Hot water cylinder flow hot return stone cold (Airlock valve in place)

[JackK]

Im really sturglgling to make sense of this but I will try wise people on this forum who have always had a lot of enthusiasm -

The flow pipe is piping hot but the return is stone cold even though the hot water cylinder has the immersion switched on so should not be drawing too much heat from the flow.

There is an airlock valve at the top of the installation - What else can I investigate? The pump speed has not changed. The cylinder was changed six months ago and I am not sure if this ever worked to be honest. The previous cylinder was much older and the return was always hot

Its 28mm reduced to 22mm to the flow and a large 3 inch return

Is it possible to have an airlock in the hot water coil itself?

Is it possible that the pipework to the flow is piping hot but from radiant heat from the main flow and the two port is faulty? I put the two port valve in manual overide mode but still no luck so I am quite sure it is not that

Any help much appreciated

 

[DP]

Cannot understand why the PTFE has been wrapped round the fitting. What does that achieve other than make the installation look like a dogs bowl. Not a professional job.

I would crack open slightly the fitting on the flow to see if any air is released. Same with return. If there is an airlock, and slight trickle past the airlock. Then flow will be hot

 

[JackK]

Cannot understand why the PTFE has been wrapped round the fitting. What does that achieve other than make the installation look like a dogs bowl. Not a professional job.

I would crack open slightly the fitting on the flow to see if any air is released. Same with return. If there is an airlock, and slight trickle past the airlock. Then flow will be hot

Wouldnt the air be released by the valve at the top of the flow pipe?

Is it possible for airlock to happen within the hot water cylinder coil itself? Or would air always get to the top? Is it worth draining the system and refilling although I dont want to do that as I will have to reinhibit the system?

 

[Johntheo5]

As above.
Slacken the compression nut ~ 1/2 to one full turn where the coil enters the cylinder and pull back on the pipe until air/water comes out, retighten.

 

[JohnD]

Please photograph the return pipe where it comes out of the cylinder, and whatever is attached to it.

I wonder why the flow pipe was formed into a shape that will collect the air at the left, and not under the vent.

 

[DP]

Wouldnt the air be released by the valve at the top of the flow pipe?

Is it possible for airlock to happen within the hot water cylinder coil itself? Or would air always get to the top? Is it worth draining the system and refilling although I dont want to do that as I will have to reinhibit the system?

The way PTFE has been applied, I wonder if the pipe bore might not be covered by the thread tape. This sealing media is called thread tape, but not to seal the threads= sealing is done by the olive, not the fitting thread.

Issue may be elsewhere, like blocked feed from the header tank

 

[JackK]

Please photograph the return pipe where it comes out of the cylinder, and whatever is attached to it.

I wonder why the flow pipe was formed into a shape that will collect the air at the left, and not under the vent.

I will send a picture as soon as I am home - Can you explain what you mean about air collecting on the left? The air vent is higher than the flow pipe so air should come out and no airlocks possible

 

[JackK]

The way PTFE has been applied, I wonder if the pipe bore might not be covered by the thread tape. This sealing media is called thread tape, but not to seal the threads= sealing is done by the olive, not the fitting thread.

Issue may be elsewhere, like blocked feed from the header tank

PTFE was overused for sure - The header tank is clear and runnig normally in both FandE and cold water storage tank

 

[Johntheo5]

I will send a picture as soon as I am home - Can you explain what you mean about air collecting on the left? The air vent is higher than the flow pipe so air should come out and no airlocks possible

Presume the cap on the AAV is open? With the motorised valve shut then yes I suppose water from the return might be expected to push any air up through the pipe and out the AAV even though the rising pipe may not be the best.

 

[JohnD]

I will send a picture as soon as I am home - Can you explain what you mean about air collecting on the left? The air vent is higher than the flow pipe so air should come out and no airlocks possible

It looks to me as if the pipe rises at it runs to the left. So air will collect at the high point on the left.

 

[JackK]

The Aav is definitely open

There is a very small rise on the left of the pipe. However the aav is higher than that so wouldn’t that release any air? I have had the boiler on all night and return is still cold sadly which means no hot water in house to brush teeth

Is a drain down and refill my only choice ?

 

[HERTS P&D]

What, you brush your teeth with hot water?

Andy

 

[Johntheo5]

What, you brush your teeth with hot water?

Andy

If the water is too hot it will break the glass containing the teeth.

 

[Johntheo5]

The Aav is definitely open

There is a very small rise on the left of the pipe. However the aav is higher than that so wouldn’t that release any air? I have had the boiler on all night and return is still cold sadly which means no hot water in house to brush teeth

Is a drain down and refill my only choice ?

Why don't you loosen the compression nut as suggested at the coil inlet to the cylinder with the mot.valve shut, that should then show if the coil outlet is blocked, do it with boiler off, then open the motorised valve, boiler on, to purge the other way.