Calculating an indirect water heater – capacity and volume

Knowing the ins and outs of your heating system is essential to maintaining a cozy and effective home. The indirect water heater is one crucial part that is frequently disregarded. It may not be as ostentatious as a high-efficiency furnace or smart thermostat, but its function in heating your home with hot water is invaluable. We’ll go into great detail in this guide on how to calculate the volume and capacity of an indirect water heater, giving you the knowledge you need to decide on the best course of action for the insulation and heating of your house.

Let’s define what an indirect water heater is and how it differs from other types before we get into the calculations. Indirect water heaters use the heat from a boiler or furnace to heat a separate reservoir of water, as opposed to traditional water heaters, which use a heating element submerged in the water. Improved energy efficiency and compatibility with different heating systems, including gas, oil, and solar energy, are two benefits of this configuration.

Let’s now tackle the essential query: why are an indirect water heater’s volume and capacity important? In other words, it establishes the maximum amount of hot water your system can produce at any given time. The volume shows the total amount of water the tank can hold, whereas the capacity describes the maximum amount of hot water the heater can produce in an hour. Correctly calculating these figures guarantees that the hot water needs of your home are satisfied without any problems or shortages.

Several aspects unique to your house and way of life must be taken into account when determining the appropriate capacity and volume for your indirect water heater. Finding out how often you use hot water should come first. Are you a single person with basic needs, or are you a large family with several bathrooms and frequent hot water demands? Properly sizing the water heater depends on knowing how much you use it typically.

Important variables also include the desired hot water temperature, the temperature of the incoming water, and the heating system’s recovery rate. A larger heater with more capacity will be needed in a colder climate or for a higher desired temperature, and a faster recovery rate will guarantee a continuous supply of hot water during periods of high usage.

Values

We drink water in liters, and degrees are used to measure its temperature. Based on its mass in kilograms, water uses heat energy in Joules to heat up. A water heater measures efficiency in percentages and outputs power in watts. Let’s combine all of these measurement systems into a single, comprehensible plane.

• According to the laws of physics, in order to raise the temperature of 1 kg of water, which is equal to 1 liter, at 1oC requires 4.187 kJ of thermal energy, which is 0.001 kWh of the power of the heating device. Type, manufacturer and losses are not taken into account. No matter who produced the heater and in what conditions this mechanism is not located water always needs exactly the same amount of energy.
• Water coming into the boiler in winter (in summer the boiler does not work), has a temperature of about 10o. Insulated supply pipes will reduce the temperature difference between the inlet and outlet of the boiler and help to save fuel.
• On the control panel of the unit the number 60o is set. This means that the liquid in the unit will be heated to this temperature. Hence, 60-10=50o. It is not worthwhile to set a higher heating value. This load will cause increased wear and tear on the equipment.
• By this value it is necessary to raise the temperature. Multiply the found difference in degrees by the energy needed to obtain each of them – 50*0,001=0,05 kWh of power will be required for the boiler for such work.

Therefore, 0.05 kWh of boiler power and an additional 1 – 0.001 kWh of labor will be required to heat 1 liter of water to 60°O.

About 40 degrees is the temperature of the hot water we use to wash our faces or dishes when we get it from the faucet. It will be hotter and colder below. We must account for the fact that we are mixing two different waters, each with a different temperature, when calculating the boiler’s work, not only for indirect heating but also for any other kind of heater.

• Hot water is heat energy. We have calculated that 1o = 0.001 kWh.
• The water we want should be 40o, so 40*0,001= 0,04 kW.
• Cold water is 10o, so 0.01 kWh is already there. This is 25% of the heat required.
• So we need to add another 75% of the temperature, which is 0.05*75%=0.0375 kWh.

As a result, 0.75 liters of fully heated water from our unit and 0.0375 kWh of its power will be contained in 1 liter of the desired mixture, which we will now refer to as warm water.

Amount of power consumption

The amount of warm water required for daily life must be determined when determining whether an indirect boiler is necessary and how big one should be. Assume the role of a family of four and conduct a weekly average analysis and peak (early in the workday) hot water consumption study.

1. Weekly analysis

• In order to wash dishes you will need about 5 liters of warm water per minute. The rinsing time is taken into account, it is about 5 minutes. Twice a day we wash plates, we get 50 liters of warm water spent on kitchen utensils per day. Multiplied by 7 days total 350 liters per week.
• Each person takes a bath 2-3 times a week, consuming about 170 liters. 4*2,5=10*170=1700 liters for 7 days.
• Another 4-5 times showering for 10 minutes at a flow rate of about 12 liters/min. 4,5*10*12=540 per family member, respectively for all 2160 liters per week.
• Minor hygiene (wash hands, shoes, clean the house) – about 10 liters per day per person will be 280 liters for the study period.

