In the US and Canada they use 50C so clearly that must be OK or they would have lots of problems with L

Mine is 50 too

shower is usually 42C

Cant see why any sane person would want to boost temp.

I'm running our (instant) DHW at somewhere around 40C, partly for efficiency and partly because we have small children so I want to eliminate scald risk.

Rgds

Damon

I've been running my DHW at 48 to 50 deg C for the past year, feeding a thermostatic shower mixer valve and have no problems. The temperature seems to be well controlled and doesn't fluctuate much when other taps or appliances demand water.

I don't have a particular legionella risk though, as DHW comes from a combi boiler. It may be that the potential for bacterial growth in storage systems is the reason companies suggest higher DHW temperatures.

good idea.

Posted By: borpin..........
I took a quick trip to Mira (random supplier) and checked out a random shower instruction. It seems that their recommendation is that the hot supply should be 60°C to 65°C with a minimum of 55°C. Seems a bit high to me but how does that fit with others experience and or design criteria?
The Ecocent for instance, quotes figures at 55°C
It also brings me back to the vexatious question of how to boost the DHW temperature when necessary.

Tony's right 55°C is too hot, 50°C is plenty hot enough even in the kitchen. and I'd say 40-45° C for showering. Any hotter and you'd be taking the skin off your back. I keep my DHW at 45 - 50°C.
For boosting DHW temp I suppose it depends what quantities and from what source the HW is coming.

Posted By: Paul in MontrealAs we have mains-pressure hot water here I have no fear of legionella...

How does that follow?

It's not the pressure which kills the spores, you know?

My Ecocent came with a 55C default setting.
Once I'd learned how to adjust the parameters I reduced this to 52C, and last year I reduced it to 48C. I like a hot shower and have no complaints. I may try reducing it further to find the tipping point - where the shower isn't quite hot enough.
Someone here will be able to work out how much energy is saved by reducing DHW by one degree (I'm too lazy to do the sums).

Posted By: qeiplMy Ecocent came with a 55C default setting.

Ho wquickly does the output temperature of the Ecocent drop? Does it stratify well (i.e. keep the top hot)?

Mines entire DHW is set at 43 and it is the perfect temp according to the 3 of us - occasionally during the winter it needs the tiniest dash of cold but just depends on how one feels - during the summer we rarely use more than a tadge of hot as we live where its hot. Everyone is happy to shower with unmixed (and wouldn't have it hotter) but I would prefer a bit hotter to the kitchen sometimes, so for those big roast wash ups we boil a kettle. Can't see why I should waste heat on the way to the outlet points. Tank-in-tank (340 in 2000) heated 100% solar at top in summer usually 80 degs, never below 65 in shoulder seasons, wood burner in winter (80 deg every day or 2) so no legionella for me!

Posted By: wookeyA bath in a cold room needs ~50C water

The room will be very cold if you're pouring super-cooled water out at -50C ... I thought water could only go down to about -40C before it had to freeze?!

Good point about the bath topping-up temperature though!

Paul in Montreal

How come there are not big problems the other side of the pond then?

I'll call one of my former colleagues later (who's a microbiologist - some here know where I used to work, a certain establishment ~5 miles north east of Salisbury) and ask about the risk of legionella from water systems. I have a feeling that legionella and sealed clean water isn't that big a big risk. It's not my field by a long stretch, but logic suggests that the bacteria need a source of food and oxygen as well as warmth and I'm not sure what they can feed on in a sealed hot water system.

Posted By: JSHarris..........I'll call one of my former colleagues later (who's a microbiologist - some here know where I used to work, a certain establishment ~5 miles north east of Salisbury) and ask about the risk of legionella from water systems.

I'll get an answer too from my Water Authority neighbour. BTW JS in another life I used to work at the other, teaching establishment a couple of miles West of your old workplace> Visited your place on three or four occasions.

I've had a chat with a former colleague who knows far more than me about this stuff, and her view is this:

The bacterium does need nutrients as well as warmth (between 20 to 40 deg C) to grow and multiply and won't generally colonise sealed tanks that have no air surface or source of nutrients in the form of biofilms, sludge, scum etc. The risk comes from the bit of the water system that can have warm water sitting in them for days and also be exposed to sources of nutrients. She knew of the work that had been done on air cooling system problems and reckoned that the main problem there was the water in them was exposed to air and dirt and so became contaminated with enough nutrients to allow the bugs to grow. The evaporative coolers acted as a way to spray the bugs into the air in a fine mist, making infection far more probable (apparently infection is from inhaling the bugs in fine water droplets, not drinking water with them in).

She thought that the chance of legionella growth in a sealed, clean hot water tank was slight, the risk would be in the parts of the system that remained open, like shower pipes and nozzles, especially as there could be enough nutrients getting into those from back flow after use or just from splashing.

When I mentioned the way that the Ecocent does a weekly hot cycle to kill the bugs she reckoned that was fairly ineffective unless the taps and shower were turned on and the hotter water allowed to flush through the pipes. Overall her view was that we might be worrying too much, in that the most probable areas for bacterial growth in showers and baths had always been around the right temperature for legionella for years, even with very hot DHW tanks (because by that point it's mixed down to around 40 deg C), and the risk of infection in this way was pretty low. In her view electric showers might be the worse culprits, as they have a tank internally that is open to the air and if allowed to stand unused at room temperature for a few days could well breed a significant population, especially if they had a build up internal scale that might harbour biofilms effectively. She did point out that she'd checked with a friend from the place next door (the Health Protection Agency) and his view was there wasn't a significant risk from a sealed system.

I should perhaps add that she made a comment about there being far more serious bugs to worry about in the house than the remote possibility of legionella in the shower, but the conversation veered off into stories of bugs you simply wouldn't want to know about!

I'm personally content that it seems to be a bit of a non-issue, provided the shower head is cleaned regularly and the pipes flushed without causing a spray after a period of a few days without use.

<blockquote><cite>Posted By: Gavin_A</cite><blockquote><cite>Posted By: tony</cite>How come there are not big problems the other side of the pond then?</blockquote>
you seem to be making an assumption there that there aren't problems. I'm not sure that's right...

"in a study of 20 Pittsburgh patients with culture-confirmed Legionnaires’ disease. A link with residential drinking water contamination was established for eight (40%) patients. This included three private homes (one single dwelling, two multidwellings), two senior-citizen homes, two out-patient hospital clinics, and one industrial plant."

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2094925/


They do conclude that 49 deg is fine for water heated via boiler coils, but higher temps are needed for immersion heaters, because they don't tend to heat the bottom of the tanks properly.

For solar water heating systems though, a higher temperature is recommended because over winter the bottom of the tank may never or rarely be heated to legionella killing temps, so the temp at the top of the tank needs to be high enough to kill an bacteria as it passes through the hot volume at the top of the tank.</blockquote>

Worth noting that I've just been told that infection isn't from drinking water with legionella in it, but by inhaling large populations in a fine water spray. A lot of bigger air conditioning systems use water evaporative cooling which is a particular problem if not regularly treated to kill off the bugs, hence the prevalence of infections in bigger multi-occupancy dwellings, nursing homes etc in the US, where air-con is pretty much standard.