Heat Pump / Immersion - diagnosing power use

[relicalpha]

Hi,

Just moved into a new place, the heat pump has it's own electric meter. I noted the reading last night, and this morning it was identical, however the whole house meter was +5kwh, with the water heated up.

There is solar boosting on the hot water during the day, but I think the only thing that can explain the usage is that the immersion was used for DHW sometime early morning rather than the heat pump.

Does anyone know how I can diagnose this?

- Legionella cycle is disabled (rightly or wrongly)
- No error codes on the Samsung HP controller with DHW set to standard mode, and it's showing as being on AU mode.
- If i turn a underfloor heating thermostat up, the HP does correctly kick in - so it's all working on that side, possibly just not being used for DHW?
- DHW set point is 40 degrees, water was about 36 before bed.

I plan to power-off the immersion for tonight, just to confirm that accounts for the kwh usage - but any ideas how I could diagnose why it might pick the immersion over HP?

Or maybe this actually makes sense to use the immersion for boosting up from 36 to 40 set point?

 

[Fireskull]

Is the immersion plugged into its own timer somewhere?

When I did my own research when looking into a heat pump most of the things I read recommended an immersion cycle to heat the water up to 60 for legionella cycle as the heat pump can't heat the water that high alone, so maybe the fact that cycle is disabled on your system maybe the previous owners had it setup differently where the immersion is the only thing that heats your tank and not use the heat pump at all.

 

[doggles]

Is the solar boost an Eddi by myenergi? Or similar ?

 

[relicalpha]

Is the immersion plugged into its own timer somewhere?

When I did my own research when looking into a heat pump most of the things I read recommended an immersion cycle to heat the water up to 60 for legionella cycle as the heat pump can't heat the water that high alone, so maybe the fact that cycle is disabled on your system maybe the previous owners had it setup differently where the immersion is the only thing that heats your tank and not use the heat pump at all.

it's a fused spur, no timer sadly. There's just the heat pump controller.

Is the solar boost an Eddi by myenergi? Or similar ?

Thanks, similar yes, solar iboost.

I also observed today that the HP did come on for DHW correctly. So something weird happens at 4am to trigger this, field setting for legionella is 100% off. Guess I'll get up early and see if I can narrow it down when it's happening

 

[doggles]

Mine has an app that's the main control.point which has a legionnaires setting for Tuesday 2am for 4 hours as default. Maybe it's the solar boost ?

 

[relicalpha]

Mine has an app that's the main control.point which has a legionnaires setting for Tuesday 2am for 4 hours as default. Maybe it's the solar boost ?

Ha thanks! Sorry I never thought the iBoost would do this....

Just to sanity check, this is wrong right? I should have the HP controller set to do it once/week. It seems plausible currently that this daily immersion boost would boost it enough to stop the HP ever kicking in for DHW in the early morning? No idea why that is set...

And 4-5am when there's presumably 0 solar anyway for the vast majority of the year

 

[doggles]

The solar boost on mine was.fitted after the heat pump. If you have a water cylinder there's probably an immersion heater in it also controlled by the heat pump ( mines a samsung.also)

The solar boost was installed and it can also do this, so they disabled it.. I set the legionnaires setting to a monday afternoon so in the summer the solar does it. In the winter the cheap electricity at thay hour does it.

The reason its normally set at night time or early morning is there doesn't tend to be any water use so thr ta k can be heated and kill off the bacteria

 

[dirtychinchilla]

DHW setpoint being at 40 C seems a little low. Is that being boosted by the immersion?

Legionella cycles are normally once a week, though they're only needed on potable water. If you take Heat Geek's word for it, as long as you're turning over that tank by at least 75%, you don't actually need it: https://www.heatgeek.com/hot-water-temperature-scalding-and-legionella/

 

[relicalpha]

Yes agree 40 seems a bit low, the iboost solar immersion seems to take it up to 50+ so long as it’s sunny and I guess that’s what the previous owner lived on. But that sucks if it’s not sunny!

Guess I need to up this to at least 45 for this time of year and add a new weekly 60+ cycle.