Honeywell Evohome Insertion Sensor

[Mark8par]

We have a Megaflo CL210 Cyclinder along with Evohome hot water kit and have come across a problem. We have had solar installed and a Myenergi Eddi solar diverter for hot water but when the Honeywell was originally installed they removed the bottom thermostat probe and inserted the Evohome insertion sensor so we have no immersion in the bottom of the tank, only the top one remains. I have looked and there are no other dry pockets on the cylinder. So basically I am at a loss and wondered if anyone can help, I have tried putting it onto the side of the tank as suggested by Honeywell but its slow to respond and I dont think its getting the right temps.

 

[ShaunCorbs]

Have to cut the outer skin which is just a vanity cover and cut a piece of insulation out so the probe can contact the tank

Why can’t it stay where it was originally fitted ?

 

[Basher]

The Evohome hot water kit comes with both an insertion sensor and a strap on sensor module to fit the side of the tank in the usual way. If you have that latter sensor it would make sense to use it following ShaunCorbs advice as above.

 

[Mark8par]

Have to cut the outer skin which is just a vanity cover and cut a piece of insulation out so the probe can contact the tank

Why can’t it stay where it was originally fitted ?

Thanks for the reply, basically it was in the pocket that should house the immersion thermostat so I currently have no bottom immersion and the solar diverter only heats the top part. I wanted to get the most out of it and have the solar heating top and bottom as it should. I did move it so it was touching the tank and applied some thermal past but it was just very slow at reacting. I spoke to megaflo and they did say two sensors could go in the same pocket but it won't fit.

This is the tank and im led to believe the strap on sensor is not designed for this type.

 

[Mark8par]

Honeywell did say I can add the sensor this way (as you suggested). I could always put it here and stick it using thermal paste on the tip and tape to keep it in place and the heat around it, what do you think?

 

[ShaunCorbs]

If you pull the running stat eg boiler control you should be able to put both of them in that pocket

 

[Basher]

I believe the Honeywell insertion sensor is a standard 10K ntc resistor, so if the problem is that your existing one is physically too big, it might be possible to swap it for an alternative.

I would have thought that fitting the sensor as per the diagram you posted, with firm contact, physical support and liberal application of thermal paste would provide satisfactory operation. You say it's slow to react, but the rate of rise of temperature is going to be slow anyway, so I wouldn't think that should be a major problem. You can provide an offset by turning up the temperature setting to achieve the desired water temperature !

ShaunCorbs and I were originally thinking you might be willing to cut a hole in the tank cladding and insulation, in an appropriate place to fit a sensor, which is why I mentioned the strap on sensor that is in the kit.

 

[Mark8par]

Thanks for your help, will have another look tonight and see what I can do.

 

[Mark8par]

I located the sensor as per the diagram but with a little more thermal paste and made sure it was firmly in place with a cable tie, seems to be working better and I can now have the lower stat added and run the solar diverter as it should. Thanks for your help, it's very much appreciated.