@william1066 mine is in "standard" mode not forced or power. Is that ok?

Posted by: @lfranklin

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@derek-m Hi, my apologies I will go out at weekend and get some thermometers etc and provide photos. Sorry for delay

No problem.

Posted by: @lfranklin

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mine is in "standard" mode not forced or power. Is that ok?

That depends on what you want to achieve and what you have installed.  If you have the right heat exchanger and hot water tank you should be able to operate on economic setting.  It is the most cost effective way of heating your water. If your plumbing config and heat exchanger/coil is not large enough then you will probably want to stick with standard. (which is probably why most installers set it to this mode, it is likely the "safe[er]" mode - no call backs)

I designed my own system, and then installed the heat pump myself with the specs I wanted.  I am able to heat my tank from 42 to 52 degC in about 30 minutes with the heat pump in economic mode.  This because the heat exchanger I am using can transfer at about 7kW per hour on average.

If your settings are on the default - as below

DHW->Heat Pump -> Max. Temp [FSV #3021] = 55 degC

DHW->Heat Pump -> Stop [FSV #3022] = 2 degC  (mine is 3 degrees here)

DHW->Heat Pump -> Start [FSV #3023] = 5 degC

DHW->Heat Pump -> Max Operating time [FSV # 3025] = 30 mins  (mine is 60 mins here)

DHW->Booster Heater -> On/Off [FSV #3031] = 1 [On]

DHW->Booster Heater -> Delay Time [FSV #3032] = 20 mins

Heating->Heat Pump->Heating/DHW priority [FSV #4011] = 0 (DHW)

The documentation is as clear as mud, from what I can work out .... for the case where max temp is 55 or less [FSV #3021]

... in standard mode, the heat pump should start heating the water when temperature in the tank is 48 deg (55-(2+5)) and stop at 55 degC.  It will use the heat pump only for the first 20 mins, then bring in the booster heater (element in tank) to help.  After 30 mins the heat pump will stop and the booster will carry on until you reach 55.

... in economic mode, the heat pump should start heating water at 48 degrees (55-(2+5)) and then stop at 53 degC (55-2)

I will switch mine to standard mode tomorrow and check what I get.

@william1066 

We have a 1.7l tank

I know when I tested on economic water mode (can set from wired controller in user mode easily) I was able to get hot water in about 30 seconds or so.

The boost heater was not enabled on mine by installers and was advised it costs more to use it to heat up last bit of water.

My standard DHW temp is set at 50° on main screen on wired controller and set to a max of 55° in the field setting value.

@lfranklin   You could try setting this to economic mode for a couple of days and see how well it works.  If you can get hot water with the tank set to 50degC then you have the right tank, for sure.

I have my schedules set to switch off DHW at 10pm and switch it on again at 4pm, this so it does not run during the day or over night.  As my wired remote controller is in the kitchen, if anyone needs a shower outside the 4pm-10pm slot it is easy enough to switch it on, and the hot water is heated up in about 25-30 mins.

@william1066 we have electric showers so don't need hot water to utilise 😊

How long does the hot water stay hot when DHW off out of interest or does it just turn on the DHW when you turn tap on to temp heat a small amount?

(Apologies in advance if dumb question.. have only ever had Combi boiler)

@lfranklin when the domestic hot water is off then it will lose temperature at a rate depending on the temperature around the cylinder and pipes. Also depends how well lagged your pipes are. As it is in your loft and if it’s freezing outside then you will see quite a loss of temperature up to 4° per hour. That is why it is best to schedule your tank to be heated just before you think you need to use it. If you have electric showers, then your hot water requirements are much less. With a solar diverter and solar PV, you have free hot water for eight months of the year or so. Therefore electric showers are going to be more expensive during that time.

The temperature probe that indicates how hot your DHW is is located lower down the cylinder, so even when it looks as if you don’t have very hot water, what comes out from the top of the cylinder and comes out of your tap often feels absolutely fine for washing hands and washing up.

@mike-h My DHW tank is in an understairs cupboard so typically at 18 or so ambient. It loses around 0.4° per hour.  I'm setting mine up to come on for an hour at 2300 (to coincide with brief heating set-back time) and 1300 (generally peak PV yield). We don't need much hot water use during the day and I reckon this will still give us plenty for early showers and evening baths.

Posted by: @lfranklin

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How long does the hot water stay hot when DHW off

My tank is not DHW, it is an indirect, and a rather old thermal store, so not too well insulated by modern standards, but is in a well insulated boiler room @ 22degC

... and it loses about  0.3 degC per hour starting at about 52 degC

... after the legionaries cycle, it will lose at a rate of 0.7 degC per hour going from 65 degC to 55degC

Both measured by the top thermometer (stratification makes measurement very approximate). 

If yours is in a cold space, it will probably lose heat at a faster rate depending on how new it is.  The tank, if new, should come with a spec sheet, that will give you an idea of the heat loss (for a properly installed and lagged system)

I'm interested to get the my Samsung Modbus connection up and running so I can monitor the DHW temperatures. I have a hot water circulation pump set up with a motion sensor in the kitchen to reduce the amount of time it takes for hot water to reach the kitchen tap when the kitchen is occupied. 

I suspect this is a big contributor to the hot water temperature loss but measuring it will give a much better picture. 

@dunlorn how are you getting on with your DHW schedule plan. Are you finding you have enough water for baths etc?

Hi @lfranklin. I'll let you know next week. I'm away at the moment and it's not really been tested with both of us in the house for too long. I'm confident it will be fine though.

I've had to have both heat pumps replaced in the last fortnight. One due to a refrigerant leak and the other cause not yet determined. Installer and Joule/Samsung have been good though and dealt with it quickly. I've a visit planned next week to help optimise and answer some queries I have.

One thing I have done is to take @derek-m advice and set the Hive higher than I want it to allow the heat pump to do the controlling. I've temporarily put the heat pump in fixed water temp mode so I can control easily and have been steadily trying to reduce LWT to achieve a flat line on the Hive heating profile at the desired indoor temp. I'm at home during the day so it's easy for me to do this and only takes a minute every now and then.

Before I went away I had the system keeping the house at the desired regular 18 ish degrees (around 6-7 outside) with LWT at 33°C and pulling just 1.4kW! That's a 4 bed stone built detached being kept comfortable for the equivalent of a single convector heater. Once you've got over the fact the central heating is running 24/7 at these ambients, the 'low and slow' setting has reduced cycling and is generating better COPs. The heat pump modulates itself to keep the buffer tank at the right temperature so it becomes the control and the Hive merely serves as a switch to stop house temp getting too high. I've more tweeking to do but this is really helping me understand a 'whole house' response.