Posted by: @gowzel

Hi everyone. I have recently had ASHP, Internal insulation and solar installed as part of a grant. It was all rather a nightmare. Located in an old stone built single storey cottage in N Wales

It has all been finished!!!!! mostly be me, no earth bonding, leaks, bolts missing and loose, bodged pipework etc.

We never had any heat loss calculations or any other paperwork, they left us with some of the manuals, but no explanation of how anything works.

Thanks to this forum and others, I now have a very good understanding of how ASHP work and should be set up, but some of the settings on the VRC 700 which was installed are some what vague, so if there is some one who knows these units well I would be glad of some help.

They have installed a Vaillant arotherm VWL 55/5 AS 230V S2 (I would have expected a plus model so don't know why they put this model in), a uniSTOR hot water tank, and a VWL 57/5 IS Hydraulic station.

Due to the weather I have not been able to test the C.H properly, the new rads got slightly warm, (we had back boiler on solid fuel stove heating before - they replaced all pipework to 15mm and put new "more efficient" rads in .

DHW seems to work well though not sure on the legionnaires settings.

Thanks for your time in reading this

Hi and welcome to the forum. I don't have any direct experience with Vaillant but there are one or two videos on youtube about your controller you can find on google. 

The fact that your rads are slightly warm shows the heating is working and it's probably working on weather compensation, which is good. 

This thread was about a user who had a few issues but it discusses Vaillant and VRC700 settings

https://renewableheatinghub.co.uk/forums/renewable-heating-air-source-heap-pumps-ashps/high-airsource-heat-pump-running-costs

Arotherm Plus is r290 so requires complicated siting of the outdoor unit because of the risk of gas leaks and pooling/explosion. A regular arotherm is r32 (or perhaps r410a, I haven't checked) so is much easier to site.

@hughf

R290 is Propane, which is indeed highly flammable and can create an explosive mixture when combined with air in the require percentage, but is more environmentally friendly should it in fact leak out. Since one of the main requirements for siting an ASHP is to have a free flow of air around and through the outdoor unit, I would sincerely hope that in the probably rare event of a gas leak, that this would not cause a serious problem other than probably stopping the unit from operating correctly.

I would also sincerely hope that the manufacturer has taken the possibility of a gas leak into account both during the equipment's design and the writing of the installation manual. I would therefore suggest that anyone with such a unit reads the installation manual to ensure that the manufacturer's specifications have been followed to the letter during its installation.

Thanks for the replies, I am pretty hopeful I understand setting the ASHP up optimally, but I am confused about some of the settings in the units, The legionnaires cycle for example, I have set it for Sunday mornings, when the sun (if it ever shone) is at max on our panels, I noticed that the attempted flow temp was 73 degrees, but have not seen where this temp was set, I am guessing that there is a 3KW?? heater in the outdoor unit which is used to get such a high flow temp, there is an immersion heater in the DHW cylinder which I thought would have been used, but do not think this has been wired to the control circuits, as when I turn it on at the mains switch it operates 24hrs and when I have tried running diagnostic tests from the hydraulic station the one titled immersion heater test switches on the circulation pump???

Is there an easier way to view the DHW temp on the VRC700 than having to enter the installers menu and scroll through everything before getting to the actual temp, surely it should be on the first screen?

I could not get the installers to return to fix leaks and serious safety issues so dont hold out any hope on them rectifying simple setup issues, I worked as a commercial heating engineer for 20 years and am a time served electrician but would prefer to understand fully these units before changing any thing,

@gowzel

The recommended legionella cycle is to heat the water to 60C for a minimum period of 10 minutes, every 7 to 10 days. Since you have solar PV I would suggest installing a power diverter, to provide much of your hot water from Spring through to Autumn and if you set the thermostat on the immersion heater at 65C, it would also perform the legionella cycle on an almost daily basis. We have an Immersun Power Diverter, but there are plenty of others on the market.

The benefit is that you would not need to run your ASHP solely for hot water production.

During the Winter months you would possibly get some water heating via solar PV with the rest provided by your heat pump.

If your desired hot water temperature is indeed set at 73C then you should lower this immediately to the level specified above. Some ASHP's do have booster heaters, but these should only be used as a last resort. Whilst an ASHP can heat water up to 60C, it does dramatically reduce the overall efficiency, but would still be more efficient than direct heating using an immersion heater.

I would suggest that you read through the operators manual and post any items of which you are uncertain.

Posted by: @gowzel

Thanks for the replies, I am pretty hopeful I understand setting the ASHP up optimally, but I am confused about some of the settings in the units, The legionnaires cycle for example, I have set it for Sunday mornings, when the sun (if it ever shone) is at max on our panels, I noticed that the attempted flow temp was 73 degrees, but have not seen where this temp was set, I am guessing that there is a 3KW?? heater in the outdoor unit which is used to get such a high flow temp, there is an immersion heater in the DHW cylinder which I thought would have been used, but do not think this has been wired to the control circuits, as when I turn it on at the mains switch it operates 24hrs and when I have tried running diagnostic tests from the hydraulic station the one titled immersion heater test switches on the circulation pump???

Is there an easier way to view the DHW temp on the VRC700 than having to enter the installers menu and scroll through everything before getting to the actual temp, surely it should be on the first screen?

I could not get the installers to return to fix leaks and serious safety issues so dont hold out any hope on them rectifying simple setup issues, I worked as a commercial heating engineer for 20 years and am a time served electrician but would prefer to understand fully these units before changing any thing,

The flow temp while heating DHW is different to the HW target temp.  When I set my DHW to 47 degrees, the ASHP flow temp is up to about 55 deg until the 47 degrees is achieved.  The ASHP 'decides' what that flow temp is;  the only way I can change it is to switch between the Eco and Normal modes.  Eco is lower and slower to heat.  That's a Mitsubishi Ecodan, others may be different.  I don't have a booster heater, the immersion does the legionella cycle. 

Thanks for info, my DHW is set at 48 at moment the 78 degrees was the target flow rate when it ran the legionella cycle, which I think would only be possible with an external heater I cannot see anywhere to set the legionella cycle time or temp.

I would love to fit a diverter but until I can find out how the immersion is supposed to be wired and what is supposed to be controlling it I a cannot. As mentioned above the test menu brought on the circ pump when it was supposed to bring on the immersion.

@gowzel

Since you have trained as an electrician I would suggest that you trace back the cabling from the immersion heater and see where it connects into the system. Find the terminal numbers and check the manufacturers connection diagrams. It may be that your installer has made a mistake.

As far as installing a diverter unit is concerned, the output from the diverter goes directly to the immersion heater, not via your ASHP Controller, though in Winter you may have to change this back to the controller.

@derek-m Hi there, apologies for piggy backing on this thread.

I'm up in North Wales too with a 15KW Vaillant Arotherm ASHP with the VRC700 controller. We’ve recently discovered the heat compensation with the adaptive heat curve was turned off by the original installer. We’ve turned this on and selected the 0.8 heat curve but the “target flow temp” in the “heating 1” menu doesn’t seem to be reducing as we’d expect with all the warm weather we’ve been having. Our electricity consumption has also remained consistent with figures before turning on the adaptive heat curve.

is there likely to be another setting we’ve missed we need to change too?

many thanks in advance for your help,

Kind regards,

Simon 

@simon Is yours fitted with a Hydraulic station inside, if so there is a different menu on the small control panel in there, I would have thought that this panel would have been over ruled by the 700, but there are different settings in this than are on the 700

@simon Did you also set the minimum flow temperature, it is one or 2 items below the curve setting, plus do not set the adaptive curve setting to on until you have seen that the heat curve you have set is working