Gas central heating
turn heating on, radiators stay cool (not a problem at this time of year) turn hot water on, radiators get hot - (problem at this time of year !!!)
what's my likely problem, and how do I find out for certain ?
K
The zone valve/valves aren't working. You find out for certain by working out how they operate, taking the covers off and seeing if they move into the right positions. They're probably jammed up with limescale.
There are lots of flavours of gas central heating, and you haven't told us what you've got - so we're having to make lots of assumptions.
Assuming that you have a conventional (not combi) boiler in a Y-Plan system - which uses a 3-port mid-position valve to direct the water to either or both HW and CH - my best guess is that the valve is jammed in the mid position.
In CH-only mode the valve isn't moving far enough to operate its microswitches and switch on the boiler. In HW-only mode, the boiler is switched on by the cylinder stat (regardless of what the valve is doing). Whenever the boiler runs with the valve in the mid position, hot water will go to *both* the HW and CH circuits. Hence the radiators will get hot until the HW demand is satisfied.
If my description fits your system, remove the actuator from the valve and make sure that the valve sprindle turns freely through at least 90 degrees. If it doesn't, you may be able to free it by turning it back and forth with a pair of pliers.
- Thats because I don't have the vocabulary - it's gas central heating, and its not a combi bolier - beyond that, it's all witchraft
It looks lik it is the control switch that is snafu'd. and i'd like to try and replace it. Two of the pipes from the control switch have valves on, fine, the third just goes up and into the h/w tank. I guess i'm going to need to drain the tank before removing the switch ?
Any chance you can photograph the components in question, and upload it somewhere and post a URL here? Failing that, what does it say on the "control switch"?
I suspect that the "control switch" to which you refer is a 3-port motorised valve, and that what you refer to as "valves" are manual gate-valves or somesuch which you can turn off by turning a handwheel.
If your control switch *is* a motorised valve, you should be able to remove the electrical part (actuator) from the 'wet' part of the valve - without any need to drain down - simply by undoing a couple of screws. Once you've done that, proceed in the way described in my previous post.
Roger I'm not at home but the phrase 'drayton mpa' sticks in the mind from looking at the switch earlier this week
its either
The first has an inlet and an outlet at the sides.. the other has an inlet at the bottom and two outlets at the sides. They are different.
No, if you look closely, you can see that they are different.
If you've only got one, it will pretty certainly be the 3-port variety. According to the Screwfix catalogue, the actuator on this model snaps on and is easily removed - presumably without having to remove any screws.
With the actuator removed you can easily check whether the spindle of the valve itself is seized. I'm becoming increasingly convinced that my original guess was right, and that it's stuck in the mid position. As I said before, you may be able to free it by turning it backwards and forwards with pliers. If not, you'll need to replace the valve - which means at least partially draining the system.
armed with the pdf manual from the screwfix site (they do have their uses !) I removed the actuator last night, and established that (a) the actuator is working -i can see the socket\keyway\callitwhatyouwill move when switching between water\heating (b) the spindle seems to move freely (c) the c/h pump is working so in theory I no longer have a problem. Perhaps the spindle/valve was seized and is now freed up, or the was not seated properly on the spindle (it does look slightly 'abused'), so I'll be putting it back together this evening and we'll see wat happens thanks for all the help K
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