There are two fundamental principles for the heat measuring (indication) which serve to the heating consumption dividing:

- measuring of the energy radiated by a heating body or
- measuring of the heat contentment.

Appliances of the first group refer to a concrete heater type and are based on different principles (evaporating, electronic, ecc.). Limitation to the only heating body measuring is their serious drawback. Other heat flows come from piping, walls and ceilings of rooms. These facts are reflected by the other mentioned method, which deduces the heating expenses distribution from the heat contentment measuring.

Principle of this method is a continuous products summarization of time spaces and differences between the external and the inner temperature. This case makes it disadvantageous for tenants of outside flats with the naturally higher heat consumption have no advantages; it is a special principle and the expenses are proportional to temperatures (to the heat contentment) - non to the supplied heat quantity.

**PROPORTIONAL HEATING CONSUMPTION MEASURING**

For proportion measurement (indication) heat serving to dividing heating cost are used two fundamental principles:

measuring of energy de-excitation heating body through detector ascertaining average temperature in reference places heating body or

measuring of heat contenment through detector ascertaining average air temperature heating rooms.

Indicator first group are outspread to concrete type heating device and work on different principle (evaporative, electronic ...). Relevant deficiency this method is limitation of measuring only on radiator. Other heat flow that is arriving from tubing, walls and top walls of rooms. While using this method is also necessary use whole order coefficients technical and dispositional character (type, form and size radiator, position rooms or flats in face of world's quarter, temperature influence surrounding walls, floor etc.). These corrective coefficient serves among others. thereto, they would not be handicap renter border flat with (of course) bigger heat rate; walks about social principle and payment is proportional to inner temperature (heat contenment) and dimension of heating room - no quantity delivered heat.

Indicator second group continuously evaluate inside room temperature in relation to external (common) temperature. In this case are not handicap renter border flat with of course greater heat consumption already from principle (without using often with difficulty specifiable coefficients). Parameter capacity heating rooms is of course applied here too.

Total heat loss of object Qc (CSN 06 0210) is given through relation:

Q_{c} = q_{o}·V·(J_{i} - J_{e}),

- V is capacity of heated space [m
^{3}] - q
_{o}is heat characteristic of object [W/m^{3}.K] - J
_{i}is inner temperature [K] - J
_{e}is external temperature [K].

Total heat loss is composing from sum heat losses of single rooms:

Q_{c} = Q_{1} + Q_{2} +
... + Q_{m},

- m is quantity of rooms.

For calculation heating costs is necessary know shares p_{x} consumption energy Q_{x} of single rooms and total power consumption Q_{c} of dwelling-house for accounting period T.

- V
_{c}= V_{1}+ V2 + ... + V_{x }+ ... + V_{m }[m^{3}] ... is total volume of heated space, that's sum total volume of single rooms ("m" is sum total of rooms) - Dt is time period periodic temperature measuring
- T is clearing period (season) T = n·Dt
- J
_{xij}is momentary measured value inner temperature "x"-room at "j"-time moment (in relative expression we can without changes come over from K to °C).

If they are in periodic time interval measured inner temperature separate rooms and external temperature, it can be find out relative power consumption p_{x} any room on total consumption for chosen time period.

Mathematical term for p_{x} is adjustable:

Final formula for calculation ratio one’s room on total heating cost is writeable this way:

- is average inner temperature "x"-room
- is external average temperature for monitored period.

The heat consumption registration system by the method of the heat contentment measuring in individual rooms (areas) is a standard accessory of ETH 1 control units. The calendar period in which the registration is run begins is adjustable at configuration (in example from the 1-st October into the 30-th April); the consumption out of this period will be divided by the same proportion like in the main season.

Temperatures are measured at fifteen minutes and saving to central unit once per hour as the "average hourly temperatures"; their values is added step by step. Average temperatures are readable only through connected PC with relevant programme (KomWin); status records CU through PC at the start and end of monitored period has to be disposable. For every address (for this period) it can read:

**average real temperature****average optimize temperatures:**

- if the real temperature is lower than the selected one, for the calculation the real one is used;

- if the real temperature is higher than the selected one, for the calculation the selected one is used;- number of the realized measurings.

Resulting statement of the average temperatures can be used to intercharging the heat expenses to individual users. The concrete intercharging algorithm depends to an agreement (to contract of lease). It can contain certain fixed part respecting for example adjoining areas heating by risers and than a movable part - deducted from control unit statements and usually adjusted by surface area of the room. Measuring of the external temperature isn't simple function for reason of correct sensor placement. Regarding this ETATHERM system refers the degrees to the 0°C temperature and in the calculation takes in consideration average outside temperature of the whole heat period in concrete place (statement of the nearest meteorological station). This proceeding is more precise and cheaper. Regarding the fact that average temperatures of the heat period usually aren't much remote from the 0°C, by circa even heat consumption of all tenants, the outside temperatures influence can be neglected.

Principle method and self calculation is simple; to its illustration serves below example.

Calculus example:

In building there are:

- 2 offices of ABA company
- 1 office of BCBcompany
- 1 office of CDCcompany

room | surface area Si(m2) | average temperature ti (°C) |

1-st ABA office | 40 |
19,25 |

2-st ABA office | 50 |
18,10 |

3-st BCB office | 50 |
17,52 |

4-st CDC office | 10 |
18,33 |

- average outside temperature of the heat period te measured +1,11°C
- total heat expenses P in the season 92/93 were: 960,- EUR

Sum of all surface areas is: 40 + 50 + 50 + 10 = 150 m^{2}.

We use formula No. 1:

- denominator of fraction (common for all partial calculation) is:

40·19,25 + 50·18,10 + 50·17,52 + 10·18,33 - 150·1,11 = 2 567,8

- individual relative shares of payments (for individual rooms):

- p
_{1}= 40·(19,25 - 1,11)/2567,8 = 0,2825765 - p
_{2}= 50·(18,10 - 1,11)/2567,8 = 0,3308279 - p
_{3}= 50·(17,52 - 1,11)/2567,8 = 0,3195342 - p
_{4}= 10·(18,33 - 1,11)/2567,8 = 0,0670612

- individual payments:

- P1 = 960·0,2825765=
**271,27 EUR**pays ABA - P2 = 960·0,3308279 =
**317,60 EUR**pays ABA - P3 = 960·0,3195342 =
**306,75 EUR**pays BCB - P4 = 960·0,0670612 = =
**64,38 EUR**pays CDC