CENTRAL HEATING HELP!
updated 07/03/04
IT'S NOT AS WARM AS IT SHOULD BE...
IT DOESN'T START EASILY, BUT GETS GOING AFTER A MINUTE OR SO...
THE BOILER LIGHTS OK, BUT ONLY THE UPSTAIRS SEEMS TO GET WARM...
THE BOILER LIGHTS OK, AND THERE IS HOT TAP WATER, BUT COLD RADIATORS...
SOME RADIATORS ONLY GET WARM AT THE BOTTOM....
HOW DO I BLEED THE SYSTEM TO GET RID OF AIR IN THE RADIATORS?
THE BOILER'S MAKING A FUNNY NOISE !
THE OVER FLOW IS RUNNING ALL THE TIME
THERE'S A TAPPING NOISE UNDER THE FLOOR
Warning - always disconnect electric appliances from the power supply before dismantling!
These comments are based on my experience with solid fuel and oil-fired systems. The solid fuel system was a Trianco anthracite boiler, and the oil-fired system uses domestic kerosene in a Riello burner. Both heat water by means of a flame, then pump it round the house through pipes of various sizes to the radiators and hot water tank.
With a solid fuel system, the fire burns continuously (until it goes out!) and is boosted by a fan when the water temperature is lower than that set by a thermostatic control somewhere in the circuit. At times set by the householder, an electric pump sends the water round the system of pipes to the radiators, and then back to the boiler or stove again to be reheated.
In an oil fired system like my present one, the flame only burns when the thermostat "tells it to".
So what can go wrong that you might be able to fix yourself. I will list some of the possible problems and their solutions (when they happened to me), and you can decide if the job is something you want to tackle.
WHAT IS NEEDED FOR THE SYSTEM TO WORK?
Well, you need fuel to burn, a flame to heat the water, some water to heat, a pump (usually) to send it round the house, and some radiators to get heated. And a supply of electricity. Disfunction in any of these areas will cause the system to either fail completely, or partially.
FUEL - SOLID
I know it sounds silly, but fuel at the top doesn't necessarily mean fuel at the bottom. Solid fuel (anthracite / coke ) stoves can get clogged up in their fuel hoppers. The hopper seems full, but its all jammed at the bottom - maybe too much ash or clinker? If a peek through the door into the firebox shows little sign of unburned fuel, try poking a long stick - or the poker - down into the fuel hopper to make sure there is no blockage in there.
FUEL - OIL In the case of oil-fired stoves, the tank might not seem to be empty, but are you relying on the sight-gauge... that glass or clear plastic tube which is usually isolated from the tank until you pull out the little plunger at the bottom? Pull it, and if you are dismayed to see the oil level in the tube drop out of sight at the bottom, then at least you know what your problem is - an empty tank! Then there is the RAF...no, not the boys in blue, the Remote Acting Firevalve, that little brass thing with a button on the top, sitting outside on the oil supply pipe, near the storage tank, and connected by a very thin copper pipe to a copper bulb near the boiler itself. Perhaps some mischievous entity has operated it and cut off the oil supply. That will not be good for the valve, but you can check to see if there is oil flowing freely through the RAF by slackening a joint in the oil pipe between the RAF and the boiler and getting a flow of oil, or looking into the de-aerator (mine is called a Tiger Loop) if you have one, and trying to spot the oil level. If it is near the top, fine, but if it is right down at the bottom and bubbles are coming through the oil when the stove is trying to burn, then perhaps the RAF is at least partly closed. In the case of my RAF valve, the plunger with the knob on the top gets pushed down by increasing pressure of mercury expanding when the bulb near the boiler becomes warmer than about 65 degrees C. (about 150 degrees F). I was fooled for weeks after I installed the system, because the plunger was only partly down! It was also very stiff to operate, and I was frightened of breaking it. So I tested it like this: I made a careful note of how far the knob was sticking up out of the RAF near the oil tank, got a jug of warm water and stood it so the RAF bulb (near the boiler) was under its surface. I then gradually added very hot water, a cup at a time, to the jug and went outside to see the result. After a few cupfuls, I was gratified to see the plunger had gone down 1/2" (1 cm or so) into the body of the RAF, just as it should do if there is a fire in the boiler room. I removed the bulb from the jug of water and had a cup of tea. Afterwards, when the bulb had cooled down, I went outside and pulled the knob - it came up nearly 1 inch (about 2 cm) and the problem was solved.
