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.

 

[bigfish]

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.

Posted pictures

 

[Best]

Only get after 10 minutes 3L

Wow! That’s very poor!
Probably just lack of good gravity circulation causing heater to heat just the water inside itself & switch off on stat.
Repipe it all and check stat

 

[bigfish]

Wow! That’s very poor!
Probably just lack of good gravity circulation causing heater to heat just the water inside itself & switch off on stat.
Repipe it all and check stat

Restricted head room above is an issue. Will have to re-pipe outlet from Willis into ceiling to get

Wow! That’s very poor!
Probably just lack of good gravity circulation causing heater to heat just the water inside itself & switch off on stat.
Repipe it all and check stat

Would I be best to connect the Willis high up the expansion feed (Pic 1 yellow area) or new pipe route feeding into top of large tank (Pic 1 red area). Or completely redo everything like in diagram flipped so willis on left:

 

[Best]

Posted pictures

Old cylinder and fittings look like they need scrapped.
Repipe the flow from Willis - offset pipe to suit clip distance on left wall & bend near 90 degree bend on pipe at least 60 or 80 cm above cylinder (I usually try to have tee off below shelf level). Clip horizontal run as well, because weight of Willis will need supported.
Is that in NI ?

 

[Best]

I guess you could try yellow area to tee off. Brass tee maybe safer than soldering there.
Just really needs that short rise up to get immersion circulation.

 

[John.g]

Where is the cylinder vent if a vented HW cylinder?.

 

[Best]

Where is the cylinder vent if a vented HW cylinder?.

I think it is tight in the corner, but difficult to see in photo

 

[bigfish]

Old cylinder and fittings look like they need scrapped.
Repipe the flow from Willis - offset pipe to suit clip distance on left wall & bend near 90 degree bend on pipe at least 60 or 80 cm above cylinder (I usually try to have tee off below shelf level). Clip horizontal run as well, because weight of Willis will need supported.
Is that in NI ?

Yes in NI

 

[bigfish]

I guess you could try yellow area to tee off. Brass tee maybe safer than soldering there.
Just really needs that short rise up to get immersion circulation.

OK thanks Will give it a go. Going to be hard to get to

Just after a quick fix at moment. Will think about replacing tank maybe later on as a bit expensive at the moment

We do not have hard water in are area so hopefully tank not that bad at moment.

 

[bigfish]

Where is the cylinder vent if a vented HW cylinder?.

Think it is the up pipe on the left going into the loft i.e. expansion feed in diagram. Is that what you mean?

 

[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?.