Sludge on a closed/sealed Combi system

[Pw123]

Hi

I have potterton Combi 80 boiler with sealed/closed system that is running on the single pipe (i.e. no separate feed and return pipes). Additionally, the radiators have single outlet on the bottom middle rather than separate inlet and outlet on each bottom side.

I have been told by British Gas to get the system powerflushed. Now my questions are:

1) how likelihood is to have the sludge on the closed/sealed system considering that there should be no (almost no) oxygen entering the system?
2) instead of powerflush, can I try to use the sludge remover (Sentinel X400 or one from Wickes) to remove the Sludge? If so, what are the steps involved in flushing the system? My understanding is
a) turn off the boiler and the thermostat from mains
b) attach the hose pipe to the drain-off and open the drain off
c) when the hose pipe is running/draining, open the rad air vent, starting from the topmost rad first
d) when system is empty, close the drain off, rad vents
e) add Sentinel x400 or equivalent using the towel rail
f) pressurise the system to 1bar while bleeding the rads
g) run the heating for 1 week and then flush again
h) add x100 or inhibitor before repressurising

Is this all? If so, are there any tips to ensure that there are no airlocks when repressurising the system?

Many thanks

 

[diamondgas]

I'd be interested in seeing those rads Pw123! Thats a new one on me ....

A combi 80, single pipe system, weird sounding radiators ... My best advice would be replace the lot!

However if that isn't an option then with what you're describing I'd say X400 in for a week or so as you describe ... Then drain it all off ... Remove each rad individually and flush through with a hose ... They must have a flow and return! ... Then refill and drain a cupl of times before adding the inhibitor on the final fill!

Even better still; get some quotes from other plumbers to verify BG's findings before you start 🙂

 

[GasManMike]

Flushing it wouldn't really help clear the rads on a 1 pipe system (if it is a 1 piper) flushing them just tends to clear the pipe work. I've never come across those rads/valves before, might be some sort of twin entry set up? Has it always been a sealed sytem? If not previous air ingress could have caused a sludge build up before it was sealed. I agree with diamondgas, get a second opinion.

 

[FD Powerflow]

Interesting that BG would advise powerflushing a one pipe system which is a complete nightmare to do and in fairness rarely ends in success. I would advise putting a bottle or can of F5 in and leaving it for 3-4 days of the boiler firing. Then dump at the lowest points, you could try main fill flushing by leaving the draincock open and the filling loop open.

 

[Pw123]

Thanks diamondgas and GasManMike - I have attached a picture of the radiator for you to take a look and give me your expert opinion.

We have had the boiler and the whole setup for 11years - it was installed by previous owners.

GasManMike - about your question that if it has been always a sealed system, as I said to my knowledge it has been like this.

The problem that I have is that the boiler locks itself out intermittently. What I have noticed is that on times the boiler will keep running even though there is no HW demand and CH is switched off. I have checked to ensure that all HW taps are turned off. When this happens, the boiler gets heated up and locks itself out. Also, the rads become hot too.

We did not have this problem in summer but has started to happen only 3 weeks ago.

Just to add, the pressure on the system is fine.

Would appreciate if someone could advise on what the issue/problem may be based on these symptoms.

 

[Pw123]

Just to add to the earlier note, the pressure on the system is fine.

 

[tamz]

Only way to clear sludge from the rads on a one pipe is to remove them and hose through.
One pipes have not been fitted domestically for about 30 years so you system predates your boiler.
Can't see your rad photo.

 

[diamondgas]

pw123 ... no pictures .. however a question B4 you replace the boiler ... when you turn the hot tap off does the flame estinguish imediatly (no call for heating) or stay on for a short period of time.

 

[Pw123]

Sorry guys forgot to attach the photo.. here it is now..

diamondgas - usually when the hot is turned off the flame goes off and the red light on the board goes off too. However, on other occasions, the flame is on and the red light on the board is on too. In these situations, the boiler locks itself out after a little while (assuming it has overheated).

 

[Pw123]

Picture of the radiator

 

[tamz]

Some kind of dual valve but i've never come across one like that.

 

[Pw123]

Just opened up the manual and looking at the fault finding page - it says that if the Red LED on modulator board is on, then it is fault with Hot Water Flow Switch. Is this the issue?

 

[diamondgas]

Those rads are ancient my friend crikey I'd forgot they existed and i've been here some 34yrs...

However it sounds like the diaphragm may have holed ... considdering your NEW finding ...........! I'd be phoning BG back out imho


BG been and said flush it!!!

Flippin heck!!!

 

[Pw123]

Diamongas - I am sure they are very old but have been working fine for ages.

I have already called BG to come tomorrow to take another look - after speaking to supervisor to convince that what they have been saying about powerflush is not necessarily true. When you say diaphragm - I assume you mean the diverter valve. Sorry for being thick 🙁

 

[Billy Bob Bob]

good god they are brave to powerflush that or charging way ott it could blow up

 

[diamondgas]

Lests back track to the actual fault pw123 ... What indication are you saying you're getting on the Cobni 80 boiler?

Initial thoughts when you mention h/w switch is that the diaphragm has failed .. however this is such an obvious fault i'd be amazed a BG engineer wouldn't no it??

 

[diamondgas]

good god they are brave to powerflush that or charging way ott it could blow up

By blow up you mean the radiator could well expand under the pressure .. :rofl: Don't want to scare the op here my friend ...lol

 

[Billy Bob Bob]

By blow up you mean the radiator could well expand under the pressure .. :rofl: Don't want to scare the op here my friend ...lol

yes sorry steve.....i do think its a boiler fault but do not have the head for pumas tonight......shes all yours.....good luck LOL

 

[Pw123]

Lests back track to the actual fault pw123 ... What indication are you saying you're getting on the Cobni 80 boiler?

Initial thoughts when you mention h/w switch is that the diaphragm has failed .. however this is such an obvious fault i'd be amazed a BG engineer wouldn't no it??

Hi Diamondgas
When the BG engineer visited last time, the boiler was working perfectly. As I said the issue is intermittent so it could work all day but next day could lock out few times. As I mentioned in the earlier post, before the boiler locks itself out, I have noticed that the boiler is continuously running even though there is no HW demand and CH is off. I also noticed that the red light on modular board was on.

 

[Pw123]

One thing I forgot to mention was that we do hear the occasional kettle-like noises or clanks from the system.