No hot water: is it the Eddi or the immersion heater?

Step 1: Check the Eddi display

The Eddi's screen tells you exactly what it thinks is happening at any given moment. Before doing anything else, look at what it's showing and match it to one of the situations below.

Step 2: Run a Manual Boost

First, rule out the weather. On a run of dull days, or on a day when the house is using most of what the panels generate, the Eddi may simply have nothing spare to divert, and the water will stay cold with nothing actually wrong. The test below settles the question either way.

The Eddi normally only diverts surplus solar energy - so on a cloudy day, it may not be sending much at all. A Manual Boost ignores that rule entirely and forces the Eddi to draw power from the grid for a set period. This is the most reliable way to test whether the Eddi's internal relay is working. A relay is simply an electrically operated switch inside the unit.

1. On the Eddi, navigate to Boost and set a duration of 30 minutes.
2. Watch the display. A working Eddi will show power flowing - typically somewhere between 2.5 kW and 3.0 kW - and a countdown timer.
3. Let the boost run to completion, then check your hot water.

What the result tells you:

If a Manual Boost works but the water never heats on its own

If the Eddi heats the cylinder perfectly during a Manual Boost but never does so on its own, the hardware is fine. The cause is almost always the Eddi's clock or its timer schedule, which decides when the unit is allowed to heat. Work through these four checks:

1. Switch the Eddi off and on again. Switch the unit off at its isolator or fuse spur, which is the switch or fuse that supplies power to it, wait 30 seconds, then switch it back on. This clears a surprising number of temporary glitches.
2. Check the time and date. Make sure the clock on the Eddi is showing the correct time and date. If it is sitting in the wrong hour or the wrong year, its schedule will fire at the wrong time, or not at all.
3. Check the boost timer. Go to Menu → Heater Settings → Boost Timer and confirm the duration is not set to 0h00, and that the days it is set to run match the days you expect it to heat.
4. Check the schedule in the app. Open the myenergi app and confirm the schedule is switched on. A schedule that has been toggled off in the app will not run, even if the Eddi itself is set up correctly.

If the water is still not heating after all four checks, get in touch with us.

Step 3: Inspect the immersion heater

If the Eddi's display and boost test suggest the unit is working, the next place to look is the heating element inside the cylinder. There are two common causes of failure.

The thermal cut-out (reset button)

Most immersion heaters include a high-temperature safety cut-out. If the cylinder ever overheated, this switch may have tripped - and it will not reset itself. That makes it a common reason for no hot water, and one worth knowing about when you speak to a technician.

Element burnout

In areas with hard water, mineral scale builds up on the heating element over time and can eventually cause it to fail completely. A burned-out element will draw no power at all. If the Eddi shows it is sending energy but your electricity meter is not moving as you would expect, a failed element is likely. This requires a replacement element to be fitted by a qualified electrician or plumber. See "What to do next" for links to find a registered tradesperson.

Quick reference: which one is it?

Use this table to match what you are seeing to the most likely cause.

What to do next

If the Eddi appears to be at fault

If the steps above point to a problem with the Eddi unit itself - such as an error code, a blank screen, or failure to send power during a Manual Boost - and PureVolt Solar installed your Eddi, please get in touch with us. We will work with you to arrange the appropriate fix.

Contact PureVolt Solar with a note of what the Eddi screen is showing and what you observed during the boost test. The more detail you can give us, the faster we can help.

If the immersion heater appears to be at fault

The immersion heater and hot water cylinder are plumbing and electrical components that sit outside the scope of your solar installation. If the fault is with the element, thermostat, or thermal cut-out, you will need a qualified technician to carry out the repair.

The following resources may help you find the right person:

Common immersion heater makes and manuals

If you need to check your heater's thermostat settings or understand the element spec, the table below links directly to the installation documentation for the most common immersion heater brands found in Irish homes. Find your make in the left column, then use the link in the right column to access the relevant manual or resource.