No hot water but heating works....

[DavidRossitter]

Hi

I noticed today that we have no hot water and having investigated further I have established the following:

- believe the boiler is OK as when I turn the heating on the boiler fires up
- otherwise the hot water timer is on and "calling for heat" but the boiler doesnt fire - otherwise everything seems dead

So I assume this is a valve or pump issue ?

I can see a valve near the hot tank and I have pump/valves upstairs in a cupboard but I havent yet worked out what is what.

What is advice on how to track down the problem? And is my assumption of a faulty valve or pump the likely cause ?

Any tips/advice on this would be much appreciated

Cheers, David

 

[kevplumb]

which valve ?

View media item 11149 View media item 11148

 

[DavidRossitter]

Hi

The valve i can see looks more like the bottom one of the two

Do you think it is a valve problem ?

 

[kevplumb]

does it have a lever on the side / end

 

[DavidRossitter]

The one near the tank has a small lever which if I pull makes a quiet wirring sound as it returns to its original position. There is a place to clip it "open" - i tried this and nothing happened. I have yet to take the panel off upstairs to see what is there.

What do you suggest ?

Thanks

 

[Agile]

If you move it and latch it then it will be open.

If you then select CH then the hot water will heat as well !

The motor has probably failed. If it looks like the one in the picture then they can be changed.

Tony

 

[kevplumb]

1 check the header tank has water in it

2 is there an air vent screw near the valve View media item 11360

 

[DavidRossitter]

Hi

In terms of the two replies...

I have a Megaflow pressuried hot water system so no header tank (I think)

Also will there be more than one motorised valve for the hot water or is the one by the tank likely to be the only one ? Can I check if it is doing anything before I go replacing it ?

Thanks

 

[kevplumb]

I have a Megaflow pressuried hot water system so no header tank (I think)

Also will there be more than one motorised valve for the hot water or is the one by the tank likely to be the only one ? Can I check if it is doing anything before I go replacing it ?

ok time for some info

what boiler make /model

you could well have other valves in the system the one i think you see is for the megaflo nothing else it's a safety device

you could also have a vented heating system and mains hot water

 

[DavidRossitter]

Hi

Well the boiler is something called an Alpha - it is oil fired range with two burners one for the cooker and the other for the CH and HW.

The hot water is a mains pressure system with a megaflow.

I have the control valve near the tank and there is a set of pipes, two pumps and other control valves upstairs. The excess heat from the boiler is fed through to some towel rails.

Couple of questions:

- If a valve has failed would it stop the hot water working in the manner described ?

- If I have several valves how can I work out which one is not working - is there a simple way to check this out ?

Thanks David

 

[kevplumb]

Couple of questions:

- If a valve has failed would it stop the hot water working in the manner described ?

possibly

Couple of questions:

- If I have several valves how can I work out which one is not working - is there a simple way to check this out ?

if they have levers on them lock them open as tony suggested

you could try following the pipework

 

[DavidRossitter]

So if i follow the pipes and locate the valves - and lock them open will that possible allow the boiler to fire up and start heating ?

Can I tell if a valve is working by looking at it or listening to it ?

Thanks again

 

[Agile]

Latching open a valve only opens the valve but it does NOT operate the switch inside to bring the boiler on.

You can see if they are open by feeling the lever is loose to move. If closed, they move slowly with a feint wiring noise as the motor is turned.

If they dont open AND are being powered then it will have failed.

You cannot tell just by looking!

You should only latch open the valve by the cylinder on test ! Its a safety device and should not be left latched open !

Its possible that a manually resettable over heat stat on the cylinder has tripped. This would be unusual and I am reluctant to suggest you go looking for it as its operation would indicate there may well be another failure of a safety device.

Since all repairs on unventeds should be by a qualified person then it sounds as if thats what you are going to need.

The complexity of your system is greater than most so you will need an above average engineer !

Tony

 

[DavidRossitter]

Hi

I have tracked this down to the thermal control unit on the megaflow - if I mover the thermostat setting up and down and press the reset button it starts working again. And then a few days later stops again.

The unit has been in about 10 years and Heatrae Sadia suggest it is likely due to scale build up and then whilst replacing thermostat may help it is not this that is scaled up so this will not cure the problem.

They suggest adding a water softener (there isnt one at present) but I wondered if it is possible to have the tanl descaled - they suggest it isnt but the cylinder wasnt exactly cheap so want to explore things further before deciding what to do.

What do people advise ?

Thanks David

 

[Agile]

Its possible that a manually resettable over heat stat on the cylinder has tripped. This would be unusual and I am reluctant to suggest you go looking for it as its operation would indicate there may well be another failure of a safety device.

Tony

You could replace the thermostat and see what effect that has! The o/h stat might be faulty but that would be unusual.

Again I warn you that work on an unvented must be by a qualified person!

I would not expect the problem to be caused by lime scale unless you have been heating it by electricity for long periods. Even so I dont expect that effect.

If it were limescale than can be dissolved by HCl but the manufacturers dont want you to do that.

Like many DIYers you want to rush into something when it does not seem likely and without an expert diagnosis.

Tony