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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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W-B 28i Junior slow hot water
It's about two years old, non-condensing, and recently is taking a
long time to come up with hot water. It fires up about five or six seconds after opening the tap, then it's anything up to about five minutes before the water gets warm, not counting the time it takes to get to the tap. The more recently it has been used, the less time it takes. It doesn't seem to depend on the water flow rate. The red light is on the whole time, but it's difficult to tell from the sound how much gas it's burning. The CH pipes stay cold. Does that ring any bells? |
#2
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W-B 28i Junior slow hot water
"Joe" wrote in message
... It's about two years old, non-condensing, and recently is taking a long time to come up with hot water. It fires up about five or six seconds after opening the tap, then it's anything up to about five minutes before the water gets warm, not counting the time it takes to get to the tap. The more recently it has been used, the less time it takes. It doesn't seem to depend on the water flow rate. The red light is on the whole time, but it's difficult to tell from the sound how much gas it's burning. The CH pipes stay cold. Does that ring any bells? I have the same problem with a 24i, waiting with anticipation for helpful replies............. Tom |
#3
Posted to uk.d-i-y
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W-B 28i Junior slow hot water
On Sun, 18 Feb 2007 13:58:15 +0000, Joe wrote:
It's about two years old, non-condensing, and recently is taking a long time to come up with hot water. It fires up about five or six seconds after opening the tap, then it's anything up to about five minutes before the water gets warm, not counting the time it takes to get to the tap. The more recently it has been used, the less time it takes. It doesn't seem to depend on the water flow rate. The red light is on the whole time, but it's difficult to tell from the sound how much gas it's burning. The CH pipes stay cold. Is the water coming out at a dribble that's taking a long time to get through the pipework? In that case it's likely to be scaled up (if you're in a hard water area). The non-condensing 24/28i Juniors have combined heat exchangers rather than separate plate heat exchangers and diverter valves so if the boiler is firing up straight away it must be heating DHW straight away: you should be able to feel the DHW pipework inside and just outside the boiler getting hot and follow the pipework getting hot. |
#4
Posted to uk.d-i-y
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W-B 28i Junior slow hot water
John Stumbles wrote:
On Sun, 18 Feb 2007 13:58:15 +0000, Joe wrote: It's about two years old, non-condensing, and recently is taking a long time to come up with hot water. It fires up about five or six seconds after opening the tap, then it's anything up to about five minutes before the water gets warm, not counting the time it takes to get to the tap. The more recently it has been used, the less time it takes. It doesn't seem to depend on the water flow rate. The red light is on the whole time, but it's difficult to tell from the sound how much gas it's burning. The CH pipes stay cold. Is the water coming out at a dribble that's taking a long time to get through the pipework? In that case it's likely to be scaled up (if you're in a hard water area). No, sorry, it's running as fast as it did a month or two ago, when the problem wasn't there. I expect a slightly slower warm-up in winter, when the incoming water is colder, but this is excessive. As I say, if I use hot water again within half an hour, there's no problem, and the flow rate hasn't changed. It's almost as if there's a huge heatsink that has to warm up before the water gets any heat. The non-condensing 24/28i Juniors have combined heat exchangers rather than separate plate heat exchangers and diverter valves so if the boiler is firing up straight away it must be heating DHW straight away: you should be able to feel the DHW pipework inside and just outside the boiler getting hot and follow the pipework getting hot. Not obviously. I did wonder where all the heat was going, and I must assume the burner is throttled back to minimum during the waiting period. |
#5
Posted to uk.d-i-y
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W-B 28i Junior slow hot water
On Mon, 19 Feb 2007 15:20:59 +0000, Joe wrote:
Is the water coming out at a dribble that's taking a long time to get through the pipework? In that case it's likely to be scaled up (if you're in a hard water area). No, sorry, it's running as fast as it did a month or two ago, when the problem wasn't there. I expect a slightly slower warm-up in winter, when the incoming water is colder, but this is excessive. As I say, if I use hot water again within half an hour, there's no problem, and the flow rate hasn't changed. It's almost as if there's a huge heatsink that has to warm up before the water gets any heat. ... I did wonder where all the heat was going, and I must assume the burner is throttled back to minimum during the waiting period. If you watch the gas meter (clock dial) while someone else turns on a hot tap can you see if the boiler is starting up at a low rate and then getting to full rate much later? |
#6
Posted to uk.d-i-y
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W-B 28i Junior slow hot water
John Stumbles wrote:
On Mon, 19 Feb 2007 15:20:59 +0000, Joe wrote: Is the water coming out at a dribble that's taking a long time to get through the pipework? In that case it's likely to be scaled up (if you're in a hard water area). No, sorry, it's running as fast as it did a month or two ago, when the problem wasn't there. I expect a slightly slower warm-up in winter, when the incoming water is colder, but this is excessive. As I say, if I use hot water again within half an hour, there's no problem, and the flow rate hasn't changed. It's almost as if there's a huge heatsink that has to warm up before the water gets any heat. ... I did wonder where all the heat was going, and I must assume the burner is throttled back to minimum during the waiting period. If you watch the gas meter (clock dial) while someone else turns on a hot tap can you see if the boiler is starting up at a low rate and then getting to full rate much later? That could be difficult. We have an old style meter literally on the floor under the stairs. I may get curious enough to try, but I assume I'll have to get the proverbial Man In to fix the boiler anyway. I was hoping to get some idea of the problem, as this seems a reasonably popular model, but it doesn't look as if anyone has seen this before. |
