How to Read a Heat Cost Allocator: Display, Values and Calculation

Why Is the Allocator Value Not in kWh?

A heat meter measures the flow rate of the water entering the apartment and the supply–return temperature difference; it shows the result in an energy unit such as kWh or MWh. A heat cost allocator, on the other hand, measures the surface temperature of the radiator and, in two-sensor operation, also the room temperature. From these measurements it accumulates a unitless number representing the share of heat given off by the radiator.

The display of the Q caloric 5.5 shows a number of up to five digits (00000–99999) without a unit. On its own, this number does not answer the question how many kWh of heat were used; it only becomes meaningful when compared with the values of the other allocators in the same building. That is why allocator values from two different buildings cannot be compared with each other. Turkish regulations refer to these devices as heat meters as well. For the difference between the two devices, see our guide What Is a Heat Meter? and our Heat Cost Allocators category.

What Does the Qundis Q caloric 5.5 Display Show?

The Qundis Q caloric 5.5 on our site has a liquid crystal (LCD) display. In normal operation the values are shown automatically and in turn in a loop; Qundis's data sheet and user brochure do not state that a button must be pressed for reading. The order and durations below are taken from the manufacturer's data sheet. One cycle takes about 14 seconds.

What does the code on the last display tell you?

The code on the last display of the cycle summarizes how the device is programmed:

• First two letters, radio mode: FS means walk-by reading and reading with a fixed receiver (AMR) in S-mode. FC indicates the same two reading types in C-mode, F0 only fixed-receiver reading in C-mode. AL indicates that the device has no radio.
• Digit after the hyphen, measuring algorithm: Can be 2, 3 or 4. Shows which calculation method the device uses.
• Last digit, number of sensors: 1 means single-sensor, 2 means two-sensor measurement. In single-sensor operation the room temperature is assumed to be a fixed value; in two-sensor operation the actual temperature difference between the radiator and the room is measured.

How to Read the Allocator Display Step by Step

1. Look at the display and wait for the cycle to return to the start. You do not need to press a button or touch the device.
2. Note the number that has no letter in front of it. This is the current consumption value.
3. Note the date shown with MD and the number shown immediately afterwards with M. These are the due date and the value stored on that date.
4. Do not confuse the checksum starting with c and the rating level starting with k with the consumption value.
5. Repeat the process for each radiator in the apartment and write down which room's radiator each value belongs to. According to Qundis, two allocators may be fitted to large radiators; on such a radiator, read both.

The value that stays on the display longest is the five-second due-date value; the current value is shown for only two seconds. Taking a photo of the display is a practical way not to confuse the two. The apartment's consumption is found not from a single device but from the total of the allocators on all radiators.

Why Was the Value Reset? How the Due Date Works

The due date (target date) is the day on which the annual value is stored; it can be programmed into the device before commissioning. In Qundis's examples this day is 31 December, but another day can also be programmed.

According to Qundis's user brochure, allocators are usually reset on the due date, and the current value shows the consumption accumulated since the last due date. Depending on its settings, the device can also continue counting without resetting. Resetting is not a loss of data: the total of the previous period is stored as the due-date value and continues to appear on the display with the M sign.

If the current value is lower than your previous reading, first check whether the due date has passed. As consumption values, only the current value and the due-date value appear on the display. Monthly values are not shown on the display; they are sent to the reading system in the radio telegram.

How Does the Reading Affect the Bill?

The number on the allocator is not an amount of money; it is used to determine your apartment's share of the heating cost. How this allocation works depends on national regulations. As an example, in Türkiye it is governed by the Regulation on the Allocation of Heating and Domestic Hot Water Costs in Central Heating and Domestic Hot Water Systems. Under this regulation, in apartments with allocators one device is fitted to each radiator group, and the apartment's consumption is found by reading all devices. The calculation uses the value read on each device and the total of the values read on all devices in the building.

Radiator factor (rating factor)

A large panel radiator at the same temperature gives off more heat than a small radiator. This difference is balanced with rating factors: KQ represents the thermal output of the radiator, KC the heat transfer depending on the radiator type and the way the device is mounted. The Q caloric 5.5 data sheet refers to these factors as K value, KC and KQ. Qundis defines two methods:

• Product scale: Each device is pre-programmed with the factors suitable for the radiator on which it is mounted. The value on the display is the same as the value in the cost allocation statement.
• Standard (uniform) scale: All devices are programmed with the same values. In the calculation, the value on the display is multiplied by the rating factor determined for that radiator. The factor depends on the radiator's heat output, type and mounting method; according to Qundis, it is usually stated on the bill.

