How to Choose the Right Domestic Hot Water Storage for You?

Michael Tobias
4 Minutes Read
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    We are sure you cannot do without a water heater in your Chicago home. In Chicago, where winters can be harsh, they are a must for every home. 

    Depending on your budget, you can go in for one that runs on natural gas or electricity to generate heat. Your budget would also determine the tank size.  However, since water heaters often consume a lot of energy, you need to go in for one that is energy efficient. 

    The question is - how can you choose the right domestic hot water storage for yourself?

    Understanding Which Water Heater is Right For You

    You've four different types of water heaters to choose from.  

    - Storage water heaters that store hot water in a storage tank.

    - Tankless water heaters that provide hot water directly.

    -  Water heaters with a heat pump that extract air from its surroundings.

    - Tankless and indirect water heaters that generate heat from the space heating system.

    Additionally, there are solar water heaters that use solar radiations to heat water.

    Top Things You Must Keep In Mind While Selecting A Water Heater

    Selecting a water heater essentially depends upon the requirements one needs in their Chicago home. Storage tank water heaters provide a less intense and steady water output while if you're going for a tankless heater, it must be sized to provide rapid heating in a short time.

    1) Hot Water Storage Water Heaters

    Storage water heaters have a reservoir for hot water whenever needed. The demand for hot water is mainly essentially in gallons per hour and not in gallons per minute. Gallons per hour value is based on the local plumbing codes of Chicago, whereas the demand and storage criteria can be found mentioned in ASHRAE codes for residential occupancies.

    Look at this example here:

    Demand for hot water-400 GPH - typical for most homes out there.

    Demand Factor- 0.3 (ASHRAE codes for private residencies)

    Storage Factor- 0.5  (ASHRAE codes for private residencies)

    Rise In Temperature- 100°F

    Firstly, we need to determine the required recovery rate that tells us how many gallons of hot water the heater must handle every hour. We can obtain the value by multiplying the total demand for hot water and the demand factor:

    Recovery rate will be 400x0.3= 120 GPH

    Now, we can find the actual heat input by

    Heat input (BTU/H) = Recovery Rate (GPH) x ΔT (°F) x Specific Heat (BTU/gal °F)

    Heat input (BTU/H) = 120 GPH x 100°F x 8.33 BTU/gal °F = 99,960 BTU/H

    Heat input (BTU/H) = 99,960 MBTU/H (thousand BTU per hour)

    We can calculate the required capacity of the tank by the storage factor:

    Tank capacity = Recovery Rate x Storage Factor

    Tank capacity (gal) = 120 GPH x 0.7 = 103 gal

    In this case, the water heater must have a storage capacity of 99,960 MBTU/H (thousand BTU per hour)

    2) Hot Water Heaters With Direct /Demand Type Supply

    First, we would need to figure out the increase in temperature required, by finding out the difference between the needed water temperature and the water temperature for the water being supplied. Like for example:

    Let's assume the required temperature is 115°F and the supply temperature is 45°F, the increase in temperature needed will be

    Increase in temperature = 115°F-45°F = 75°F

    Now, let's look at the needed flow rate in gallons per minute or (GPM). For example let's assume:

    Bath lavatory sink = 0.4 GPM

    Standard shower = 2.5 to 3 GPM

    Total demand = 3.4 GPM.

    In this case, we would need a water heater that runs at 3.4 GPM with a 75°F rise in temperature. Since the full-temperature must be attained the moment water starts flowing it would be very different than storing water at 115°F in a storage tank.

    Types Of Hot Water Storage Tanks

    Here are some of the popular domestic hot water storage options for you.

    1. Vented- The traditional type of water heater tanks where cold water is stored in the loft, it has a copper cylinder in the airing cupboard and an expansion tank in the loft which is smaller than the header tank, and it provides the vent for excess water to go out. The difference in height between the cylinder and the tank provides the water pressure in the taps.
    1. Unvented- Water is fed in this type of storage tanks directly from the supply. The header or expansion tanks provide hot water at the mains supply. Since these tanks are pressurized they have valves and thermostats to prevent explosion due to excess pressure and therefore more expensive.

    Unvented water heaters are still more popular as they ensure good water pressure without the need for header tanks.

    Advantages And Disadvantages Of Storage Water Heaters

    Every engineering choice has its pro and cons; the same thing applies to water heaters, they also have their own pros and cons. Here we will be talking about their pros and cons:

    Storage Water Heaters/ Water Heaters With Tank - The Advantages

    - Low upfront cost as storage water heats almost cost half than tankless water heaters

    - Easy and cheap to replace

    - They are good for Chicago homes that require a regular supply of hot water round the clock.

    Cons Of Storage Water Heaters/ Water Heaters With Tank:

    - More expensive energy bills- Since storage water heaters store water at a specified temperature regardless of the use, they consume more energy, especially during winters.

    - For one, they occupy more space.

    - They can run out of hot water after a point if a lot of people are using it.

    - They have a shorter lifespan as compared to tankless water heaters.

    Still have doubts when getting a water heater for your Chicago home?  A professional can help make sure you take the right decision.


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    Tags : domestic hot water storage water heater

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