Any plumbers or heating engineers in the house?

[reflexboy]

Morning gents
I have the dreaded Potterton Suprima 50 boiler (3 PCBs later). More or less cured the 'lockout' problem by having installed the latest PCB, but still get a 'lockout' every week or so. I have put this down to the fact that my pipes are constantly gurgling with when the boiler/pump is on. It is worse in the summer when just the HW is on, so I have ruled out the CH pipework and I know the 3 way valve is good as I recently replaced it too. In HW mode, I can vent air from just above the 3 way valve which is by the HW cyclinder and by either of the two manual vents a couple of inches above the boiler on the flow and return pipes. There was an auto bleed valve there which I suspected to be stuck but that was not the case.(Now removed and replaced with the manual valve). It is an open vented system, venting back to the filling/expansion tank in the loft, so I have done what the interweb forums suggest and tryed altering the pump speed in case the pump was running too fast and drawing air into the system that way but that made zero difference. The pump is a three speed Grundfos set to position two.
I just can seem to rid the air from the system, hence it's causing weekly lockouts. I've even spent three weeks bleeding the air daily to no avail....Any ideas oh wise ones? TIA muchly.

 

[mercmanuk]

i'm a spark by trade but i wire all heating systems and fault find most combi boilers.
out of the group of 20 heating engineers i work with 15 have the british gas level 100 boiler cover.£13 per month for full boiler cover with unlimited callouts and breakdowns.
my worcester 30 cdi kept coming up with the ea error message,printed circuit board usually the problem,the part is nearly £200.took out cover and 1 week later new board fitted for free,well worth £13 month.as long as the boiler is working when the policy is taken out then all ok.

 

[jasonyw]

Not on a Sunday.

If it still under guarantee take it back to Potterton otherwise leave it to the Gas Safe engineers.

I had nightmare getting someone just to replace a regular with combi boiler for the last 3 months. I have sympathy with you with all the stress even though it less complicated than a laptop but more expensive than one.

Shouldn't be going for a combi boiler in the first place but got enticed with saving of £300 a year, what a bull, I ended a lot of DIY plumbing myself converting a regular system to a combi with direct plumbing.

If you are not careful you may end up with an explosion on your water storage tanks, never heard of it before.

 

[Rory]

Has it always done this?

If it's not emptying the vent pipe due to pump suction (does the water level of the header tank rise significantly when the pump is on?) then you must have a tiny leak which is drawing air in when the pump is on.

I'm assuming the amount of air you seem to be talking about really is air and not hydrogen.

 

[portzy]

Air or hydrogen?

A few things that you can do to see if it is air;

Check to see if the pump is on the return side of the system. If it is then there is the potential for the system to be introducing air when the the pump is running from such things as radiator valve stems, bleed points, compression connections, etc. The reason for this is that when the pump is on the return side of the system it creates negative pressure, relative to atmospheric, when it is running.

Another trick is to fill a large/tall measuring jug with water and place it under the expansion pipe, in the loft usually, with the expansion pipe right at the bottom of the jug/water and get someone to fire the boiler/system. If there is a tendency for the pump effect to draw all of the water from the jug, (slight change in level is normal btw and to be expected), then the chances are that the system is introducing air and will need some slight modification. Moving the pump to the flow side and re-orientating the cold feed and expansion usually cures this.

Hydrogen? Yup, could be. If you are introducing so much air so frequently then there could be some corrosion going on. You could try some inhibitor, I recommend Sentinel, but the air problems need sorting 1st.

HTH?

Portzy.

 

[reflexboy]

Has it always done this?

If it's not emptying the vent pipe due to pump suction (does the water level of the header tank rise significantly when the pump is on?) then you must have a tiny leak which is drawing air in when the pump is on.

I'm assuming the amount of air you seem to be talking about really is air and not hydrogen.

I've no idea how to tell if it air or hydrogen or what the significance is. The level in the header tank does not seem change at all if the boiler and pump are on or not.

 

[reflexboy]

Air or hydrogen?

A few things that you can do to see if it is air;

Check to see if the pump is on the return side of the system. If it is then there is the potential for the system to be introducing air when the the pump is running from such things as radiator valve stems, bleed points, compression connections, etc. The reason for this is that when the pump is on the return side of the system it creates negative pressure, relative to atmospheric, when it is running.

Another trick is to fill a large/tall measuring jug with water and place it under the expansion pipe, in the loft usually, with the expansion pipe right at the bottom of the jug/water and get someone to fire the boiler/system. If there is a tendency for the pump effect to draw all of the water from the jug, (slight change in level is normal btw and to be expected), then the chances are that the system is introducing air and will need some slight modification. Moving the pump to the flow side and re-orientating the cold feed and expansion usually cures this.

