Hi All,
I decided to go ahead with a gravity circulation (plus immerser) to S-Plan conversion earlier than I originally planned as discussed in other threads.
I have the hot water kit and have been doing some preliminary testing before the real conversion work begins later this week, however I seem to have hit a stumbling block. The cylinder is a vented, 95 litre combined indirect loop and immerser system, currently connected in a gravity loop configuration - eg very slow to reheat and requires the boiler temperature set very high to get any gravity circulation....so we tend to use the immerser a lot, especially in summer.
Just so I could play around with the evohome hot water configuration I went ahead and installed the strap on sensor on the cylinder - I cut back a section of insulation about 1/4 of the way up as documented, cleaned the copper until it was nice and shiny then fitted the sensor and strap. The sensor is bound and the relay is connected to a test power lead so I could finish the binding process.
I thought a good test would be to turn on the immerser and see what the reading went up to - well, it went up to 34 degrees and didn't go any higher, even though after an hour turned on the hot water coming out of the tap was easily 50+ degrees.
Anyone have any ideas ? Is it possible that the cylinder has a double skin, and therefore the outside copper layer is not in direct contact with the hot water, preventing me from getting a meaningful reading ? When I remove the sensor and touch the copper it feels cool (less than body temperature) to the touch, so 34 degrees seems plausible given how cool it feels.
Or could it be that the location of the immerser element near the top prevents much heat transfer to the casing of the cylinder low down where the sensor is installed, and that heating via the indirect loop which I believe is nearer the bottom would heat the bottom of the cylinder much more ? (Grasping at straws here)
If it is double skinned I guess that means an insertion sensor would be necessary - there is an insertion hole through the top for the thermostat for the electrical element that could potentially be used, however (a) this would disable the immerser not leaving it available as a backup (not a big deal if the new configuration performs much better) and (b) the insertion sensor provided with the hot water kit looks bigger diameter than the existing thermostat.
I'd have to pull the existing thermostat out and measure it to be sure of that, I have replaced it in the past however I don't recall exactly what size it was. If the insertion hole is too small for the sensor I'm kind of screwed even though I've ordered all the hardware to do the S-Plan conversion ?
Another question - is it normal for the hot water sensor reading on the controller to only update once every 8-10 minutes ? This seems very infrequent if you had a quick re-heat cylinder - it seems that overshooting the set temperature would be a problem if it could continue to heat for another 10 minutes after the set temperature had been reached ?
This is not a quick re-heat cylinder but it seems strange to me that HR92's would report their temperature every 4 minutes but the hot water sensor only every 8 minutes.
I decided to go ahead with a gravity circulation (plus immerser) to S-Plan conversion earlier than I originally planned as discussed in other threads.
I have the hot water kit and have been doing some preliminary testing before the real conversion work begins later this week, however I seem to have hit a stumbling block. The cylinder is a vented, 95 litre combined indirect loop and immerser system, currently connected in a gravity loop configuration - eg very slow to reheat and requires the boiler temperature set very high to get any gravity circulation....so we tend to use the immerser a lot, especially in summer.
Just so I could play around with the evohome hot water configuration I went ahead and installed the strap on sensor on the cylinder - I cut back a section of insulation about 1/4 of the way up as documented, cleaned the copper until it was nice and shiny then fitted the sensor and strap. The sensor is bound and the relay is connected to a test power lead so I could finish the binding process.
I thought a good test would be to turn on the immerser and see what the reading went up to - well, it went up to 34 degrees and didn't go any higher, even though after an hour turned on the hot water coming out of the tap was easily 50+ degrees.
Anyone have any ideas ? Is it possible that the cylinder has a double skin, and therefore the outside copper layer is not in direct contact with the hot water, preventing me from getting a meaningful reading ? When I remove the sensor and touch the copper it feels cool (less than body temperature) to the touch, so 34 degrees seems plausible given how cool it feels.
Or could it be that the location of the immerser element near the top prevents much heat transfer to the casing of the cylinder low down where the sensor is installed, and that heating via the indirect loop which I believe is nearer the bottom would heat the bottom of the cylinder much more ? (Grasping at straws here)
If it is double skinned I guess that means an insertion sensor would be necessary - there is an insertion hole through the top for the thermostat for the electrical element that could potentially be used, however (a) this would disable the immerser not leaving it available as a backup (not a big deal if the new configuration performs much better) and (b) the insertion sensor provided with the hot water kit looks bigger diameter than the existing thermostat.
I'd have to pull the existing thermostat out and measure it to be sure of that, I have replaced it in the past however I don't recall exactly what size it was. If the insertion hole is too small for the sensor I'm kind of screwed even though I've ordered all the hardware to do the S-Plan conversion ?
Another question - is it normal for the hot water sensor reading on the controller to only update once every 8-10 minutes ? This seems very infrequent if you had a quick re-heat cylinder - it seems that overshooting the set temperature would be a problem if it could continue to heat for another 10 minutes after the set temperature had been reached ?
This is not a quick re-heat cylinder but it seems strange to me that HR92's would report their temperature every 4 minutes but the hot water sensor only every 8 minutes.
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