#7
Posted to uk.d-i-y
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W-B 28i Junior slow hot water
"Joe" wrote in message
... John Stumbles wrote: On Mon, 19 Feb 2007 15:20:59 +0000, Joe wrote: Is the water coming out at a dribble that's taking a long time to get through the pipework? In that case it's likely to be scaled up (if you're in a hard water area). No, sorry, it's running as fast as it did a month or two ago, when the problem wasn't there. I expect a slightly slower warm-up in winter, when the incoming water is colder, but this is excessive. As I say, if I use hot water again within half an hour, there's no problem, and the flow rate hasn't changed. It's almost as if there's a huge heatsink that has to warm up before the water gets any heat. ... I did wonder where all the heat was going, and I must assume the burner is throttled back to minimum during the waiting period. If you watch the gas meter (clock dial) while someone else turns on a hot tap can you see if the boiler is starting up at a low rate and then getting to full rate much later? That could be difficult. We have an old style meter literally on the floor under the stairs. I may get curious enough to try, but I assume I'll have to get the proverbial Man In to fix the boiler anyway. I was hoping to get some idea of the problem, as this seems a reasonably popular model, but it doesn't look as if anyone has seen this before. Sorry Joe but our boiler has seemed to cure itself! I wont believe until we have at least a week of trouble free hot water supplies. Tom |
#8
Posted to uk.d-i-y
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W-B 28i Junior slow hot water
Joe wrote:
John Stumbles wrote: On Mon, 19 Feb 2007 15:20:59 +0000, Joe wrote: Is the water coming out at a dribble that's taking a long time to get through the pipework? In that case it's likely to be scaled up (if you're in a hard water area). No, sorry, it's running as fast as it did a month or two ago, when the problem wasn't there. I expect a slightly slower warm-up in winter, when the incoming water is colder, but this is excessive. As I say, if I use hot water again within half an hour, there's no problem, and the flow rate hasn't changed. It's almost as if there's a huge heatsink that has to warm up before the water gets any heat. ... I did wonder where all the heat was going, and I must assume the burner is throttled back to minimum during the waiting period. If you watch the gas meter (clock dial) while someone else turns on a hot tap can you see if the boiler is starting up at a low rate and then getting to full rate much later? That could be difficult. We have an old style meter literally on the floor under the stairs. I may get curious enough to try, but I assume I'll have to get the proverbial Man In to fix the boiler anyway. I was hoping to get some idea of the problem, as this seems a reasonably popular model, but it doesn't look as if anyone has seen this before. More information: I confirmed that no pipes get hot during the dead period, and being an electronics engineer, I gave the cabinet a few thumps was rewarded with a blinking 'computer crashed' light. Turned off the tap, reset it and tried again. Again the pipes stayed cold, and the flue showed only a very slight heat haze. Then after about twenty seconds, the sound started to fluctuate slightly and then the pipe got hot. So this looks like a flame-failure device fault. Does anyone know whether this is purely thermo-mechanical, or whether it's an electric valve and sensor? The latter would seem to imply that the computer crash was the result of a dodgy joint, and it might be worth reseating everything. I would assume if it's purely mechanical then it needs replacing. |
#9
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W-B 28i Junior slow hot water
In message , Joe
writes So this looks like a flame-failure device fault. Does anyone know whether this is purely thermo-mechanical, or whether it's an electric valve and sensor? The latter would seem to imply that the computer crash was the result of a dodgy joint, and it might be worth reseating everything. I would assume if it's purely mechanical then it needs replacing. It's not a computer, it's a very naughty boy That's why it's called junior the 28i Jnr uses purely electronic sensing, nothing magic about that, the pcb just detects a small rectified current from the flame Now, this is where it gets embarrassing ... I'm the boiler pcb expert and I have a W-B 28i Jnr, and I can't remember whether the pcb senses the flame over the HT lead or a separate sensing lead, I think the latter (It will be in the manual, which I am too lazy to go and check) Sources of flame sense failure are 1) pcb fault (prolly not much you can do about tis unless you are fairly clued up, engineer or not) the 28i Jnr isn't so prone to cracked solder joiints, but worth checking around the HT transformer area 2) Broken flame sensing lead 3) Flame sense electrode not in the flame 4) earthing problems - without a good earth, flame sensing will fail -- geoff |
#10
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W-B 28i Junior slow hot water
raden wrote:
In message , Joe writes So this looks like a flame-failure device fault. Does anyone know whether this is purely thermo-mechanical, or whether it's an electric valve and sensor? The latter would seem to imply that the computer crash was the result of a dodgy joint, and it might be worth reseating everything. I would assume if it's purely mechanical then it needs replacing. It's not a computer, it's a very naughty boy That's why it's called junior the 28i Jnr uses purely electronic sensing, nothing magic about that, the pcb just detects a small rectified current from the flame Now, this is where it gets embarrassing ... I'm the boiler pcb expert and I have a W-B 28i Jnr, and I can't remember whether the pcb senses the flame over the HT lead or a separate sensing lead, I think the latter (It will be in the manual, which I am too lazy to go and check) Sources of flame sense failure are 1) pcb fault (prolly not much you can do about tis unless you are fairly clued up, engineer or not) the 28i Jnr isn't so prone to cracked solder joiints, but worth checking around the HT transformer area 2) Broken flame sensing lead 3) Flame sense electrode not in the flame 4) earthing problems - without a good earth, flame sensing will fail Thanks for your time. I can expect The Man to tell me I need a new PCB, then. I'll have a quick look at any accessible wiring and connectors, but I have no interest in dismantling anything with a seal. |
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