Why run a disinfectant cycle ?
My heat pump has been dutifully running the disinfectant cycle every week, but I read and hear that the jury is still out on whether this is really necessary. What do other people think ?
I have to go into Installer mode to change it, and I can only run it at the same time every week, or not at all. As it uses a significant amount of energy I would have liked to be able to control the timing eg run it when the grid is producing lower co2 electricity, or when the outside temperature is warmest.
If it's not really necessary I'm going to switch it off and get a much better COP.
Posted by: @heat-pump-newbieMy heat pump has been dutifully running the disinfectant cycle every week, but I read and hear that the jury is still out on whether this is really necessary. What do other people think ?
I have to go into Installer mode to change it, and I can only run it at the same time every week, or not at all. As it uses a significant amount of energy I would have liked to be able to control the timing eg run it when the grid is producing lower co2 electricity, or when the outside temperature is warmest.
If it's not really necessary I'm going to switch it off and get a much better COP.
If your water is already at 50C then you're going to have to heat it 10 deg to 60. For a 200l tank that's circa 8kwh at a COP of 1. So a couple of quid a week at the most. You could always have a really hot legionella-free bath to make up for it.
On the other hand the risk is extremely low (1) of legionella getting into your unvented cylinder and (2) you catching it from said cylinder.
It also doesn't like even moderately hot water (this from Wikipedia):
Temperature affects the survival of Legionella as follows:[3]
- Above 70 °C (158 °F) – Legionella dies almost instantly
- At 60 °C (140 °F) – 90% die in 2 minutes (Decimal reduction time (D) = 2 minutes)
- At 50 °C (122 °F) – 90% die in 80–124 minutes, depending on strain (D = 80–124 minutes)
- 48 to 50 °C (118 to 122 °F) – can survive but do not multiply
- 32 to 42 °C (90 to 108 °F) – ideal growth range
- 25 to 45 °C (77 to 113 °F) – growth range
- Below 20 °C (68 °F) – can survive, even below freezing, but are dormant
I would have thought the risk with HW at 48 deg is vanishingly small and that you're in more danger from scalding yourself with your 60 degree, guaranteed legionella free water once a week.
I think it is probably unnecessary but we will never hear the end of it from boiler fans if a heatpumped tank hosts an infection, so I have the standard controller set to still run the cycle the least often as a safeguard (monthly I think, at 0100GMT so cheap electricity and before the coldest part of night) and my add-on smart controller heats a tank of 52˚c water on any moderately warm late afternoon (so cheaper heating) which should kill most of it.
For best risk reduction, remember to run any seldom-used hot taps every so often, especially if the pipe to it is in a warm place such as next to heating pipes. Still water in pipes is probably a far bigger risk than the tank.
-
Nibe F2040 periodic warm water increase fails
2 months ago
-
Heat Pump, DHW, UFH and Radiator Install
9 months ago
-
Sudden drop in COP
1 year ago
-
Mitsubishi Ecodan - Hot Water Settings
2 years ago
-
Legionella cycle: Heat Pump or Immersion Heater?
2 years ago
Currently viewing this topic 1 guest.
- 26 Forums
- 2,117 Topics
- 46.5 K Posts
- 63 Online
- 4,521 Members
Latest Posts
-
Not sure that's what you meant albeit that the industry...
By JamesPa , 2 hours ago
-
RE: Replacing Refrigerant on Mitsubishi Heat Pump
So the manual is correct and looks fine to me, to abbre...
By ASHP-BOBBA , 3 hours ago
-
RE: Heat Pump Books For Beginners – Bodge Buster & From Zero To Heat Pump Hero
Hi I, like others, avoid Amazon for ethical reasons....
By Topher , 4 hours ago
-
RE: Benefits of an extra horizontal loop for GSHP
I would deffo install an additional slinky run, especia...
By Transparent , 4 hours ago
-
RE: Say hello and introduce yourself
@editor fab - thanks Mars, and keep up the great work o...
By normpang , 5 hours ago
-
RE: Compressor and Evaporator Stratification
@trebor12345 So I think the 1st zigzag section shows so...
By ASHP-BOBBA , 20 hours ago
-
RE: Is this just haze or something more?
@majordennisbloodnok I was giving a talk to primary sch...
By Toodles , 24 hours ago
-
RE: Tesla Powerwall – More of a ‘Luxury’ Than an ROI Winner!
We had our Tesla Powerwall 3 (and Gateway) installed ea...
By Old_Scientist , 1 day ago
-
Indeed. With a battery its presumably the battery con...
By JamesPa , 1 day ago
-
RE: No-code, plug-and-play monitoring for your heat pump
To update an ESP device using ESPHome in Home Assistant...
By Grantmethestrength , 2 days ago
-
RE: The good, the bad and the not that great – my heat pump installation
Said I would pop back with a update. Only Mr Jesus h...
By Burtis , 5 days ago
-
RE: Buffers, hot water and cooling
Thats presumably heat pump DT, what about radiator DT a...
By JamesPa , 5 days ago
-
RE: Who's your electricity provider and what's your tariff?
@chandykris Exactly the same here. We now have 13.5kWh ...
By Old_Scientist , 5 days ago
-
RE: Wood burner with ASHP - direct air?
This depends on the size of your wood burner and size/t...
By Lucia , 6 days ago
-
RE: Difficult positioning of air source heat pump
@rikiarn It's a not a buffer it's a volumiser which is ...
By Lucia , 6 days ago
-
RE: Is your heat pump insured?
To make things clear, lots of insurance companies cover...
By Lucia , 6 days ago
-
RE: Boxt Heat Pump Installation Experience
@adrian any updates since installation? How is it perfo...
By Ashfp , 6 days ago
-
@seatonian got your email. Will connect you with a reco...
By Mars , 1 week ago
-
@downfield and @toddles, this isn’t in the settings cur...
By Mars , 1 week ago
-
RE: Homely launched for Grant Aerona ASHP control
I haven't bought the Aerona Smart Controller (£700!) bu...
By Prunus , 1 week ago