Which model Samsung.  if its an older one and the max FT is 55, which is quite possible, then its equally possible that the DHW is limited to 55-5=50.  I dont know this from Samsung specifically, just applying general principles

@imb123 There are some settings that you need to adjust for DHW max setting:

1. You need to go into the "Field Settings" and navigate to #3021 which sets the maximum the pump can heat to

2. Navigate to field setting #3022 and ensure it is set to zero otherwise the pump will only heat to Max - Stop value

3. Ensure you have enough user tank temperature control range by checking field setting #1051

I assume your pump is capable of acheiving 55 C tank temperature which would require a leaving water temp of approx 63 C? (High Temp ASHP)

Hope this helps.

@imb123 which model do you have? 

DHW temperature can be set higher but anything above 50C will probably engage the immersion heater. As far as I know though, this setting is not accessible to homeowners.

Posted by: @editor

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DHW temperature can be set higher but anything above 50C will probably engage the immersion heater. As far as I know though, this setting is not accessible to homeowners.

As you say that will almost certainly be the case with an 'older' (low or medium temp) Samsung model, but possibly not with the HT models.

Vaillant, for example, with their R290 models, do the disinfection run natively and don't (by default) rely on or require any connection with the immersion heater at all.  I have no idea if Samsung do similar but of course this is only possible with models where FT can go up to 70/75C

@jamespa I have the Samsung high temp quiet model and when set to economic mode the pump can heat to a maximum of 55C. To heat it higher (Standard etc) it has to engage the immersion but also the user temp range needs to have been set to allow this. Mine is currently set to 65C however the pump never gets there because I do not have immersion support set up on the pump (it is controlled independently). 🙂 The pump and controller are less than a year old so should be the latest model.

@technogeek I have the very same issue. I've bought HT Quiet (R32) just because it is capable to heat water to 70C (at least this is what they say in advertising) but for some reason I can't set up more than 55C for DHW. Also disinfection cycle is not working without booster heater connected do DHW tank (written in manual). This is huge disappointment an honestly does not understand why is that. I understand that flow temp must be higher to achieve 55 water temp but I would expect more. Did you find any solution for that ? What water temperature do you use for DHW ? Seems my only possibility is to buy 3KW booster heater.

@misiak Hello. The Samsung pump is capable of generating a flow temperature of up to 70C. The heat transfer into DHW (depends on storage tank efficiency) from the tanks coil is about 8C - 10C less. This means your heat pump on its own can only produce up to 55C DHW. To achieve 60C or above you need to finish the DHW cycle using the immersion boost if fitted.

Its a matter of physics, the flow temperature needs to be at least 8C hotter than the required DHW temperature for heat transfer to happen.

Using this process is expensive and to be honest not needed. You will find 55C plenty hot enough. If you have a high turnover of hot water then a legionella cycle is only required after being on holiday or a length of extended time the water has been stagnant in the tank.

The HeatGeek team do a very good video on the subject of DHW generation and legionella cycles etc, well worth a watch 🙂

@technogeek thanks for a reply. I really found a field setting for controller which allows to set 70Cbut (it was set to 55C so I was confused at first) as you have said this is not possible to achieve without immersion heater. At 70C this is a torture for the pump anyway and it yields with max. 60C for a DHW temperature.

So now it matters what do you consider as stagnant water. I've intentionally bought a bigger tank (280L) to run with a lower temp ~48C. Before I had 120L electric boiler with 70C water. My turnover is mostly 25%. Middle week and weekend maybe 50 - 75%. But some days it could be even less than 25%. Can you see it as a problem with water heated to 48C (middle of the tank) or it's fine. For me this legionella is kind of theoretical problem since I've never encountered any issue from it so not sure if this is overrated issue or not. 

Would you mind to share video to that cycle ? 

Thanks!

@misiak I think this is a link to the heatgeek resource