FLAME
You need a flame if the system is to work.
With a solid fuel system, you have a clue that the fire has gone out if the fan is blowing but the pipes coming from the top of the boiler are cold. You'll probably need to rake out the ashes / cinders / clinker - whatever you call them - and light the stove again.
With an oil fired system, the fan starts first to clear any gases from the flue, then after a few seconds the burner starts to spray an oil mist into the boiler, and an electric spark is provided to ignite it. Most systems will cut out after a few failed attempts, to avoid a build-up of fuel in the boiler. There may be a red warning light somewhere to warn you that this has happened. My burner has a label telling me not to reset the cut-out for than three times. That means "now figure out the problem".
If your oil-fired boiler gradually gets more reluctant to get going, think about the simple things first. Is the oil getting through - as discussed above? There will be a filter somewhere in the oil line, often attached to the tank itself. Make sure this is not blocked with water and leaves and rust. Turn off the valve and remove the bowl of the filter, taking care to dispose of the small quantity of oil from the bowl sensibly. Clean the bowl, replace it, turn on the valve again and check for leaks before leaving the scene!
The burner also needs a good supply of air. If the air intake is outside the house, make sure it is clear of leaves, grass, etc. If the intake is inside the boiler room, make sure it is not partially blocked with fluff, dog or cat hair, or anything else. My own boiler suffered a gradual loss of "starting ability". When I took the lid off, I found there was a lot of soot in inside...(take care, this soot is bad for your health). Reading the instructions, I thought it could be needing a new nozzle, so I went out and bought one. I then removed the burner unit from the boiler to fit it, only to find that the metal spiral device just behind the oil nozzle, which causes the air to spin round and burn the oil efficiently, was nicely coated with cat hair! Once removed, the burner worked perfectly again. I now have a spare nozzle. The partial blockage of the air supply also explains the soot in the combustion chamber...there was not enough air to burn the oil properly.
The heat gets sent around your house in the form of hot water. In many houses, central heating water pipes run underneath the floor, in that cold damp space no-one likes to think about. In very cold weather, they could freeze and burst, and, later, thaw and leak. Or maybe your system doesn't have an automatic topping up system, or it has failed, another reason why your pipes could be empty. One way to check is to find one of those little keys for "bleeding" air out of the radiators, and slightly open a bleed valve on one of your upstairs radiators. Make sure the radiator is turned on ( or turn the thermostatic valve to maximum temperature) first! A little air may come out to start with, but if the air stops coming out and water does not follow it within ten seconds or so, or you hear air actually being sucked IN, close it again. This suggests that the water level in the system is below the height of that radiator. Next, go downstairs and do the same to a radiator there. If there is still no water to be had, close that bleed valve also. Now, on one of the large pipes near the bottom of your boiler, (sometimes outside the house on the wall near the boiler) there should be a drain valve - they often have a nozzle for attaching a hose pipe so you can collect the water in a bucket. Turn the knob / nut on the drain valve anticlockwise (looking at the end of the shaft) and water should come out. If so, turn it off again. If it was already open, perhaps mischievous spirits have drained your system for you? Close it, and refill the system, adding the correct anti-corrosion additive if possible . You should by now have an idea of the water level in your system. Why isn't it full? You need to find out if the top-up system is working. There will usually be a header tank above the level of the highest radiators - often in the loft - with a ball-cock system like a toilet cistern. The normal level in the tank will be low to middling. If there is no water in there at all, lift and lower the ball cock to see if it is jammed. If the tank is dry but the valve seems to work, check that there is not a valve or cock on that supply pipe which is turned off or blocked with grit.( Tip - when turning on valves and stop-cocks which need two or three complete turns to open fully, always open them all the way and then turn the wheel a quarter turn back the other way: why? well sometimes they get really stiff, and you might try to turn it off, but then get confused about which way to turn it. If it was fully open, and you turn it the wrong way, you might just apply enough force to break the central spindle. If it is a quarter turn away from the end of its travel you can apply your efforts in both directions until it starts to turn, safe in the knowledge that you are not trying to turn it the "wrong" way.) If water is flowing into the tank from the ball cock and disappearing down the hole into the boiler at the same rate, then you may well have a burst pipe in the system, so be ready to turn off the water supply to the ball cock and the electrical supply to the boiler and pump, to avoid further damage. Find and fix the leak, and refill the system.
