Immersion Thermostat wire burns out

[johntheo]

With reference to the 20A control stat I discovered this while searching for its technical specification: ​

Cotherm TSD01106 Thermostat​ Cotherm TSD01106 20A Control Thermostat A Cotherm brand adjustable control thermostat with a range of approximately 5°C - 85°C. The TSD01106 is a rod thermostat with single pole break-on-rise action rated at 20A 240v. The stem (rod) is 265mm long and 7.5mm in diameter making suitable for use in all standard 280mm x 8mm (11" x 5/16") thermostat pockets. It is ideal for use in commercial products for direct control of single phase loads up to 3kW or to operate a contactor for higher loads or three phase applications. Note: This device does not include a safety cut-out and is only designed to control the water temperature. This thermostat is NOT SUITABLE for DOMESTIC without there bring an additional a safety cut-out as required by law. Condition: New and unused in original manufacturer's packaging.

Delivery​ Orders received before 2pm Monday to Friday will be despatched the same day. Orders received after 2pm Friday, Saturday or Sunday will be dispatched the following Monday. Orders received after 2pm will be treated as having arrived the following day. All goods are dispatched, professionally packed, on a signed for service. In most cases our carrier can leave the goods in a safe place, or with a neighbour for no extra charge. Should you require this service please detail it in the notes when placing your order together with a contact telephone number. If you do not receive the goods within three working days (Monday to Friday) of placing your order we would ask that you contact us. We can then investigate the problem and authorise a replacement where necessary. If you wish to purchase more than one listed item, we can usually ship these together for a reduced overall carriage charge. In this instance please contact us before paying so that we can advise you of the combined carriage charge. Hours​

A bit strange because they have a 4kw (at 230V) element here with a ST7 thermostat which doesn't look anything special, no mention of a contactor.
The OP has a 4kw element which he measured at 14 ohms which is more than likely 4kw @ 240V = 3.8kw @ 230V or 16.5A and is using a 20A stat!.

14” TITANIUM SINGLE IMMERSION ELEMENTS - 4KW - 1 3/4”BSP - 230V - SIDE ENTRY WITH STAT - TSDR7

IDL091009SC 091009SC Heating and Ventilation Ideal Elements Domestic & Industrial Elements Heating and Ventilation Water Heating Immersion 4KW Ideal 230V

www.eurosales.ie

 

[marconi]

Today I sent a question on current rating and immersion element power to the Backer Electric Company Limited. They confirmed as Johntheo mentioned above that their Backer stats rated 20A can indeed directly control a 4kW IH element. Whether other makes of stat can is another matter.

brixtonia: 1. The question about the rcd is to see whether the 4kW element albeit a new one is leaking current to earth - unlikely if new but maybe this is a cause of overcurrent.

2. I'd love to have some pictures of the installation to study. Are push on spade terminals used for any of the connections? Are they bare metal or shrouded types?

3. What is the supply voltage?

4. Does the installation have a large solar pv system feeding into the grid which might be elevating the local mains voltage? Are the large solar pv arrays nearby which might be raising the supply voltage?

5. Forgive me - is the wiring definitely 2.5mm2 csa?

6. The 16A safety stat is under-rated.

7. What temp do you have the control stat set at?

8. What is the length of the link between the control and safety stats?

Probably enough for now. But some images of the point of failure on the control stat external terminals would be useful to see.

 

[brixtonia]

Today I sent a question on current rating and immersion element power to the Backer Electric Company Limited. They confirmed as Johntheo mentioned above that their Backer stats rated 20A can indeed directly control a 4kW IH element. Whether other makes of stat can is another matter.

brixtonia: 1. The question about the rcd is to see whether the 4kW element albeit a new one is leaking current to earth - unlikely if new but maybe this is a cause of overcurrent.

2. I'd love to have some pictures of the installation to study. Are push on spade terminals used for any of the connections? Are they bare metal or shrouded types?

3. What is the supply voltage?

4. Does the installation have a large solar pv system feeding into the grid which might be elevating the local mains voltage? Are the large solar pv arrays nearby which might be raising the supply voltage?

