Willis Immersion issue - no hot water getting to main tank

[bigfish]

Replaced a Willis (Belfast) immersion heating in an open vent heating system. Willis is working ok but flow of heated water see wrong and does not generate a lot of hot water.

Symptoms are (See diagram):

1. Flow from hot tapes fine (no air locks).
2. Tank heats up using house oil indirect heating system ok therefore no locks in tank.
3. When immersion turned on heated water going to pipes in red, i.e. away from the main tank, only hot water in pipes leading to house hot water tap. Does not generate lots of hot water in volume.

Noticed there is a slight incline from the pipe connected emersion to pipe leading to tanks (marked as A in diagram). Possibly caused by new immersion being slightly shorter than original. May be cause but not certain.

Anyone any ideas would be greatly appreciated 🙂

 

[John.g]

No, the vent normally comes straight off the very top of the cylinder and goes up and is bent over the CWST. The pipe you refer to is properly called the feed & expansion pipe, having no vent will certainly affect the proper circulation IMO.

 

[John.g]

If the pipe you refer to (on the left) comes off the cylinder top then yes, that is a vent if not connected to the cold feed.
Its the one going to the top of the CWST below.

https://www.plumbersforums.net/attachments/willis-fliped-jpg.60438/

 

[John.g]

Have you checked if the immersion element is cutting in/out rapidly?.