|
Faulty Thermostat or faulty installation
Next door neighbour has just had their HW tank replaced under
maintenance contract by BG. The old tank was copper but I think the new one is SS - it is certainly very flat topped (still open vented). They transferred the immersion heater (the immersion heater is not used and is a back up for boiler failure only) and thermostat from old tank to new but now they seem unable to get satisfactory HW temperature. One minute it is scalding hot, reduce the thermostat setting by 1Deg and the water ends up dropping to luke warm before the boiler wakes up to warm it up. When moving the thermostat manually there is about a 5C "backlash" between switch on/off operations. Any suggestions as to whether this is 1) a thermostat that didn't like being moved and has failed due to the disturbance 2) Lack of thermal connection between the new tank and the thermostat (should there be any form of heat transfer compound between them) - I think this would be my first point of call if it was my tank) 3) Incorrect positioning of the thermostat 4) any other ideas. He has the maintenance contact with BG so they will be called in to fix it but he would like some confidence that the problem can be fixed. -- Chris B (News) |
Faulty Thermostat or faulty installation
Chris B wrote:
Lack of thermal connection between the new tank and the thermostat Is it the strap-on with curtain wire, or shoved in a pocket/tube type? |
Faulty Thermostat or faulty installation
On 18/04/2021 10:55, Andy Burns wrote:
Chris B wrote: Lack of thermal connection between the new tank and the thermostat Is it the strap-on with curtain wire, or shoved in a pocket/tube type? Its held on with a flat metallic strap about 5mm wide that goes right round the tank. -- Chris B (News) |
Faulty Thermostat or faulty installation
On Sunday, 18 April 2021 at 10:58:21 UTC+1, Chris B wrote:
On 18/04/2021 10:55, Andy Burns wrote: Chris B wrote: Lack of thermal connection between the new tank and the thermostat Is it the strap-on with curtain wire, or shoved in a pocket/tube type? Its held on with a flat metallic strap about 5mm wide that goes right round the tank. -- Chris B (News) Whereabouts on the tank is it? It should normally be about 1/3 of the way up, too high and because hot water rises it will constantly monitor the water temperature where it is hottest so the bottom half of the tank does not warm up. Richard |
Faulty Thermostat or faulty installation
On 18/04/2021 11:03, Tricky Dicky wrote:
On Sunday, 18 April 2021 at 10:58:21 UTC+1, Chris B wrote: On 18/04/2021 10:55, Andy Burns wrote: Chris B wrote: Lack of thermal connection between the new tank and the thermostat Is it the strap-on with curtain wire, or shoved in a pocket/tube type? Its held on with a flat metallic strap about 5mm wide that goes right round the tank. -- Chris B (News) Whereabouts on the tank is it? It should normally be about 1/3 of the way up, too high and because hot water rises it will constantly monitor the water temperature where it is hottest so the bottom half of the tank does not warm up. Richard Well I haven't actually measured it but yes at a guess I would say its about 1/3 of the way from the bottom -- Chris B (News) |
Faulty Thermostat or faulty installation
On 18/04/2021 10:38, Chris B wrote:
When moving the thermostat manually there is about a 5C "backlash" between switch on/off operations. Is that just the normal hysteresis of 5 to 10C? 1) a thermostat that didn't like being moved and has failed due to the disturbance It is probably a simple bi-metal strip with little to go wrong - except in moving it the installer has created a high resistance electrical connection - wire connected with screw through the insulation and only just making electrical contact. 2) Lack of thermal connection between the new tank and the thermostat (should there be any form of heat transfer compound between them)Â* - I think this would be my first point of call if it was my tank) The strap may not be tight enough to hold the thermostat tightly against the tank. As far as I'm aware no compound is used between the tank and thermostat 3) Incorrect positioning of the thermostat Where is it positioned? The position may only be relevant to what temperature you set it to. Currently on by tank I have installed two (Ebay special) temperature probes/displays. One half way down the tank where the thermostat is fitted and one at the very top. While water is heating from cold there is a approx a 10C difference in reading with the top of the tank being hotter. 4) any other ideas. He has the maintenance contact with BG so they will be called in to fix it but he would like some confidence that the problem can be fixed. -- mailto : news {at} admac {dot} myzen {dot} co {dot} uk |
