Central Heating

[ms08]

Have been having issues with the heating playing up recently - gurgling, air in rads etc - keep bleeding. Old back boiler Baxi and pumped gravity system.
Decided to drain down and re-fresh and add some Fernox. Mistake but at least I now know possible issue as discovered from this that the cold feed form F&E tank is blocked - possibly cause of some of the issues with boiler.
I have ordered a gallows gun - arriving today to try and blast through any blockage in the cold feed but it this fails as a temp measure, can i back fill the system from the drain cock using a hose connected to mains water supply?
Just a thought......

 

[Blobber]

The pipe normally blocks on the point the feed from the tank joins the heating pipework, normally the 1st "T" piece you come too

I have in the past filled from drain cocks when encountering troublesome systems! depending on the type of cock it may be a bit leaky!

 

[hunter27]

As Blobber says, It's a common problem, the pipework where the cold feed with relatively static water enters the main warm circulating pipework. This usually involves cutting out the junction that's often totally blocked, rodding the three ends a foot or two and re-piping.

 

[gaz1]

becareful with full pressure mains on backflowing back to the tank

you will get a full jet of flow of water out of the tank

cap the return flow and pick the closest point to the feed flow to backflow from

water ossilation is known to shift the crud in the pipes

hunters comment is the last resort

 

[ms08]

Thanks all
Tried a couple of blasts with gallows gun but no joy so fully blocked with crud so will try and back fill for now.
Yes read a lot about the T joint - on the Baxi it is right down by the boiler rather than near the pump in the circuit.
I can see it and will give that a go if all else fails but need to take the gas fire out to get to it and only source of heat at present.
If that fails then get a professional in......

 

[hunter27]

Gravity systems usually have the cold feed connected into the gravity (domestic) return pipe usually in the bottom cylinder return connection, and the expansion pipe is taken off the top of the gravity flow connection. This is done mainly because it saves running the cold feed right back to the boiler as used to be done in really old systems. I have fitted hundreds of Baxi back boilers so I appreciate the real difficulty of doing anything in the small space you have available by the boiler.
If the system was working slightly albeit gurgling, the blockage may be mainly in the cold feed pipe part of the junction rather than the larger gravity return pipe and the system is only short of water, and assuming the cold feed drops down through the cylinder cupboard (as is very common) I would cut the cold feed in the cupboard branch that into the gravity return pipe and just cap the end that went down to the boiler. Be aware that it's possible you may need metric to imperial adaptors to do this so check sizes before you cut into the pipework.

 

[Perry Owens]

My 86 year old sister lives in an old farmhouse in Normandy. Last autumn the oil-fired central heating boiler died and she has been after a replacement ever since. Apparently the French government does not allow the sale of oil fired boilers any more. Are they still available in the UK? if so we could take one over and get it fitted.

 

[OJCar]

My 86 year old sister lives in an old farmhouse in Normandy. Last autumn the oil-fired central heating boiler died and she has been after a replacement ever since. Apparently the French government does not allow the sale of oil fired boilers any more. Are they still available in the UK? if so we could take one over and get it fitted.

Yes still for sale in the UK.
I had an Oil Boiler supplied and fitted in October to replace our coal fired back boiler.
The joys of a time switch and a thermostat!

 

[badabec]

 

[rtcosic]

....... Apparently the French government does not allow the sale of oil fired boilers any more.....

Colbertism and Dirigism at its finest!

 

[jmp49]

My 86 year old sister lives in an old farmhouse in Normandy. Last autumn the oil-fired central heating boiler died and she has been after a replacement ever since. Apparently the French government does not allow the sale of oil fired boilers any more. Are they still available in the UK? if so we could take one over and get it fitted.

Personlly I wouldn't fit a new replacement oil only fired boiler here(in France)... The cost of fuel oil is about 3x the price of alternatives. I have a oil burner as backup for wood burning furnace and I havent even bothered connecting it up to the tank in 12 years its so expensive to run, and shortly we'll be replacing the oil burner with a wood pellet burner setup. Pellets are cheaper and everywhere here in convienient bags and they go in a self feeding hopper for easy handling.
For clarity Its not a total ban on fuel oil boilers, its a ban on new installations using traditional fossil based fuel oil as the primary fuel source that emit more than 300g of CO2 per kWh of energy. You can fit one as a backup against other energy sources, and you can get the system maintained and repaired still if its possible to fix the existing one. If there's valid technical reasons you cant use a alternative fuel, you can still buy and fit a new oil fired installation after getting a exemption from the rules.
Also new replacement complete oil burning chaudiers (central heating furnaces) are still legal if they run on biofuel as their primary fuel & even 5% biofuel mixes are legal and for sale still. Its only a jet difference inside the burner and some different material seals that can cope with ethanol in the fuel...

Most of the boilers I see here have a burner that hangs off on a plate that is a separate module, and you can just screw it to a replacement furnace if the furance itself is bad. Or you can still buy just the bruler/burner itself as a replacement part. You could even buy a new burner for fossil fuel use as a repair part, and fit it to a bio chaudier in place of the bio fuel burner, it'd be more expensive to run, but its possible...