THE BOILER LIGHTS OK, BUT ONLY THE UPSTAIRS SEEMS TO GET WARM...
Assuming that all the radiators are turned on, it could be that the circulating pump is not operating. How can you tell? Feel the large pipes coming from the top of the boiler...hot, yes? Now feel those going into the bottom of the boiler...if they are cold, or much cooler than the top ones, maybe the pump is not working. The pump is that big metal lump with pipes going in and out of it, and an electric supply cable, (usually) located near where the big pipe goes into the bottom of the boiler. Pumps are very quiet, virtually silent, so you might not be able to hear it running. But you might be able to feel it running - a faint vibration? Of course, if while feeling it you will notice that it is stone cold, yet the top pipes are hot, then you can be fairly confident that you have a stopped pump and no water circulation!
This could be because the pump has broken, is jammed, or has no power supply. Pumps usually have a switch on them to allow you to select from the two or three different speeds. The power to the pump usually comes via a timeswitch, so before blaming the pump for not working, make sure the timeswitch, if you have one, is set to 24HRS or Continuous, or something similar. Is it running? Gently turn the speed selector ...sometimes the pump will get blocked up with sludge after a long summer rest, and won't have the oomph to churn the mud that has settled on its impeller. Select MAX or HIGH or 3....does it go now? You will soon know, because the pipes in and out of the pump will warm up if it is running. If that was successful, and the failure occurred after a period of disuse, then it could be a sludge problem. See also the next section...One way of getting rid of it is to get it all circulating round the system, and then drain the system. Refill the system, get it circulating again, and drain it a second time, repeat if necessary, until the drained water is more or less clear. When you fill it for the final time, be sure to add some proprietary anti-corrosion compound, (it is usually added at the header tank before you start to fill the system) because that sludge was mostly iron from the inside surfaces of your radiators, slowly dissolving away!
THE BOILER LIGHTS OK, AND THERE IS HOT TAP WATER, BUT COLD RADIATORS...
Do you have an electric valve which causes the boiler to produce hot water for the taps but not for the radiators? If you have, study it and try to figure out if it is working properly. They usually have a manual override lever that you can use to test them. (Mine moves very slowly when pressed - don't rush it) Remember the safety rules for electrical things - disconnect - not just switch off - from the power supply before starting your maintenance. If you are not too confident about electrical disconnection, seek advice, or turn off the entire power to your house using the big switch at the main fuse board or "consumer unit", and work by flashlight. (Consumer unit...there's a vague term if ever there was one...!)
The pump really won't go? It could need bleeding, venting or purging. There will probably be a brass nut with a slot in it on one end of the pump body. Next to it, you might even find instructions! They will probably say " Loosen nut until all air has been expelled", meaning of course that only water is coming out. If nothing at all comes out, there is either no water at all in the system, or the rotor (aka impeller) is surrounded with sludge and unable to move, like a dinosaur in a tar pit. The pump has an induction motor, and will happily hum without turning for quite a while before giving up the ghost.
For the next bit, let the system cool down if it isn't already cold. Some water might (hopefully) spurt out, and you don't want to get scalded.
