So it’s starting to get a little bit chillier of an evening so I decided to test the central heating just in case there was a problem.
There is a problem damnit! The boiler doesn’t seem to be heating and cycling the water around the system.
With the thermostat all the way up, the boiler motor clicks into life, but it doesn’t appear to heat the water at all.

I’ve left it on for several hours now as I forgot to turn it off when I went out, and the radiators are now just very mildly warm.

Any ideas?

Is there a pump and if so, is it working?

Or the three way diverted valve thingy? I changed one of these myself on about 15 mins despite not knowing what they’re called!

Is the boiler firing up?
When switched onto hot water only does the hot water get heated?
When turned to central heating only do the radiators warm up?

any more info on the type of boiler and system? A combi? A boiler and hot water tank? Vented/unvented?

Have you been using the boiler to heat the water over the Summer – if so if ain’t the boiler or the pump. Perhaps the 3 way valve has jammed – give it a bash with a hammer to loosen it up. You can get them reasonably cheap on ebay and they’re easy to replace yourself – did mine with no specialist knowledge – just a bit of “I’ll give it a go” spirit.

Sorry, it’s not a combi, rather the type with a hot water tank. The hot water is absolutely fine! In fact, when the hot water comes on, the boiler fires up perfectly. It’s just the central heating its having issue with.

Where would I locate the 3 way valve thingy to give it a whack? 🙂

The three way valve is a mechanical valve with a solenoid on top so will look like a normal T-valve fitting with a plastic box on top with a wire coming out. It should be located close to your pump and had a feed into it from your boiler (so probably coming up from the floor) and a feed out to your water tank (entering about halfway up) and out to your radiator circuit (so probably disappearing down though the floor or into a wall). The solenoid controls the valve and diverts hot water from your boiler to either your hot water cylinder or your radiator circuit or both.

The solenoid can pack up or get weak over time or the valve seize or get stiff such that the solenoid can no longer operate it. With some you can replace the solenoid, but I replaced the whole thing.

It should have a mechanical override lever on it somewhere so you can test it is this unit. Mine looks like this…. It’s the grey box. The red thing above it is the pump. The mechanical override is located just under the grey cap along one of its sides, you have to feel for it but its obvious.

image by wobbliscott, on Flickr

Where would I locate the 3 way valve thingy to give it a whack?

Directly above (or close to) the pump – some new boilers have them incorporated or try the loft/cupboards. Before wacking it try switching from Heating/HotWater/Both several times to unjam.

http://www.ebay.co.uk/itm/DRAYTON-3-THREE-PORT-MID-POSITION-MOTORISED-ZONE-VALVE-22mm-MA1-/151082620137?pt=UK_Home_Garden_Hearing_Cooling_Air&hash=item232d39d4e9

Thanks guys, I’ll have a hunt around to see if I can find it.

Appreciate your time taken to reply 🙂

Most likely the synchronous motor on the top of the valve has gone phut. When you switch from HW to CH there should be a zzzzzzziiiiizzzz noise from the motor. If not, it needs replacing. They are not cheap but they are easy to replace. Don’t electrocute yourself.

….and if you can’t find a valve anywhere it means you have a gravity fed hot water tank :). In which case it will most likely be a faulty pump.

I can’t find a valve anywhere 🙁

Faulty pump huh? Where abouts does the pump live and more to the point, how much is it gonna cost me :/

Can’t be the pump if your hot water is working fine. The pump also circulates hot water from your boiler through the hot water cylinder. You can also hear your pump, if you can’t look for a Hi/Lo speed adjustment on the pump and test if its on hi, you should definitely hear it on high speed setting. I wonder if the diverted valve is incorporated into your boiler or located close to your boiler?

Can be the pump if your hot water is working.

You could have a gravity circuit for hot water or the pumps performance could be reduced so that it is ok to overcome the low resistance round a cylinder but not the higher resistance of the heating circuits.

You may have an S plan which would have 2 motorised valves, you may have some air trapped in a local high spot to the heating, you may have debris in the system stopping it from circulating……

However as you appear to not know what you are looking for I suggest you get someone in to sort for you, find someone your friends / colleagues recommend.

Probably three way valve stuck in position as it’s been set to circulate around the tank coil all summer. Put the heating on & try turning hot tap on/off. Might move it. Depends on type as I think some can be swapped easily, other wise system will need draining below the valve level.
Some newer system boilers have the pump & valve inside the boiler (I think).
If it’s a gravity fed system you should see two header tanks in the attic.

There does appear to be two tanks in the loft, I get the feeling it is gravity fed as the shower output is quite poor (another story entirely).
There’s definitely no external pump or three way valve that I can see :/

SSE are now due to come out on Friday.

Ok, slight update.

So I’m a bit of a numpty (no surprise there). It would appear this new (to me) house has a weird CH set up whereby you have to have the HW on for the boiler to heat the CH as well.
There are no valves to be seen and is gravity fed. Surely this is ridiculously inefficient?

The person who installed the timer on the wall had it set to pump mode and not gravity mode which meant we had to manually set the HW on before the CH would work.

Stupid system.

Since we have an electric shower, we rarely use the hot water at all , except maybe for a bowl of washing up every other day…

No its fine, my last house was gravity fed hot water with cylinder, HW only or CH and HW.

Gravity fed works fine (hot water will rise from the boiler to tank and cold water will drop leave the tank to head down to the boiler.

If you want the heating on then it doesn’t matter that the hot water is on too, as the cylinder is just a very well insulated radiator. Any heat lost will just help the radiators do their job.

Also, if the tank has a decent amount of insulation and you don’t use any hot water, it probably only needs a few minutes top up every few hours so its not a huge gas consumer.

Edit: Even if it was pumped rather than gravity fed, it would make no difference to your shower as it is central heating water being circulated through the cylinder via coil, it wouldn’t pressurise the tank (unless the coil was leaking, and thats a different problem) The shower itself is the reason its slow, it can only heat water at a particular rate so has to slow the flow down. Bigger Kw = faster shower, but you would probably need a new bigger cable running to it.

The cylinder tank is the original 70’s tank with absolutely NO lagging or insulation. I think maybe a trip to Wickes is in order…

heheh, slightly better as a radiator then 🙂

Get some pipe lagging as well, you probably have four pipes connected to the cylinder and they bleed heat, often overlook. The top one is the most important. You may need a combination of 15 and 22mm pipe lagging.

You could also wrap an old duvet/sleeping bag around it. You may find the three way valve whilst digging around the tank, along with previous occupants socks and pants down the back :d

A good shout with the pipe lagging, cheers for the advice!

You guys are ACE.

OK then how in a gravity system does the water from the boiler circulate without a pump? Seriously i’m now confused. In a gravity (or mains pressurised system) the water that goes through the boiler is not the water that comes out of the tap.

The way it works is simply hot water is less dense so rises to the tank coil, and the cooler water is more dense so sinks down the return pipe back to the boiler.