Central Heating Open vented - Air problem

[nairb999]

I have a Potterton Prima 60F Central Heating system - simple heating system with 16 rads each with TVR so no room stat. Had problems with air in the system for a number of years. As the system worked OK I just bled a number of radiators weekly to remedy problem.

12 months ago I had to replace the pump and since then the system has ran very noisily after a couple of hours ie loud running water noise round the pipework in the airing cupboard - this is a new noise.

So after discussing on this site was advised to get rid of air problem first as it looked like my pipework arrangement could have been causing air to be sucked into the system via expansion tank. Recommendations included lowering horizontal pipe above pump ie increase static height plus increase its length so the pump would not be pulling directly on the feed/expansion pipe.

Pipework before mods

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• nairb999
• 1 Sep 2008
• 1

The 2 pictures below show new pipework arrangement. On the picture showing the pipework going into the loft - expansion tank, I decided to create 2 right angle bends enabling me to not change the siting of the tank connector. Could this be the reason why I am still getting air in the system?

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• nairb999
• 1 Sep 2008
• 1

Untitled

• nairb999
• 1 Sep 2008
• 1

[/img]

 

[Gasguru]

....16 rads each with TVR so no room stat.

You should not have TRVs on all the rads, you should have at least one uncontrolled rad and a room stat in the vicinity. On 2 x 2port valve setups you also need an auto bypass valve to allow flow on pump overrun.

Have you considered changing to a sealed system?

 

[nairb999]

....16 rads each with TVR so no room stat.

You should not have TRVs on all the rads, you should have at least one uncontrolled rad and a room stat in the vicinity. On 2 x 2port valve setups you also need an auto bypass valve to allow flow on pump overrun.

Have you considered changing to a sealed system?

14 rads have TVR's - sorry for incorrect information. I have 1 tiny radiator upstairs and 1 downstairs. So I presume 1 has been set up for bypass. No valves in system as hot water system is separate to central heating - gas fired.

Yes I have thought of changing to sealed system but wanted to try and get this system working properly. Any thoughts on feed/expansion pipe - would 3 right angle bends in less then 8" create problems ?

 

[nairb999]

I have a Potterton Prima 60F Central Heating system - simple heating system with 16 rads each with TVR so no room stat. Had problems with air in the system for a number of years. As the system worked OK I just bled a number of radiators weekly to remedy problem.

12 months ago I had to replace the pump and since then the system has ran very noisily after a couple of hours ie loud running water noise round the pipework in the airing cupboard - this is a new noise.

So after discussing on this site was advised to get rid of air problem first as it looked like my pipework arrangement could have been causing air to be sucked into the system via expansion tank. Recommendations included lowering horizontal pipe above pump ie increase static height plus increase its length so the pump would not be pulling directly on the feed/expansion pipe.

Pipework before mods

Untitled

• nairb999
• 1 Sep 2008
• 1

The 2 pictures below show new pipework arrangement. On the picture showing the pipework going into the loft - expansion tank, I decided to create 2 right angle bends enabling me to not change the siting of the tank connector. Could this be the reason why I am still getting air in the system?

Untitled

• nairb999
• 1 Sep 2008
• 1

Untitled

• nairb999
• 1 Sep 2008
• 1

[/img]

Any more suggestions ??????????

 

[D_Hailsham]

I see from earlier posts that you have had this problem since you changed your pump to one made by Circulating Pumps. You also have been suffering from air in the system for many years, had many solutions proposed but not had any real success.

What is the Model No of your new pump?
Can you remember what your old pump was?

 

[nairb999]

What is the Model No of your new pump? CP 63
Can you remember what your old pump was Myson

I believe the CP63 was a direct replacement for the Myson Pump

 

[Deleted member 105431]

What is the Model No of your new pump? CP 63
Can you remember what your old pump was Myson

I believe the CP63 was a direct replacement for the Myson Pump

try a decent correctly sized pump like a grundfos 15/50 on number 1 or 2.

 

[mickyg]

Just a side note, I'm pretty sure pottertons used to recommend a combined c/f&o/v on profiles, and assume its the same on the prima. Might have been a better option. The amount of air in your system could well be due to a high level of corrosion taking place, even after correcting the c/f&o/v.

