ASHP - Configuration Guidance

[andy]

Hi all

 

So I have my 8kW Samsung ASHP all up and running and heating the house and I'm trying to understand the bloody awful Samsung manual and general behavioural patterns of the ASHP.

 

Whilst it does get the house nice and warm and as expected it's slow to respond due to the depth of the UFH pipes (on insulation under 125mm reinforced slab - don't ask..., was supposed to be on rebar but due to the winter from hell end of last year, it had to go on the insulation) I am confused about the behaviour of the pump and what to set on the controller...

 

I've set Water Out Temp. for Heat to 40C max and 25C min and it seems that the flow temp seems to aim to be circa 5C more than the return temp, which is I assume a target delta which is also set in the Samsung?

 

In addition, it seems to be doing a defrost cycle about every hour, which seems excessive compared to what I've read of other ASHP set to 40C on here.

 

Is anyone familiar with the Samsung control unit and what the most sensible settings are?  I am concerned that I'm using a lot more electricity that I maybe need to to get heat into the slab at present.  Do you need to know any other settings that would infulence this?

 

I am triggering the ASHP from Loxone and associated manifold pumps, which is all working fine (albeit somewhat basic at present but I'll get there!).

[joe90]

My single heat temp on my kingspan unit is set to 48’ and I have yet to see it defrost!.

[PeterW]

50 minutes ago, andy said:

seems that the flow temp seems to aim to be circa 5C more than the return temp,

Sounds about right for an 8kW unit - they steadily increase the flow temperature as they can’t just Chuck high grade heat in like a boiler does. 
 

Defrost hourly sounds a bit much but it may be the outside humidity is causing this - that has a much greater effect than the temperature. 

[andy]

1 minute ago, PeterW said:

Sounds about right for an 8kW unit - they steadily increase the flow temperature as they can’t just Chuck high grade heat in like a boiler does. 
 

Defrost hourly sounds a bit much but it may be the outside humidity is causing this - that has a much greater effect than the temperature. 

 

Cool thanks, that's good to know it's working as expected in that respect.  I will just keep an eye on the daily consumption in kWh at this point I think and see what it's chewing up...

 

I've got 1-Wire sensors on the flow and return to/from the ASHP in the loft (long 28mm Hep2O runs, no joins - that was fun!) and at present it's 34.4C flow and 28.3C return.  Eventually I'll have more 1-Wire sensors on each manifold and the outside unit and I will start collecting stats but for now I had to go for minimal viable house!

[andy]

13 minutes ago, joe90 said:

My single heat temp on my kingspan unit is set to 48’ and I have yet to see it defrost!.

 

Perhaps the Samsung is more demanding in that respect?  Seems odd though as I'm clearly heating the outside every time it does a defrost

[jack]

What do you mean by max 40 and min 25? Are they weather compensation values?

 

What's your under-slab insulation like? 40 seems a high temperature if you have a lot of insulation. I have 300mm EPS under our slab and never have the temperature exceed 30 for heating. Generally I run it at 25, the lowest temp the unit will do, with weather compensation ramping up between 7 and 0. 

 

Bear in mind that the worst situation for defrosting is high humidity, cold outside temperatures, and high heat demand. Often, this peaks when the outside temperature is in the low single figures. As the temperature drops further towards and beyond zero, the humidity tends to fall quite fast too, which reduces icing.

 

I don't know whether the delta value can be set in your ASHP. Unlikely, I'd have thought. Certainly there's no such setting I'm aware of in my Panasonic ASHP.

 

How are you using Loxone to trigger the heating? Hopefully not with one of the intelligent heating controllers. I don't think they cope well very long time-constant situations, like UFH in a deep slab.

[ProDave]

If you have the water temperature set point at 40 degrees and it's only currently achieving about 35 degree flow, then the compressor will be working flat out trying to get as much heat in as it can to reach it's target.  And if the air temperature is only just above 0 with high humidity that is the worst condition for icing and the need for defrosting.

 

Perhaps lower the target temperature a bit until the slab has thoroughly warmed through to make it work a little less hard?

 

It's well below 0 here and strangely icing becomes less of an issue as there is no moisture in the air.

[andy]

I think it ramps up to 40 max based on delta between flow and return? So until the return nears the desired flow temp, it will keep ramping slowly up I think?

 

Loxone is just sending the run command to Samsung controller and that’s working out what needs to be done to control ASHP itself.  DHW is left solely under Samsung control at present but I may change that to Loxone too later on with the run signal coming to Samsung from Loxone, with Loxone configured to avoid running heating during that window.

 

It’s currently about 2C here and

wet so it’s the worst possible conditions I guess!

 

Slab is 300mm EPS and I am not sure what the Samsung lingo is for weather compensation, the manual is terrible... I don’t know what the impact is of max/min water out temps tbh but I assume they are the target operating ranges?

 

I could turn it down to 25-35 and see what that does.

[jack]

23 minutes ago, andy said:

Slab is 300mm EPS and I am not sure what the Samsung lingo is for weather compensation, the manual is terrible... I don’t know what the impact is of max/min water out temps tbh but I assume they are the target operating ranges?

 

I could turn it down to 25-35 and see what that does.

 

Re weather compensation, perhaps look for a drawing that looks something like this (from my Panasonic ASHP manual):

 

 

Given the level of insulation you have, I'd say that 40 is too high. Hard to say for sure given how deep your pipes are buried, but I suspect if anything that would encourage the use of lower temperatures over a longer period of time.

