ESi Electronic Hot Water Cylinder Thermostat – ESCTDE/B – Part 1

UPDATED -27 April 2022

Background

In order to save energy and better regulate the temperature of my domestic hot water in my Santon Premier Plus unvented cylinder, I decided to install a ESCTDE/B Electronic Dual Cylinder Thermostat manufactured by ESI Controls, I bought online from PlumbNation.

box

Installation

The ESCTDE/B has two thermisters, one for the temperature reading and control, the other is for over-temperature trip and is set for 80℃, I must have a big problem if this operates as my boiler output temperature is set to 68℃.

thermistor

Fortunately the Santon Premier Plus has a spare dry thermostat pocket which the thermistors are a perfect fit.

pocket

I marked the location of the thermister pocket on the outside of the cylinder cover and offered up the ESCTDE/B back-plate and marked the centre hole.  I’m not sure what the ESCTDE/B is specifically designed to fit, but the rear fixing was perplexing and I didn’t want to modify the casing of the unit in case I invalidated the warranty.

back
Rear fixing arrangment

I used a cut down 20mm Female Adapter as a center bush, this was cut to size and fixed to the front cylinder cover.

bush
20mm Female Adapter
bush
Cut down female adapter used as a through cover fixing method.
bush
Fixing bush installed.
bush
Inside cover showing bush and thermostat pocket.

ESCTDE/B fixed to the bush with the three back-plate screws and as the female adapter has a serrated edge, it holds very well, the existing cylinder thermostat was turned up to position 5 which is 72℃, I have left this in circuit as another backup to over-temperature, as mentioned earlier, my boiler output temperature is set to 68℃, so only under a fault condition should this protection operate.

fixed
Indirect temperature setting and top view of fixing to ESCTDE/B.
Cover
Thermistors sliding into cylinder pocket.

Connections

NOTE – The mains supply to the ESCTBE/B MUST be from the same source as the heating systems programmer, this will ensure that there is only one point of electrical isolation for safe working.

I used 1mm 4 core and earth from the ESCTDE/B to the heating connection box, the ESCTDE/B does not have an earth connection, so this wire was parked, the unit requires a permanent 230v feed, the temperature calling relay changeover contacts are NOT volt free, although they are simply wired in series with the existing cylinder thermostat.

If the Legionella setting is active on the ESCTDE/B, the unit will automatically switch 230v to the Domestic Hot Water motorised valve (NOTE- this overrides any programmer settings), which in turn will bring on the heating, the output from the ESCTDE/B will remain on for 1 hour when the tank temperature is above 61℃.

As the bending radius of the connecting wires within the unit is quite tight, I used ferrules on the end of the wires, this ensures that no ‘whiskers’ can cause problems later.

wire
Ready for wire stripping.
wires
Insulation removed and conductors twisted.
wire
Bootlace ferrule pushed on.
wires
Bootlace crimped and job done.

Conclusion

Finished installation all working, as my hot water system is directly fed, (no header tank), I did not need to enable the ‘disinfection mode’, this mode increases the water temperature to 61℃ for 1 hour to kill Legionella, however, as the feature exists, I set it to activate once per week.

finished
We had been away for a few days hence the water temperature was showing 21℃, the unit was initially set for 48℃ and the Red LED shows the cylinder is calling for heat.
finished
Picture showing wiring from ESCTDE/B to heating terminal box and the tank temperature now reached the set-point of 48℃.

Problem

Apologies for not updating this blog and a recent comment made me revisit this, so thank you.

I have decide to make a Part 2 to the ESi showing how I addressed the problem of the the heating coming on outside of the scheduled time due to the ‘legionella’ setting being on.

Part 2 is HERE.

19 thoughts on “ESi Electronic Hot Water Cylinder Thermostat – ESCTDE/B – Part 1”

  1. Actually, the contacts are not volt free on this product as I just found out when I tried to fit it today… Maybe my product is faulty but it trips my house rcd breaker every time it calls for heat. Weirdly I get 120v across the common and n/o terminals when calling for heat. I was expecting that it would at least provide 240v on the n/o when calling for heat even if it doesn’t connect common and n/o

  2. You are correct, it does not have volt free contacts and I’ll change my blog as that is what I assumed until the heating came on outside of the programmed time.

    Investigating what was going on my conclusion confirmed by the manufacturer, was that the product sends 240v to the motorised valve, which in turn operates the heating when the devices has been set to a ‘disinfect’ schedule, in this event the devices internal clock asks for heat to kill Legionella, this output remains active for 1 hour once the tanks water temperature is above 61C.

    The disinfect mode can be set from once a day, to seven days a week, however, the time of when it does this can’t, hence the boiler woke me when I knew it was outside of the programmed time.

    One thing to ensure is that the supply to unit is shared with the boiler so their is one point of isolation, otherwise their is a shock risk if working on heating system wiring and the ESCTDE/B calls for heat!

  3. I’m trying to install this cylinder thermostat to my unvented cylinder. Hot water and central heating are connected to a Honeywell programmer and wiring box. Any chance a photo could be posted showing how the ESCTDEB has been wired to the control box? Wiring examples for a S plan are confusing and cables colours are not specified. Thanks

  4. Hi and thanks for checking out my blog.

    A picture wont help much as the installer could have used different colours or configurations from mine, the way I did it was as follows:

    Using multi-core cable to ESCTDEB – Live = Brown
    Neutral = Blue
    Common = Grey
    Hot Water ON = Black

    In the wiring center find a permanent live and neutral and connect the Brown & Blue.

