Not stupid questions at all. How much information has your installer given you ? Do you know how they have set it up ? 

Having looked up Dimplex Smart Radiators they seem to be the complete opposite of mine ! Low thermal mass, very low water content, room by room control ?

Is your house a new build ? 

It was built in 1969. We have been in for 8 years the system was put in when we moved in. The ASHP works ok. It’s just the two smart rads at the end of the line that come on much later than all the others and go off much sooner. I am wondering if tweaking the the flow temp a bit higher may help, although not sure how to do this, is it called the LW temp?

Yes. Leaving Water is what’s in the radiators, DHW is the Domestic Hot Water ie what’s in your hot water cylinder or Tank. The heat pump will heat either the radiators or the tank, but not both at the same time.
 

The LWT is set either as Fixed temperature or using a Weather Dependent (WD) curve, actually a straight line graph, where the LWT varies with the outside temperature to balance the heat loss from the house. 

Say your DHW Reheat value is 40 deg, and your DHW is set to ‘reheat’ (it can be just reheat or reheat+schedule),  then when the tank temp drop below 30 the system switches to reheat it until it reaches 40. That assumes Hysteresis is set to the default value of 10 degrees.

Does that help !!??

Thanks for that, all helpful thank you. I think I am ok with the DHW settings etc.

my main issue is why those two rads at the end of line are operating as efficiently as all the others. I am just wondering if increasing the LWT will help. The LWT is currently set at 48 degrees C. 
 

I am also wondering what difference setting the weather dependency to ON, would have on the running of the system in general, economy wise and efficiency wise. 

I don’t know enough about your radiators to know the answer ! With my system I have all the TVRs open to keep flow unrestricted, it depends on a large volume of circulating water, that means I can have a lower flow temperature. I think that’s an ‘open loop’. I’m using the weather dependent curve and my flow temp is around 30 at 14 deg outside.

Great topic, great question @Boots and Bens. It will be helpful for anyone else looking for the same answer. 

Let me check if @amanda1 or @M.isterW can advise. Different heat pump, same question topic here:

Also I know @hydrosam’s Daikon experiences are something to be reckoned with. Perhaps they can advise. 

@Tim_OVO I’m not sure my Daikin experiences are a good thing to be sharing

@Boots and Bens a lower operating temperature, or leaving water temperature will make the system more efficient. But you also have to keep in mind what temperature the system was designed to operate at. If you know your way around the settings you won’t do any harm dropping the temperature a couple of degrees, it’ll just take the house a little longer to warm up. However the Daikin unit you have is likely to be the same as mine and is not intuitive to operate. 
 

Regarding your two rads that aren’t getting warm, this is likely a balancing issue and changing temperature won’t make much difference. There are plenty of guides on line with advice on this, or call a competent heating engineer. Do you get it serviced annually? Maybe the same company could do that, or try a heat geek who’ll be able to check all the settings and set up the system optimally

 https://www.heatgeek.com/find-a-heat-geek/

Thanks for the info. Am I right in thinking that if I lower my LWT by a few degrees, it may be more economically beneficial but because it takes longer to reach the operating temp that will negate any benefit from lowering the temp of the LWT, of course that may be rubbish as I don’t really know.

is the LW the actual water that runs round the rads? Does this just keep circulating round, arriving back at a lower temp to be reheated again continuously until the temp set by the wall thermostat, 19, in my case?

What is the inlet water?

I have looked at info on balancing but cannot find anything on Dimplex Smart Rads.

Who are HeatGeeks please?

Thank you 

Hello

We have fan assisted rads (not the Dimplex ones but they work the same way). The issue with them is that they need a minimum water temperature to operate. For best heat pump efficiency you want the lowest flow temperature but if it's too low your rads won't work. We run a flow temp of 35. We don't use weather compensation because it can be tricky to use with fan assisted rads. You risk dropping the flow temp below a level that will trigger the rads. We already run at the lowest temp we can.

The reason the two rads come on later is because the other rads take the heat before it gets to them. This is a problem with most heating systems but you notice it because you can see when the rad switches on. You might get a small improvement by increasing your heat pump flow temperature but that will decrease the efficiency and increase your bills.

Actually, you might get better results all-round with a lower flow temperature. 48 is quite high for a heat pump. Heat your house slowly and don't let it get too cold. Expect the rads to stay on longer.

Hi that’s very interesting. Before I try anything can you please tell me I am correct in my thinking. I am reading LWT Main as the LW temp, which is set at 48. When I look at the sensor when the rads are convecting it gets up to a temp of around 40. So to lower the LWT then I just reduce this setting from 48 to say 40 or 35. I was told by Dimplex that the rads need a temp of 35 before they start convection, so would an LWT of 35 maybe to low? I guess it’s a case of trial and error. My query is that if a LW temp Of 48 is not sending warm enough water to those two rads, how would a lower LW temp work?

thanks

I have a different heat pump so I'm not sure how to reduce the flow temp on yours. 35 would be too low as you lose some heat in the pipes. 40 is worth trying.

