Air in Grundfos Alpha 2

[Jon Cottingham]

Afternoon all.

I've been looking in this forum for similar problems at it seams the Alpha 2 isn't without its problems.

We've got a Grundfos Alpha 2 15-60 130. Fitted by British Gas 3 years ago, it's been fine but this winter it's be really quite noisy regardless of what setting I switch it to. There's a gurgling sound, so I'm guessing there's air in there but it cannot be bled, and the pump generally is noisy where as before it was almost silent.

We're covered by British Gas for all service and breakdowns. The engineer came out yesterday and serviced our boiler and we mentioned the noises we were getting from the pump. He briefly bled the radiators but said there was nothing he could do with the pump and that it was fine, nothing to be concerned about.

Sounds like he didn't really want to deal with it as he was only in the house for about 25 mins.

Should I be smelling a rat?

Cheers Jon

 

[ollski]

You can remove the electrical unit and the front to get to the bleed screw but I wouldn't bother. If it's getting noisy it's probably running too fast and pulling air in down the vent.

 

[Jon Cottingham]

Right I see.
I've set it to a slower setting and it's definitely quieter. I'll see if it manages to keep the radiators warm. It's only running at 3 watts.

 

[D_Hailsham]

Grundfos recommend running the pump at max speed (III) for a few minutes to get rid of air in the pump.

Have you bleed all the rads? It's best done when the system is cold; do the downstairs rads first.

Is there an air vent on the system? Often on the pipe from motorized valve to the HW cylinder.

 

[Jon Cottingham]

I've ran the pump on setting III for 5 mins. Bled any air from the bleed valve, just off the feed to the HW tank. A little air came out.

The radiators were bled yesterday by the BG engineer.
He left it on the II setting. I could hear air in the pump and it was generally a bit noisy, like a low drone. We've only noticed this noise lately.

I've now switched it to Auto. It's much quieter although I'm guessing that's because the pump is running much slower (from 11W on II to 3W on Auto).

 

[JohnD]

can you post a pic of the pump and the pipes around it? Interested to see which direction it is pumping, and if the spindle is horizontal

 

[Jon Cottingham]

Here you go.

 

[JohnD]

'mmmm

pumping vertically as I suspected

Is it pumping upwards or downwards? Pumps that push downwards may collect air that can't get away.

 

[Jon Cottingham]

As I understand it, the feed comes into the bottom of the pump via the aerator (I think that's what it's called). Then up to the diversion valve.
Bleed screw cap at the top of the feed to the HW tank.

 

[JohnD]

well that should be right, but it's not unknown for heating engineers to pump systems backwards by mistake.

There may be an arrow cast into the iron body of the pump. Or if you can photograph the other end of it, the shape may show.

If you can lay your hands on a strong magnet, see if it is attracted to that grey thing, or to the small pipe leading to the air vent at the side of the cylinder.

I am a householder, not a gasman.

When the boiler and pump are turned off, bleed the highest radiator in the house. Does water (not air) squirt out forcefully, without dying away?

 

[Jon Cottingham]

Can confirm the arrow on the casting points upwards and therefore in the correct orientation to the pipework.

The highest radiator in the house is in the bathroom, the first radiator after the pump. Water flows well when bleed screw opened.

Appreciate the help.

 

[JohnD]

'mmm.

@ollski thought it might be sucking air down the vent. If, in your loft, the small feed and expansion tank has a pipe bent into an inverted "U" hook curved over it, with the open end discharging into the tank above water level, see if you can rig up a jam-jar or milk-bottle of water, with the pipe dipped into it. If the vent is sucking, it will suck out some of the water. Give it a day and see if the level drops. If you have an assistant, you can get them to turn the heating on and off while you watch the jar.

There is also a possibility it could be sucking through a leaky joint on the suction side of the pump. In this case you may see a limescale or green copper deposit round the leak where water has oozed through and evaporated.

 

[Jon Cottingham]

I see what you're saying but why is it only doing this after 3 years? It's ran faultlessly up until now so I can only presume the system is ok in principal.

 

[Jon Cottingham]

Well the Auto setting is pointless. Nothing is warm this morning. It wasn't moving enough water.
Set it back to II. The drone noise from the pump is horrible though, enough to keep you awake.

I'll contact BG this morning and get a different engineer in.

 

[muggles]

Sounds like he didn't really want to deal with it as he was only in the house for about 25 mins.

Should I be smelling a rat?

Cheers Jon

If he thinks he can service your boiler properly and bleed some radiators in 25 mins you should almost certainly be smelling a rat - most proper boiler services should take longer than that! What boiler do you have?