Rogue CH System

[willemm]

Hi. My bungalow has an oil-fired Wallstar open vented CH system with 6 rads. Since new 2000 (bungalow & CH) it has been plagued with CH problems. The most repetitive is boiler cutting out after 2 minutes, off for 10 mins + then on for 2 mins. Etc. Naturally rads just about warm, or one rad hot if other 5 off. Boiler exonerated by engineer visit from HRM Wallstar whose checks indicated circulation problems. I've had a section of pipe above boiler in loft cut out and replaced, said to have been location of lock. Pump has been replaced. 3 port valve replaced. Circulation vent added to loft pipes (never included in original plumbing!).
All rads and circulation bleed only water, no air. Grundfos pump now giving off swishing noises, so removed its centre screw - vanes fully running, but no water coming out.

Sorry for long intro but needs to be explained. Since problem has been on and off for last 10 years, it couldn't have been sludge in those early years although could be now. Inhibitor was in original installation but no doubt very weak now.

Looking at many forums I see a number of options but all seem to have drawbacks or insufficient info. Am now considering two options (i) to drain system and use Fernox F3, but do I need to drain all 6 rads or will any one be enough ? Can't I just drain enough to get the F3 into the system to do its work, then flush it out after a week or so ? (ii) Bite the bullet and get a Power Flush costing an arm and a leg, but I've read that this could do more harm than good on a small bore system.

I think, from blogs I have read, and from location of pipe noise in loft close to header outlet that I have a cold supply blockage, said by some to be near pump. This tallies with where pipe noise heard. But if so, how do I get at it ?

Will be grateful for any advice

 

[Tibbot]

System might not be full and free of air. May be incorrectly piped if problems existed from outset.

Your ideas may be a waste of time until someone can prove as above.

 

[willemm]

Thanks Tibbot
Air was indeed in system - by connecting mains supply to return pipe a short burst sent a fair amount of air into header tank. Took another burst to make a real difference, but as boiler still cuts out before room temperature met (as it used to), seems as though there could yet be more air somewhere. But where can it come from - the header level is well above outlet. Although same problem has been around for a long time, I have gone for a year or two at a stretch without it happening.

 

[twgas]

If, as suggested, the boiler is fine the system must be wrongly installed.
where is the pump in relation to f&e tank, where are the cold feed and open vent connected to the system, maybe (if the boiler is suitable) converting to a sealed system would resolve your problem.

 

[willemm]

Thanks twgas. Bungalow, conventional straight layout. Boiler on kitchen wall at front end of house, piped into loft with straight runs 8 metres to opposite end with F&E tank. Pump in airing/HW cylinder cupboard teed down some 2 metres along from F&E tank. Microbores to 6 rads teed off at intervals in loft.
Can’t figure how installation could be incorrect in such a simple layout. As I see it in practical terms – with a 3” head of water above E & F outlet and rads plus circulation vents not giving off air, it is "sealed" there being no means for air getting into the system. Except for Fernox info at http://www.fernox.com/?cccpage=air_in_CHS&sub=3 where they list a whole range of possibilities.
Maybe topping up with inhibitor will reduce any chemically generated gases.

 

[Tibbot]

As I see it in practical terms – with a 3” head of water above E & F outlet and rads plus circulation vents not giving off air, it is "sealed" there being no means for air getting into the system.

Kindly suggest you acquaint yourself with the definition of 'sealed system' before posting such comments.

A system that appears full of water doesn't mean it's purged of air. You shouldn't need to back fill it with the main if it's installed correctly.

By the way Wallstars are sealed system compatible.

 

[Agile]

A small and not fully informed aspect which you casually allude to is that you have a microbore system.

There is a 10 mm system which is usually OK and then there is an 8 mm which can be very difficult. Even the smallest blockage can reduce the flow. As the pipes have significant resistance the flow rate is lower and thats less likely to blow out any air.

Your problem is probably mostly just caused by air and a less ideal layout.

You seem to have this dream that all you need to do is to put some chemical in the system and all will be cured. Thats most unliklely in the real world. It probably needs some pipework modifications and possibly some desludging.

What speed are you running the pump at? What is the model number?

Tony

 

[griggs]

OV microbore systems can be a real pain to get the air out of.

 

[willemm]

From the various replies I have obtained - as a complete lay person - from asking a simple question - how can air get into my CH system - I seem to be getting drawn into irrelevant debates of a technical nature including the definition of a microbore system. Perhaps Agile should inform Trading Standards that the likes of Wickes and Screwfix are mis-selling 10mm copper tubing as Microbore Tubing. How casual of them.
I referred to a "sealed" system deliberately in quotes in the context of my remarks (yes I do know the difference) since I could not understand how air could enter the system. Thankfully an enlightening article on the Fernox website has provided a number of possibe causes that don't necessitate applying any of their chemicals presumably only sold to dreamers.
As my bungalow was built by a reputable company known for their high standards, I didn't feel it necessary to ask to see the installing plumber's credentials. Perhaps I should have done. But then he too must have been a dreamer since he put Fernox inhibitor into the system. What a waste.

 

[doitall]

Clearly the pipework hasn't been installed correctly, so answer this;

How high above the pipes in the loft is the bottom of the tank.

What size pipes drop to the pump in the cupboard.

Is there a 3port valve after the pump.

What provision has been made to get the air out of the flow and return pipe in the loft, especially where it drops down.

Do the heating pipes go under the floor or back up into the loft.

I would say without a doubt if you hold a glass of water under the vent and turn the pump on, it will suck it dry.

 

[griggs]

from asking a simple question - how can air get into my CH system - quote]


Air can be drawn into systems in a number of ways. Through the vent pipe, AAV on retun pipework, minute leaks on rad valves. Poor design is often the fault, and seems most likley in your case as it has never worked correctly. Microbore can often make poor design even worse.

 

[Nige F]

As my bungalow was built by a reputable company known for their high standards, I didn't feel it necessary to ask to see the installing plumber's credentials. Perhaps I should have done. .

Just Google ...Subbie...and ....LUMP labour in the 1960`s. Read and learn .

 

[Agile]

Boiler on kitchen wall at front end of house, piped into loft with straight runs 8 metres to opposite end with F&E tank. Pump in airing/HW cylinder cupboard teed down some 2 metres along from F&E tank. Microbores to 6 rads teed off at intervals in loft.

Can’t figure how installation could be incorrect in such a simple layout. As I see it in practical terms – with a 3” head of water above E & F outlet and rads plus circulation vents not giving off air, it is "sealed" there being no means for air getting into the system.

You have made some rather negative comments with reference to me. I am surprised that you have done his when I work within our industry and so I am likely to know what I am talking about.

Your level of knowledge is demonstrated when you say you have a sealed system with an F&E tank ! You then go on to say you know what a sealed system is!

Everyone will be laughing at you!

Tony

 

[transam]

As a matter of interest I know of several sealed systems that have F & (E) tanks fitted , although technically they are only feed tanks/cisterns .

 

[doitall]

As a matter of interest I know of several sealed systems that have F & (E) tanks fitted , although technically they are only feed tanks/cisterns .

Do tell I'm all ears

You can install an pressurized top up vessel, but you can't call it an F&E tank.