There
are 2 separate heating systems on a solar hot water system, and they have
nothing in common except the water.
They don’t even “know” that the other system exists.
1) Solar Heating
2) Electric Backup
Heating
You
can easily tell if the solar portion is working, using this
For now we focus on
the electric backup heating, because having no solar hot water costs you a few dollars
a day, but having NO HOT WATER can be a major annoyance.
The
disconnect is only occasionally a problem, unless of course, someone pulled out
the disconnect to work on the system, and then failed to put the spade
connector back in, or put it in upside down.
If
the timer spins (keeps the correct time), then you know that the timer is
getting power (and you also know that the disconnect is fine)
If
the timer does not spin, then the first thing to check is the
breaker. Breakers can be tricky, they can look not tripped
but really be tripped. So you push them firmly off, and then firmly
back on. Set the timer for the correct time.
Read
this to get to know your timer
If
the timer spins, and the outside little handle is in the on position, then it
should be sending power to the “High Limit Reset” Switch which is on top of the
Thermostat (actually part of it, it’s an assembly). If
the High Limit Reset safety switch was activated (by really hot temperature
like 160F or 170F) then the power stops right there, and never gets to the
thermostat. It’s a simple “reset”
just push the little round Burgundy colored button, and if you feel a very
slight click, pay attention!, then it was activated, and now it is reset….your
problem is likely solved.
The
second red link on this page explains more the on High Limit Reset
How
can you tell if the element is actually heating the
water? We call this the “ear
test”.
1) The thermostat setting must be above the temperature in the
tank.
2) If the tank is fairly warm (say from the Sun), but you want
to test the T-stat, you can turn it up to a high temperature by turning
clockwise with a small flat bladed screwdriver. As the setting
exceeds the water temperature, you should hear a little click, indicating that
it is now sending power to the heating element.
3) Put your ear right on the tank, if you hear a faint humming,
that is the element heating the water. One caveat though….in rare
occasions, you will hear some humming, but the Element will actually be mostly
broke, and it really won’t make hot water.
If you hear the humming, but never get hot water, you have a bad
Element, OR the below, a bad Mixing Valve.
It can be a real bear to change an element. It needs special tools, and if you strip it, the whole tank is shot. Any leakage or rust in this whole area can be a real electrocution or fire hazard. Just because you have a breaker (sitting in your breaker panel for 30 years, never moving) does not mean that it will work when needed!
But
let’s finish on the Thermostat. If you
turn the T-stat all the way up, and it never clicks indicating sending power to
the element (and everything upstream is OK, breaker, disconnect, time, high
limit reset), then the T-stat is likely bad.
If you have an electrical tester, and the knowledge to use it safety,
you can read the voltage into the T-stat, and the voltage to the Element, both
should be 240V AC.
One thing that will
confound even the best troubleshooting in the world, is the Mixing Valve.
If the Mixing Valve (MX) has gone bad and gets occasionally stuck, nothing else
that you do or change will make the system work well and
consistently. MX is usually reliable, and a bit pricey
to change, it’s $315 labor and material to change, unless repiping is needed
then it is more. So when nothing else makes sense, and
especially if system is over 7 years old, then it’s time to bite the bullet and
replace the MX. The MX is usually a red colored cap in the
top center of tank (sometimes blue or green).