With the standard scale, the display values of two radiators cannot be compared directly; a comparison only makes sense after the factor has been applied. To determine the factor correctly, the radiator's type and output must be known. You can find out from your meter reading company which scale is used in your building.

Example calculation

Example: In a building where the factors have been applied or which works with the product scale, suppose the allocators on an apartment's three radiators counted 420, 310 and 150 units during the period. The apartment's total is 880 units. If the total of all allocators in the building is 22,000 units, the apartment's share is 880 ÷ 22,000 = 4%. This percentage is applied to the part of the cost that is allocated according to measured consumption.

The whole cost is not distributed according to the allocator values. In Türkiye, for example, the regulation allocates 70% of the total heating cost in central heating according to measured consumption and 30% according to enclosed floor area, to cover common areas, system losses, minimum heating and operating costs; check the rules that apply in your country. For the full calculation, see our articles How Is Central Heating Cost Allocation Calculated? and, for minimum heating, What Is the 15 °C Minimum Heating Limit? The Turkish regulation requires the cost allocation statement to include the previous and latest values of the allocators and the difference between them; this way you can compare the value you read on the display with your statement.

Remote Reading: Without Entering the Apartment

The Q caloric 5.5 sends wireless M-Bus (EN 13757-4) radio telegrams in the 868 MHz band; reading can be done without entering the apartment. The P2 type on our site supports two reading methods at the same time:

• Walk-by reading: The reader walks around inside or in front of the building with a portable receiver. The device sends these telegrams between 08:00 and 18:00: in C-mode every day of the year, in S-mode only on specific reading days.
• Reading with a fixed receiver (AMR): Receivers installed in the building collect the telegrams 24 hours a day. In C-mode the device also sends OMS (Open Metering System) compliant telegrams; receivers that support OMS can read them too.

The telegrams contain the current value, last month's value and the due-date value with their dates; the error code and error date are also sent. The walk-by telegram also carries the values of the previous 12 months. This makes monthly allocation possible without looking at the display. At Novus Energy we provide remote reading and heat cost allocation services for buildings with heat cost allocators; details on our Remote Meter Reading and Billing page. For heat meters read wirelessly in installations with manifolds, see our Wireless Heat Meters category.

Common Situations

The value is zero or very low

If the due date has just passed, it is normal for the current value to start from zero; the previous period's value remains on the display marked M. If the display shows SLEEP, the device is in sleep mode and does not measure. Qundis ships its devices from the factory in this mode; when the device is fitted to the mounting plate, cLOSE appears briefly and the normal cycle then starts. If SLEEP is still shown after installation, inform your meter reading company.

The value increases while the radiator is off

According to Qundis, the allocator works when the radiator temperature is higher than the room temperature. What matters is not the valve position but the temperature of the radiator surface: even if the valve appears closed, the device can continue counting if the radiator is warmer than the room. The manufacturer states that the Q caloric is programmed to distinguish the radiator's own heat from other heat sources such as sunlight.

The display appears blank

The display going completely blank for half a second within the cycle is the display test and is normal. If the display stays blank for longer, inform your meter reading company.

The display shows Err, five dashes or bAt

• Err 1: An error message that stays on the display permanently. Other error messages are shown briefly, alternating with the consumption values.
• ----- (five dashes): Shown instead of a consumption value that is invalid because of an error; this behavior depends on the device settings.
• bAt: Indicates that the battery life has ended. Qundis gives the life of the device's 3 V lithium battery as 10 years of operation plus 1 year of reserve.

These are not situations that the user can resolve; inform your meter reading company. If an allocator cannot measure correctly because of a fault, the Turkish regulation, for example, provides that the apartment's share is determined according to its consumption in similar previous periods or the consumption of similar apartments in the same period.

The display shows cOPEn or a small c

The device detects tampering or opening of its housing. Depending on its settings, it shows this either with the text cOPEn or with a small letter c on the left of all displays; the c on the checksum display does not have this meaning. Do not remove the allocator from the radiator or change its position. The mounting point is determined according to EN 834 depending on the radiator type; Qundis states that it is generally at 75% of the radiator height but may vary depending on the radiator.

During installation and commissioning, other brief messages may also appear: a countdown from InSt8 to InSt1 shows that radio installation telegrams are being sent, -FF- that the remote sensor has been detected, and -S- that the infrared data interface is active. These are normal.