Pump noise and sometimes pulsing

[mattg4321]

Hi guys

Have moved into a house with a fairly old plumbing system from 70’s. However boiler has been replaced around a decade ago by a Worcester- working great. Pump is around 5 years old.

I have a bit of a strange problem (to me at least). In the morning after the boiler has been off all night everything seems to work great. All rads get hot and pump is pretty quiet and as expected. This seems to run great for at least a few hours then during the day the problems seem to begin.

The pump gets noisier and noisier with loud humming that can be heard throughout the house. Some of the downstairs rads then appear to struggle to get hot In the evening. Also in the evening the pump starts pulsing. If you turn it off it stops the pulsing and noise for a time. But usually only a few minutes before it comes back. You have to leave it off for hours (like overnight) it seems to get a good run of quiet operation with no pulsing.

Is the pump just done? Why does it run quietly and properly for hours at a time in the mornings?

Other things to note. We use hot water much more heavily later in the day, although it is on in the mornings. Also there is a short gurgling noise that happens when the pump switches off after it’s been pulsing. It doesn’t do this when switched off when it’s not been pulsing - like in the mornings.

It’s been doing this for a good week or two now since the weather turned.

Hope someone can help!

Edit. Forgot to add that it’s fed from a tank in the loft and is a y plan system.

 

[mattg4321]

Pumping downwards yes.

The H is a combined vent and cold feed.

It pumps into the bottom of the coil in the cylinder - just out of shot.

 

[Radian]

Looks like originally there was an Airject in that maze of compression fittings.

 

[mattg4321]

Looks like originally there was an Airject in that maze of compression fittings.

There was and that didn't solve the problem either!

 

[Radian]

The dead-end pipe (probably part of a bypass) won't be helping as it will be full of air and act like a trampoline when the circulator starts and stops. Water can then bounce up and down the vent. The same thing happens if there's air trapped in pipework or radiators but at least you stand a chance of bleeding them!

 

[John.g]

Not good but It looks like there is a manual vent plug on the top. That combined vent & cold feed will only work IMO if its "static", ie that the vent is just that without teeing off to supply other rads etc and ditto with the cold feed with no returns above the H. I have a 50 year old combined vent and cold feed where the vent passes up (and over) adjacent to the F&E tank with the cold feed teed straight in to it with a very short (<100mm) piece of pipe from the end of the tank, works perfectly well.

 

[akkeosflomdis]

Is the pump external to the boiler, if so, what make/model and setting?

 

[mattg4321]

Just thought I'd update this as we finally got it sorted!

First the plumber sealed the system and this improved the situation a little as air was no longer being sucked in. However we still had problems with pump noise and pulsing unless the pump was set very low.

Pump inspected again, all ok. The only plausible explanation was then a blockage somewhere/air lock. Narrowed it down to somewhere on the primaries. Took apart again and through process of elimination decided on a blockage in the heat exchanger.

Took a punt on a refurbed one at £75 and got my plumber to fit. Refurbed one looked almost new and came with new seals. Most importantly it's solved the problem finally. Weird symptoms for a blockage in the heat exchanger maybe but there we go. Cut the old one open and it was partially blocked around the flow connection into it.

Thanks all for previous help.

 

[John.g]

Very interesting, any photos of the old Hx??.

 

[mattg4321]

It’s been outside a few days now but I’m sure you get the idea.