Chromagen LO Error — Low Temperature / Frost Protection Alert

What Does This Error Mean?

The LO code on your Chromagen controller means the water temperature has dropped to a very low level — usually below 4–7 °C. In frost protection mode, the controller may activate the pump or the electric element to prevent pipes from freezing.

Affected Models

Chromagen CR Series
Chromagen Optima
Chromagen Crown
Chromagen Prisma

Common Causes

Very cold overnight temperatures (frost / near-freezing conditions)
System left without water flow for extended period in cold weather
Cold water inlet temperature unusually low
Sensor reading incorrectly low (faulty sensor — if LO appears in warm weather, suspect this)

How to Fix It

Check the outside temperature

If it is a cold night or early morning in winter, LO is completely normal. The controller is doing its job protecting the system from frost.
Wait for temperatures to rise

LO should clear automatically once the sensor reads above the threshold. You do not need to do anything.
Check if frost protection ran overnight

Some Chromagen models use a small amount of electricity to circulate warm water through the pipes when frost is detected. This is normal operation.
If LO appears in warm weather, check sensor

An LO code on a summer day or mild evening suggests the lower sensor (E2) may be reading incorrectly. Power-cycle the controller and if LO persists, book a service.

When to Call a Professional

Only if LO appears during warm weather (suggesting a faulty sensor), or if it does not clear after temperatures rise.

What Does LO Mean on a Chromagen Solar Water Heater?

LO (or Lo) is the low temperature / frost protection alert. It appears when the sensor detects that water temperature has dropped close to freezing point.

This is a protective feature, not a fault. The controller is telling you it has detected near-freezing conditions and may be taking action to protect your pipes.

When to Expect LO

Winter mornings after a cold night
In regions that occasionally experience frost
After extended periods without any hot water draw (pipes cool down)

When to Be Concerned

If LO appears on a warm day, or the code does not clear after temperatures rise above 10 °C, the lower temperature sensor may be faulty. In that case, check for Error E2.

Frequently Asked Questions

Is LO bad for my solar water heater?

No — LO is an informational/protective code, not a failure. It means the system is actively preventing frost damage. In most cases it clears on its own.

Does frost protection use a lot of electricity?

Frost protection cycles are short and infrequent. The energy used is minimal — typically less than running a light bulb for a few hours.