Twiddling my knob
I am not a plumber.
Having said that, I did once install a full central heating system including a Baxi back-boiler fire with the aid of a library book and a lot of sweat. When I cracked the input tap for the first time to fill the system, I only found one small leak and the whole thing worked beautifully. I was proud of that.
So I'm not a plumber but I know a little bit about plumbing.
Now however, I am stumped.
I came into the kitchen this morning and there was a most peculiar racket. It sounded like a cross between waves breaking on a shingly beach and a steam pump – rhythmic swooshing noises that were really load. The fucking central heating was acting up.
I didn't install the system in this house, and I can't make head nor tail of it. Apparently it's a "closed system" and it needs to be pressurised or something. Instead of just a pump, it has a setup that would do an oil refinery proud, with little taps and guages and pipes going everywhere.
One of the dials is nicely hidden behind a pipe and faces away towards the wall so I haven't a fucking clue what it does or what it says. I hope it's not important.
The one guage that I can see has a little red marker on it. I have discovered through trial and error that if the needle drops much below the red marker that the system makes a bit of noise and the upstairs heating doesn't work. I also discovered a tiny black tap just below what I assume is an expansion tank and if I twist that tap then the needle on the guage climbs up to the red marker again.
Anyhows, when I heard the racket in the kitchen, I checked the wee dial. Fucking thing was at zero. So I twiddled the black knob until the needle reached the red. The noise quietened a little but not much. I went and bled the radiators. No change. I checked the dial. Back to near zero again. I lit the heating. I twiddled the knob. I bled the radiators. I twiddled the knob.
It's working all right now. It's quiet and it's heating the house.
I got pissed off twiddling the knob though as it's not easy to reach, so I just left the fucking thing in the on position.
The needle is above the red marker now.
I'm just waiting for the explosion.
Possibly the diaphragm in the expansion vessel is on its way out.
Better get the diaphragm replaced, you don't want the expansion vessel to get pregnant.
Maybe the Pill would be cheaper?
Damn! That sounds expensive. I didn't even know I had a diaphragm….
Bound to have a diaphragm – it's just above the thingymejig!
Underneath the whatyoumaycallit?
Exactly!
We too have a closed system and over a long period the air slowly leaked out of the expansion vessel. I didn't know this at he time and kept topping up with water until one day there was nowhere to expand to and the safety valve on the boiler started blowing out hot water. I guess I have a slow puncture in the diaphragm because I need to re pressurise the expansion vessel about once a year. This is a lot easier than fitting a new expansion vessel, it only takes a couple of minutes to do. There should be a valve like you have on a car tyre somewhere and you simply give it a few strokes with a tyre pump and all should be well. You don't want a dodgy heating system when this winter's global warming strikes.
I checked the big red blob thing [expansion tank?] and there is a screw or bolt or something on top. I'd be wary about mucking with it though as it's probably holding the whole lot together.
I have the system running at full tilt at the moment [it's gone a little nippy here in the mountains] and it seems to be holding up well.
So far….
Sounds like you might be spending too much time twiddling your knob and not enough time trying to fix the heating. I knew a plumber like once ………..
If I want to twiddle my knob [or play with the Old Boiler] then that's my business
As long as you're on the job I suppose.
Hi GD. Not wishing to alarm you, but I had a similar problem. The result was that the expansion tank burst in the middle of the night and mains water ran from the upstairs boiler for about 4 hours. Got up in the morning and splashed my way to the kettle for my morning brew…. Bastard thing!
Best get a plumber out.
Bugger! As I didn't have enough on my plate.
I'm not that worried about things going bang as water pressure here is almost nonexistent, and if any of the bits above do blow there is nothing underneath them. I'm not kidding. I never bothered with flooring under them so it's a clear drop to the foundations and below.
The red expansion vessel is just a larger version of the "Spheres" used on Citroen Hydropneumatic suspension, and similar to British Leyland's Hydragas suspension units, which I did a lot of experimentation on. The seam in the middle holds a rubber diaphragm which should have air one side (the top, where the small filling valve is), and the bottom which is connected to your heating system. The idea is that it accommodates the variation in volume as the water heats up and cools down. Without this "give" the blow-off valve will constantly be working when the heating is warming up, and then you'll have airlocks forming as it cools down.
The flexible braided hose should be the filling connection – it appears to be fed from some sort of pressure reducing valve immediately below the black knob. I take it the 15mm pipe is your cold water supply, and the 22mm stuff is the heating? Turn off the heating and let it cool down, then shut off the black fill valve. Now open a vent somewhere until no water flows out, but leave the vent open with a container under it. Remove the cap at the top of the expansion vessel, and there should be a normal car type Schrader valve underneath. See what (if any) pressure it holds. If none, connect a pump and apply a few strokes (to the pump, NOT your knob) and see if any water comes out of the open vent. If the diaphragm is good there may be a small leakage, but this should stop when it is fully extended to the bottom of the vessel. If it's split you would expect water to carry on flowing, as the air you're pumping in would escape into the heating circuit.
What you do now depends on whether it's OK – if it holds pressure go for about 15psi. Then close the vent and open the fill valve gently. You really need to be able see the system pressure as you do this, I can't be sure from your picture which of the two gauges will give this – probably the one on the left, which looks as if it's on the feed side of the blow-off valve. If your mains pressure really IS low you might not get much more than the expansion vessel pre-charge value, but 20-30 psi would be ample. Go round and bleed all the radiators and any other vents, whilst someone else keeps an eye on the pressure (topping up if needed), then close the fill valve. Finally run the heating and see if it's made any improvement. You would expect to see the pressure increase with temperature, but this should fall back to the charge value when it's cooled down.
Right, that'll be £30 for my time, thank you very much…
What a decent thing to do, microdave. Three cheers for you
Very remiss of me to omit my thanks!
Six cheers for you, Microdave.
I'm letting the system run as-is at the moment and it's holding out well. I'll give the above a full run trough when and if I have sobered up a bit. :;