system design and air problem

[Nobbyone]

Hi,


I seem to be getting a lot of air in the system if I take the pump off its bare minimum setting, just left of the venting setting.


I have a open vented S-plan, originally a british gas installation, fitted to a bungalow.


The pump and valves are in the airing cupboard together with the hot water storage tank. By-pass radiator in the hall 4m away from room thermostat. All other radiators have 2-way TRVs fitted, some on the flow and some on the return.


The boiler, a mynute VHE, is on the kitchen wall around 7m away from the pump.


There is one manual air vent between the boiler and the air separator along return to the boiler, located in the loft and at the top of vertical pipework (hell of a job to get to)


An air separator (with a separate cold feed inlet port) lies in the loft between the boiler and the pump on the flow. This air separator has been fitted standing up rather and length wise. All of its connections to the ports are correct: to pump, from boiler, to vent, from tank.

The air separator is attached to the expansion tank using 22mm copper and at the air separator 15mm, somewhere it changes width. The separate vent pipe is also 22mm copper and its bend is more than 50cm above the expansion tank.


The bottom of the expansion tank is 1.3m above the pump. The pump is 80 cm below the level of the air separator.


There is 60cm in height between the air separator and the bottom of the expansion tank (tower separator diagram gives 1m as a minimum).


The pump (wilo variable type Yonos PICO) is pumping down to the valves. I realise that pumping down should be avoided to reduce the chance of air getting trapped in the pump, which in my case is very often, but I can see why the installer has done it for convenience. As it is pumping down I would think that is the reason why the air separator has been installed.

The air has been sucked in for the last 7 years before I changed the old pump british gas pump. I thought that as I had to changed the pump it would also remove the air problem, but it has only lessened it, it not removed it completely. When I put the pump on full speed I can hear a large amount of air being pushed around. I then have to tackle the remote manual air vent in the loft to try to remove it.


My question: Will the air separator, as it is installed on its end with the vent port at the top, together with the lack of the minimum 1m head between the bottom of the expansion tank air separator cause air to be sucked in regardless of what the pump speed setting is?


I just want to know if I should give up trying to fix the air problem. Any glimmer of a possible fix to my problem would be nice. I can live with the low pump speed now but not sure if I could in the cold long winter that we are due this year.


Sorry for writing so much, more info is better than less?

 

[joni os]

Magnet and check cold feed is not partially blocked.

 

[Nobbyone]

Magnet and check cold feed is not partially blocked.

My very strong magnet (from a PC hard drive) does stick to most of the flow pipe upto and including all around the air separator, including around the cold feed port.

It had already a week of corgi system cleaner going through it.

Should I add boiler descaler in the system or will it be a waste of time?

 

[Last Plumber]

ooooooo, Everytime I see one of those air separators I know it's gonna be trouble.

 

[joni os]

Problem not limescale but iron oxide as confirmed by magnet test. Cut out and clean/replace. System will work without separator if suitably arrangement of pipework is possible.

 

[Nobbyone]

I contacted Tower tech support and they said that a three port air separator will work ok with a combined vent and feed pipe (which the manufacturers recommends). There is also no chance to change the flow direction of the pump.

I plan to remove the dodgy air separator completely from the layout and tee in a combined vent and feed pipe, but should I really keep using an air separator for a pump that pumps downwards even though my system is maintained properly?

 

[Last Plumber]

I would re-pipe it and if I knew how to post a link to things I would !
Unfortunately, I can't sorry.
Maybe someone else can.

The diagram I'm thinking of used to be in the glow worm hideaway manual.
It's a recognised way of doing things and it's how I've always done it. But that diagram explains it best !

 

[Nobbyone]

I would re-pipe it and if I knew how to post a link to things I would !
Unfortunately, I can't sorry.
Maybe someone else can.

The diagram I'm thinking of used to be in the glow worm hideaway manual.
It's a recognised way of doing things and it's how I've always done it. But that diagram explains it best !

Thanks. I will have a look for the manual.

 

[Nobbyone]

My feed tank has a gate valve in it supply pipework. A true combined vent and feed pipe should not have a valve in it as it would stop the vent from working if it were to be closed. I have read that it is down to my local water authority requirements. How do I find them?

 

[joni os]

I'm getting confused with references to combined vent and fill. Forgive me if I'm misunderstanding the situation but if using the separator the 22mm outlet at the top should rise vertically with the sole function of being the vent pipe and the cold feed from F&E tank connects directly to the 15mm port that tees in, just past the main body.

 

[gassafe]

Go to a sealed system...

The air separator is likely to be full of sludge & cold feed sounds like it'll soon be blocked too... That's British Gas for ya

 

[Nobbyone]

I'm getting confused with references to combined vent and fill. Forgive me if I'm misunderstanding the situation but if using the separator the 22mm outlet at the top should rise vertically with the sole function of being the vent pipe and the cold feed from F&E tank connects directly to the 15mm port that tees in, just past the main body.

I thought that if I am going to change the pipework that I would go down the route of doing it using the boiler manufacturers preferred layout which is combined vent and fill but also include the air separator as the tee connection. I am concerned that the air separator does seem to be a good design for a sludge catcher. The pump that is fitted is a Wilo without a vent screw just a setting on the pump which I suspect just pump the air out by reversing the pumping direction. I think that, when it does vent, it is also disturbing and moving sludge around.

I am still confused about the required use of an air separator. Can I remove the air separator completely regardless that my pump is pumping downwards?