Hydrogen? Yup, could be. If you are introducing so much air so frequently then there could be some corrosion going on. You could try some inhibitor, I recommend Sentinel, but the air problems need sorting 1st.

HTH?

Portzy.

Portzy-Thanks for your reply. I just did what you said with the jug of water and got someone to fire up the system. The water level in the jug does not change at all so I'm pretty confident that no air is being drawn into the system by the vent pipe or the pump being set at too fast a speed. I'm pretty sure by looking at the pipework/pump and so on by the HW cylinder that the pump is on the flow side, not the return side. It's not so much the lockouts that bother me(probably caused by the air in the system), just the gurgling pipes and whooshing noise from the pump. I last drained the system about 3 months ago and did add Sentinal inhibitor at the correct dosage. I'm pretty sure it is air in the system as before the boiler was moved to my new kitchen extension three years ago it was as quiet as a button

 

[portzy]

I've no idea how to tell if it air or hydrogen or what the significance is. The level in the header tank does not seem change at all if the boiler and pump are on or not.

Hydrogen would indicate that corrosion was/is taking place and if you have bled the system a good number of times since the boiler was repositioned then the inhibitor will be well diluted by now plus, the fresh water will be very oxygenated i.e. steel + water + oxygen = corrosion. One way to check if it is hydrogen, and if you have the nerve! is to apply a flame, say a match, to the bleed point then open the bleed point slighly, if its hydrogen it will light. I have done this 100's of times but its your call.

HTH Oh, and be careful

Portzy.

 

[reflexboy]

Matches at the ready!! Will let the air/hydrogen build up for a couple of hours and report back....If I'm not back and you live in Surrey and hear a loud bang........

 

[reflexboy]

Portzy-Tried the flame trick a couple of times last night and this afternoon and it definately won't ignite with a match, so I think we can rule out hydrogen and corrosion. It's got to be trapped air-Question is, how the heck can I get rid of it? Any suggestions?

 

[Rory]

Question is, how the heck can I get rid of it? Any suggestions?

My system (which I installed myself) has an air separator - I'm sure it's a Myson Aerjec, but I think they've changed the design. Mine looks similar to this, except the feed (from the header tank) tees directly into the left hand side (which is flow from the boiler) tube

I had no idea what they were, but the place where I bought all the stuff from (10 years+ ago) advised me to fit one, and it's a convenient way of attaching the feed and vent and being sure you won't get pumping over.

I don't know how my system would be without it, but I never get any air in it whatsoever. Either that or, if I do, the Aerjec expels it.

By the way, I doubt it's the air causing the lock-outs - I have a Suprima too and have replace the PCB maybe 3 years ago. I've started to get random lockouts again too. I was lucky and picked up a new PCB very cheap off eBay but there's a place that refurbs them and I might buy another there, and hope it's better soldered. http://www.cetltd.com

 

[portzy]

Portzy-Tried the flame trick a couple of times last night and this afternoon and it definately won't ignite with a match, so I think we can rule out hydrogen and corrosion. It's got to be trapped air-Question is, how the heck can I get rid of it? Any suggestions?

If you are certain that it is trapped air which had accumulated since/when the boiler reposition took place then its just a matter of persevering with the process of bleeding it all out. If its a continual problem then the Airjec solution from Rory would work, just follow the installation instructions properly because you need to rid the air as soon as it gets in before it has had chance to get into the system proper.

Have you considered making the system a sealed/closed one?

Portzy.

 

[reflexboy]

If you are certain that it is trapped air which had accumulated since/when the boiler reposition took place then its just a matter of persevering with the process of bleeding it all out. If its a continual problem then the Airjec solution from Rory would work, just follow the installation instructions properly because you need to rid the air as soon as it gets in before it has had chance to get into the system proper.

Have you considered making the system a sealed/closed one?

Portzy.

The Airjec thingy seems a good idea. How would I make it a closed system and would that be an advantage?

 

[portzy]

The Airjec thingy seems a good idea. How would I make it a closed system and would that be an advantage?

First off, check with Potterton that your boiler model will be suitable for a sealed system. I'm pretty much certain that it will be because, from memory, it has a low water content copper/alloy heat exchanger and all the limit stats/interlocks/low pressure cut offs that are required. I advise though that you must double check with Potts.

What you do is remove and cap off, on the system side, the small heating header tank/cold feed/expansion etc and fit to the system an expansion vessel and associated pressure gauge in a suitable and accessible location. Run a cold feed supply to the expansion vessel position and fit a double check valve and filling loop to the system. This then becomes the method of topping up the system but it is, however, a manual intervention operation and not automatic as you have now.

