View Full Version : Daikin LT ASHP: Optimising Settings for DHW

20-10-2012, 07:51 PM
Um I am trying to work out the best options for DHW for my LT system consisiting fo the following.

•Heat pump outdoor unit is a Daikin ERHQ016BAV3
•Heat pump indoor unit is a Daikin EKHBH016BB6V3
•Tank is a Daikin EKHW5U300B3V3

I have been watching it for about 7 months now and with DHW on all the time it heats water every hour or 2 for a few minutes even when none has been used, as soon as there is demand it heats as well (as expected).

I am now going to put a timer on for DHW but I can't decide the best time to do it. We have a 5 bed house which is highly insulated and normally only has 2 people in it. We have showers between about 0600-0900 most days and then use almost no hot water for the rest of the day. We also have 2 solar panels which may heat during the day.

My initial thought was to set the DHW timer to run from about 0400-0800 which should mean hot water for when we shower and a good change that it will be reheated after the shower. However this will also probably be the coldest time of the day outside which will mean the ASHP will be working hard and be less efficient. So next thought was run it for about 4 hours from approx 1600-2000 and then again for 1 hour from 0500-0600. This would proobably be more efficient in terms of the pump but I am not sure how much heat will be lost dirung the night from the tank and if 1 hour will be enough for reheat.

Obviously I alslo want to gain from any solar heat I can pickup during the day.

So grateful for any thoughts and suggestions.

24-10-2012, 11:03 PM

any thoughts on this?

02-12-2012, 09:19 PM
Hi wytco0,

To make the best use of your solar thermal I would suggest moving your 04:00 - 08:00 window to 12:00 to 16:00 hours. If you start at 04:00 them when the sun comes up it you will already of heated your tank with the heat pump. If the sun hasn't been out before 12:00 hrs the chances are you will need to heat your water so I would suggest that is the time to bring it on. In addition I would also suggest an hours boost just after teatime to ensure that you have enough to use in the evening if you wish and some for the morning. With the high level of insulation on the tank I would suggest that losses will be minimal. Also be sure to set the pasturiation to come on after the tank has finished its time slot in the evening for hot water this ensures the heat pump has done the initial work and the last little bit is carried out by the immersion. I always set the pasturisation for the weekend to make sure that I get the most out of it.

Hope this helps.

03-12-2012, 09:47 AM
The system will heat your DHW depending on the time schedule, set point, solar priority, heating/DHW priority and temperature differential.

If you have the time schedules on all day then the system will cycle on the set point differential, as the cylinder either looses heat from usage, drawoff or stratification.

To save energy (money), the first thing I would do is change the time schedules, allowing a heat up time of 90 minutes before usage, so, if you want a shower at 6am, have your system come on at 4:30am. If you don't use hot water after breakfast, then allow the solar to do it's work for the rest of the day.

As the unit can only do your heating or hot water at any one time, consider the amount of heating you need and at what time to make sure the house is nice and toasty warm for when you get up and have your shower :)

Also, you might consider having Economy 7/10 installed, which will save you even more money.