Try taking the brass nut out completely. If a bit of gentle poking inside doesn't reward you with some black gungy water, then the pump could be completely full of sludge, and need to be removed. Read on. There are usually isolating valves either side (or above and below) the pump to allow you to remove it without draining down the system. In my system, they are in the big brass "nut" which screws on to the pump itself. There is a small square or hexagonal nut on the side, with a line marked on it. It will be pointing along the line of the pipe when it is open. Turn it with a proper sized spanner until the line is running at right angles to the line of the pipe - and the valve should be closed. Remember to close both valves, either side of the pump, and then you can undo the big nuts on the pipes to release the pump. Take care - only a little water will come out if those valves are really closed! The pump is heavy, so make sure it doesn't get left hanging on its cable. If you can see that it is full of lots of black sludge, clean it out. If you can see the little impeller, poke it with something to find out if it will turn freely. It you can't get it to turn, then you may need to get a replacement pump, and you are practically halfway through the process. If you can eventually get it to turn, clean it up as best you can, then try re-installing it. Open the isolating valves, bleed the pump itself, reconnect the power supply to the timeswitch and switch it on. Remember to reset the timeswitch if necessary. So why did only the upstairs radiators get warm? The water was circulating of its own accord - the hot ("lighter") water was rising and the colder - and denser ("heavier") water - was falling in the pipe system. It is sometimes called "gravity circulation".
SOME RADIATORS ONLY GET WARM AT THE BOTTOM....
This can be caused by air bubbles being pumped around the system and collecting in one or more radiators. The part that gets warm has water in it, and the part higher up is full of air. You need to the bleed the air out.
HOW DO I BLEED THE SYSTEM TO GET RID OF AIR IN THE RADIATORS?
First, you must make sure that the circulating pump is switched off. Second, make sure the valves at either end of the radiator are both open, Third, make sure any electric valves in the system are also open, and Fourth, If you have just done some work which required you to drain the system, make sure the water supply to the header tank is turned back on. If you try to bleed the system with the pump running, you will probably suck more air into the system. Get one of those little radiator keys that came with each radiator, and use it to open the bleed screw - that little brass plug in one end of the top of the radiator - maybe half a turn, anticlockwise, maybe a little more - until you hear air hissing out. After a short period, during which the warm part of the radiator will spread upwards if your boiler has been on recently, a little spray of water will come out of the recess where the bleed screw is located. It isn't bled until it squirts! Now retighten the bleed screw until the water stops coming out and go on to the next radiator. A little later, go back and check that they are still tight and dry. Finally, if you have drained the system, don't forget that the circulating pump might need bleeding too.
THE BOILER'S MAKING A FUNNY NOISE !Mine did that, too. If it coincides with the fan running, then maybe there is debris in the air intake to the burner. If the air to your burner comes in through a duct from outside, maybe leaves have got sucked in, and are vibrating in the ducting, or in the burner itself. If the air is drawn in from the boiler room itself, maybe bits of paper and cat hair ( they just love it in there, don't they?) are to blame. Mine sounded like a vacuum cleaner that had just swallowed a toffee wrapper. Try taking off the ducting to the air intake - it's often 4 inch (10 cm) diameter flexible plastic with a wire spiral holding it open, and will just pull off the air intake on the burner. Try starting the boiler up again. If the noise has gone after disconnecting the ducting, it's probable that the debris is in the ducting. Take a torch (US flashlight) and have a look up the ducting - and from the outside too, if you can. Remove whatever junk is in there. Then look into the burner air intake and see if there is debris in there, again removing whatever rubbish you can see. If the noise can be heard inside the air intake and you can't see anything unusual, then the debris could well be near the burner nozzle. Mine was. I took the covers off the burner unit, spotted the couple of bolts which hold the burner to the boiler itself, and removed those bolts. I was then able to withdraw the entire burner unit from the boiler and set it on the floor. Take care not to tear any gasket material between the burner and the boiler. ( My unit has flexible oil pipes - if yours has rigid pipework then you'll probably need to turn off the oil supply valve and disconnect the oil pipe[s].) The bit of the burner which pokes through into the boiler will probably consist of a nozzle, igniter electrodes which produce the sparks to light the fuel, and a