 

[ms08]

Thanks Pete (Hunter), all
Some success as now have hot water again and heat after filling through the drain cock a couple times - the F&E nearly filled up but the overflow spewing out warned to turn the tap off on mains water supply via a hose pipe.
There is still lots of air in the system and can hear lots of gurgling when it starts in the morning and the pump cavitates until the boiler warms up and pushes water round the system and then it all settles.
The ground floor rads are fine now once up and running but 1st floor are only heating part way up despite bleeding many times. I suspect now that the water levels need topping up more as possibly too low in the system to fill the upper rads and all the pipework?
I am sure the cold feed definitely comes down to the boiler and T's in - have traced the pipe across the loft and down through the bedroom - the vent pipe goes up the same route - I can see it come in from above but will double check again.
I suspect the only solution will be to break the compression joint here and check clean out any sludge but that will meaning drain down again which i am going to swerve for now.
The system/boiler is around 40 years old now so doing well but not efficient at all but like a Morris Minor - easy to work on.
If i can limp it through the cold period can focus when warmer.
The system has been noisy, though not as bad until very recently when the rads were not heating up and it took me some fiddling - drawing off hot water in the morning to get things going after which ok until the next day and repeat - this only started last week so muggins thought drain down flush etc after which the refill was hampered by the blocked cold feed.
I think it is now pointing at low water in the system and the blocked feed. As i said gallows gun wouldn't shift this - have read about tapping the T with a small hammer but not sure that will resolve but no harm in trying if i am going to leave alone for now until i can break the joint.
Not sure when the cold feed blocked up but it could have been some time.
Ideally would like to top up using the vent pipe but not sure i have a hose to reach and it has ninety degree bend to get a hose around above the F&E tank so will try via the drain cock again.
I guess now to let the system cool and settle and see i can get some more water in - easier said than done trying to keep on everything with the missus as apprentice! Would be harder on my own though!
Apologies for long post but up to date now.
Mike

 

[knighty]

I'd try to avoid tapping on it... the crud blocking it will just drop out and go around the system?

fixed the same problem on my brothers central heating years ago, the 90' under the Tee was blocked solid, had to cut it out and replace... if yours is compression it should be pretty easy to swap?

search for leaks... even a tiny leak means there's a constant drip of fresh water coming into the system... which is where the oxygen/mineral rich water comes from and causes the blockage :-(

after that get some system cleaner in and flush it through, then drain and re-fill with some preservative stuff in it

 

[ms08]

Thanks knighty
I was trying to avoid another drain down just now as it stands and understand it will be in the system if it moved but was then hoping I add some cleaner and at least the refill would be easier this time round and then clean the whole system properly and then flush again etc.

 

[roofman]

get a mag filter fitted...i fitted one to mine and you will be amazed at the iron based sludge they pick up

 

[ms08]

Thanks roofman for tip on that.
The plan today is to top up the system a little more.
The process i used last time was to open a bleed valve on an upper rad until water came out, backing filling from drain cock. Obviously this has now settled in the system and much less noise/gurgling of pipes etc and system is working now pretty much but upper rads only half full/half warm
Should i open the radiator bleed valves as before to allow the upper rads to fill up or just fill until it comes out from the pipe into the F&E tank again?
I am leaning towards the former but don't want to flood the house out now...lol
I can see me and the missus with be using phones for internal comms today
Mike

 

[hunter27]

You will have to open the radiator vents or the air in the radiator will prevent them filling. You could try filling really slowly while bleeding the rads but as the expansion pipe should be 22mm it will be the the easiest way for the water to go, filling up the tank which will then overflow.

Its a 3 man job communicating with each another,
1 The filler
2 The bleeder
3 The tank inspector

 

[Onoff]

Oil fired CH & HW here. Boiler went in in 1998. The pipework however is: downstairs a ¾" nominal bore single pipe, perimeter system. Upstairs a modern flow & return.

Before the oil it was a wood / coal boiler. Used to get real hot with lots of scale. The oil boiler was put in after just a drain down.

I put a cleaner through the now oil boiler system a few years ago then ran a power flush for 24 hours. The crud that came out was incredible.

https://flic.kr/p/RoGCVY

https://flic.kr/p/2dwxGjg

I think the pipework on the single pipe system is about 50 years old, all swept tees etc. Had been drained on occasion but never cleaned / flushed. Had to change the drain port on the boiler that was both weeping but you couldn't undo it to drain down! I also chucked a kilo of citric acid powder in the power flush rig to help things along.

https://flic.kr/p/2k4hZoN

https://flic.kr/p/2k1r5QJ

New pump, 2 new 2 port and 1 new 3 port valve. Inhibitor added afterwards and a mag filter. The clean made a huge difference. Rads on single pipe systems are apparently susceptible to dead spots and clogging.

 

[ms08]

Thanks Pete/all again for tips advice.
Slow filling then and watch each rad in turn and when the overflow starts again as is right above my head onto the conservatory roof where i will be filling from i know to turn off

 

[ms08]

Some success so far in that the top radiators are now full of water which was the objective today. Not cranked up the heating yet as such a nice day here - typical - but can't moan. If this solves the issue for now will limp through this cold period and then once i can drain down again and check the T joint.
The F&E tank filled up and out the overflow with no disasters and not too much water from where i was filling up from.
Thanks for all your help with this and will update as we progress.
Apologies for all the dumb questions as i can usually sort these things out with appropriate research but my head is not in a great place at present and this was adding to my anxiety. I am usually pretty level headed but can't seem to think straight at the moment so many thanks to all who replied, especially Pete.
I will update once the heating is cranked up. Be nice not to be woken every morning at 5.30 am with noisy pipes though the Grandfos pump has put up with a lot of abuse lately .
Phones were used for coms plus me dashing up and down stairs!
Now all i have to do is change the radiator in the Saab - see avatar. It is in its box in the living room waiting for me to do but not crawling around under it in the recent wet/cold weather
Kind regards
Mike