 

[nairb999]

Just a side note, I'm pretty sure pottertons used to recommend a combined c/f&o/v on profiles, and assume its the same on the prima. Might have been a better option. The amount of air in your system could well be due to a high level of corrosion taking place, even after correcting the c/f&o/v.

I have looked in the manual and they show a sealed configuration and a combined feed and vent. If I were to change to this configuration would that help ie just extend horizontal section of feed pipe close to the ceiling and t into the vent.

With regard to to air in the system if I run the system with the stat off you can hear air gurgling for 5 mins or so and then it settles down and is fairly quiet. On turning the stat up the noise reappears and gradually gets louder

 

[D_Hailsham]

On 11th March Nairb999 wrote:

How important is the depth. The level in my expansion tank is 175mm ensuring that the bottom of the overflow pipe is always under water. Could this explain why I continually have to bleed the system ?

Are you saying that your overflow is under water? If so that is very wrong. This diagram shows what it should look like.

The water level, when cold should be a couple of inches above the bottom outlet. The idea is that, as the water in the system expands when it is heated up, there is enough room in the F/E tank to hold the expansion without an water escaping out of the overflow pipe. Your system will hold about 85 litres and as the water will expand about 3% you will require at least 3 litres space between the cold level and the overflow.

View media item 4313

 

[nairb999]

On 11th March Nairb999 wrote:

How important is the depth. The level in my expansion tank is 175mm ensuring that the bottom of the overflow pipe is always under water. Could this explain why I continually have to bleed the system ?

Are you saying that your overflow is under water? If so that is very wrong. This diagram shows what it should look like.

The water level, when cold should be a couple of inches above the bottom outlet. The idea is that, as the water in the system expands when it is heated up, there is enough room in the F/E tank to hold the expansion without an water escaping out of the overflow pipe. Your system will hold about 85 litres and as the water will expand about 3% you will require at least 3 litres space between the cold level and the overflow.

View media item 4313

I did not explain myself too well on that post.The overflow has a connection to it inside the tank which is about 4" long and points vertically down. I presume it is fitted to stop bugs/insects getting into the tank. The water level is 4" above the cold feed outlet. I hope that makes sense and many thanks for taking the time to dig through the history

 

[mickyg]

I have looked in the manual and they show a sealed configuration and a combined feed and vent. If I were to change to this configuration would that help ie just extend horizontal section of feed pipe close to the ceiling and t into the vent

Well it depends really, if the pump is drawing air down the open vent, then yes this should help. If gases are being created in the system due to corrosion then no it won't. Either way, it certainly won't make it any worse.

 

[DP]

Myson CP63 is a 6m heat pump (I think).

End of the day a pump is a pump. If the pump is giving correct temperature drop across the radiators, I would not recommend a replacement.

Is the pump fitted in the flow or the return pipe. Setup should be boiler flow with first tee branch going to vent, within 150mm second tee branch going to feed (usually branch points downwards- feed/ expansion pipe inverts on itself to connect to this tee). Pump is fitted now to pump forward (away from aforementioned tees)

I take it the cylinder and heating flows are made after the pump.

 

[D_Hailsham]

I did not explain myself too well on that post.The overflow has a connection to it inside the tank which is about 4" long and points vertically down. I presume it is fitted to stop bugs/insects getting into the tank. The water level is 4" above the cold feed outlet. I hope that makes sense and many thanks for taking the time to dig through the history

That sound OK,though the vertical extension to the overflow is odd, unless it has a mesh or similar inside to prevent bugs entering.

Have you ever had your system balanced? If so, what was the procedure followed?

 

[nairb999]

Myson CP63 is a 6m heat pump (I think).

End of the day a pump is a pump. If the pump is giving correct temperature drop across the radiators, I would not recommend a replacement.

Is the pump fitted in the flow or the return pipe. Setup should be boiler flow with first tee branch going to vent, within 150mm second tee branch going to feed (usually branch points downwards- feed/ expansion pipe inverts on itself to connect to this tee). Pump is fitted now to pump forward (away from aforementioned tees)

I take it the cylinder and heating flows are made after the pump.

Everything lines up with your recommendations other than second t which points up - as per photograph