set of steel blades which cause the air to swirl around and burn the fuel efficiently. In my case, the blades were pretty clogged up with leaves and bits of paper and cat hair, and this is what was causing the noise. I removed the debris and reassembled the system and all was well. Left to itself, the problem would just get worse; the air flow would reduce further over time, combustion would be less efficient (using more fuel than necessary) and you might eventually see black smoke coming out of the chimney. By then, the inside of your boiler combustion chamber will have a nice insulating coating of soot, which prevents the heat from the burning fuel getting through the boiler wall to the water, which causes the burner to switch on more often, causing more soot...and so on. You burn more fuel to stay less warm and your boiler system is wearing itself out that little bit faster :-(
If the noise is a bit like a million mosquitoes, or a rapid knocking sound, which continues for a while after the burner has stopped burning, then it could be localised boiling of the water. Have you turned up the water temperature on the boiler thermostat lately? Have you selected a lower circulating pump speed for some reason, or is the pump simply not working / switched off ? Any of these reduce the speed at which the heat is taken away from the combustion chamber by the water, and could allow water to boil near a "hot-spot" on the boiler wall. I don't think this is serious in itself, but you should try to figure out what is causing it. If in doubt, get another opinion! Displaced baffles inside the combustion chamber could also account for a hot-spot. These are the flat metal plates, sometimes with a hole in, which rest on little ledges at two or more different levels inside the combustion chamber. You can see them if you take the lid off the boiler and take a peek inside ( boiler switched off, of course!) They are usually an inch or two shorter than the combustion chamber, and should be arranged so that they are against alternate ends of the chamber. The lowest one should be hard up against the end of the chamber nearest the burner, the next one hard up against the other end, and so on. This makes the hot gases (combustion products) travel further as they go up the chamber in a zig-zag fashion, so they can transfer more of their heat to the surrounding water jacket. If you do open up the boiler this way and decide to remove the soot or reddish deposits from the walls and baffles, be aware that these deposits are toxic, so don't spread them around or get them on or in your body. I used a vacuum cleaner and disposed of the bag afterwards.
THE OVER FLOW IS RUNNING ALL THE TIME
There is only one way that water should be getting into your central heating system, and that is through the header tank and its topping up system. Many header tanks have a ball-cock or float valve which allows water into the tank to make up for losses. Check to see if that is jammed, or has got grit in it, causing it to add water continuously. If you cannot do this easily, maybe there is a valve or tap up there between the water supply pipe and the header tank which you can turn off. If that stops the water coming out of the overflow pipe, then you know where the problem lies, and can proceed to fix it. If that has no effect, and your domestic hot water is heated by a coil inside an immersion tank, then it could be that the coil is damaged or corroded and is leaking "domestic" water into your central heating system. If the pipe carrying cold water into the immersion tank feels colder than normal, and you are not drawing any hot water off at the time, it's possible that fresh cold water from your friendly water company is leaking through into your central heating system and causing it to overflow.
I'm afraid that it is probably time for a new immersion tank, my friend.
THERE'S A TAPPING NOISE UNDER THE FLOOR
When the boiler switches itself on, or the timeswitch activates the circulating pump, hot water is pumped through copper pipes which were previously cold. These copper pipes then expand, and get a little longer. If they are jammed tightly against insulation, floor-boards or joists forces will build up at the points of contact, and eventually overcome the friction. The pipe and the thing it is in contact with will then jump past each other, making a tapping or ticking noise at each movement. It's harmless, but if it annoys you, you could lift the floor boards, find the source of the noise and either create more clearance between the pipe and the fixed object, or try some lubrication like graphite powder or high melting point grease. If this isn't the cause of the noise, then it's probably the Thing from Planet Zarg, and you are on your own!
Warning - always disconnect appliances from the power supply before beginning your maintenance!
Disclaimer: All information on this web site is given freely and in good faith. I hope it helps you solve your problem, but you remain responsible for your own actions! Please let me know if you find other solutions to the problems outlined so I can add them to the site. Thanks, friends.
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