Help diagnosing bubbling originating in hot water cylinder

[Shea89]

Hi there,

I recently replaced a dead central heating pump in my home, so drained down the system completely, fitted new pump and filled up. What I'm experiencing now is a periodic bubbling noise, it starts in the hot water cylinder on the 1st floor and makes its way to the boiler on the ground floor which in turn starts making gulping noises and then onto the pump which makes a high pitched noise.

So it sounds like air in the system but I would have expected this air to make it's way from the pump through to the radiators and I'd be able to bleed from there? All the radiators have no air in them.

So then I decided to turn off the flow valve to the HWC coil and what do you know the bubbling noise completely disappears.

My system is an open system from what I can determine, I have two tanks in the attic, a small one for the CH and the larger cold water tank. Neither tank has a return pipe but the CH tank has a T-Junction, one side feeds the system and the other side leads to an expansion vessel which I thought was used in closed systems.

Thesystem is basic, the water and heating operate at the same time, by turning off the flow valve on the HWC I can then get the radiators to work without issue. I've been using the immersion heater on the HWC to see me through. Also to add I believe this issue was possibly occurring before I replaced the pump and may have been the cause of the original pump dying.

Any ideas? Thanks!

 

[Last Plumber]

Did you put the pump in the right way round?
Only asking to rule out the obvious.

 

[Shea89]

Did you put the pump in the right way round?
Only asking to rule out the obvious

Just went and checked the old pump there, it could only be orientated a certain way for the wiring to fit so I'm able to say for certain that the pump is the right way round

 

[Shea89]

Just went and checked the old pump there, it could only be orientated a certain way for the wiring to fit so I'm able to say for certain that the pump is the right way round

 

[Last Plumber]

Just went and checked the old pump there, it could only be orientated a certain way for the wiring to fit so I'm able to say for certain that the pump is the right way round

The head will spin round to a different position to make wiring accessible so I wouldn't go of that.
There is a directional arrow on the body normally.
If you are unsure, can you post photo's?

 

[Shea89]

The head will spin round to a different position to make wiring accessible so I wouldn't go of that.
There is a directional arrow on the body normally.
If you are unsure, can you post photo's?

Hi, sorry what I mean is I remember the position the original pump was in and that the wire went into the bottom of the little black controller box. So I held the old pump back up to the new pump and noted that both the stamped directional arrows are pointing upwards towards the first floor and away from the boiler (pump is situated above the gas boiler). I replaced the pump with a like for like unit to try and make the install as handy as possible

 

[Last Plumber]

Hi, sorry what I mean is I remember the position the original pump was in and that the wire went into the bottom of the little black controller box. So I held the old pump back up to the new pump and noted that both the stamped directional arrows are pointing upwards towards the first floor and away from the boiler (pump is situated above the gas boiler). I replaced the pump with a like for like unit to try and make the install as handy as possible

I see.
Have you vented everything properly?
Is there a vent off the cylinder coil flow?
Any photo's

 

[Deleted member 120897]

The hot water coil is the same circuit as the flow from the boiler that goes around the heating too. As per @Last Plumber check for an air vent on the cylinder feeds. Check for air vents in the loft too.

 

[Shea89]

OK pics are below, I need to make a few corrections on what I said above, there is a return to the bigger cold water tank in the loft. And also the red expansion tank just looked as though it was connected to the out pipe of the smaller CT tank because the insulation was wrapped around the two pipes. Hope this helps!

 

[Shea89]

The hot water coil is the same circuit as the flow from the boiler that goes around the heating too. As per @Last Plumber check for an air vent on the cylinder feeds. Check for air vents in the loft too.

I can't see any air vents unfortunately, my understanding was also that the rads and boiler are part of the same circuit so I would have expected the air to find it's way into a rad, probably the first after the pump and then rise to the top of that rad, would that be correct? but all my rads have no air in them

 

[Last Plumber]

From the photo's and what I can see, you don't have a vent on the flow to the coil and it also looks to have a high point where it shouldn't but it could be photo's.
You need to vent that top pipe from filter to cylinder. I think you're going to have to crack open a fitting. If you're confident and competent you should be OK but if not, get a Plumber in.

 

[Ben-gee]

I would have expected the air to find it's way into a rad, probably the first after the pump and then rise to the top of that rad, would that be correct? but all my rads have no air in them

You misunderstand, if you have an actual airlock there is no flow there and so the air will not move once it’s at the ‘top’ of it’s pipe. Well designed pipework stops this from happening, or at least provides an airvent at these positions to release the air and re-establish flow.
Ok, with jiggling of pump speed and on/off switching you can sometimes shift the air by ‘pulsing’ , but releasing it from where it’s trapped at high spots is more effective.