Faulty Thermostat or faulty installation
On 18/04/2021 11:08, Chris B wrote:
On 18/04/2021 11:03, Tricky Dicky wrote: On Sunday, 18 April 2021 at 10:58:21 UTC+1, Chris B wrote: On 18/04/2021 10:55, Andy Burns wrote: Chris B wrote: Lack of thermal connection between the new tank and the thermostat Is it the strap-on with curtain wire, or shoved in a pocket/tube type? Its held on with a flat metallic strap about 5mm wide that goes right round the tank. -- Chris B (News) Whereabouts on the tank is it? It should normally be about 1/3 of the way up, too high and because hot water rises it will constantly monitor the water temperature where it is hottest so the bottom half of the tank does not warm up. Richard Well I haven't actually measured it but yes at a guess I would say its about 1/3 of the way from the bottom Is the tank insulated? Normally on a foamed copper cylinder, you would cut a pocket in the foam to allow the stat to make contact with the metal. Many of the SS cylinders are dual skinned with a metal outer cover over the insulation, which in turn is over the inner cylinder. This could make the stat unable to "feel" the change in temperature effectively, and also make it such that even a quite substantial temperature change in the cylinder is reflected in a small change visible to the stat. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
Faulty Thermostat or faulty installation
The first type are as useful as a chocolate fireguard in my experience, do
these still exist? Brian -- This newsgroup posting comes to you directly from... The Sofa of Brian Gaff... Blind user, so no pictures please Note this Signature is meaningless.! "Andy Burns" wrote in message ... Chris B wrote: Lack of thermal connection between the new tank and the thermostat Is it the strap-on with curtain wire, or shoved in a pocket/tube type? |
Faulty Thermostat or faulty installation
Yes but does not the water come from the top and in to the bottom?
Brian -- This newsgroup posting comes to you directly from... The Sofa of Brian Gaff... Blind user, so no pictures please Note this Signature is meaningless.! "Tricky Dicky" wrote in message ... On Sunday, 18 April 2021 at 10:58:21 UTC+1, Chris B wrote: On 18/04/2021 10:55, Andy Burns wrote: Chris B wrote: Lack of thermal connection between the new tank and the thermostat Is it the strap-on with curtain wire, or shoved in a pocket/tube type? Its held on with a flat metallic strap about 5mm wide that goes right round the tank. -- Chris B (News) Whereabouts on the tank is it? It should normally be about 1/3 of the way up, too high and because hot water rises it will constantly monitor the water temperature where it is hottest so the bottom half of the tank does not warm up. Richard |
Faulty Thermostat or faulty installation
If its the old one where was it before?
Brian -- This newsgroup posting comes to you directly from... The Sofa of Brian Gaff... Blind user, so no pictures please Note this Signature is meaningless.! "Chris B" wrote in message ... On 18/04/2021 11:03, Tricky Dicky wrote: On Sunday, 18 April 2021 at 10:58:21 UTC+1, Chris B wrote: On 18/04/2021 10:55, Andy Burns wrote: Chris B wrote: Lack of thermal connection between the new tank and the thermostat Is it the strap-on with curtain wire, or shoved in a pocket/tube type? Its held on with a flat metallic strap about 5mm wide that goes right round the tank. -- Chris B (News) Whereabouts on the tank is it? It should normally be about 1/3 of the way up, too high and because hot water rises it will constantly monitor the water temperature where it is hottest so the bottom half of the tank does not warm up. Richard Well I haven't actually measured it but yes at a guess I would say its about 1/3 of the way from the bottom -- Chris B (News) |
Faulty Thermostat or faulty installation
Brian Gaff wrote:
The first type are as useful as a chocolate fireguard in my experience, do these still exist? Yep 15 quid from screwfix, if you've got a hot water cylinder with separate lagging, there's nothing wrong with a strap-on stat, it's what I have here. |
Faulty Thermostat or faulty installation
If it is a double skinned tank then surely it has the pocket type thingy for