5. Forgive me - is the wiring definitely 2.5mm2 csa?

6. The 16A safety stat is under-rated.

7. What temp do you have the control stat set at?

8. What is the length of the link between the control and safety stats?

Probably enough for now. But some images of the point of failure on the control stat external terminals would be useful to see.

Firstly to answer your questions:

1) Not on an RCD.
2)

3) 240
4) No solar PV.
5) That's what I specified when I bought it.
6) yes the 16A cut out stat is underrated - nevertheless it has been working for about 4yrs.
7) Temp control set at 75-80C as per manual supplied with UFH and Thermalstore.
8) 100mm approx.

 

[brixtonia]

This may be resolved although I am not sure why.

I purchased a Sunvic VK4351 20A rod thermostat which I mistakenly believed had a safety cutout but did not - it is just a straightforward 20A stat. I fitted this with the 20A cotherm TSD01106 stat (mains>sunvic>cotherm>immersion) which is the same as the one supplied with the immersion. (I appreciate that this is a little pointless but I wanted to see if having removed the 16A cutout things worked OK). The connection into the 20A Cotherm quickly began to overheat as before and melt the insulation. It also cycled perhaps 10s on 40s off as before.

So I removed the Cotherm and replaced it with the Sunvik VKL2352 cutout with manual reset (the 16A cutout which has been working fine for a couple of years). So (mains > new sunvic 20A stat > old sunvic 16A cutout > immersion). And it's been working fine for a week.

I was struggling to find an 11" (or 7") rod stat which was 20A rated and had a variable temp range up to 80C and an inbuilt safety.

It seems to be the Cotherms which have been causing the problems.

 

[brixtonia]

With reference to the 20A control stat I discovered this while searching for its technical specification: ​

Cotherm TSD01106 Thermostat​ Cotherm TSD01106 20A Control Thermostat A Cotherm brand adjustable control thermostat with a range of approximately 5°C - 85°C. The TSD01106 is a rod thermostat with single pole break-on-rise action rated at 20A 240v. The stem (rod) is 265mm long and 7.5mm in diameter making suitable for use in all standard 280mm x 8mm (11" x 5/16") thermostat pockets. It is ideal for use in commercial products for direct control of single phase loads up to 3kW or to operate a contactor for higher loads or three phase applications. Note: This device does not include a safety cut-out and is only designed to control the water temperature. This thermostat is NOT SUITABLE for DOMESTIC without there bring an additional a safety cut-out as required by law. Condition: New and unused in original manufacturer's packaging.

Delivery​ Orders received before 2pm Monday to Friday will be despatched the same day. Orders received after 2pm Friday, Saturday or Sunday will be dispatched the following Monday. Orders received after 2pm will be treated as having arrived the following day. All goods are dispatched, professionally packed, on a signed for service. In most cases our carrier can leave the goods in a safe place, or with a neighbour for no extra charge. Should you require this service please detail it in the notes when placing your order together with a contact telephone number. If you do not receive the goods within three working days (Monday to Friday) of placing your order we would ask that you contact us. We can then investigate the problem and authorise a replacement where necessary. If you wish to purchase more than one listed item, we can usually ship these together for a reduced overall carriage charge. In this instance please contact us before paying so that we can advise you of the combined carriage charge. Hours​

Interesting - especially as this was the stat supplied with this 4kW immersion.

 

[marconi]

Good evening from London. Thank you for the information. That element has 3 separate elements wired in parallel. Could you give me manufacturer and part number for it please so I can learn more about it?

 

[brixtonia]

Good evening from London. Thank you for the information. That element has 3 separate elements wired in parallel. Could you give me manufacturer and part number for it please so I can learn more about it?

Made in Italy I believe.