[Pete]

20 hours ago, andy said:

I think it ramps up to 40 max based on delta between flow and return? So until the return nears the desired flow temp, it will keep ramping slowly up I think?

 

Loxone is just sending the run command to Samsung controller and that’s working out what needs to be done to control ASHP itself.  DHW is left solely under Samsung control at present but I may change that to Loxone too later on with the run signal coming to Samsung from Loxone, with Loxone configured to avoid running heating during that window.

 

It’s currently about 2C here and

wet so it’s the worst possible conditions I guess!

 

Slab is 300mm EPS and I am not sure what the Samsung lingo is for weather compensation, the manual is terrible... I don’t know what the impact is of max/min water out temps tbh but I assume they are the target operating ranges?

 

I could turn it down to 25-35 and see what that does.

I am currently going through this with my Panasonic Aquarea 9kw. Everytime I go past the plant room I check the parameters on my ashp. With help from @jack(many thanks) I have turned the heat down now to reduce the hot flow as it was over 35 degrees. I also think you have to get to know your house as mine is predominantly ground floor (26m x 9m ish internal) so will take more heat than a smaller footprint. It is a steep learning curve and you do not get instant results like a boiler so you have to persevere! 

[andy]

Lowest flow rate I can set on the Samsung is 37, which is what it's now set to.

 

My house is only ground floor (apart from unheated mezzanine) and an inefficient shape to boot, so I knew it would take more ASHP running than if I had built a cube.  At present, just got the heating on a timer running 06:00-11:45 then 14:00-20:00 (with DHW being done in the gap) and the house is nice and warm.  Electricity bills to be worried about later

[SteamyTea]

Does your defrost come on at set times, and run for a set time?

Wondering if it is a preventative measure, rather than the weather.

As you have a deep slab that the pipes are in, is it driving a lot water out of it i.e. is your house humid.

Water takes over 4 times as much energy to heat up, and the the evaporation losses are added to that. To evaporate a kg of water takes 2450 kJ/kg.

[PeterW]

5 hours ago, andy said:

Lowest flow rate I can set on the Samsung is 37, which is what it's now set to.

 

My house is only ground floor (apart from unheated mezzanine) and an inefficient shape to boot, so I knew it would take more ASHP running than if I had built a cube.  At present, just got the heating on a timer running 06:00-11:45 then 14:00-20:00 (with DHW being done in the gap) and the house is nice and warm.  Electricity bills to be worried about later

E7 meter ..?? Run it overnight ..?? Do a big chunk of heat at low cost, same with the hot water tank. 

[andy]

23 minutes ago, SteamyTea said:

Does your defrost come on at set times, and run for a set time?

Wondering if it is a preventative measure, rather than the weather.

As you have a deep slab that the pipes are in, is it driving a lot water out of it i.e. is your house humid.

Water takes over 4 times as much energy to heat up, and the the evaporation losses are added to that. To evaporate a kg of water takes 2450 kJ/kg.

 

No slab is fully dry now and the MVHR is showing circa 50% humidity.  To be honest, as long as I find a sweet spot for the heating to run at, I'm not bothered - yes, it would have been better to have the pipes 50mm higher up the slab but hey ho, that's just the way the build ended up - next time   Next time I will definitely buy a larger, flat plot and do an insulated raft foundation...

 

More importantly, utility wall hung loo all ready to slot on now and bathroom is getting ready to have a tray and be tanked - so steady progress on other matters.

[andy]

13 minutes ago, PeterW said:

E7 meter ..?? Run it overnight ..?? Do a big chunk of heat at low cost, same with the hot water tank. 

I'll find a suitable tarrif at some point once I see what the consumption is like.  Original plan was to have a Tesla Powerwall 2 to accompany the 6kW of PV but as we've ended up going 3 phase, SSEN are saying that I need to buy 3 (yes 3!) of them, one per phase... so that's on hold right now.

[andy]

On 28/12/2020 at 13:03, jack said:

 

Re weather compensation, perhaps look for a drawing that looks something like this (from my Panasonic ASHP manual):

 

 

Given the level of insulation you have, I'd say that 40 is too high. Hard to say for sure given how deep your pipes are buried, but I suspect if anything that would encourage the use of lower temperatures over a longer period of time.

 

So it seems it does, it's just the terminology and menu layout leaves a little to be desired... anyway!

 

What I have it set to now is max temp of 42C at -2C outside or lower and 37C at 15C outside, so it should work harder in colder as per your compensation curve.

 

Right now for DHW and heating on a 180m2 single storey, stretched building with UFH pipes that are too deep I am using circe 25kWh/day - and that's having a bath 'cos shower is still on the things to do list   House is nice and warm but power consumption higher than I had imagined but c'est la vie.

 

As an aside, I've given up on the idea of Loxone actuators now though, going to go with Salus instead to balance flow temps, still TBC about what Loxone switches I will configure to trigger the heating to come on as I think I will just heat the whole house as an entity, seems to be working at present doing that approach with the binary controls I have in place!

[jack]

Bear in mind this is the absolute worst time of year for power consumption.

 

But even if it stayed like this for the entire year, you'd be paying a bit more than £1000 (depending on tariff) for all heating, hot water and electricity - doesn't seem that expensive to me for a decent-sized house.

[andy]

11 minutes ago, jack said:

Bear in mind this is the absolute worst time of year for power consumption.

 

But even if it stayed like this for the entire year, you'd be paying a bit more than £1000 (depending on tariff) for all heating, hot water and electricity - doesn't seem that expensive to me for a decent-sized house.

True, and 6kW of solar will mean I'll be using a lot less in summer - need to get my Eddi ordered though!