bigfish Posted April 2, 2021 Share Posted April 2, 2021 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): Flow from hot tapes fine (no air locks). Tank heats up using house oil heating system ok therefore no locks in tank. 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 :) Link to comment Share on other sites More sharing options...
dpmiller Posted April 2, 2021 Share Posted April 2, 2021 where does the bottom of the Willis connect to the tank? Looks like it's circulating in the F&E pipe instead of the tank... 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted April 2, 2021 Share Posted April 2, 2021 Which way is heat converting? You may need an anti gravity valve in the return of the boiler to the cylinder to stop unwanted ‘reverse’ convection. 1 Link to comment Share on other sites More sharing options...
bigfish Posted April 2, 2021 Author Share Posted April 2, 2021 dpMiller thanks for response. Split in pipe feeds larger tank and Willis immersion. This was the way it was I only replaced Willis. From what I know it was working ok before. Link to comment Share on other sites More sharing options...
bigfish Posted April 2, 2021 Author Share Posted April 2, 2021 Nickfromwales, thanks for reply. Which way is heat converting? Electric immersion heater The outlet from the immersion heater and the water heater tank is shared into the hotwater outlet pipe. Standard setup diagram, below, makes no mention of an anti gravity valve, but then, maybe not accurate Link to comment Share on other sites More sharing options...
Nickfromwales Posted April 2, 2021 Share Posted April 2, 2021 1 hour ago, bigfish said: Which way is heat converting? Should have asked which direction the heat is convecting. Eg it sounds like it’s heading away from the cylinder in a reverse direction vs travelling through the cylinder and back in itself. 1 Link to comment Share on other sites More sharing options...
bigfish Posted April 2, 2021 Author Share Posted April 2, 2021 On original diagram at point A it is going left and no heat going right into tank. From my understanding it should go mostly right. Would I be correct in saying need gravity to flow down into tank to build up hot water. Link to comment Share on other sites More sharing options...
dpmiller Posted April 2, 2021 Share Posted April 2, 2021 it's a thermosphon. Cold in at the bottom, hot water rises as it's less dense. What temperature is the stat set too, and how long are you leaving it on for? 1 Link to comment Share on other sites More sharing options...
bigfish Posted April 3, 2021 Author Share Posted April 3, 2021 There is no adjustable setting available on these devices are far as I can see. The pipes are extremely hot when touched. Very strange that no heat at all going right of the T connector. Completely cold. https://www.amazon.co.uk/Tesla-External-Immersion-Heater-Willis/dp/B00XLBAAEG not sure what red button is prob thermostat. Instructions are below but for example 10 minutes only give 3L of hot water. : OPERATING INSTRUCTIONS A Willis Immersion heats approximately 4.5 litres of water to a high temperature every 5 minutes, so if one can decide before switching on how much water is required the pre-heating time can be calculated as follows: 4.5 litres for hand-washing, baby’s bath, shaving, breakfast dishes etc. = Pre-heat for 5 minutes 9 litres required for washing-up dinner dishes, medium sized clothes wash = Pre-heat for 10 minutes 9–14 litres required for a shower = Pre-heat for 10/15 minutes 54 litres required for a bath = Pre-heat for 1 hour Link to comment Share on other sites More sharing options...
dpmiller Posted April 3, 2021 Share Posted April 3, 2021 there's an adjustable stat under the cover. 1 Link to comment Share on other sites More sharing options...
bigfish Posted April 4, 2021 Author Share Posted April 4, 2021 Thanks, will have a look for the thermostat and see if increasing the setting helps I thought the hot water was supposed to build up in the hot water tank. I have looked at someone else's and theirs does. The plumbing in theirs is more like in the second official diagram. Do not under stand why it is not going right. Link to comment Share on other sites More sharing options...
Nickfromwales Posted April 4, 2021 Share Posted April 4, 2021 There is nothing wrong with the heater!! Don’t touch it. The issue is the heat is taking the easiest path of convention, which is NOT through the tank. You need to disassemble the plumbing and check the T and the connection to the cylinder aren’t blocked before doing anything more. On 02/04/2021 at 12:56, bigfish said: Nickfromwales, thanks for reply. Which way is heat converting? Electric immersion heater The outlet from the immersion heater and the water heater tank is shared into the hotwater outlet pipe. Standard setup diagram, below, makes no mention of an anti gravity valve, but then, maybe not accurate This diagram doesn’t show a boiler feed T’d into the Willis flow / boiler return. Do you have some pics of this arrangement? Has this ever worked? If so, it could just be an airlock in the Willis heater pipework. Or a gate valve that hasn’t been reopened ( or has been manually turned open but the guts of the gate valve sometimes stay stuck in the closed position ). 1 Link to comment Share on other sites More sharing options...
bigfish Posted April 4, 2021 Author Share Posted April 4, 2021 27 minutes ago, Nickfromwales said: There is nothing wrong with the heater!! Don’t touch it. The issue is the heat is taking the easiest path of convention, which is NOT through the tank. You need to disassemble the plumbing and check the T and the connection to the cylinder aren’t blocked before doing anything more. This diagram doesn’t show a boiler feed T’d into the Willis flow / boiler return. Do you have some pics of this arrangement? Has this ever worked? If so, it could just be an airlock in the Willis heater pipework. Or a gate valve that hasn’t been reopened ( or has been manually turned open but the guts of the gate valve sometimes stay stuck in the closed position ). Thanks for reply When I turn on the oil central heating, the indirect heating in the large hot water tank is heating ok, top to bottom. Taps then run with hot water. If there was a blockage between top of tank and the T would I be able to get hot water. I was thinking this also ruled out air lock at top of large tank. It was working for 30+ years. One inlet pipe comes in low behind the tank (this has a gate valve), is then split to go to bottom of big tank and bottom of the Willis immersion. That gate has been reopened. Will get a picture when back in the house and post it Link to comment Share on other sites More sharing options...
bigfish Posted April 5, 2021 Author Share Posted April 5, 2021 Some pictures Link to comment Share on other sites More sharing options...
ProDave Posted April 5, 2021 Share Posted April 5, 2021 Don't take this the wrong way, but the best thing you could do there is change that for a new, well insulated tank, with a built in immersion heater. Or if you don't want to do that, isn't that a blanked off immersion port in the top? Put a long immersion in there to directly heat the tank and forget the willis in this application. Link to comment Share on other sites More sharing options...
bigfish Posted April 5, 2021 Author Share Posted April 5, 2021 Hi ProDave, Yes tank very old, may change at some point as they are a bit expensive to get a good rated one. Willis immersion have a big advantage over normal ones. They produce hot water faster and more efficiently, from what I know (probably not a lot lol). Link to comment Share on other sites More sharing options...
dpmiller Posted April 5, 2021 Share Posted April 5, 2021 can we get a shot of the plumbing at the bottom of the tank plz? Link to comment Share on other sites More sharing options...
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