Honeywell DT90E thermostat setting up help needed

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Today i purchased a a Honeywell DT90E Thermostat to replace a dial type Honeywell thermostat. I swopped then over without much hassle but the DT90E was showing a room temperature of 18 degrees when i was around 12 degrees. Is there some way of calibrating the room temperature.
The new thermostat seems to be cutting the boiler in and out with no apparent rhyme nor reason as the room temperature doesn't seem to be anywhere near the temperature set.
So could somebody give me in laymans terms how to set it up as the very basic instructions obviously aren't basic enough for me.

Thanks in advance Ben.
 
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Hi,

The stat is going on/off as it is a TPI stat, if you register at the Honeywell site and look at their faq's there is a pdf about it.

But basically its going on/off to edge the room temp towards the wanted temp, bit disconcerting at first, but the idea is that it should stop the room temp overshooting the wanted temp. It cycles on/off 6 times an hour once its within 1.5 degs ish of the wanted temp, more than 1.5 degs below and it just stay on all the time.

Ermm with regards to the calibration you can do that through the installer mode. Have you got the MIs still, it says somewhere on there. What are you measuring the DT90E against? Is it the old stat?

Hope that helps.
 
Thanks Tripty.

I have the instructions, what i don't understand is the difference between:
Set temperature, inquiry
Set temperature, adjustment
Heat/cool change over

The parameters i have to change in the installer mode are:
Minimum on/off time
Cycle rate
Proportional band width
Temperature measurement offset
Upper set point limit
Lower set point limit
Eco temperature
Heat/cool change over
Offset point adjust
Electric heat
Reset parameters

This has a lot more adjustment and settings that i didn't have with my dial and don't understand.
 
Set temperature, inquiry
The "set temperature" is the temperature you want, e.g 21C.

The thermostat will normally show the actual room temperature.

Press the Inquiry (down) button so you can remind yourself of what the set temperature is.
Set temperature, adjustment
This is so you can change the set temperature to meet your requirements.
Heat/cool change over
The thermostat can also be used with air conditioning and other cooling devices. It then has to work the other way round - turn the cooler on when it gets above the set temperature. Just leave it on "heat"

Minimum on/off time
Cycle rate
These are only changed if you have an oil fired boiler. leave them as set.

Proportional band width
Leave at 1.5C

Temperature measurement offset
If the thermostat is located in a very hot/cold location you can compensate for this by changing the offset. Say you want the temperature to read 21C but when it does the thermostat only reads 19C. You can change the offset so the thermostat shows 21C. This stops people looking at the stat and saying: "No wonder I'm feeling cold! It's only 19 degrees in here" and they turn the stat up two degrees, warming the house up to 23C!

Upper set point limit
Lower set point limit
Upper set point prevents any one setting the house to a ridiculously high temperature. Set it to 25C
Lower set point is the opposite - stops anyone turning the temperature too low. Useful if there are elderly people living in the house.

Eco temperature
This allows you to set a different temperature for a specific time; it saves having to adjust your timer. For example, say you are going out for the day, you could set the Eco temperature to 10C for six hours when you leave. The heating will go off (assuming the house is above 10C) and the house will cool down. But if it cools below 10C the heating will come on to maintain 10C. After six hours the heating will go back to 21C.

Reset parameters
Sets the thermostat back to the factory settings.
 
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Minimum on/off time
Cycle rate
These are only changed if you have an oil fired boiler. leave them as set.


I have this stat on an oil boiler and its making the boiler kick in very often, even when it reaches the desired temperature.

What are the ideal settings for the oil boiler?

And, what does cycle rate and on/off time actually mean?
 
Read the Honeywell FAQ on TPI

TPI uses the cycle rate as the base for deciding how long the boiler need to be on; for oil boiler the cycle rate is 3 cycles per hour (20min/cycle). So if TPI says the boiler needs to be on for 50% of the time it will be on for 10 minutes then off for 10 minutes. The nearer the actual temperature is to the set temperature, the less time the boiler will be on, It may even stay off for the whole of a 20 minute period.

Minimum time is the least the boiler will be on, so if TPI says 10% (2 mins) but the minimum on time is 5 minutes, the boiler will stay on for 5 minutes.

Honeywell's recommended settings for an oil boiler are:

On time (Ot) = 4
Cycle rate (Cr) = 3
 
I have recently installed Honeywell DT90E in my flat and it was working okay until a yesterday. Now when I switch on thermostat it shows 18 deg and when I push up arrow to try and raise temp setting, it just flashes 35 degrees a couple of times and then goes back to 18. Same thing happens if I press down arrow. Any suggestions?
 
When you say "switch on the thermostat", I assume you mean you hold the bottom button down for a couple of seconds.

What else appears with the 18?

What else appears with the 35?
 
Yea hold the button down for a couple of secs, the flame on right hand corner comes on but the temp doesn t change, if i try to change it it just goes to 35 deg flashes and then goes back to 18 . I ve checked the boiler and it appears to be firing but for some reason the temp won t go above the 18 deg. Thermostat is a few days old so don t think it s malfunctioned but i guess that s only explanation?
 
18 is the default ECO temperature.

What happens if you press the green button?

Do you have the User Instructions and Installation Instructions? Have you read them?
 

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