The advantages are:-

The system is "closed" relative to atmosphere so no air can get in from expansion pipes or header tanks etc.

The system is under pressure, usually 1bar cold, relative to atmosphere so air cannot be drawn in like it can with open vented negative pressure situations from, typically, weak valve stem seals and the like.

With the system under pressure you can run it hotter because water boils at a higher temperature when under more pressure relative to atmospheric, just like your car radiator.

The disadvantage:-

If any of your connections are suspect, and "hold" under the open vented scenario, they could well leak in a sealed situation however, that might not be a bad thing because these connections could be what is causing the the problems that you currently have. Continual air problems in open vented heating systems are sometimes caused because of a leak, albeit often small and often out of the way so they go unnoticed. What does not go unnoticed is the air problem and this is because the header tank will attempt to make up the losses with fresh oxygenated water and as soon as this oxygenated water is heated by the boiler the oxygen separates and manifests itself as trapped air.

Hope that helps? if not let me know, if you want me to explain how you fill up and vent? again, let me know.

Cheers.
Portzy.

 

[antonyw124]

I am a city and guild, qualified Plumber. If this has always happened it sounds like a design fault in the way the system has been installed. if you post some photos of the pipe work around the pump and if i can see what goes to where, I might be able to help

 

[reflexboy]

I hope these help your diagnosis:bannana:

 

[antonyw124]

Hi it looks to me as if the pump is drawing air in form the vent/expansion pipe.
If you look on the body of the pump, there will be a arrow pointing in a direction. If i have "read" the photo correctly the pump will have an arrow pointing downwards towards the floor. I think you will find it on the opposite side of the pump.
The pipe that comes from the floor on the right hand side of the pump, goes in to a T is the flow from the boiler.
It then goes from the T right and up in towards the roof this part is only the the vent/expansion pipe.
What I believe is happening is that when the pump is in operation it pulling or pushing the water through the system, but it is allso sucking air in from the vent/expansion pipe.
because of the poor instalation design. basicaly as the pump pulls the water there is not enough distance from the pump, and where the vent pipe terminates which is probably just above the airing cuboard.
How to fix?!
One solution would be to take the vent from the top of the flow pipe from the boiler,directly to the central heating cold water feed cistern in the loft. and disconnent the Vent/expansion pipe from the flow pipe in the airing cuboard. So the system has its own independent vent/expansion pipe. At the moment part of the pipe work acts as Flow to the diverter valve and also a Vent/expansion pipe.
The second solution would be to use one of the air separaters which has been mentioned previously.
Whatever you do you must make sure at all times that the system has an vent/expansion pipe which goes up in to the loft and over the top of the central heating cold water feed, tank/cistern. This must not go through the diverter valve. this is of the greatest importance as this is safety critical.
If I have not explained this very well please ask.
Regards Antony

 

[antonyw124]

Just another quick observation but do you get air in the hot water at all?

 

[reflexboy]

Just another quick observation but do you get air in the hot water at all?

Hi Anthony-When you ask if I get air in the HW I presume you mean the HW coming out of the taps? If that is the case, then no. It runs air free from the taps.
When you say run a vent pipe to the header tank in the loft from the boiler flow pipe, do you mean actually just above the boiler? Reason I ask is that the boiler is down stairs in the kitchen and the cylinder, pump, diverter valve etc is upstairs. I would almost be impossible due to the layout of the boiler being in a single storey kitchen extension.
Secondly, a previous poster said put a jug of water under the vent pipe in the loft and see if when the boiler is fired up and the pump running does it suck some water down. that would prove air is entering the system that way. No water was sucked up. Now i'm at a loss."scratch head"

 

[antonyw124]

Hi I did mean air in the hot water from the tap. the reason i asked is because the pipe that comes of the top of the hot water cylinder should turn as soon as it leaves the hot water cylinder. but in this case it goes straight up and then turns which can lead to one pipe circulation where the water cools and then goes back to the hot water cylinder which creates air. This would not create an air problem in the central heating Sorry if this confuesd the situation.
I did mean that the vent and expansion pipe could come of the top of the boiler. the pipe that comes of the top of the boiler ends up in the Airing cuboard and goes to the pump/diverter valve ect, So it could follow that pipe. However this would seam like a lot of work by the sounds of it.
Because the pipe did not suck up the water does not mean it is not sucking air up. Because of the way it is installed, it is easy for the pump to pull the water down from this vent pipe which would create air.
I would try the air separater