Is my heating about to blow?
Discussion
We have a trditional type central heating system that has decided to start making strange vibration type noises.
I have beled all the radiators, which doesn't seem to have had any long term effect. There seems to be 2 ways of stopping the noise - 1. turn off system, and 2. move any of the thermostatic rad. valves by a fraction. The latter solution only lasts for a few mins though and then the din starts again.
Any ideas folks?
PS - One thing I have noticed is that the tall heated towel rail in the bathroom regularly needs bleeding, so maybe there is a leak somewhere?
Nightmare!!!
I have beled all the radiators, which doesn't seem to have had any long term effect. There seems to be 2 ways of stopping the noise - 1. turn off system, and 2. move any of the thermostatic rad. valves by a fraction. The latter solution only lasts for a few mins though and then the din starts again.
Any ideas folks?
PS - One thing I have noticed is that the tall heated towel rail in the bathroom regularly needs bleeding, so maybe there is a leak somewhere?
Nightmare!!!
Try checking your expansion tank is correctly filled. If not, this will always cause bangs in the system as there is not enough water in the tank to compensate for expansion. if this doesnt work, try reducing the pressure in your system. my new pipes bang a bit and i just closed the valve slightly bringing the supply into the house and bled the system and topped the expansion tank, and this seems to have worked fine. 
andygo said:
Been in the house for about a year now. We have not added or modded anything to do with the heating system.
It may be starting now because you're turning the heating down after the winter. Older thermostatic valves have to be on the right end of the radiator or they bang due to the flow going the wrong way. Ours do it (the plumber put the whole lot on the wrong ends
) when we turn the thermostats to the mid part of their range. If they have an arrow on them then they're directional. To find out which way the water flows, wait til the system is cold then feel which end of the rad gets warm first.
If it's not that then it's pretty definately a leak/airlock. EDIT>>>Or some of the other suggestions
>> Edited by mechsympathy on Wednesday 6th April 10:22
Sounds like an airlock somewhere. The fact that you need to keep bleeding the towel rail either means air's getting in somewhere or else bits of the bubble are gradually making their way to the highest point in the system. I assume that the towel rail is upstairs and is taller than the rest of your rads?
pdV6 said:
Sounds like an airlock somewhere. The fact that you need to keep bleeding the towel rail either means air's getting in somewhere or else bits of the bubble are gradually making their way to the highest point in the system. I assume that the towel rail is upstairs and is taller than the rest of your rads?
Ok lots of views but little practical advice.
It could be an a worn bearing in the pump, that the servo that moves the hot water/central heating selector is broken, that a thermostatic valve is stuck, an airlock, or a build up of crud in the system. I would guess a build up of crud as this would explain why you have to keep bleeding the towel rail.
So what to do.
1. Put your hand on the pump you will tell from the vibration, if any, if you have a problem. It is not hard to replace but you may prefer to use a plumber.
2. Test the servo for central heating/ water, there is normally a T near the hot water tank which splits the hot from the boiler to go to the tank, the radiators, or both. This has a box on top with wires into it. This is a servo which moves the valve in the T to send the water in the correct direction. Change the selection on the system control and you will see the servo move. It is not hard to replace but you may prefer to use a plumber.
3. Turn the system on and the thermostat up to maximum. Now check all the thermostatic values. These often break and can cause this problem. They are not hard to fix if you are happy to drain the system.
4. Go and look in the header tank.
a) Check it is filling correctly the ball valves can get stuck.
b) What does the water look like, if it looks very dirty then this is your problem.
5. If you are up to draining and rebalancing the system, which is pretty easy. Go to a DIY store and buy some cleaning solution and come inhibitor.
a) Tie up the ball cock in the tank.
b) Open all thermostatic values to full on and the valves at the other end of the radiators full on.
c) Drain some water from the system. You should have a drain point down stairs. A hose fits on to this to direct the water outside, and a square valve opens and closes the valve. Put a towel underneath as these always leak. Drain water from the system so the header tank is completely empty.
d) Then close the drain valve, pore the cleaner into the header tank and untie the ball cock.
e) Bleed all the radiators until they are all full.
f) Run the system on high for a couple of days, with all the valves full on.
6. To change a thermostatic valve or to get rid of the cleaner you need to drain the system completely.
a) Tie up the ball cock in the tank.
b) Drain all the water from the system. You may have to use several drain point down stairs, it depends on the low points of the system. Look for the pipes going down to a downstairs radiators. As the water drains undo the bleed values to ensure the system drains completely.
c) Then close the drain valve and close all the bleed valves and untie the ball cock. Bleed all the radiators until they are all full.
d) With all the thermostatic and other valves full on and run the system on high for a an hour.
e) Repeat the process twice.
d) On the last time you will refill the system pore the inhibitor into the tank.
f) To balance the system with all the valves open and the system running find the hottest radiator(s), if you have one (if not you can just stop). and close the valve on the other end of the thermostatic, or adjustable valve by ½ turn. If you then wait the cooler radiators will start to warm up. Do this until all the radiators are the same temperatures.
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