Better programmable stat..

[wipeoutdude]

Is there a wireless programmable stat that has a small temperature range between on and off switch points?

What I mean is that the one I have (only one day and two on.off times) seems to have about 1.5C between on and off switch points so it starts to feel cold before it switches on again.. Is there a stat that is more accurate and will keep the temperature more constant?

Thanks..

 

[Rob]

What do you have?

Decent ones like a Honeywell will have Tpi which is designed to give more a constant temperature by firing the boiler on and off regularly

 

[wipeoutdude]

What do you have?

Decent ones like a Honeywell will have Tpi which is designed to give more a constant temperature by firing the boiler on and off regularly

I have a Siemens RDJ10RF.. According to the screen its switching on at 21C and off at 22.5C, it's set at 22C.. According to other thermometers (link on my Origan scientific weatherstattion clock thing) it's getting to about 20C before it comes on..

So either there is an issue with the location (in the hallway) or the stat has too large a temperature difference between on and off or the temperature sensing is very slow so it responds after the temperature has fallen lower than it thinks it is..

Are Honewell the only recommended ones? They seem a bit expensive but I suppose you pay for what you get..

Just had a search on TPI.. It looks interesting and maybe what I need to keep a stable temperature..

Would a TPI stat be suitable for a Worcester Bosch 32CDI compact combi boiler?

House is a 3 bed bungalow so no real need for multi-zones because it probably wouldn't be cost effective..

What wireless stats would you recommend?

 

[D_Hailsham]

According to the spec, the RDJ10RF has a switching differential of 1°C. However the display is only shows the temperature on 0.5°C steps.

How do you know your weather station is any more accurate?

 

[wipeoutdude]

According to the spec, the RDJ10RF has a switching differential of 1°C. However the display is only shows the temperature on 0.5°C steps.

How do you know your weather station is any more accurate?

I don't but I do know that it starts feeling decidedly chilly a while before it switches back on at 21C in the screen.. It then heats all the way to 22.5C on the screen before shutting off so on the stat its a 1.5C difference..

In reading the TPI ones seem to have a much smaller variance between on and off to keep a more constant temperature.. At least on paper it sounds like it makes it more comfortable..

 

[D_Hailsham]

In reading the TPI ones seem to have a much smaller variance between on and off to keep a more constant temperature.. At least on paper it sounds like it makes it more comfortable..

I have had a Honeywell TPI programmable thermostat for eight years and it keeps the house at a rock steady 21C.

 

[wipeoutdude]

In reading the TPI ones seem to have a much smaller variance between on and off to keep a more constant temperature.. At least on paper it sounds like it makes it more comfortable..

I have had a Honeywell TPI programmable thermostat for eight years and it keeps the house at a rock steady 21C.

Sounds like that's what I need..

What's the cheapest 7 day TPI enagles wireless stat you would recommend?

 

[D_Hailsham]

What's the cheapest 7 day TPI enabled wireless stat you would recommend?

Honeywell CM927.

 

[JohnD]

It's also probably the best

 

[D_Hailsham]

It's also probably the best

Of course! I don't do cheapest.

 

[wipeoutdude]

Fitted a Honeywell CM927 today and its switching on and off as it should to maintain the temperature but the boiler doesn't start burning immediately and by the time it starts it turns off again..

Boiler is a Worcester Bosch 32 CDI compact..

Is there a setting either on the stat to not turn off so fast or on the boiler to light the burner straight away?

I know it has to learn for a week but it's freezing in the house..

 

[dreadnoughtheating]

to the OP, it may be cheaper and quicker to nip to Primark and buy yourself a jumper?

Repeated firing/cooling ('cycling') of the system is detrimental to boiler component life and your fuel bill.

DH

 

[wipeoutdude]

to the OP, it may be cheaper and quicker to nip to Primark and buy yourself a jumper?

Repeated firing/cooling ('cycling') of the system is detrimental to boiler component life and your fuel bill.

DH

The TPI functionality in the thermostat is what is causing the boiler to fire for shooter periods. So this is as designed.

From the Honeywell site.
A TPI room thermostat works by continuously measuring the room temperature and calculating a difference between measured and target temperature. When the difference is greater than 1.5 degrees C (known as outside proportional band) it fires the boiler continuously. When the room temperature gets within 1.5 degrees C of the set point you have chosen on your room thermostat, the TPI software in the thermostat comes into action. It performs a series of calculations where it calculates how long the boiler needs to be fired to reach and maintain the set temperature. The calculation is based on the previously learnt characteristics of the room in which the controller is placed and the current measured temperature. This ‘smart’ firing of the boiler will mean that the boiler is fired just long enough to achieve the set temperature and no longer, thus increasing energy efficiency.

Just have to get the boiler and the stat onto the same page.

 

[scoobydo123]

I have had issues whereby the software of the boiler has a slow ramp up before putting any real heat out. Thus boiler waits 5mins before ramping up (flow temp not rising despite boiler fired at min rate) boiler finally fires at increased rate but logic of stat is at the max burn length so stat then removes call for heat. Not sure of the logic on your boiler. Think WB do a smart stat with WC not sure how effective it is sure someone will be along with experience.

 

[St0rmer66]

TPI is at odds with what you want from a condensing boiler IMO. Long burn, no cycling at as low a flow temperature as you can. TPI is switching it on and off all the time, fine on a non-condensing boiler I suppose.