Hot water but no central heating

[dal]

Hi all, our Worcester combi boiler stopped working last week, the plumber came round yesterday and sorted it, well part sorted it, we have hot water but still don't have central heating. I've got the heating on the thermostat turned up enough to trigger the boiler, the boiler seems to fire up for about 5-10 seconds then stops.

 

[Martynt74]

Hows the pressure on the boiler? Is it a closed or open system?

Could any of the radiators need bleeding?

 

[Orionaut]

is the pump running?

 

[stevenreader]

Is the three way valve working correctly? Ours used to get stuck which led to a similar situation to yours. That and a new circuit board on the boiler sorted the problem.

 

[nataliediaz]

I had the similar kind of problem the plumber came and he replaced the pump. Now its working fine. Have your pump replaced this can work for you.

 

[Stretch]

I've had this problem. Had a couple of plumbers look at it. The first said it was the divertor valve which I changed myself but didn't fix the problem. The second said it was probably the pcb not switching the divertor valve correctly. I eventually cut my losses and bought a new boiler. A pcb was £200 and the boiler was **** brand.

 

[Mickie]

Why contribute to a thread about a combi when you don't know anything about them?

His hot water works, dont you think if it was the pump the hot water would also stop ? if you knew anything about combi boilers you'd know the pump still has to run in order to get hot water..

Cold water runs through the combi and comes out hot but the pump needs to run to flow hot water which is separate from the cold supply to heat hot water to your tap.

Flowing hot water within the boiler doesn't come into contact with cold mains water, hot water to your taps, its heated within the boiler through a hot water heat exchanger..



anyway the op hasnt said what boiler he has...

Its like saying you have a ford to a mechanic and asking him to guess whats wrong with the car when it could be anything from a ford ka to a ford mustang..

worst thread ever

 

[Stretch]

Why contribute to a thread about a combi when you don't know anything about them?

His hot water works, dont you think if it was the pump the hot water would also stop ? if you knew anything about combi boilers you'd know the pump still has to run in order to get hot water..

Cold water runs through the combi and comes out hot but the pump needs to run to flow hot water which is separate from the cold supply to heat hot water to your tap.

Flowing hot water within the boiler doesn't come into contact with cold mains water, hot water to your taps, its heated within the boiler through a hot water heat exchanger..



anyway the op hasnt said what boiler he has...

Its like saying you have a ford to a mechanic and asking him to guess whats wrong with the car when it could be anything from a ford ka to a ford mustang..

worst thread ever

I think you should take your own advice.

The pump isn't used for hot water, only the heating. The hot water works from mains preasure, it's not seperate from the cold water supply. You're not allowed to pump water directly from the mains.

 

[Mickie]

seeing as hot water to the tap is hot and the boiler has hot water in it and heating is also hot water, i'll call the boilers hot water primary, hot water to the taps, taps and hot water to heating, heating..


if you turn the heating on, the boiler runs, pump turns on and diverter valve sends heating to the radiators..


when you turn on the hot tap, the pump kicks in, heating the boiler, primary pipes (not heating) pump kicks in, fan runs, air switch activates, diverter valve keeping heat within the boiler and the pump sending heat around the boiler and hot water heat exchanger..

cold water at the same time flowing through this hot water heat exchanger.. this keeps fresh clean cold water apart from dirty primary boiler water..

the end result being hot water at your taps.. ive tried to explain as best i could for people too lazy to search google..

i hope ive explained now that if he has hot water, his pump is fine and that the op should ignore other members claims that he should look at the pump when in fact he'd be wasting his time..

 

[Mickie]

I think you should take your own advice.

The pump isn't used for hot water, only the heating. The hot water works from mains preasure, it's not seperate from the cold water supply. You're not allowed to pump water directly from the mains.

If the pump isn't used in the aid to supply hot water at the taps explain how cold mains pressure alone turns on a combi boiler automatically ?

how most combis separate dirty heating water from clean mains water supplying the hot tap ?

 

[Stretch]

The boiler has a flow sensor which detects when you turn the hot tap on.

There are seperate feeds for the central heating circuit and cold water main that pass through the heat exchanger. The central heating circuit is a closed system which is pumped, the cold water is a simple pass though under mains pressure.

You're not allowed to pump mains water directly. This is why you can't have a power shower with a combi boiler.

 

[Mickie]

Ever heard of a fully pumped system? Well think of a combo as being the same in a way.

The pump is required to turn on in order to get hot water at the taps.

Obviously the pump isn't attached to the mains, what would be the point in that when its got a big enough flow rate unlike the boilers standing water.

 

[Stretch]

Fully pumped are for open vent systems, not combi.

If you disconnect the power from a combi boiler, water will still flow from the hot taps as normal, albeit cold. All a combi boiler dose is heat the water as it flows through.

A pump isn't used for delivering water to the taps in any system without a seperate hot water tank i.e. 99.99% of combi boiler setups.

Try it

 

[Mickie]

Do I have to give you links? Are you even reading what I'm trying to say? Are you trying to troll?

Mains water to a combi boiler will flow through it even if the boiler is off but you're correct in saying the hot water will run cold with the boiler turned off.

Cold water runs through a plate heat exchanger then onto the hot tap

The plate heat exchanger is heated by the boilers own sealed water. It is separate from the cold mains.

The water inside the boiler has inhibitor in it to stop corrosion so the water has to be separate from cold mains.

So then the boilers own sealed water which heats the plate heat exchanger needs to flow as its standing water. It can't move or flow without the aid of a pump

So a pump flows hot water around the plate heat exchanger

At the same time cold mains water also flows through the plate heat exchanger and provides hot water to the tap


The job of the plate is to heat mains cold water without coming into contact with the boilers own inhibited dirty water.

Now can you see that the pump is required to run in order to supply hot water to your tap ?


I hope you now understand you don't know what you're talking about.

 

[ZG002]

Fully pumped are for open vent systems, not combi.

If you disconnect the power from a combi boiler, water will still flow from the hot taps as normal, albeit cold. All a combi boiler dose is heat the water as it flows through.

A pump isn't used for delivering water to the taps in any system without a seperate hot water tank i.e. 99.99% of combi boiler setups.

Try it

Dude you know not what you say. You couldn't even fix your own boiler with the help of two "plumbers" and just swapped it over. You need to realise we have heating engineers on this site, one of them you are busy arguing the toss with. We have electricians,plumbers,joiners loads of trades folk. Go run your hot tap and touch your pump (you don't seem afraid of messing with your combi) then come back and tell us again that the pump isn't running.