I think serious scale build-up can cause boiling noises, too, with the scale causing localised over-heating of the water. If there's a drain on the HW tank it could be checked for sediment.
cheers
Jules
One other thing - when that happens you will really be able to tell f the whole tank heats up - just touch different bits carefully.
The electric heating element presumably consists of a coil of suitable wire which gets hot when current passes through it. This wire will be enclosed within a sealed metal tube.
If perchance this tube had corroded and sprung a leak, allowing water to come in direct contact with the heating coil, I dare say this would also result in boiling noises.
I think it's a Drayton. See P31 of their catalogue (P16 of the PDF)
Hopefully that would blown a fuse or tripped an RCD before getting that far.
obviously worked on the same principle.
With electronic controls being what they are today, I would have thought that nice simple things like this would have died out by now.
TF
Yes, maybe they're there as replacements for existing valves - I can't see many people fitting these from choice on new systems. By sensing tank temperature, they are at least an improvement over the earlier Cyltrol valves. These just sensed return flow temperature on gravity circuits, and if - as happened to me a few times - the primary circuit decided to circulate the wrong way, you got no hot water!
Hi,
You don't say whether you have just moved in or whether you have been there a while. If you've lived there a while, have you always had poor heating or has this happened recently? The reason I ask is that if this has started to happen only recently, then something must have gone wrong or broken recently. If it has always been like that, it could just be a poorly designed system.
There may be a thermostat on the immersion heater but it will be hidden under the lid (see below). Have you checked that there is not a thermostat buried under the cylinder jacket? Many old systems did not have cylinder thermostats. I know I had to add one to my gravity fed HW system (now converted to fully pumped too).
This puzzled me too but other posters have said it could be a capillary valve. My boiler is oil fired and they have to have a fire valve. Whilst this is nothing like your set-up, my fire valve had a fine capillary tube (a very thin metal tube only a couple of millimetres wide) and I managed to break it. I've never understood how, I was tightening the compression nut and was very careful to keep hands and tools away from the valve at the time but I digress. I see in your photo a Wickes jacket bag and I wonder whether you may have snapped the capillary on your valve whilst fitting this? Don't be embarrassed if you have, like I said we've all done it (well, me at least).
Before you fitted the jacket, what did the cylinder look like? Was it bare metal or did it have a couple of inches of foam insulation on?
Do you hear the bubbling only when using the electric heater or when using either electric or gas?
The water in the cylinder should get hot but it should never get hot enough to boil. The recommended temperature is 60C: you need it this hot to kill any germs living in the water.
Immersion heaters have a built in thermostat which can fail, causing the heater to stay on. When this happens the water will boil. If the boiling water gets into a plastic tank, it can make the plastic melt. Then the boiling water pours everywhere. There have been some terrible stories of people being killed when boiling water poured through their ceiling onto them.
New immersion heaters now have two thermostats: one that you can adjust and another set to, I think, 85C so that if the first one fails, the second one will switch off the heater.
Often the thermostat is replaceable and you can replace it without having to empty the cylinder first. You need to make sure the electricity is switched off and remove the circular cap over the end of the immersion heater and temporarily unscrew the wires (making a note of which one went where - a digital photo may help you with this). The thermostat should slide out.
You don't get second chances with electricity, so if you aren't sure what to do, don't do it.
The thermostat should have a dial on it and what looks like a screw in the middle. You put a screwdriver into the "screw" and turn it to adjust the temperature. This will only adjust the temperature that the electric heater will heat to; it will not make any difference to how hot the gas boiler will heat the water. It may be that you need to turn your setting up if the water is too cold or down if it is boiling.
The cylinder should vent into a header tank. Is this the small plastic tank on the wall in your photo? Do any pipes run between the cylinder and this? Does this plastic tank feel very hot, especially when you hear the boiling?
It seems a very small tank. Usually such small tanks are used for the CH not the HW. Is there a second, larger, tank somewhere?
Do you know which pipes you are feeling? Like you said in your introduction, there is a HW circuit and a CH circuit. Are both hot or just the CH ones?
Why would you need to top up with the electric? Use the gas to heat it to the desired temperature. I think gas is the cheapest way to heat your home. Electricity is nearly always the most expensive way, unless you have economy seven and use the immersion heater overnight.
Have you tried the highest setting to see if that makes any difference?
It depends on your system. Some systems might allow water through both radiators and the cylinder at the same time and you are right, in some systems this could cause the HW to not get enough heat. On the other hand, if the system is designed to have both on at the same time, it may be balanced to allow both circuits to get their fair share of the heat. If you have a gravity fed hot water system, I wonder whether that makes it more likely that the HW will be starved of heat when the rads are on?
How many stories are in the house and where is the bathroom in relation to the tank? Do all hot taps run cool or just the bath?
Other systems (particularly combi boilers, which you don't have) have a valve that switches the heat to one circuit or the other. The combi boiler in my last house would always give the water the priority, so there was no CH whilst the bath was running.
Do your radiators have TRVs on them? The "rule" about having the bathroom rad fully open is that if all your radiators had TRVS on and the rooms got hot, they would stop the flow of water through the rads. If the boiler came on, there would be nowhere for the hot water to go and this could damage your boiler, so by having one radiator always open, it means there is always somewhere for the water to flow, so you never have the possibility of expensive damage to your boiler. It doesn't have to be the bathroom rad; you should never have a TRV on a radiator in the same room as the thermostat. This is so the thermostat controls the radiator not the TRV.
HTH
I don't know if this analogy will help but if you think about your electricity fuse box, you have a circuit for lights, a circuit for sockets, etc. if you switch your tv or your toaster on, the lights should not dim because there is enough electricity to go around both circuits. It is the same with your boiler.
Your boiler may produce something like 15kW of heat but a very big radiator will only emit 2kW, so even if you have 10kW of heat being "used" by your radiators, you should have 5kW "spare" to heat your water.
You are right that it's not quite as simple as that though. Pipes can only carry so much heat away from the boiler. The bigger the pipe, the more heat it can carry. So if the pipes are too small, this can limit how the systems performs.
HTH
I typed "Treolar plumbing" into amazon and it found a few books on plumbing by this author. Was it this one:
Was it this "I had to send this back, because it's essentially identical to the
1990 edition which I had already", and he goes on to say: "the CH control system section had actually got less thorough." This implies that the 1990 edition is more thorough than the later edition, which is the opposite of what I would expect.On a slightly related note, the "which wiring" book is recommended here but later editions are very expensive second hand. The first edition is quite cheap but I imagine that there are big differences between editions what with electrical regs. changing so often. Is it worth getting the cheap but dated first edition?
TIA
Not necessarily. Water is apretty good insulator, unless it's got plenty of ions in it.
Dunno about that. Maybe AC and DC are different in this respect? When CH systems start tripping RCDs, the advice given here is usually to check the pump first - because that's the point in the system where water and electricity are closest together.
It may be that the circulating water, with all its corrosion inhibitor additives, is a good-ish conductor, but if we're talking about an immersion heater, the water around it in the HW tank is just tap water, which should be quite low on ions.
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