 

[brixtonia]

With reference to the 20A control stat I discovered this while searching for its technical specification: ​

Cotherm TSD01106 Thermostat​ Cotherm TSD01106 20A Control Thermostat A Cotherm brand adjustable control thermostat with a range of approximately 5°C - 85°C. The TSD01106 is a rod thermostat with single pole break-on-rise action rated at 20A 240v. The stem (rod) is 265mm long and 7.5mm in diameter making suitable for use in all standard 280mm x 8mm (11" x 5/16") thermostat pockets. It is ideal for use in commercial products for direct control of single phase loads up to 3kW or to operate a contactor for higher loads or three phase applications. Note: This device does not include a safety cut-out and is only designed to control the water temperature. This thermostat is NOT SUITABLE for DOMESTIC without there bring an additional a safety cut-out as required by law. Condition: New and unused in original manufacturer's packaging.

Delivery​ Orders received before 2pm Monday to Friday will be despatched the same day. Orders received after 2pm Friday, Saturday or Sunday will be dispatched the following Monday. Orders received after 2pm will be treated as having arrived the following day. All goods are dispatched, professionally packed, on a signed for service. In most cases our carrier can leave the goods in a safe place, or with a neighbour for no extra charge. Should you require this service please detail it in the notes when placing your order together with a contact telephone number. If you do not receive the goods within three working days (Monday to Friday) of placing your order we would ask that you contact us. We can then investigate the problem and authorise a replacement where necessary. If you wish to purchase more than one listed item, we can usually ship these together for a reduced overall carriage charge. In this instance please contact us before paying so that we can advise you of the combined carriage charge. Hours​

Can you provide a link to this info? I'd like to share it with the supplier.

 

[brixtonia]

Incidentally, my supply is single phase so I guess that must have been the problem. Why would single vs three phase make a difference to the amp rating of the stat?

 

[brianmoooore]

If this was fed by a three phase supply, you wouldn't be able to control it directly with a single 'stat, which possibly explains why there appears to be two 'stat pockets.
You could also fit two stats with your single phase supply, controlling two elements with one, and the third with the other. This would bring the 'stat current well within the limits of a 16A version.

 

[marconi]

Can you provide a link to this info? I'd like to share it with the supplier.

I will see if I still have it.

 

[marconi]

Cotherm TSD01106 Thermostat - 280mm Stem, 20AMP | eBay - https://www.ebay.co.uk/itm/183661179944

It was this company advertising on ebay to sell the control stat that included the advice I pointed out in red. Perhaps email or call them for further information. If you learn more from this company on why the advice was given would you mind sending another post so others can know too please?

Regards
Marconi

WH (Water Heating) Co Ltd
Trevor Guy
2 Horsecroft Place
Harlow
Essex
CM19 5BT

Phone: 01279641722
Email: [email protected]

 

[johntheo]

Total resistance was measured at 14 ohms so 3 elements in parallel = approx 42 ohms/element but total current through stats is still the same, "4kw" immersion is 3.779kw @ 230V = 16.43A. or 4.114kw @ 240V = 17.14A so new stat is just doing what it's supposed to do and not burning out?. (single phase supply).

 

[brixtonia]

Wrote to supplier who replied:

The thermostats are designed for single phase elements, or three phase elements wired in single phase configuration up to 4kw.
To use with elements wired in three phase configuration, the thermostat needs to switch a contactor.
So, the thermostat you received with your 4kw element is suitable for single phase use.
The 4kw element is rated at 17.5a and the thermostat is rated at 20a.
We have never had a thermostat burn out. Please check your wiring as the problem is not with the thermostat.

However, it seems to contradict the instruction leaflet (not received with the immersion - emailed after) which seems to say that higher loadings than 3kW need a contactor?

 

[Avo Mk8]

I'm suspicious of the binary pricing of the Cotherm thermostat in the marketplace - around £12 general outlets, around £30 from reputable suppliers, one of whom publishes this footnote with the details of the stat:

SANTON S8203 THERMOSTAT TSD01106 11" 5-80'C COTHERM
This part is compatible for use with:

• Santon DF range R25/R45/R70/R115

PLEASE BE AWARE: This a genuine Heatrae Sadia manufactured part, unlike many of our competitors.

The genuine part seems to have a 'properly approved' 20A resistive rating, so I would have thought capable of handling the 4kW load. Perhaps your leaflet covers the, dare I say, " Chinese Export" version