My thought on a using a lower flow temp is to gradually bring your house up to temperature, rather than doing it quickly using a high flow temp. Initially it will still be slow to heat those two rads but once the house is warm they will work fine. Just don't play around with the house temperature and don't let it drop too much. You can't treat it like a gas boiler.

To answer a couple of your other questions:

Look at https://www.heatgeek.com/  - they have lots of videos about running a heat pump and getting the most out of it. A lot is technical stuff for installers, but there’s advice for homeowners too. If you’re lucky there’ll be one in your area who might be able to check over your system. They have a map at https://www.heatgeek.com/find-a-heat-geek/

My Daikin controller has this display which shows, amongst other things, the temperatures of the water which flows through the radiators.

Leaving Water is what leaves the heat pump (also called flow in plumbing terms) so 37 deg in this case.

Inlet Water is the same water, now cooler, returning to the heat pump to be reheated (called return in plumbing terms). 

PHE is the Plate Heat Exchanger (don’t ask!).

If your controller is like this let me know and I can tell you how to alter the LWT, though it sounds more like @hydrosam has the same one as you.

Yes just the same 

Juliamc 

who are HeatGeeks? What makes them different from other installers please?

My brain has been pondering your problems overnight. Do you have isolation valves on the pipes to the radiators? I don't know if this is recommended but you could limit the flow to the rads at the start of the circuit by partially closing the isolation valves.

The other thing you could try is bleeding the rads. I think the instructions for this are in the manual.

Hi

the installers added butterfly valves to several of the rads a few years back to try what you suggest. It is such a faff to try how open or closed each valve needs to be for best effect. Also I can’t get my head around how slowing the flow down will help? Won’t this even take longer for the flow to the end rads reach the desired temp to set them off?

I have tried bleeding but when I loosing the screws only water drips out and I am not sure if this means there is no air in the system??

Enthusiasm. Training. Attention to detail. They won’t just sling in a heat pump and leave the customer to work out how to get the best out of it. There are installers who are just as good but a HeatGeek badge makes them easy to spot!!

Great thanks 

Mon the map there are different colours, do you know what they mean? We have one in Elgin which is nearest. If I call him should I mention Heat Geeks. Cheers again

On their website it shows the various levels of training courses they’ve completed. Yes def mention you found them via the HeatGeek website. Btw I don’t have any connection to them except I was lucky enough to get a top heat geek to check over my heat pump and advise my installer what needed doing to improve the performance. 

I, too, have a Daikin ASHP and the control panel seems to be the same too.

I had issues with the rads that were furthest away in the system not heating up and to solve this i balanced the system, by which i mean i tweaked the rad valves (not the trv’s) in a way that from cold all rads warmed up evenly together.  I restricted water flow to the rads nearest the pump, moving the heated water on to the next.  This is time-consuming but worth it as you have to restart the process from cold every time you have tweaked the system until you get all rads to warm up evenly together.

Worked a treat, i also tweaked the trv’s afterwards to turn off the rads in rooms that i didn’t want to get too warm, such as my bedroom (i prefer a cool bedroom, no more than18 otherwise i can’t sleep, far too warm!).

Haven’t explored tweaking the LWT controls at all yet and Weather Comp is enabled

Thanks for sharing this, @akwe-xavante. 

I’d love to understand this a bit more, and get the thoughts of @juliamc and @Boots and Bens. I know @M.isterW doesn’t have a Daikin but perhaps they’d also be interested. 

When you say:

I just don’t understand the process. Is this a one off to find optimised individual rad levels that ensure they all heat up evenly? Is it literally a case of turning the rad valves up and down? How do you know the right adjustments to make? 

If you are finding that one or more rads are heating faster than others and or just not heating up at all or not as much as some then the systems radiators need balancing. 

Balancing the radiators in a system ensures that radiators warm up together evenly. 

Open up / turn all tvr's to their maximum setting, typically 5.

From cold turn heating on and work out which radiators warm up first, you have a radiator valve opposite to the trv, using either an Alan key or a pair of pliers turn the valves on the warmest radiators clockwise 1/4 turn. This restricts the flow of heated water through those radiators and moves it on to those radiators that need more. Turn heating off and let things go cold and start again and repeat until you get all radiators warming up evenly together. The heating system is now balanced and heating up your home correctly. 

With a balanced system then you can use the tvr's to adjust temperatures room to room. 

An example may be that you like a cool bedroom and it's too warm. Turn the tvr to no2, the tvr will turn off that radiator at 15 degrees and the heated water in the system moves the water elsewhere in the system. If no 2 is too cool, turn it up a tad until you find what your happy with.

Turn clockwise to close or restrict water flow. Turn anticlockwise to open or increase water flow. 

Thank you for clarifying, @akwe-xavante. 

@hydrosam may also be interested in this ^^^

Thanks @Tim_OVO 

One I am well aware of, it’s one of the basic things that you want to get right when a new system is installed (and one neither of my installers did…).

If anyone wants to get really geeky on balancing there are a good few articles here. https://www.heatgeek.com/category/balancing/