Combined heat and vent pipe location

[bobby_la_mesma]

Dear All

I have a worcester bosh 30CDI conventional boiler fitted into an open vented system. I have a "S" plan design which has the correct dose of Sentinel X100 in it.

I have found that if I set the boiler temperature control to above setting 5, that the system is noisy when the TRV's open and constantly requires bleeding from one radiator. It is particulary noisy after the system has been off for over 24hrs. A glugging noise will come up through the motorised valve which controls the feed to the central heating pipes.

I have fitted manual air vents to the system at the highest points and have bled the system from these valves and radiators daily for the past 6 weeks. The system runs smoothly and quietly for a couple of days and then needs to be re-bled

The pipes are all free from blockages and I have a combined feed and expansion pipe. I have done the test at the cistern, with a glass of water and found that the system is not drawing air in through the expansion pipe. Due to the layout in my building the cistern is only about 50cm above the boiler, which does conform to the min height as published in the manual.

I know the simple answer is to not set the boiler temperature control above 5, however I just like to ask the experts who visit this site if they have any ideas which I could i try.

My grundfos pump is set to 2.

My feed and expansion pipe is fitted to the flow pipe at the highest point. I have seen a diagram on the web where a combined heat and vent pipe should be fitted to the return pipe. Is this correct and would it make a difference, since it seems to me hat the trapped air collects at the motorised valve.

It has been mentioned to make the system sealed but I wanted to explore is an easy option exists

I welcome your opinions.

 

[superdupergasman]

It could be nitrogen being produce by corrosion, Is there plenty inhibitor in the system??

 

[D_Hailsham]

1. Which Grundfos pump do you have?

2. Is it pumping downwards - arrow on body?

3. What is the height between the pump inlet and the water level in the F/E tank?

 

[D_Hailsham]

It could be nitrogen being produce by corrosion, Is there plenty inhibitor in the system??

Do you mean hydrogen?

 

[bobby_la_mesma]

I have a Grundfos UPS 15-60 130. Pumping downwards.

The head tank is 80cm above the pump, in the loft. The pump, pumps dowards towards two motorised valves which are 50cm below the pump. The whole system (boiler, valves, hot water tank, pump, automatc bypass, control gear) is all fitted in an upstairs airing cupboard.

The system was dosed with Sentinel X100. Would this not stop the nitrogen problem?

 

[superdupergasman]

It could be nitrogen being produce by corrosion, Is there plenty inhibitor in the system??

Do you mean hydrogen?

Yes which ever is produced...I always get confused between the two!!

 

[D_Hailsham]

I have a Grundfos UPS 15-60 130. Pumping downwards.

From Grundfos Literature:

It is preferable to install Grundfos circulators in a vertical pipe pumping upwards. This position ensures that the pump shaft is horizontal, which reduces the thrust bearing load and ensures positive air purging from both the rotor chamber and impeller housing.

Pumping downwards in a vertical pipe is not recommended as this may lead to air locking of the pump, with resultant loss of performance. However, pumping downwards is acceptable provided an effective air vent is incorporated in the system, before the pump.

The head tank is 80cm above the pump, in the loft.

Grundfos recommend 1.4m minimum.

The system was dosed with Sentinel X100. Would this not stop the nitrogen problem?

Yes - but it's hydrogen which is produced, not nitrogen.

 

[bobby_la_mesma]

I have air vents in the systems before the pump and at the highest points. I tested the vent pipe for sucking air in using a glass of water and it was not pulling air in. Is there any point trying moving the combined feed/vent pipe onto the return side like in the diagram I saw?

Would making it a sealed system alleviate this problem and cancel the effect of pumping downwards?

 

[russ1629]

I have air vents in the systems before the pump and at the highest points. I tested the vent pipe for sucking air in using a glass of water and it was not pulling air in. Is there any point trying moving the combined feed/vent pipe onto the return side like in the diagram I saw?

Would making it a sealed system alleviate this problem and cancel the effect of pumping downwards?

 

[D_Hailsham]

I have air vents in the systems before the pump and at the highest points. I tested the vent pipe for sucking air in using a glass of water and it was not pulling air in.

Don't see how you can test the vent pipe when you have a combined feed and vent!