Water not getting hot. Random!!

[ladyrose]

Hi everyone. We have an ancient Potterton boiler, Flamingo 50s, which so far been regularly serviced and cleaned.
Twice now we have woken up to no hot water. The timer clock is set, the boiler casing feels warm but when we run the hot tap the water is tepid. The system is gravity feed for hot water. The motor valve and thermostat are not connected on the upstairs tank and we have a pump as usual for the heating. If we switch on the central heating everything fires up ok. The water-only bit is then fine until the next time. Any ideas? The heat exchanger has a small crack and "kettles". Could it be this?

 

[ChrisR]

The motor valve and thermostat are not connected on the upstairs tank

Eh?

 

[ladyrose]

Sorry!! The motor valve is connected into the system but is open. The tank stat is disconnected. I control the temp of the water using the boiler dial. Not good I know, but YOU tell my husband!!!

 

[Gasguru]

The heat exchanger has a small crack and "kettles". Could it be this?

Not sure we should go any further with this posting. Do you mean the heat exchanger is leaking water? Kettling noise can be caused by water dripping onto the burner. If so this is classed as "Immediately Dangerous" and the boiler should not be used.

I have come across leaking Flamingo heat exchangers that have then rotted out the casing. Boiler replacement time.

 

[ladyrose]

The heat exchanger is cracked but not leaking water at the moment. Our engineer has told us that the boiler will need replacing and that is our next big spend item. I just would like to know any suggestions as to why the water isn't heating up.

 

[ladyrose]

I think I've found the problem. There is a valve on the side of the boiler which stops the heat going in to the radiators in a hot-water-only situation. I think it has failed. Last time it broke the radiators were warm all the time, althouygh they aren't now.The engineer changed the valve in a few minutes. I could have had a manual turn off one but decided on an automatic one.
Now, the only way to heat the water is to run the heating as well!!
Can't remember how he changed the valve. How do we stop the water flooding out? Do we drain the system? We have done that before and know exactly what to do if that is the case.
After a while, when I turn the room thermostat down the system rights itself and the water is hot as I would expect.

 

[Agile]

This latest valve you have discovered may be manually "locked" onto the open position.

Try looking for a laver on one side or end !

Tony

 

[ladyrose]

Hi
The valve is an automatic one. We had a choice of manual but settled for this one instead as we are not always there to turn it on and off. It is definetly this valve playing up as the radiators are now getting warm when I am only set for hot water. Just like last time