    Locate the BROWN wire in the wiring center from the Hot Water motorised valve, disconnect this wire and connect it to the ESCTDEB Black wire.

    Where the Brown wire was originally connected, now connect the Grey.

    This should all now work, but I do not accept any responsibility if it goes wrong or if you get hurt.

  5. Unfortunately wiring the ESCTDEB thermostat this way has not worked for me.

    It seems that the wiring center needs something to the connected to the common port of the CYL stat for the Hot Water valve to be triggered.

    Thank you very much for your help anyway

  6. Hi,

    The existing cylinder stat on my system was disconnected and replaced with the ESCTDEB and the two themistors where pushed in the cylinders dry pocket.

    The two wires which went to my original cylinder stat now go to the ESCTDEB common and switched contact and I ensured that the 240v feed to the ESCTDEB came from the same permanent supply which goes to the motorised valves, if it is set up this way, I’m unsure as to why its not working for you.

    The switched live to the motorised valves comes from the programmer when hot water is selected and is switched by the cylinder stat when the water is hot enough, the ESCTDEB does exactly the same job of switching the live to the motorised valve, with the addition of overriding the programmer if the legionela setting is used.

  7. Hi, I have the above mentioned cylinder stat installed however I have an issue which i dont understand. My cylinder stat temperature shows a lower temperature to the actual water temperature, e.g today it shows 20 degrees, however the temperature from the tap is around 45 degrees which is what I have set it to from the stat.

    Any ideas what the problem could be please?

    Thank you.

  8. Hi,
    To be honest I would be guessing as that is a large variation, you could remove the thermister from the dry pocket and check that it is reading correctly against a known temperature source, that would prove, one way or another, that the sensor is good/bad.

    One thought could be that the outside of the dry pocket has scaled up insulating the sensor from gaining a true reading which is worst case, you could also try using heat transfer paste, like that used on heat sinks, on the sensor in the the dry pocket (or get it in contact with the cylinder wall), which may help gaining a more accurate reading.

    Let me know how you get on.

  9. I have one of these fitted in my home.

    Have been really confused recently as the water heater has been kicking on during the middle of the night. The controllers are set to off for heating , its June and hot water on demand.

    The thermostat is set to 50 deg C but the display reads 59 deg C and the red LED is on calling for heat.

    I read the bit about the boost to kill bacteria, when is this supposed to kick in, I’m Tempted to disable and see if this effects it.

  10. Hi and thanks for checking out my blog.

    I was initially baffled as to why my hot water was calling for heat at random times outside of the scheduled setting, I contacted ESi and they confirmed my suspicion that the ESCTDE/B is causing the issue and this is the normal operating condition.

    It appears that when the 60 deg legionella setting is enabled and the time between cycles set, the ESCDE/B will, when the internal countdown triggers, fire the boiler calling for the hot water to reach and maintain 60 deg for 1 hour before being satisfied. The internal timer now resets, and the countdown timer to the next cycle begins, irrespective of the time of day.

    I was disappointed by this and had to disable the legionella function as, in my case the boiler was coming on in the night :-(.

    When I bought the electronic thermostat, I assumed that, when the schedule for hot water was active, the ESCTDE/B was clever enough to automatically increase the demand temperature from the set point for the required duration when the day timer had counted down.

    I have updated the blog to include a circuit which I will try to see if I can get a workaround

  11. I have changed my dual manual tank thermostat as the original failed.
    I would like to know if it can be recalibrated as the dial appears to be out to achieve 56c it must be set at 40c.
    If it’s set at 55c it achieved 69c.

  12. Hi Harvey,
    In answer to your question, I’m not sure if the unit can be recalibrated to offset the error your seeing, contacting ESi technical would be the best bet.

    I think the problem is that the thermistors sit inside a ‘dry pocket’ within the cylinder, try using heat transfer compound/thermal paste in the pocket to see if that will improve accuracy.

    Let me know how you get on.

  13. In my experience, the reason that thermostat setting is less than actual water temperature is that the sensors on the stat are not properly picking up the HW temperature deep inside the cylinder. This is usually due to the probes not being long enough to reach deep inside the pocket usually fitted to modern unvented cylinders (mine is 180mm deep with 30mm protruding outside cylinder, and another 50mm actually inside the insulation, leaving 100mm protruding into the HW inside. Most of the dual thermostats on the market only have 100mm long sensors, so they will only be 20mm into the ‘HW’portion of the pocket. Another reason is that the sensor diameter is much less than the 18mm I/D of the pocket, so really poor sensor contact. If you have a decent pocket fitted, then make sure you get a stat with nice long sensors and also smear some ‘heat conducting grease’ all over them and plug the senor pocket with blu-tac or similar before fitting the stat controller box to the pocket.

  14. I replaced a defective ESI.. ESCTDEB thermostat
    ( 3 years old .. h/w permanently on) on my unvented cylinder with an identical model. It worked perfectly for four weeks and then died no response no light etc.
    reset didn’t do anything . Another ESCTDEB fitted and working fine .. anyone else had issues with this ESI model or am I doing something wrong..

  15. Hi,

    I think you have been unlucky, maybe send the other unit back to manufacture to see what they say, could have been a bad batch?

  16. Yes am going to send back and ask for a replacement as a stand-by.. it only takes 10 mins to change over but waited a week for this one to arrive by EVRI

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