Old boiler with central heating but no hot water

[The Bedwetter]

An old Potterton Flamingo has working CH but no HW – water comes out cold. The HW cylinder is completely cold other than the CH flow pipe which is hot. As said, all of the pipes to the rads and around the boiler are hot. I was hoping to find an air vent which I could bleed but both the boiler and HW cylinder are located in a very restricted cupboard. Any ideas or advice much appreciated?

 

[hary_j]

If you think it's an Air problem, you can lightly back up a nut or fitting somewhere to release the air. But i very much doubt this will be the issue.

Any potential blockages anywhere?

Found this: https://www.dhsspares.co.uk/userfiles/Boiler_Manuals/POT097.pdf

Might be of some help..

 

[The Bedwetter]

Yes. I might try loosening a nut as a shot in the dark but I think you are probably right, hary, and the problem will lie elsewhere. I cannot see where there could be a blockage as the CH water is circulating perfectly well as I said. There are no motorized zone valves to fail; it’s just a pretty basic gravity fed HW & pumped CH. The only thing I did notice was that the flowpipe into the cylinder (which is hot) is run in 22mm, yet the return pipe (cold) is 15mm. Of course it has been this way since it was installed so I may seem like I am clutching at straws?

Thanks for the link. :wink_smile:

 

[Simon F]

have you checked the f+e tank has water in it?

 

[The Bedwetter]

have you checked the f+e tank has water in it?

Yes, sorry, I should have said. The F&E was the first thing that I checked and it was fine.

 

[stevetheplumber]

isit gravity hw?

 

[PhoenixServices]

Is it a new cylinder or been changed recently?

 

[The Bedwetter]

stevetheplumber: Yes, it's gravity HW.

PhoenixServices: No, the cylinder is original and the system has been installed for around 20 years.

 

[Leo21]

Blocked cold feed from the f and e tank. Find the blockage, unblock. Fannys your aunt.

 

[efficiencyman]

The only thing I did notice was that the flowpipe into the cylinder (which is hot) is run in 22mm, yet the return pipe (cold) is 15mm. Of course it has been this way since it was installed so I may seem like I am clutching at straws?
:wink_smile:

I recon there is blockage in that 15mm pipe, poke something through this pipe and prove me wrong !
I have found this before a few times, I had to replace a section of pipe that was solid with rusty sludge.

Fit a TF1 or Magnaclean to stop future build up.

 

[Leo21]

I recon there is blockage in that 15mm pipe, poke something through this pipe and prove me wrong !
I have found this before a few times, I had to replace a section of pipe that was solid with rusty sludge.

Fit a TF1 or Magnaclean to stop future build up.

A tf1 wouldn't work in that scenario. Water doesn't circulate in the cold feed, so wouldn't collect it from that area. The water crystallises, something to do with the water not moving and being hot.

 

[efficiencyman]

Where did he write that it`s a blocked F & E ? He wrote that that the CH works fine but there was no hot DHW did he not ? -- surely that`s blocked the cylinder indirect not blocked from the F & E. That is just like the problem I have found a few times. He could not bleed much air from system if it was a blocked F & E.

 

[Leo21]

It's gravity hot water and pumped heating. The blockage will be in the cold feed, the water will have evaporated so the water can't circulate around the coil. But the heating will still work, coils very very rarely block up.
ive come across this scenario loads of times, either that or the diverted seized. But the way I read it, it doesn't have a diverted.

 

[stevetheplumber]

agree with leo it willbe the cold feed blocked esay to find out turn of main drain some water out the heating drain of and see if the tank empties
hot water is always the first to fail as usually the top of the coil ,especially on old cylinders ,is the highest point and no pump to push it round

 

[efficiencyman]

I agree that the water can't circulate around the coil, but the heating will still work. I have never known coils to block up either, I have found it has blocked in the bottom return pipe though as gravity it`s slow moving. In this case I would check the top flow into the coil first, prove that there is no Air that would prevent gravity flow (crack top hexagon nut if there is no air vent ) If there is air I would advise fitting a stem & air vent. If no air ( as I have found a few times ) it was blocked in the return bottom pipe, when I removed this section of pipe it was blocked solid. If this proves to be the case I Fit a TF1 or Magnaclean to stop future build up.