Weekly total: 350 + 1700 + 2160 + 280 = 4490 liters. Including visitors and a contingency plan, we arrive at a rough estimate of 5,000 liters per week. However, we must convert the boiler’s hourly count into its units. A family of four uses 30 liters of warm water per hour on average (5000 / 7 / 24).

The necessary average power consumption is determined by multiplying the temperature and power ratio by 30 to obtain 1.125 kWh.

In figuring out the size and capacity of an indirect water heater for your home, several factors come into play. First off, consider the number of people in your household and their hot water needs. Then, take into account the peak demand times, like mornings when everyone is getting ready for the day. Next, factor in the type of heating system you have and its efficiency. You"ll also want to think about the recovery rate, which is how quickly the water heater can reheat the water after it"s been used. Finally, consider any future changes in your household size or hot water usage. By carefully considering these factors, you can determine the right size and capacity for your indirect water heater, ensuring you have enough hot water when you need it without overspending on a unit that"s too large for your needs.

Peak consumption

It appears that even the smallest heater will be adequate based on the information above. But life isn’t always that easy. The fact that the entire family gets up and leaves for work or school at roughly the same time each morning must be considered when estimating the tank’s capacity and the unit’s power requirements. It is just not possible to wait for the boiler’s water to reach its full temperature. When it comes time for consumers to consume the liquid, there should be an adequate supply of accumulated liquid and heating of flowing liquid.

• According to statistics, utility services morning consumption of hot water is about 30%-40% of the average daily value for 1.5 hours. The period from 7 a.m. to 8:30 a.m. is taken. Let"s take the average figure of 35% and get that our family will use up 5000 / 7 * 35% = 250 liters in 1.5 hours, which equals 170 liters per hour of warm water. For this amount we will need 170 * 75% = about 130 liters of hot water and 170 * 0.0375 = 6.5 kW of power of the water heater.
• But that"s not all. As fully heated water is consumed from the tank, cold water will be added to the tank, which needs to be heated, and this takes time.
• The average heating rate in the flow mode depends on the temperature of the coolant and the surface area of the circuit. Since the heating liquid comes from the boiler its temperature will be constantly about 70 – 75o, and the heat exchanger is calculated in relation to the volume of the tank and the declared power of the device.
• The average values are approximately equal for devices of all manufacturers and are for a boiler with a load of heat exchange circuit 10 kW about 0.3 l / min at a given temperature difference of 50 °o. For one hour the volume of heated running water will be 60 * 0,3 = 18 liters.

Therefore, based on the indirect boiler volume calculation, a family of four will require a device with a minimum capacity of 10 kW and a tank capacity of more than 100 liters for one morning of the working day. The heating rate will rise in direct proportion to the power increase due to the heat exchange circuit’s increased capacity, but the boiler’s heat output will also rise.

To ensure effective heating and hot water supply in your home, it’s important to select the appropriate capacity and volume for your indirect water heater. Homeowners can meet their household’s needs while optimizing energy efficiency by knowing the factors that affect these calculations and making informed decisions.

The first and most important step is determining how big your household is and how much hot water it needs. The right water heater capacity depends on a number of factors, including the number of occupants, usage habits, and simultaneous hot water needs. In general, a larger home with more bathrooms and people will need a larger capacity to guarantee a consistent supply of hot water during periods of high usage.

It’s also very important to take the insulation and heating system efficiency of your home into account. Better heat retention in well-insulated homes eases the strain on the water heater and may even allow for a smaller unit. On the other hand, homes with inadequate insulation might need a higher capacity to make up for heat loss and guarantee steady access to hot water.

The kind of fuel or energy source that is available should also be considered when selecting the capacity of the water heater. While choosing the right size, it is important to consider the costs and heating efficiencies of various fuel types. For instance, a house with inexpensive natural gas access might decide to go with a bigger capacity water heater in order to save money on maintenance.

Finally, it is wise to plan for potential increases or decreases in the demand for hot water. Predicting future increases in household size or hot water usage can help avoid the need for premature upgrades or replacements, even though meeting current needs is still imperative. Without compromising efficiency, choosing a water heater that is marginally larger than what is now needed can offer flexibility and future-proofing.

To sum up, the process of determining the volume and capacity of an indirect water heater necessitates a meticulous evaluation of factors such as household size, hot water consumption habits, insulation levels, fuel type, and anticipated future growth. By considering these variables, homeowners can select an efficient water heater that minimizes energy expenses and environmental impact while guaranteeing a steady supply of hot water.

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