Radiator gurgling noise

[RonO]

I have a gas CH system I think they call it open vented (header tank in loft). Last year we had TVRs fitted to all but the hall and bathroom rads, since then two radiators - a single about 5ft upstairs and a double about 5ft downstairs gurgle like crazy for a good ten minutes when the pump kicks in, especially first thing in the morning when it first switches on.

I have bled, and bled the system....did I mention I had bled the system?

The odd thing is this only happens when the TVRs (Drayton TRV4) are set to a number other than Max - we normally have then set to 3. If the valve is fully open there is no noticeable gurgling.

I contacted Drayton who make the TRVs and they suggested I fully open the lockshield valve as it sounds like a 'restriction of flow'. I did that but it made little difference.

Over to you guys!!! I'll try anything that stops the CH waking me at 6am!

A little more information: 7 rads in total in the house. 3 doubles downstairs 4 singles up, no TRVs in hall or bathroom. System was cleaned with Fernox before valves fitted (Spt 2010) and cleaned again with Fernox last week.

 

[45yearsagasman]

I would suspect that air is being drawn into the system on pump startup.
There are many reasons for this and I would firstly check for blockages around the cold feed and open vent connections on your system.
If air is being drawn in you can test for this by holding a glass jar (full of water)over the end of the open vent pipe and get someone to turn the system on and see if the water is sucked from the jar.
Fernox will not remove solid blockages.

 

[RonO]

OK just climbed down from the loft. As I don't know technical terms, I am assuming the 'vent pipe' is the 22mm pipe that hangs like an overflow pipe over the small header tank.

That being so, I held a jar full of water under it with the pipe end submersed in it. When the pump kicked in it did not suck any water out, instead, a few bubbles could be seen implying air was blown from that pipe into the jar of water.

What does that tell me?

 

[45yearsagasman]

It means good news that your cold feed and vent seem to be open and clear.
I presume the TRV's were set as you said in your opening post?
Are your valves all fitted on the bottom tappings of the rads?
Next time you bleed air from them test for hydrogen by collecting some in a container and then apply a match and see what happens.

 

[RonO]

Wicked! A hydrogen bomb in my bedroom!

Ah, now I didn't set the TRVs to 3 I kept them open, I'll try again tomorrow wither them set on 3.

One thing might be worth mentioning. I only noticed today that some of my rads have the TRVs on the out put and lockshield on the input end of the flow. Including the bathroom which doesn't have a TRV and one of the two radiators that gurgles a lot.

 

[Jordon]

Gurgling noises can be down to bad design say if the pump is set to max and the trv on low this can restrict the flow and cause the boiler to heat the water to quick resulting in a gurgle sound like when a kettle boils and it rumbles, usually a auto bypass on the system or a modulating pump can stop this. When you bleed the system do you always get air out? Also check to see if the main storage tank is cold with no hot water in coil splits can cause air pockets and make gurgle sounds.

 

[RonO]

Jordan: interesting point you made there because we had the pump replaed several years ago and the guy was a little miffed by it because for some stupid reason the pump lies under the bathroom floor and is face down becaause of the dirction of travel and position of joists the pump faces down thus the dial (or whatever) is inaccessible once it is installed, Thus the guy was unable to accurately set the speed of the pump.

Ifelt that the pump was kicking in more often than before and I've not been able to successfully balance the system, The downstairs radiator lockshields would have to be damn near off to try to get that 11c difference, which suggested to me that the water is circulating too fast, not sure if that is fact though. Anyway I put the lockshields back to how they were, allthe rads are warm so thought it must be ok.

In the last couple of years, and despite cleaning the system, we do get a lot of 'kettling', which I was told could be due to incorrectly set pump. I put Fernox noise reducer for that.

I have no idea what an auto by-pass (sounds like a road) or a modulating pump.

One upstairs radiator gives air often, the downstairs rads are always ok. but 2 of the 4 upstairs rads have Aladdin self bleed valves.

The main water tank (the big one next to the header) is very cold always.

I don't know what you means about 'coil splits' where would they be?

 

[Jordon]

Could be pump cavitation if it is face down, if you know the make of pump it will show how the pump should be fitted and I believe if it's face down for long enough then the pump will be strained and work harder then gurgling could be because the pump stalls then ramps back up, be good to know what pump it is and what speed. A auto bypass is a unit that goes after the pump then before the motorized valve and links to the flow and return and is set to relive the system, the coil is in the cylinder but if the storage is cold probably not a problem.

 

[RonO]

Th pump is a Grundfoss or something like that. I think the guy who fitted it said there were 3 settings and he had it on the 2nd position (middle).

There is also an odd looking valive on the boiler side of the pump which this guy did twiddle with on a return visit - can't remember what he was clled back for now. Ill try and photograph it tomorrow and post the picture here

 

[RonO]

OK so I took a couple of photos of the pump and the weird looking little valve(?) next to it. Most pumps I've seen have very simple in-line isolating valves like those you'd fit on the pipe leading to taps etc, I've not seen one of these before. The boiler position relative to this photo is on this 'valve' side of the pump about 2ft further along and then a 2 ft drop down into the kitchen.

I did the test with the vent pipe in a jug of water again with the TRVs set to their normal operating position, same result air blown into the water not water sucked out.

Untitled

• RonO
• 6 Oct 2011
• 1

Untitled

• RonO
• 6 Oct 2011
• 1