My thermostat had ‘TPI’ functionality but I don’t understand how that can help me? Modern controls are designed to ensure that you get the best energy efficiency possible from your heating system. TPI (Time Proportional & Integral) is a feature in your room thermostat that ensures that your boiler fires for the shortest possible time in order to reach and maintain your room at the comfort level selected: How it works: Firstly, there are two things you need to understand about your room thermostat: It has a simple memory included in its software and it ‘learns’ how the room temperatures are achieved and maintained. It also has a basic calculation capability so that it can work with the learned data and current temperatures to predict how long the boiler needs to be fired for. TPI in action: 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. What you may notice: In normal operations you will not notice any difference in how your heating system functions. You may, if you listen carefully, hear the boiler firing for shorter and shorter periods as it approaches the correct temperature. When the room set point is reached, you will notice that the boiler is fired for short periods in order to maintain the temperature. The thermostat is calculating the rate at which the room is losing heat and topping up with the precise amount required to counteract it. There is normally an overshoot of around 0.5 degrees C when first reaching set point. This is because the thermostat tries to reach the set point as quickly as possible, after that it should settle at exactly the set point. The thermostat learns the room’s heat loss characteristics over the first week of operation and you will find that the initial overshoot is higher during that period. It will quickly learn the characteristics and become more accurate. Why is this different to non TPI thermostats? In non TPI thermostats (commonly older devices), the boiler will continually fire until it gets past the set point and then when the temperature drops to a specified amount below the set point the boiler is then fired again. This creates greater temperature fluctuations and less control of your comfort levels. Temperature variation with a TPI room thermostat Temperature Set point Time Proportional band Frequently Asked Questions TPI functionality explained
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My thermostat had ‘TPI’ functionality but I don’t understand how that can help me?
Modern controls are designed to ensure that you get the best energy efficiency possible from your heating system. TPI (Time Proportional & Integral) is a feature in your room thermostat that ensures that your boiler fires for the shortest possible time in order to reach and maintain your room at the comfort level selected:
How it works:
Firstly, there are two things you need to understand about your room thermostat:
It has a simple memory included in its software and it ‘learns’ how the room temperatures are achieved and maintained. It also has a basic calculation capability so that it can work with the learned data and current temperatures to predict how long the boiler needs to be fired for.
TPI in action:
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.
What you may notice:In normal operations you will not notice any difference in how your heating system functions. You may, if you listen carefully, hear the boiler firing for shorter and shorter periods as it approaches the correct temperature. When the room set point is reached, you will notice that the boiler is fired for short periods in order to maintain the temperature. The thermostat is calculating the rate at which the room is losing heat and topping up with the precise amount required to counteract it.
There is normally an overshoot of around 0.5 degrees C when first reaching set point. This is because the thermostat tries to reach the set point as quickly as possible, after that it should settle at exactly the set point. The thermostat learns the room’s heat loss characteristics over the first week of operation and you will find that the initial overshoot is higher during that period. It will quickly learn the characteristics and become more accurate.
Why is this different to non TPI thermostats?In non TPI thermostats (commonly older devices), the boiler will continually fire until it gets past the set point and then when the temperature drops to a specified amount below the set point the boiler is then fired again. This creates greater temperature fluctuations and less control of your comfort levels.
What you may notice:In normal operations you will not notice any difference in how your heating system functions. You may, if you listen carefully, hear the boiler firing for shorter and shorter periods as it approaches the correct temperature. When the room set point is reached, you will notice that the boiler is fired for short periods in order to maintain the temperature. The thermostat is calculating the rate at which the room is losing heat and topping up with the precise amount required to counteract it.
There is normally an overshoot of around 0.5 degrees C when first reaching set point. This is because the thermostat tries to reach the set point as quickly as possible, after that it should settle at exactly the set point. The thermostat learns the room’s heat loss characteristics over the first week of operation and you will find that the initial overshoot is higher during that period. It will quickly learn the characteristics and become more accurate.
Why is this different to non TPI thermostats?In non TPI thermostats (commonly older devices), the boiler will continually fire until it gets past the set point and then when the temperature drops to a specified amount below the set point the boiler is then fired again. This creates greater temperature fluctuations and less control of your comfort levels.
Temperature variation with a TPI room thermostat
Tem
pera
ture
Set point
Time
Proportional band
Frequently Asked Questions TPI functionality explained
What advantages does TPI give me?
As your boiler is working more swiftly to maintain your comfort levels, you can either be reassured that these levels can be maintained over the period or you can set a lower comfort level, safe in the knowledge that you are not going to drop below that point – thus saving you energy. Even a decrease of one degree will have an effect on your fuel bill.
Can TPI controls be used on all boilers?
Yes.
What is required of heating controls in the Building Regulations?
Building Regulations require that every system has a room thermostat, whether old or new. This will form an essential part of the Boiler Interlock, providing the means to switch the boiler off when it is no longer required. This performance can be enhanced using a TPI thermostat.
