Radiator valves banging/whining

[b0ng0]

Hi all,

We had a new replacement Grundfos pump (Grundfos 15-90N) installed late last year. Shortly after, the TRVs on all the rads (although only one at a time) started making a really loud banging/whining/clunking sound when starting to reach temperature.

The valves are Myson One-Way TRVs (about 15-20 years old at a guess). I have tried feeling which pipe gets hot first when turning on the rads and it appears to be the side with the lockshield that gets hot first - which would indicate to me that the flow is going in the wrong direction relative to the TRV position.

I'm a bit confused, as the new pump was an exact replacement of the old one and it's installed horizontally so surely by replacing the pump the water direction shouldn't have changed.

Also worth noting, that there was never any issue before the pump was replaced. Could the new pump have pulled some sludge around the system and its accumulated around the valves?? I'm totally at a loss as to how to proceed with fixing this without doing anything unnecessary.

 

[Madrab]

Check that the pump hasn't been installed upside down or set too high. Banging, as you have nicely pointed out, can be a symptom of directional TRV's that are flowing the wrong way. The TRV's usually have arrows on them, if the lockshield side is heating 1st and the arrow on the TRV valve is pointing towards the rad, then it's flowing the wrong way.

Do you have a hot water cylinder and 2/3 port valve(s)? Is the pump near them? If so the arrow (flow) on the pump should be pointing towards them.

Certainly sounds like it's been installed back to front or set too high but i'd check the direction 1st.

 

[oilhead]

Either the new pump has been fitted back to front, or it is now pumping much more water than before.
Do you have a 3 port valve? If so, is the pump pumping into the valve? There will be an arrow on the pump showing the direction.

 

[b0ng0]

Check that the pump hasn't been installed upside down or set too high. Banging, as you have nicely pointed out, can be a symptom of directional TRV's that are flowing the wrong way. The TRV's usually have arrows on them, if the lockshield side is heating 1st and the arrow on the TRV valve is pointing towards the rad, then it's flowing the wrong way.

Do you have a hot water cylinder and 2/3 port valve(s)? Is the pump near them? If so the arrow (flow) on the pump should be pointing towards them.

Certainly sounds like it's been installed back to front or set too high but i'd check the direction 1st.

The pump can really only go in one way (it's installed horizontally and it's the same orientation as the old one).

I'm no expert but there are about three pipes coming off the hot water cylinder - I will check for the arrow on the pump and make sure it's pointing towards then.

There's like a junction box/diverter valve near the pump with a switch on it - could this have any effect?

 

[Madrab]

The pump can really only go in one way (it's installed horizontally and it's the same orientation as the old one).

Yes but it is symmetrical meaning it could be installed facing left or right but as it's directional and only pumps one way the arrow on the pump body would usually be pointing towards the valve(s).

A cple of pictures of the pump and its location would help, is it in an airing cupboard with a hot water cylinder?

 

[b0ng0]

The pump can really only go in one way (it's installed horizontally and it's the same orientation as the old one).

Yes but it is symmetrical meaning it could be installed facing left or right but as it's directional and only pumps one way the arrow on the pump body would usually be pointing towards the valve(s).

A cple of pictures of the pump and its location would help, is it in an airing cupboard with a hot water cylinder?

Pics below, yes it's usual airing cupboard and cylinder.

Close-up of pump

Hot water cylinder and pipes

Pipes, pump and acctuator

 

[Madrab]

duplicate

 

[Madrab]

I would say that pump is on backwards, the arrow on the side of the pump, usually under the control box on the side of the pump head, should be pointing towards the 3 port valve, to the left on your pic.
View media item 89601
You need to check for the arrow and ensure it's pointing towards the valve as in the pic

Oh and btw it's a 15-60 not a 15-90 - the 15-90N is a booster pump for a hot water outlet!

 

[b0ng0]

I would say that pump is on backwards, the arrow on the side of the pump, usually under the control box on the side of the pump head, should be pointing towards the 3 port valve, to the left on your pic.
View media item 89601
You need to check for the arrow and ensure it's pointing towards the valve as in the pic

Oh and btw it's a 15-60 not a 15-90 - the 15-90N is a booster pump for a hot water outlet!

Yeah the arrow is pointing away from it, and having had a really good butchers at it last night I am quite convinced it's pumping the wrong way.

Is there an easy way to reverse the flow direction? The pump is in quite a tight space and I don't think it would fit if I just rotated it 180 degrees

 

[Madrab]

The only way is to turn it around. If it was just installed a couple of months ago, I'd be getting the installer back in to fix his silly mistake.

 

[D_Hailsham]

The pump will have to be split in two (four allen bolts) and the back part, with pipe connections, rotated through 180°. This is necessary so the control box does not go under the pump.

Also, the pump needs to be more horizontal.

Grundfos Instructions (my emphasis)
Where pumps can only be installed in horizontal pipework, it is imperative that the pump shaft is horizontal, or slightly higher at the vent plug end.

The shaft must not fall below the horizontal plane, even by a few degrees, as this causes premature wear of the top bearing and shaft.

Pumps should not be installed with the shaft in a vertical plane, as this may lead to dry running of the top bearing, noise and possible pump failure.

As currently installed the shaft is more than "slightly higher" and is tending towards the vertical. I know there's not much room, but it really needs to be nearer the horizontal.