I’ve been using an ASHP for the last few months. The tap water generally comes out at between 45 and 50C
I was looking at thermistatic shower and bath taps, and they all seem to state that they will only work when the hot water is between 55 and 60C
Does anyone have experience of how true this is? I’d quite like to put a thermostatic mixer on the bath and shower since with the tank the hot water temperature is more variable than with the old combi - but not if it will struggle to cope with the slightly lower temperatures I now have compared to when using a combi that might be a bad idea….
I’ve used a Mira Platinum ‘Digital’ thermostatic shower with a heat pump for nearly 10 years and I’ve never noticed any issues running it with hot water stored at max. 50C. Checking the specs just now, it does say it wants 55 - 65C.
(I chose a ‘digital’ model because the control box is best mounted outside the bathroom - it’s in a nearby built-in wardrobe - leaving it easily accessible for servicing, if required.)
I am aware I prefer my showers cooler than some people though; I typically run the shower at 35C whereas some family members who visit have commented they wish it would go higher than 45C!
That’s interesting. I asked Mira about this in relation to the digital product last week and they said:
“
Our products have a recommended temperature range of 55 degrees to 65 degrees.
Temperatures below our recommendations will not work with our products and will cause error codes.
That’s certainly not my experience - I’ve never seen an error code related to low hot-water temperature, and there have definitely been times when the DHW cylinder dropped well below 50C.
It’s possible they’ve added some extra error checks in their latest models, I suppose.
The scenario of “running out of hot water” is hardly unusual and - in my view - the least-bad thing for a shower to do in that scenario is to continue supplying water at a lower temperature than requested. There’s no risk of scalding.
I’ve run a Daikin HP with 230 litre HW tank, with a normal HW temperature set to 50C, rising to 60C once a week for the Legionella cycle. I heat the HW at midday and we usually take showers either first thing in the morning or sometimes in the evening. We have two normal Grohe thermostatic mixers on the showers and never have any problems at all. Sometimes the water tank is down to 45C or less if the kids got there first but still no problem.
I prefer to store water normally at 50C as it’s safer (minimal scald risk) and more efficient both in heating up and heat loss. Central Heating is not normally needed at midday as I’m usually cooking and also has the benefit of warmer outside temperatures to help the HP.
I think the reason some valves require a higher temperature is that its hard to design a reliable valve that seals off the cold properly, without sticking. Its easier/cheaper to design a valve with faitly loose moving parts. This means there is always some cold getting through. Its a matter of finding a valve with a good design that shuts off well. Sorry, I dont know what ones are best,but the spec should tell, and a good quality, good brand should be best
We have recently had a new en suite wet room installed using an Aqualla concealed shower valve and it works absolutely fine with DHW stored at 48C. We heat our water at 3am to utilise off peak cheap electricity and again around 3pm to utilise maximum outside air temperature. I prefer a morning shower and my wife prefers an evening shower and we’ve never run out of hot water or had any weird behaviour with the mixer valve. HTH
I have several thermostatic mixers (Mira shower, outside dog shower and a bath filler), all fed by 45C hot water and have never had any issues. The manufacturers are probably saying that to cover themselves but I would say flow rate is important when your hot water feed temperature is close to your desired outlet temperature, otherwise you may experience poor performance.