doings of it please? I did see a description on this forum, but can't find it now.

 

[bengasman]

with such an old system, you need to drain and fill several times and may well need to repeat the treatment with the cleaner
and once it is really clean, don't forget the inhibitor

 

[doninator]

change the pump to a larger pump