Ecodan - Legionnaires Cycle
Does anyone else observe this behaviour with their Ecodan?
When the Legionnaires cycle kicks in, the ASHP raises the LWT to around 60 degrees very quickly but as soon as it gets there it peaks and then starts falling again, at which point the immersion kicks in.
However, I never really get the tank temperature up to 60 degrees. I would have thought the ASHP could have operated for longer at 60 degrees LWT and use that to do a longer job of heating up the tank.
Is it something to do with how long I have set the ‘hold at temperature’ setting for? I thought this was referring to holding the tank temperature but perhaps it means holding the LWT temperature?
Thoughts?
Posted by: @hjdDoes anyone else observe this behaviour with their Ecodan?
When the Legionnaires cycle kicks in, the ASHP raises the LWT to around 60 degrees very quickly but as soon as it gets there it peaks and then starts falling again, at which point the immersion kicks in.
However, I never really get the tank temperature up to 60 degrees. I would have thought the ASHP could have operated for longer at 60 degrees LWT and use that to do a longer job of heating up the tank.
Is it something to do with how long I have set the ‘hold at temperature’ setting for? I thought this was referring to holding the tank temperature but perhaps it means holding the LWT temperature?
Thoughts?
I hadn't looked at this before but I did and this is what mine does. This was one of mine in October. I don't know if the immersion is used; I didn't think it was but I have never looked. Looks similar to what you describe.
With a 60degC legionella set point, my ASHP takes the DHW temperature up to 50degC and then goes to standby, and the immersion heater takes over for the rest of the legionella cycle. I've seen it work the same way at a 65degC set point too. The immersion seems happy to support whatever duraiton I specify for holding the tank temperature. The immersion is the 3kW Ecodan element that came with their water cylinder.Posted by: @hjdDoes anyone else observe this behaviour with their Ecodan?
When the Legionnaires cycle kicks in, the ASHP raises the LWT to around 60 degrees very quickly but as soon as it gets there it peaks and then starts falling again, at which point the immersion kicks in.
However, I never really get the tank temperature up to 60 degrees. I would have thought the ASHP could have operated for longer at 60 degrees LWT and use that to do a longer job of heating up the tank.
Is it something to do with how long I have set the ‘hold at temperature’ setting for? I thought this was referring to holding the tank temperature but perhaps it means holding the LWT temperature?
Thoughts?
What rating of immersion element do you have?
Mitsubishi Ecodan 11.2kW R32 ASHP; Ecodan DHW cylinder; UFH+rads
20x430W Jinko TOPCON Tiger Neo solar; Luxpower 6+4kW hybrid inverter; 20kWh LFP battery storage
@skd I think the pump will raise the LWT temp to the setting for the maximum heat pump flow temperature. I increased that to 60C and during the legionella cycle it raised the tank temp and handed over to the immersion. My actual normal Hot Water tank temp is 46 - we have a big tank and low usage.
Unfortunately my issue it that I have two thermostats: one on the immersion and one measuring temperature for the heat pump. The immersion is in the middle of the tank, not the bottom and stratification happens quickly when it's running so the tank immersion cuts out even though it's set at it's maximum thermostatic setting because the layer of water it's in is over the temp, however just a little below it is the heat pump temperature sensor where it can be 5-20c lower temp, and even lower towards the bottom of the tank.
Result: Heat pump gets the whole tank well over 50 then stops, immersion takes over until it cuts out when the top layer of the tank is maybe over 65 but I can't heat the whole tank to 60, I can get most of it well above 50 and then I try and make sure it's left there for at least 4 hours which is a fair legionella killer.
In an unvented system, I really don't feel the legionella risk is high and this is reasonable mitigation once every 30 days.
I need a destrat pump.
@rod thanks, yes that figures. My max ASHP temp is currently set to 50degC. I need to increase it too
Mitsubishi Ecodan 11.2kW R32 ASHP; Ecodan DHW cylinder; UFH+rads
20x430W Jinko TOPCON Tiger Neo solar; Luxpower 6+4kW hybrid inverter; 20kWh LFP battery storage
Thanks all. Very helpful. I shall have a play changing some of the settings
- 22 Forums
- 2,054 Topics
- 44.8 K Posts
- 54 Online
- 3,285 Members
Join Us!
Trusted Installers
Struggling to find a reliable heat pump installer? A poor installation can lead to inefficiencies and high running costs. We now connect homeowners with top-rated installers who deliver quality work and excellent service.
✅ Verified, trusted & experienced installers
✅ Nationwide coverage expanding
✅ Special offers available
Latest Posts
-
RE: Volumisers in Heat Pump Systems: Does Placement Matter?
You’re absolutely right that during defrost the refrige...
By Mars , 39 minutes ago
-
RE: Advice for ground source heat pump in new build with PV and batteries
When looking at room sealed stoves, you need to ensure ...
By Johnmo , 53 minutes ago
-
RE: Yes, the "zoning with ASHP" topic again...
@johnmo That’s a clever use of defrost behaviour to gui...
By HarryRea , 1 hour ago
-
RE: Plate heat exchanger considerations
Useful information thanks, we have a cupboard where all...
By Scalextrix , 2 hours ago
-
@editor thanks Mars that’s the same table I found in th...
By Gary , 6 hours ago
-
RE: Tariff and charging strategy advice please
They haven't asked me to prove that I have an EV (I do)...
By JamesPa , 9 hours ago
-
RE: Solar Power Output – Let’s Compare Generation Figures
Took a while to find on the OFGEN site: ”The FIT sche...
By AgentGeorge , 14 hours ago
-
RE: why solar diverters for HW instead of the heat pump?
For me there are few factors why you may want to heat w...
By Johnmo , 15 hours ago
-
RE: Hydronic plinth heaters and ASHPs
@editor yes I think so. It will be a while until I get ...
By benson , 15 hours ago
-
RE: Aira Heat Pump: Stylish Scandinavian Heating
I’m an Aira customer with a 6kW Outdoor Unit in a small...
By KevinPotts , 1 day ago
-
RE: Is your heat pump insured?
@richard24738 good to hear. I’ll also review them this ...
By Mars , 1 day ago
-
RE: Warm weather and heat pumps.
Just looked at my WC setting, it is programmed for 25 D...
By Johnmo , 1 day ago
-
RE: How to disable radiator heating in LG HM161MR
Just to add to above,when adjusting WC heat pump should...
By JamesPa , 1 day ago
-
@johnmo yes I can believe that. It seems to be human na...
By SUNandAIR , 2 days ago
-
RE: Help optimising my system!
I would be doing things a little more simply. Your heat...
By Johnmo , 2 days ago
-
RE: Renewables & Heat Pumps in the News
If you want to read a huge amount of speculation, fabri...
By Judith , 2 days ago
-
IVT Greenline high pressure switch and electrical cassette errors
I have an IVT Greenline HT Plus C heat pump that is con...
By tdudgeon , 2 days ago
-
RE: Additional Battery v Wind Turbine v Ripple
There was a call today for Ripple investors and amongst...
By Judith , 3 days ago
-