Modern room stats?

[londonboy123]

Do modern room stat's / digital room stats that do not require the neutral wire to make an anticiaptor work - have a resistor instead which is operated by a battery? i take it the resistor is a thermistor actually though?

Just been bugging me today as I was thinking of chainging but not 100% sure yet what one to buy.

 

[Paul Barker]

they just don't anticipate as there it serves no useful purpose to do so.

 

[simond]

The heater (anticipator) is used to heat the bimetallic strip in old school room thermostats.

This helps reduce hysteresis, which is where there is a big swing between the air temperature going up and down due to overshoot.

The heater needed a neutral connection.

In modern thermostats not using a bimetallic sensor, this form of trimming the response is not required. The software in the stat reading the thermistor makes allowances for hysteresis. The thermistor also has a faster response time.

The Honeywell CM range are currently my favourite; easy to use, easy on the eye, and accurate and reliable.

 

[D_Hailsham]

i take it the resistor is a thermistor.

Got it in one!

they just don't anticipate as there it serves no useful purpose to do so.

It's not that the anticipator serves no purpose but that one is not necessary if the temperature sensing element is a thermistor.

In the days of mechanical thermostats, when the sensing element was a bi-metallic strip, the temperature differential between open and close was as much as 10C - not very useful for central heating but OK for cylinder stats.
The anticipator resistor, which is wired so that it carries current only when the stat contacts are closed - I wonder how many stats were wired back-to front - warmed up the innards of the stat faster than it would without the anticipator; which meant that the stat would shut off earlier, This reduced the temperature differential to 1 or 2C.

 

[JohnD]

my new Honeywell Room Stat seem to maintain the temp within about 1/2 a degree up or down of the setting (I put a thermometer on top of it to check)

though I did have to recalibrate the knob by pulling it off and pushing it back on the splines different (maybe it got disturbed when being fitted)