Hi
My question is about the heating element in my solar hot water system.
Am I right in thinking that it is a resistive element?
If so, with 240VAC across it and measuring 7.5A with a digital meter, the
element would have a 1800W rating.
Is this correct or is there something else to know about water heater
elements?
Thanks in advance
Gordon
Yes you are right, it is a resistive element.
What you need to know depends on your role. If you are
designing them, there is a whole load of things to know. If
you are selecting one to use for a particular system, likewise.
If you are a householder with one in a solar system, you are
possibly interested in how to minimise the electricity it
uses for your particular system and to check that your
system design is most appropriate for your particular
requirements.
This generally means heating the minimum amount of water to
the lowest temperature that is acceptable, with the heating
system as near to where it will be used and heated "just in
time" to meet the demand - unless you can make use of
reduced-price electricity at off-peak hours.
The design of the system will thus typically be radically
different between a system designed to use single rate
electricity and one designed for multiple rates.
So, if you would care to identify what your specific
interest in electrical water heaters within a solar hot
water system is?
Thank you Sue for your reply.
I'm the householder type.
When I bought the system I understood it came with a 2.4KW heater. After a
couple of cloudy days recently it didn't seem to heat as quickly as I
thought it should.
Thinking the heating element may have gone I put a meter in the circuit and
got 7.5A instead of the 10A I expected. A 1.8KW heater could explain the
longer heating time unless there was something else I didn't know about
heating elements. Hence the above post.
I can live with an 1.8KW heater now that I know what to expect.
Thank you again for your help
Gordon
A quick calculation leads me to suspect that peak value has been used in
rating your elements rather than RMS. At a nominal UK voltage of 230V RMS
the Peak Value of the sine wave is 230x1.4 = 322 v. Then 322x7.5 =
2415watts. A bit of a con really but is a bit like saying you have a 30 inch
tv when you do but only measuring corner to corner.
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