one of those thermostats?At least then it will be in the standard place and no bits of left over insulation will be causing issues. Brian -- This newsgroup posting comes to you directly from... The Sofa of Brian Gaff... Blind user, so no pictures please Note this Signature is meaningless.! "alan_m" wrote in message ... On 18/04/2021 10:38, Chris B wrote: When moving the thermostat manually there is about a 5C "backlash" between switch on/off operations. Is that just the normal hysteresis of 5 to 10C? 1) a thermostat that didn't like being moved and has failed due to the disturbance It is probably a simple bi-metal strip with little to go wrong - except in moving it the installer has created a high resistance electrical connection - wire connected with screw through the insulation and only just making electrical contact. 2) Lack of thermal connection between the new tank and the thermostat (should there be any form of heat transfer compound between them) - I think this would be my first point of call if it was my tank) The strap may not be tight enough to hold the thermostat tightly against the tank. As far as I'm aware no compound is used between the tank and thermostat 3) Incorrect positioning of the thermostat Where is it positioned? The position may only be relevant to what temperature you set it to. Currently on by tank I have installed two (Ebay special) temperature probes/displays. One half way down the tank where the thermostat is fitted and one at the very top. While water is heating from cold there is a approx a 10C difference in reading with the top of the tank being hotter. 4) any other ideas. He has the maintenance contact with BG so they will be called in to fix it but he would like some confidence that the problem can be fixed. -- mailto : news {at} admac {dot} myzen {dot} co {dot} uk |
Faulty Thermostat or faulty installation
On 19/04/2021 07:50, Brian Gaff (Sofa) wrote:
If it is a double skinned tank then surely it has the pocket type thingy for one of those thermostats?At least then it will be in the standard place and no bits of left over insulation will be causing issues. Brian To answer all the questions at once, it seems to be foam covered (best equivalent picture I can find on the net is like this - although not this brand) https://www.wolseley.co.uk/product/g...ainless-steel/ The thermostat is definitely measuring (or trying to) the outside temperature of the tank and not the water. the fitters have cut out a section of foam about half a mm bigger than the thermostat (just like the thermostat fitment on my own clyinder). Might they have not fully cleared the foam from the side of the tank? -- Chris B (News) |
Faulty Thermostat or faulty installation
Chris B wrote:
Might they have not fully cleared the foam from the side of the tank? I think only you can answer that! Remove the strap and have a look. Tim -- Please don't feed the trolls |
Faulty Thermostat or faulty installation
On 19/04/2021 10:21, Tim+ wrote:
Chris B wrote: Might they have not fully cleared the foam from the side of the tank? I think only you can answer that! Remove the strap and have a look. Tim once you have made sure that all the foam has been removed from the cylinder where the thermostat makes contact, ensure that it makes good mechanical contact with the cylinder. if you have some thermal grease, the stuff used with CPU cooling 'radiators', put a smear of that on the tank before refitting the thermostat. |
Faulty Thermostat or faulty installation
On 18/04/2021 15:52, John Rumm wrote:
On 18/04/2021 11:08, Chris B wrote: On 18/04/2021 11:03, Tricky Dicky wrote: On Sunday, 18 April 2021 at 10:58:21 UTC+1, Chris B wrote: On 18/04/2021 10:55, Andy Burns wrote: Chris B wrote: Lack of thermal connection between the new tank and the thermostat Is it the strap-on with curtain wire, or shoved in a pocket/tube type? Its held on with a flat metallic strap about 5mm wide that goes right round the tank. -- Chris B (News) Whereabouts on the tank is it? It should normally be about 1/3 of the way up, too high and because hot water rises it will constantly monitor the water temperature where it is hottest so the bottom half of the tank does not warm up. Richard Well I haven't actually measured it but yes at a guess I would say its about 1/3 of the way from the bottom Is the tank insulated? Normally on a foamed copper cylinder, you would cut a pocket in the foam to allow the stat to make contact with the metal. Many of the SS cylinders are dual skinned with a metal outer cover over the insulation, which in turn is over the inner cylinder. This could make the stat unable to "feel" the change in temperature effectively, and also make it such that even a quite substantial temperature change in the cylinder is reflected in a small change visible to the stat. BG installers could not be so stupid...could they? |
| All times are GMT +1. The time now is 11:22 PM. |
Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
Copyright ©2004 - 2014 DIYbanter