How can a system be improved from Building Regulation requirements?
By fitting a TPI thermostat, the boiler efficiency is improved, TACMA tests indicate that under steady state conditions this can be as much as 10%. This would be reduced by seasonal and operational losses.
But in addition, because the control is so much more accurate, the set point can be reduced, without loss of comfort, introducing extra savings.
What TPI room thermostats should I be asking to be installed:
Full details about all TPI Room Thermostats and TPI Programmable thermostats can be found at the Honeywell UK website www.honeywelluk.com. A full listing of all products with TPI control included is at the bottom of this document.
How can I get one of these products fitted?
We recommend that you use a qualified heating engineer. To find one in your area you can use the Find an Installer feature on our website. http://www.honeywelluk.com/find-an-installer/Find-An-Installer/
Frequently Asked Questions TPI functionality explained
Honeywell Control Systems, Honeywell House, Skimped Hill Lane, Bracknell, Berkshire RG12 1EB
Products this document covers:Room Thermostats:DT90E Wired Digital Thermostat: http://www.honeywelluk.com/products/Temperature-Controls/Temperature-TPI-Control/DT90E/DT92E Wireless Digital Thermostat http://www.honeywelluk.com/products/Temperature-Controls/Temperature-TPI-Control/DT92E/Y6630D Wireless Room Thermostat http://www.honeywelluk.com/products/Temperature-Controls/Temperature-TPI-Control/Y6630D/Room Thermostats within Sundial RF² Heating Control Packs 1, 2, 3 and 5 http://www.honeywelluk.com/products/Temperature-Controls/Temperature-TPI-Control/Sundial-RF2-Pack-1/http://www.honeywelluk.com/products/Temperature-Controls/Temperature-TPI-Control/Sundial-RF2-Pack-2/http://www.honeywelluk.com/products/Temperature-Controls/Temperature-TPI-Control/Sundial-RF2-Pack-3/http://www.honeywelluk.com/products/Temperature-Controls/Temperature-TPI-Control/Sundial-RF2-Pack-5/
Programmable Thermostats:CM700 Programmable Thermostat Rangehttp://www.honeywelluk.com/products/Programmable-Thermostats/Wired-Programmable-Thermostats/CM701/http://www.honeywelluk.com/products/Programmable-Thermostats/Wired-Programmable-Thermostats/CM707/CM721 1 Day Wireless Programmable Thermostathttp://www.honeywelluk.com/products/Programmable-Thermostats/Wireless-Programmable-Thermostats/CM721/ CM727 7 Day Wireless Programmable Thermostat http://www.honeywelluk.com/products/Programmable-Thermostats/Wireless-Programmable-Thermostats/CM727/CM900 Programmable Thermostat Rangehttp://www.honeywelluk.com/products/Programmable-Thermostats/Wired-Programmable-Thermostats/CM901-1-Day-Programmable-Thermostat/http://www.honeywelluk.com/products/Programmable-Thermostats/Wired-Programmable-Thermostats/CM907-7-Day-Programmable-Thermostat/CM921 1 Day Wireless Programmable Thermostathttp://www.honeywelluk.com/products/Programmable-Thermostats/Wireless-Programmable-Thermostats/CM921/CM927 7 Day Wireless Programmable Thermostat http://www.honeywelluk.com/products/Programmable-Thermostats/Wireless-Programmable-Thermostats/CM927/
Other Honeywell FAQ’sThere are a wide range of FAQ’s available on a variety of different topics. They can all be accessed via our website www.honeywelluk.com
Installation & User GuidesAll our Installation and User Guides for Honeywell heating control products sold in the UK can be found on the website www.honeywelluk.comFull details of our product range can also be accessed by visiting www.honeywelluk.com. Our products can be purchased from Professional Plumbing & Heating Merchants; Builders Merchants and other suppliers of professional products to the heating and plumbing industry across the UK.
Contacting Honeywell:Technical Support: Please note, we are unable to offer technical support to householders. Please contact your local installer for assistance.
08457 678999 (charged at local rates) +44 (0)1344 656125 (calls from outside the UK)Available from Monday - Thursday 09:00 - 17:00 Friday 09:00 - 16:00
This line is often busy during peak periods. If your enquiry is not of an urgent nature, please send an email, an automatic email form is available on the contact page on www.honeywelluk.com
Installer Training Courses : 01344 656352Please note that calls cannot be transferred between geographical numbers.
This FAQ sheet is for guidance only and at the time of production represented the latest information available to Honeywell from various sources. Honeywell reserves the right at any time and without notice to change any product, specification or any other information contained in this publication and cannot accept any responsibility for loss or damage arising out of any errors that may inadvertently be contained herein.
Frequently Asked Questions TPI functionality explained
EN1H-2581 UK01 R0513
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