When purchasing a tankless water
heater, it is important to know the factors that effect to the size of the
unit, so that the correct unit for the specific need would be purchased. The top
five most relevant ones are the principal need, the type of the unit, incoming
water temperature, use of multiple faucets at the same time, and the point of
installation.
1. The principal need
What kind of need the water heater
needs to fill up? Whether the unit is for basic household’s water heating need,
for outside use e.g. camping, outside shower or pet care, or for summer cabin use,
it all effects to the units type and size. Purchasing too big unit, might cause
functional problems, not to mention the extra money spend for no good reason.
Also, a unit that might need electricity or ventilation might not be the most
convenient one in a certain situation, so to really find out the principal need
and use is the first key factor.
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2. Electricity or gas? One point- or
whole house heating?
You can find from the tankless water
heater markets units that are for one point- or whole house heating need,
running with electricity or gas. When choosing the electric one, it is
important to find out the needed voltage and amperage of the heater so that the
heater can be actually installed to your home and the maximum capacity can be
taken out if needed. When the unit’s capacity gets higher, the need for more
power increases as well.
For the gas heaters, it has to be
decided whether to use natural gas (NG) or Liquid Propane (LPG). The gas heater
differs from the electric ones by its need of ventilation, as the gas has to be
directed outside of the living area. So it is important to find out beforehand
how the installation of the exhaust pipe has to be done for that gas unit so
that it can be installed properly for the use. However, there are also portable
gas tankless water heaters that do not require exhaust pipe as they are
designed for outdoor use.
3. Incoming water temperature
The effect of the incoming water temperature
to the unit’s size is quite obvious and very important, but is easily forgotten
in the purchase moment. The tankless water heater heats the incoming water instantly
to the set out coming water temperature. If the incoming water temperature in
the usage area is low, the heater needs to be able to provide higher
temperature increases so that the set out coming water temperature would be
met. If the incoming water temperature is already high, the heater does not
need to work that hard. So roughly said, in the northern areas, where the
incoming water temperature is low, the capacity requirements of the tankless
water heater becomes higher and vise verse in the southern areas.
4. Using multiple faucets at the
same time
As the incoming water circulates
through the unit to the usage point, the water pressure also has a significant
role for the tankelss water heaters capacity requirements. When the water
pressure need is higher, for example multiple faucets running at the same time
or the faucet is using high water pressure and is turned on to the highest
level, the water circulates faster through the unit giving the unit less time
to heat it. A general rule is that a higher capacity unit is needed when the
water pressure need is high - e.g. multiple users in the household using hot
water at the same time.
The capacity of the different types
of units can be compared by the temperature increase in a certain water flow
rate (gallons per minute - GPM). For example, if a unit gives a maximum
increase of 65F in 1.5 GPM, and your incoming water temperature is 45F, you can
expect to have a good shower in a total of 110F, which is normally used
temperature for a hot shower. If you would be using two showers at the same
time with the 1.5 GPM water flow, the capacity need for the unit would equal to
3.0 GPM, which gives lower increase to the incoming water temperature with the
same settings in the unit, and this affects to the out coming water
temperature.
5. Point of installation
The point of installation is also
important factor. Normally the tankless water heaters are recommended to be
installed as close as possible to the point of use, as this reduces the
possibility for the water to cool in the way from the unit to the faucet.
Tankless water heaters actual size comes now in handy, as some of them are so
small that they can be installed for example below the bathroom sink or to a
small closet and thus give better energy efficiency. This is not possible with
the old tank water heaters, as they normally take so much space that are needed
to be installed to the basement or larger areas.
