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

 

[Aquarius]

Not something I’ve seen or heard of before, however this site seems to imply it’s upside down? Correct installation of Willis Heaters - https://forum.buildhub.org.uk/topic/13094-correct-installation-of-willis-heaters/

 

[exedon2]

Saw these years ago when I did some consultancy work in Northern Ireland.
Above link is correct can also be installed on there side with side connection facing upwards.

 

[bigfish]

Not something I’ve seen or heard of before, however this site seems to imply it’s upside down? Correct installation of Willis Heaters - https://forum.buildhub.org.uk/topic/13094-correct-installation-of-willis-heaters/

It is the correct way round ok. Just like on that post. Pointed end at top Was a straight replacement. Probably just my bad drawing

 

[Best]

It is piped wrong. The pipe from top of Willis heater must come off the cylinder vent pipe, usually to be teed off about 800mm or higher typically in my opinion above level of top of copper cylinder (although can work okay at lower levels).
The flow pipe should rise including to have a continual slight rise on any horizontal run towards the cylinder vent tee off.
The return connection to bottom of copper cylinder should ideally only have independent direct connection - often using the 1/2” (drain off) tapping.
Remember Willis heaters must have good gravity flow to keep their thermostats from cutting out too quickly and thus resulting in slow heat up.
Brilliant wee heaters and should give rapid heat up of useable fully heated water in a mere 2 or 3 minutes if piped correct

 

[John.g]

See if the immersion stat is cutting out rapidly (watch power somewhere, if you cannot hear it) which as indicated above means poor/no circulation, otherwise you may have "excessive" circulation resulting in very low deltaT (unlikely), and presume the element is actually powering up.

 

[John.g]

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

It's essentially a instant water heater so would take the same time as a 3kw? internal immersion to heat the whole cylinder, say ~ 2.5 hrs to heat 150 litres from 15C to 60C, it should continuously supply ~ 1 LPM for the same temperature rise so give a volume of 10 Litres after 10 minutes. By my rough calculations the pipe dia from the outlet should be as small as 10mm ID to give you this sort of temperature rise.

 

[Best]

Would have been good to see a photo of how the Willis heater is piped.
But I suggest the flow pipe from Willis is connected into cylinder vent high above top of cylinder, as I previously mentioned and that the horizontal hot pipe from top of cylinder is repiped so it has no dip in it, rising a tad to the tee off for vent.
I come across a lot of Willis heaters often installed for many years that are connected lazily just above cylinder to horizontal draw off and the Willis is abysmally slow at heating. I repipe them, typically when replacing cylinders and customers are surprised to find their heater now very rapid and continuous heat up.

 

[bigfish]

It's essentially a instant water heater so would take the same time as a 3kw? internal immersion to heat the whole cylinder, say ~ 2.5 hrs to heat 150 litres from 15C to 60C, it should continuously supply ~ 1 LPM for the same temperature rise so give a volume of 10 Litres after 10 minutes. By my rough calculations the pipe dia from the outlet should be as small as 10mm ID to give you this sort of temperature rise.

Only get after 10 minutes 3L

 

[bigfish]

Here is some images. Little room up top. Image 2 and 3 show lower inlets one into large tank and one into willis.