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
- 26 Forums
- 2,199 Topics
- 48.4 K Posts
- 84 Online
- 5,854 Members
Join Us!
Podcast Picks
Latest Posts
-
Bosch CS5800i 5kW - Experience So Far
Around two years ago, my partner and I moved into a new...
By Steelbadger , 2 minutes ago
-
RE: How to Understand Wiring Up a Heat Pump
I've learned from experience rather than received any f...
By Transparent , 31 minutes ago
-
I recently asked my energy supplier Octopus about gas m...
By Scalextrix , 48 minutes ago
-
-
-
RE: Why Air Release Valves and Deaerators are Non-Negotiable
I think that's a key point. An air-release valve shou...
By Transparent , 1 hour ago
-
RE: Air source heat pump roll call – what heat pump brand and model do you have?
Manufacturer: Worcester Bosch, Earth Save ProductsModel...
By Steelbadger , 2 hours ago
-
RE: Say hello and introduce yourself
Hello everyone. My partner and I recently had a Bosch C...
By Steelbadger , 3 hours ago
-
RE: Heat Pump Installers: Competence, Illusion and the Hard Truth Homeowners Must Face
@pirate-rich there’s a lot to do and plan, and the wish...
By Mars , 15 hours ago
-
RE: Help me keep the faith with my air source heat pump installation
@adamk Its a bit complex: My 28mm primaries run for a...
By JamesPa , 17 hours ago
-
Can you separate out the scop data between hot water an...
By Andrew J H , 19 hours ago
-
RE: Solar Power Output – Let’s Compare Generation Figures
Further, these bar charts may throw a few more lumens o...
By Toodles , 20 hours ago
-
RE: Heat pump and wifi kit connection.
Wi-Fi kit covers any Samsung device that has a modem in...
By Alfapat , 2 days ago
-
RE: Sizing - Save me from my headache
If you get an R290 pump you should be able to heat the ...
By JamesPa , 2 days ago
-
RE: Large heat pump options for church building
@aventus-eco Thanks Sean, will drop you a line.
By Josephiah , 2 days ago
-
RE: Moving FIT array onto a Tesla Powerwall 3 possible?
@toodles that’s good news for @adamk
By Judith , 2 days ago
-
RE: Samsung Gen 6 - Schedules not working
@technogeek That sounds very logical :-). I will give i...
By bontwoody , 2 days ago
-
RE: Heat Pump + Tado Setup: Smarter Control for Secondary Pumps?
@pirate-rich thanks for the reply. If I were to explo...
By Lloydi , 2 days ago