Installed new TRV- Kettling

[halton1957]

Hi All
My system is microbore 9 single rads, Gloworm fuelsaver. Myson aereject.
All the rads on microbore have TRVs. So a low volume system.
The bathroom rad is on 1/2" pipe and didn't have TRV until a friend ( a plumber) advised me to fit a TRV when I could. This rad is directly above the boiler.
From what I can see of the system the flow and return are 3/4" going down to 1/2" at bathroom rad. 8mm microbore tapped off the 3/4 feeds the remaining rads.
There is also a 2 way valve feeding the HW cylinder.
I had a few stuck TRVs so when I drained down to replace/repair these I fitted the bathroom rad with a new TRV.
Severe kettling was the result, although slight occasional kettling before.
Kettling only happens on the third or fourth cycle of the boiler on start up from cold when HW is off. Selecting HW on appears to cure the problem.
When the system is thoroughly hot there is no kettling, even with HW off.
I have had 2 litres of Noise reducer in the system for 3 weeks with no noticeable improvement.
Any ideas please?

 

[twgas]

Take the head off the bathroom TRV, it might have been fitted as a by-pass and if so needs an open route through and back to boiler to dissipate the heat.

 

[halton1957]

Thanks Mick, I'll give that a try today.

 

[halton1957]

Sadly no different with the head off the TRV.

Perhaps it's not kettling, It makes violent noises which appear to come from the Myson Aerjec which is about 12" from the boiler and is fitted sideways. (I've been told that is OK.)

The pipework around Aerjec bangs and moves a bit.

The 1/2" cold feed gets hot where it enters the Aerjec for about 30" till it disappears into ceiling. Expansion pipe also hot.

The banging noises only happen when the system is starting from cold, and settle down after 3-4 mins. The system runs perfectly then.

I can prevent the problem by ensuring HW comes on with CH, Presumably increasing flow rate.

Any more ideas please?

 

[halton1957]

Any suggestions please?

 

[gasmanstu72]

What you're describing sounds like what happens when the pump seizes up, the water in the system is almost boiling and the pipes rattle about and start banging.

You could try messing around with the pump speed or try turning the boiler stat down a touch and see if that helps.

It could be a blockage in the pipes, perhaps when you drained it down to fit the new TRV you may have sucked some crud in.
Drain down again, put some cleanser in, and fill back up might be an idea too.

 

[halton1957]

Thanks Gasmanstu.
I'm reluctant to drain down t the moment as I already have 2 litres of cleaner in the system (3 weeks) It's only the No nonsense stuff from Screwfix, is that any good or should I try Sentinel/Fernox?
I'll try altering pump speed and boiler stat first.

 

[gasmanstu72]

You don't have to drain it all, are the pump and the air separator quite high up on the system?
You only need to drain to below that level if so, leaving plenty of inhibitor in.

Are you confident enough to cut that section out and have a look at it and put it back in? Or try a magnet and see if it sticks to anywhere on the pipework.

Fernox is the stuff I use, it's pretty good.

 

[halton1957]

Hello again Stu,
Thanks for your advice again. Pump is alongside the boiler level with the heat exchanger. Air separator is 6" above top of boiler, It's a Myson aerjec II, I've had a close look at it and the connections don't match any of the layouts suggested on their leaflet (20yrs old!) The vent connection is upwards, the boiler and pump connections are straight through low down, leaving cold feed above the flow. Not sure if this makes any difference but grasping at straws now.
The whole installation is high up in a downstairs airing cupboard, cutting out would be beyond my engineers hacksaw/ propane torch capabilities. Probably best if it was sweated out but I wouldn't like to do the job as I used to be in the local Fire brigade and I don't want to provide them with a cheap laugh.

 

[halton1957]

PS should have said before, I had Sentinel x400 circulating all through December and drained off/flushed early Jan. Flush consisted of fill and drain twice
Magnet did stick to separator before but not now.