Classic heat exchanger blockage?

[Andygasman2010]

Anyone had any problems with classic heat exchangers blocking up inside? It's about 10 years old, model before the one with the red/blue sensors that fail. It's cycling on and off and the rads don't really get up to temperature and there's a gargling noise from the boiler when the pump is on. It's got 28mm circs with 22mm hot water and 10mm manifolds for the rads. I don't suspect the manifolds are blocked because the boiler still cycles and makes the noise when on hot water. I've had fernox F3 in for 2 weeks then did a mains flush (made no difference) removed the heat ex completely and checked there wasn't a blockage at the flow/return connections. None of the pipework that's visible is magnetic so i'm a bit stuck now! I've not tried a sensor yet as the heat exchanger get's really hot at the flow connection before the burner cuts out. Other than take up the floors to check the pipes or replacing the heat exchanger completely i'm not sure.

I've applied to join the CC but not got a response yet so though't i'd give it a go one here. Any suggestions would be muchly appreciated!

 

[onlyfitidealboilers]

daft question but you sure the pump is getting the heat away, it may be running really slow

 

[Andygasman2010]

daft question but you sure the pump is getting the heat away, it may be running really slow

Ah sorry, I should have mentioned really. It's a new pump. Someone else has recently changed the mid-pos valve for some other reason, and I converted from close-coupling which was blocked to a combined cold feed/open vent.

I supose i'm grabbing at straws by now, looks like i'll have to take up the floors first seeing as the heat exchanger is about £300 quid!

 

[twgas]

I reckon you've got a partial blockage somewhere, did you check the pump valves and the pipe from the feed/vent to pump?

 

[45yearsagasman]

It is very rare for one of these exchangers to block.A circulation fault is almost sure to be the cause,either air lock,debris in pipework,poor pump performance.Check with a magnet every visible piece of copper/brass especially in airing cup if applicable.The best way of diagnosing this type of fault is to touch and feel and listen.

 

[Andygasman2010]

Yea the pump/valves I fitted myself, and I cut-out the feed/vent pipe when installed the combined vent/feed pipe, which is directly behind the pump. I'm suspiscious of the heat exchanger as there is a strange gargling noise coming from it when the pump is on. .

 

[Andygasman2010]

It is very rare for one of these exchangers to block.A circulation fault is almost sure to be the cause,either air lock,debris in pipework,poor pump performance.Check with a magnet every visible piece of copper/brass especially in airing cup if applicable.The best way of diagnosing this type of fault is to touch and feel and listen.

Thanks. I've tried with a magnet as described in my first post, to no avail!. Plus, most of the pipework in the airing cupboard is new as I replaced it myself. The only thing I haven't checked is where the hot water coil return tee's into the heating return. You think it's worth checking even though it's not magnetic?

 

[Agile]

Flow and return temps?

Tony

 

[tamz]

I converted from close-coupling which was blocked to a combined cold feed/open vent.

There is your clue FFS!

You would have been as well pyshing in the FE tank and leaving it for 3 weeks than using F3. That is for pre-commissioning cleansing of new systems and only disolves flux residues.

I've tried with a magnet as described in my first post, to no avail!

Canny be much of a magnet if it won't stick to a lump of cast


Stick some X800 or something stronger in it and clean it properly. A powerflush would not do any harm either if you are stuck for work

 

[tamz]

Double post

 

[Agile]

I was not so sure exactly what Fernox expect of their F3 Cleanser as I have normally used Sentinel chemicals as its important to fully understand how these products behave in different situations. So I looked it up on their web site.

It seems they are selling it as a dual purpose product for cleansing both old and new systems. It does what Sentinel X300 and X400 do. I think I will stick to using the Sentinel as dedicated chemicals are likely to be better at the specific task they are targeted towards.


Product Description

Cleaner F3 Universal Cleanser is a quick and effective neutral cleanser for central heating systems. It is designed to remove all debris, sludge and scale from existing systems of all ages. In this way, it will restore heating efficiency and eliminate or reduce boiler noise. It has also been designed for pre-commission cleansing new installations in accordance with BS7593:1992, removing flux residues and other debris, thereby helping extend the life of a system.



For older sludged systems, Cleaner F3 is particularly effective when used in conjunction with a powerflushing unit. If the system is heavily scaled the use of Fernox Superconcentrate System Cleaner is recommended. Cleaner F3 is a neutral, non-hazardous product that is well inhibited and compatible with all metals and materials commonly used in heating systems.

 

[Andygasman2010]

I converted from close-coupling which was blocked to a combined cold feed/open vent.

There is your clue FFS!

You would have been as well pyshing in the FE tank and leaving it for 3 weeks than using F3. That is for pre-commissioning cleansing of new systems and only disolves flux residues.

I've tried with a magnet as described in my first post, to no avail!

Canny be much of a magnet if it won't stick to a lump of cast


Stick some X800 or something stronger in it and clean it properly. A powerflush would not do any harm either if you are stuck for work

Not sure what you men by FFS...?

Reading the bottle of F3 i thought it would be adequate, may need to try a stronger one then.

Oh and the magnet test, not sure if you've read what i said wrong but i was talking about where the coil return meets the heating return NOT being magnetic, and wether or not it's still worth cutting out. I'm not quite stupid enough to test the heat exchanger with a magnet ha

agile, i've not measured the flow/return temps other than by hand. The top left corner of the heat exchanger (where the thermistor is) gets untouchably hot and the return side is still cold.

 

[tamz]

Not sure what you men by FFS...?

You have had to alter pipes before because of blockage so do you think the shyte just sticks to the one part of the system near the feed?

The top left corner of the heat exchanger (where the thermistor is) gets untouchably hot and the return side is still cold.

Another clue. BAD circulation caused by shyte in the system.

Oh and the magnet test, not sure if you've read what i said wrong but i was talking about where the coil return meets the heating return NOT being magnetic, and wether or not it's still worth cutting out.

I know what you meant. Just ripping you. Cutting out is always best. Why phish about for hours when you can easily fix it?

Reading the bottle of F3 i thought it would be adequate

Don't believe all you read from the manu's. It is shyte. No better than X300 and should only be used in pre-commision work. If you believe the Fernox lit F3 is some kind of one shot does all wonder treatment. Learn more about the products. You now now F3 is pysh through "experience".

Give the system a good dose of X800 or FX-2 (needs neutralising) maybe combined with a powerflush

 

[Agile]

agile, i've not measured the flow/return temps other than by hand. The top left corner of the heat exchanger (where the thermistor is) gets untouchably hot and the return side is still cold.

Thats all you need to have done then!

Either the system is totally blocked or there is no flow!

I would be checking the pump and its valves first.

Its unusual for a boiler heat exchanger to completely block. It would usually crack when it was just half full of dirt.

Tony

 

[Andygasman2010]

Yep it's certainly unusual, that's why I thought i'd ask you guys! I'll post-back when I get to the bottom of it, thanks.