Louder humming noise from pump after drain down.

Hi,

Hope someone can advise on this.

I have an open vent system with 3-way valve and Baxi-Bermuda back boiler and live in a bungalow with only 5 rads.

I have drained down the central heating system in order to get some inhibitor into the pipes (it had'nt been done in a few years).

I managed to refill the system, bled all the rads and they all now heat up fine however the pump (which was replaced 3 weeks ago with a Grundfos) is now making a much nore noticeable humming noise. You can also hear when turning on the system an initial rush of water and some bubbling from the pipes.

Is the louder pump noise (and pipe bubbling) likely to be due to still having air in the system ?

I have bled as much as I thought I could from the rads (only water is now coming out) and from the pump but do I need to bleed further from the pump ?

If someone could advise on the best method for this it would be greatly appreciated. Should I bleed from the pump with the system on and should I have the large nut on the pump slighltly open or removed totally ? Was a bit worred that more air could be pulled in from the pump where I had the screw open.

Many thanks

Barrie

did you lock the valve on "man" when refilling

are there any bleed points on the cylinder View media item 11360

Hi kevplumb,

Thanks for the reply.

I think I may have forgotten to switch that over from auto when doing the draining\refilling. Doh.

Would this have caused air to be locked in ? In this case is there a way around getting the excess air out rather than draining down fully again ?

As for bleed points on cylinder, will need to look but I think the only bleed point is for what is actually in the cylinder rather than the coil. Am at work at the moment so wont be able to look till tonight.

If you could advise that would be great. Thanks.

Hi,

Could someone advise if I would be OK to bleed air from the system when the pump is running ?

Is this a safe method to get air out as it passes through the pipes ?

When bleeding from the rads I only get water coming out but I can hear the gushing sound when the system first starts.

Thanks from a desperate man.

Generally I believe it is advised NOT to bleed the system with it running, as that can allow air to get sucked INTO a fast flowing water pipe.
What you can do with the system running is; on your pump there should be a speed control switch. If you move it to a position 'between' settings the pump will stop pumping, then switch it back to the highest setting.
I usually do the stop for about 3 seconds, then let it run again for 5, and repeat this a few times, sometimes the 'surge' is enough to shift any trapped air. Other than that I think it is just a case of leaving the pump on high, and try bleeding the rads again in a few days when the air might have worked it's way around the pipes and into a rad, (or up the vent pipe )

Thanks for the advice Schmill. I'll give it a go.

Did you ever bleed the pump from the big screw in its middle?

Tony

barriegreen said:

Could someone advise if I would be OK to bleed air from the system when the pump is running ?

Click to expand...

Bleeding should always be done with the pump off. It is better if it done with the water cold. Always bleed the downstairs radiators first.

Is there an air valve on the pipe from the motorized valve to the cylinder? If so release it until some water comes out. It may be an automatic valve with a screw cap (usually red), in which case make sure the screw cap is undone about one turn.

Thanks all for the advice. I went up to the loft and found a couple of air valves not far from above the cylinder which I bled, also bled the pump again whilst off.

Tested and all is fine. No gurgling\bubbling noises from the pipes and pump down to normal noise level.

Thank you all.