Central Heating noise

[hallra]

Hi Forum,

Since changing pump, expansion vessel and cleaning/flushing/inhibiting the system twice (so far), I have a lot of noise in the three radiators on the top floor of the three storey house.

The house is a new build, 3 yrs old, with a sealed CH system using microbore throughout...

The noises are random, not constant, don't appear to be linked to either heating or cooling, tempreature setting is set to be constant day/night, the sounds from the raditators can be described as gurgling, rushing water, clicking, a drip without a leak.
- I've bleed all three radiators and the rest of the system, there is no air.

The largest of the three top radiators I took off the wall and flushed it with a hose, it was badly coke'd up inside, took a while to fully flush, however the cleaning didn't change the sound generation.

I've left a 2nd lot of Adey MC3+ in the system for the last week.

I've run out of ideas with what is causing the sound and what to do to address it.

Any advice would be appreciated.

 

[Riley]

I would be nigh on positive that it’s air maybe open your filling loop slightly disconnect the radiators at the top and bleed the valves into a bucket

 

[hallra]

Thanks Riley for your comment.

Do you think that air is getting tapped somewhere in the system and it’s taking a long time to make its way through the system up to the top radiators?

Last night, I isolated each of the top radiators...

With the two steel radiators, I used their drainage valves to empty, both spurted as they drained down, suggesting air was trapped in the radiator...

But with them isolated, of course, air was sucked in as they emptied.

When I refilled, I did so by having the TRV off and water in via the lockshield side... I did this as the bleed valve is opposite end to the lockshield, my theory was any air would be pushed out and couldn’t get trapped.

However, again after and today, I have the same noises and air appears to be back in both those radiators.

Trying to understand your approach, are you suggesting by opening up the fill loop slightly, it will put a balancing pressure on the fill side, so that when a bleed valve is opened, it stops any air being sucked in at the bleed valve?
- I think that is what you mean, but then I’m lost where you say isolate the top radiators and bleed into bucket... if you isolate, then what will bleeding do? As water is let out, it’ll be replaced by air as radiator is isolated?

 

[hallra]

Btw, the third radiator is a towel radiator without a drain valve.

 

[Last Plumber]

How high above the Boiler are the rads on the top floor?
and what pressure do you have the Boiler set too?

 

[hallra]

Hi Last Plumber,

The boiler is on ground floor, pump, hot water cylinder, expansion vessels, zone valves on 1st, 2nd floor top radiators.

Boiler is about head height.

So I would say:

Boiler to 1st floor components about 2 metres

Boiler to bottom of rads on 3rd floor is 4.5 - 5 metres.

System Pressure was originally was set at 1.5bar, however a fellow plumber on here advised me to reduce down to 1bar, so that at boiler approx 1.3bar, 1st floor approx 1 bar, 2nd floor approx 0.7 bar.

As expansion is on 1st floor, the advice was to pressure it at 1bar.

I’ve been having this noise, air issue for a while now, I’ve had the expansion vessel, pump, automatic air vent and combination/control valve changed and two lots of cleaner, flush, inhibitor through system...

Could say it’s doing my head in

 

[Riley]

Is this on the recommendation of other plumbers?? Wow they really are just throwing parts at a problem hoping it will go away

 

[hallra]

All parts that were placed were knackered and I check with this forum beforehand.

it all started with the En-Suite towelrail banging in the middle of the night.

The 1yr old pump was changed because it was making grinding noises.

Then the pressure on Expansion Vessel was dropping after being charged and it was undersized, so I had it changed to an 18L.

Then when the system was cold I notived the AAV was leaking water.

Then the inlet control valve was hissing air out of when hot water was on.

This new build 'Persimmons' house has been nothing but trouble, all the heating electrics were wired incorrectly at the start....
- I've had two of the 2 way valves replaced in the past as well!


I turned off the CH and checked all radiators, no air came out of any bleed valves, a little did come out of an manual air vent in the cylinder/pump cupboard.

However, when I turned pump back on, in the pipework around pump, a large rush of water, some glugging and then silence...

 

[Riley]

Did you bleed the pump

 

[hallra]

Did you bleed the pump

It's a Grundfos Alpha 3 with a Self Venting Mode, I've run this mode on numerous occasions, including once yesterday and once today.

 

[ShaunCorbs]

There crud can't beet the old vent screw

 

[hallra]

Could the position of the Automatic Air Vent (AAV) cause air to be pulled into the sealed system?

It’s correctly on the flow side of the pump, but with the pipework the way it is...

When hot water is on, the water is pushed up from the pump, it turns right and then drops down past the 2 way valve into the hot water cylinder...

with the AAV on a straight vertical above the drop to the hot water cylinder flow... could air be pulled in?

- I ask as I’ve notice that the noise (air) seems to be more prominent after hot water has been on.

 

[hallra]

Interestingly, I spoke with Glowworm yesterday about system pressure, they told me it must be kept in the 1.1 - 1.4 bar range, with 1.4 being ideal and to ignore the pressure diff caused by the pressure gauge being 2 metre above boiler in the cylinder cupboard.
- I had lowered the pressure to 1bar on advice of a member here.

So, I partially drained the system to drop the pressure, increased the expansion tank pressure to 1.4bar, added water to increase system pressure to 1.4bar, bleed radiators.

Since then, absolute silence, no more trapped air, no gurgling, nowt, very happy.

A couple of questions:

1) what did the increase of pressure do that solved the noise problem?

2) As mentioned in a previous post, the system pressure gauge isn't moving up when the system heats up, though it does when water is added.
- I moved the red needle out the way in the pressure gauge in case it was affecting/blocking the pressure needle, made no difference.

Should I change the pressure gauge, is it broken?

 

[ShaunCorbs]

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Bit far to travel India