Why won't my central heating start?

As subject.

 

When that happened to us it turned out the LPG tank was empty.

Do you still get hot water?

 

Hot water is by leccy heater.

It's an oil fired, pressurised system. The oil tank is full. Yesterday
it fired up ok when I tested it.

Due to a leaking pressure relief valve I drained the entire system today
to replace it.

Since it burned up quite a lot of oil last year with the thermostat on
the frost setting, I realised it made more sense to put anti-freeze[1]
in the rads. Which is what I have done today.

Now it won't start. There's a button I can press on the boiler that
starts the pump and fires it up, so that's ok. It's looking like the
thermostat. The only thing I can think of at the moment is that it's
still too warm.

[1] Guess hfm for 20 litres of the stuff.

 

Or the timeclock isn't calling for heat. Or else you've blown a fuse or
forgotten that you isolated something electrical.

 

You must be confusing me with someone who's sensible with electricity.

 

I mean, perhaps you turned it off at the consumer unit?

 

Heh. No, it was all left on. It's actually quite simple - just a plug in
the wall powers it all up. It only does CH, no hot water, as far as I
can see there are only three wires going into the 'stat.

The 'stat/controller's a bit weird. It has a low temp setting, a high
temp setting, a timer, then a four position selector (frost, timer,
high, low). It has a power indicator so I know it's on. It just won't
fire the stupid boiler up. Grrrr.

 

Could it need bleeding, if you've been letting water out?

It may have some sort of protection to stop it firing-up if it thinks it's
dry.

Just a guess mind.

 

Is the pump primed ?

Really, I need a bit more info than

"It doesn't work and I'm a girl"

Err what ?

What happens if you short out the thermostat ?

 

Yep, it def does need bleeding.

I'm wondering that, although it did fire up when I pressed the button on
the boiler itself.

My money's still on the 'stat at the moment. I've (finally) got it off
the wall, and it only has two wires going into it.

I'm going to bridge them, what could possibly go wrong?

 

There ought to be a little gauge that says what pressure the system
should be at. Often has a 'grey area' rather than a value where the
needle should be.
Often over looked, even by those who should know (BTDT).
Especially if:

...you have just refilled it.

 

Have you bled the rads and what system pressure do you have ? greater
than one bar ?

These lines totally confuse me

 

Find a lifejacket and some shark repellent, just in case.

 

Nothing.
Do it.

 

Easy enough to check if it's the 'stat - by shorting it out, Live In to
Live Out. The boiler is dumb and will just go.
It's possible there's a low-pressure interlock and if you haven't
re-filled it to the correct pressure minimum of 1Bar, it won't go.
Such LP interlocks are not common on domestic installations though, so
don't waste a lot of time looking for one. If it's anywhere near the
boiler (and it should be) it will be fairly obvious.
Since the boiler is firing up when you press a button on it, I'd assume
the 'stat is fucked, but first I'd do a continuity and livewire check
from fusebox->stat->LP(if there)->boiler.

Come to think of it, if the boiler is firing up on test mode, wtf is it
getting a supply from?

 

I'll try again.

Last year, over winter, the house was mainly empty. Rather than drain
the entire system to avoid it freezing, I left the heating on, with the
thermostat on the 'frost' setting. It kicked in quite a few times,
burning up a load of oil when there was no-one home.

So, I've now discovered you can buy central heating anti-freeze. Drained
the system, replaced the leaking valve, tip in anti-freeze, refill.

I've just done that, and yep, it works. I need to have a poke around
inside and see if there's anything obvious.

 

Thanks for all the replies. Rad's are all toasty - just need to brindle
the 'stat now.

 

If the boiler start when you short the therm. wires, the boiler is ok :
it is a thermostat problem.

Did the clock run? (check batteries in the thermostat if applicable)
Did you correctly set the hot/cold hours and hot/cold temperature?
Try setting "cold temp" very high to verify if it start the boiler.

 

Is this at the French place? If so, is it a pressurised cylinder
system? We'll be making sure ours is totally drained down when we
leave, and again after Xmas.

 

Yup. Yes, pressurised. It's now got a nice lot of expensive anti-freeze
in it. I'm not sure I CBA to drain/refill it everytime.

I've also now sent off for a new thermostat with a built in webserver -
internet-appliances-r-us. So I can monitor the temp and turn the heating
on and off whenever I feel like it.