Air in system question?

[furrock]

Hi guys,

I posted a while back about some circulation issue's i am having with my central heating system. I have now had 4 plumbers look at my problem to no avail. I have always had sound advice in here so here goes again.

Problem:

Boiler short cycling due to heat not getting away from boiler. Flow pipe is scalding hot at the boiler and yet at the pump (4 meters of pipe away) it is luke warm at best. Return luke warm at best. Due to this is takes the system ages to get up to heat as the boiler only stays on for 8 mins initially, then on for 1 off for 4 after that.

Its definatly some circulation issue as the hot water is fine, and when i open the bypass the return heats up no probs.

I think this could be down to air in the system. Whenever a plumber opens up the syste i.e. change pump etc the rads burn so much better for a short period after that.

Last night i tried just having one rad open and the heating on. There was lots of air going through the pipes at the boiler, so much so that i thought the boiler was going to come off the wall!!

Could air be causing the blockage in the system? I have to bleed the towel rail and the small rad in the hall (first rad) weekly.

If this could be the cause is it worth while fitting auto bleed valves that i seen in B&Q to these two rads, and also a AAV (http://www.screwfix.com/prods/97868/Plumbing/Brassware/Bottle-Air-Vent-15mm#) ?

Any help appreciated.

PS. new pump has been fitted and system de-sludged, drained and inhibitor put in. All new rads and Hep pipework with manifolds

 

[Letitbnown]

Furrock, I am assuming that you have a combi boiler? You also do not mention system pressure, whether this is normal all the while, falls off etc.
With you saying that when the by-pass is opened then the heat is normalised, then there could well be a problem between this valve and the pump.
Any condition where the boiler sounds 'explosive' is when there is a definite pressure/water shortage. When a system has been drained down and refilled there will always be noises due to the air within. This is normally vented off as the boiler picks up the flow.
Any plumbers who have checked your system should have concentrated on the immediate connecting pipework and flow, to see that all is as it should be.
For the cost of your works to date it might well have been better to have had a good company fit you a new boiler. This might yet prove to be the answer to your problems.
Good Luck!

 

[clf-gas]

Furrock, I am assuming that you have a combi boiler?

Pump 4m away

 

[furrock]

It is an open vented system with a potteron 80 L suprima boiler.

Another question, is it worth while getting a power flush?

With regards to hearing noises after a drain down the last time the system was drained was over a month ago.

 

[furrock]

Is having the pump 4m away an issue?

 

[clf-gas]

Is having the pump 4m away an issue?

No, it was a clue to letitbeknown as to your system being open vent.


Have any of the "plumbers" changed the pump. Is your system fully pumped, ie, Y plan.

 

[diy]

[potteron 80 L suprima boiler.


short cycling... has anybody suggested changing the pcb, known fault on these.

 

[furrock]

Yes, PCB has been chaged, as has stat in the boiler. Also a new pump has been fitted.

Not sure what you mean by "y" system?

 

[namsag]

Can you follow the pipework properly to make sure the flow is actually the flow same with return /Pipework possibbly crossed

 

[furrock]

Checked that, all seems ok on that front.