Ashp settings

[sirpatchuk]

Hi,

 

I posted before about our ashp not getting up to temperature and it turns out a zone thermostat was in the wrong place.

 

Now I would like advice on where to start with testing the settings. Granted, probably not the best time to test them with the current weather.

 

Grant ASHP 17KW

UFH downstairs (3 zones)

7 oversized radiators upstairs (all smart thermostats)

 

We have a 1950s detached, 4 bed house in a village.

No cavity wall insulation (but booked in to be done)

Good loft insulation.

- weather compensation on/off?

- thermostats set high or temp we want to achieve? 

- we have two log burners… use them?

 

[sirpatchuk]

The minimum and maximum outside temperature for weather compensation what should these be?

[sirpatchuk]

I am thinking put the minimum and maximum flow rate at 35, turn weather compensation off and set the thermostats to 25. Then it will always be calling for heat and therefore be running constantly at the low flow rate. 
 

We can use the log burners in the evening for the extra heat…

 

thoughts?

[JohnMo]

Go on to heat geek website read up on weather compensation, zones and system balancing. Spending a hour of your time, read and watch the videos.

 

Get some basics understanding and then most of your questions will answer themselves.

[Marvin]

9 hours ago, sirpatchuk said:

The minimum and maximum outside temperature for weather compensation what should these be?

Tricky.

 

The minimum outside temperature we set ours at was -4 degrees centigrade (the coldest temp in the last few years where we are) and the heating water temperature 45 degrees centigrade 

 

The maximum outside temperature for our home is 10 degrees Centigrade and the heating water temperature 35 degrees Centigrade.  

 

These were based on estimates taken from our building thermal calculations spreadsheet. 

 

 

[ReedRichards]

1 hour ago, JohnMo said:

Go on to heat geek website read up on weather compensation, zones and system balancing. Spending a hour of your time, read and watch the videos.

 

Get some basics understanding and then most of your questions will answer themselves.

 

The Heat Geek website preaches a very hard core style of weather compensation.  You can still use weather compensation to reduce your running costs without abandoning the use of thermostatic controls.  And when it's very cold outside, weather compensation will make the least difference.

Edited December 12, 2022 by ReedRichards

[crooksey]

My heatpump runs at 35-38 degrees normally, these last few days I upped it to 45 as 38 didnt give us enough heat for the rads (upstairs) but 38 was still plenty for the UFH.

 

I turned off weather compensation as my lowest water heating flow temp is 35 degrees, which is fine all the time the outside air temp is above 0. But when it drops below, It takes me 10 seconds to increase it from my phone so more efficient to leave it off and run at the lowest flow temp I can.

 

[Ralph]

I think cold weather is probably the best time to try and set the weather compensation. I'm playing about with ours now.
It's -7°C here and I have the Thermostat set to 23°C to act almost as a limiter and the weather compensation is set as below. It could be that the flow temp is a bit high so I'll bring it down over the next few days, depending on how it performs. 

Currently the house is at 22°C and I've burned 1KWh on heating since midnight.

 

If I had a log burner it would be going when it's this cold for sure.

 

 

 

 

Edited December 12, 2022 by Ralph

[sirpatchuk]

14 minutes ago, Ralph said:

I think cold weather is probably the best time to try and set the weather compensation. I'm playing about with ours now.
It's -7°C here and I have the Thermostat set to 23°C to act almost as a limiter and the weather compensation is set as below. It could be that the flow temp is a bit high so I'll bring it down over the next few days, depending on how it performs. 

Currently the house is at 22°C and I've burned 1KWh on heating since midnight.

 

If I had a log burner it would be going when it's this cold for sure.

 

 

 

 

Wow, 1kw

 

[sirpatchuk]

17 minutes ago, crooksey said:

My heatpump runs at 35-38 degrees normally, these last few days I upped it to 45 as 38 didnt give us enough heat for the rads (upstairs) but 38 was still plenty for the UFH.

 

I turned off weather compensation as my lowest water heating flow temp is 35 degrees, which is fine all the time the outside air temp is above 0. But when it drops below, It takes me 10 seconds to increase it from my phone so more efficient to leave it off and run at the lowest flow temp I can.

 

what have you got your thermostats set to? Are they always calling for heat?

 

we have three zones downstairs for UFH and each room upstairs is it’s own zone with a thermostat radiator 

[Ralph]

24 minutes ago, sirpatchuk said:

Wow, 1kw

 

I'm pretty sure that will get smashed in the next few hours and I'll be dropping the the flow temp to 40.

[crooksey]

35 minutes ago, sirpatchuk said:

what have you got your thermostats set to? Are they always calling for heat?

 

we have three zones downstairs for UFH and each room upstairs is it’s own zone with a thermostat radiator 

 

My radiators in the bedroom are calling for heat on a timer, I have them on constant between 5pm and 7am, got two young children so have the house heated all night. Especially when we are -5C here. And we are mid-refurb, the rooms below the kids rooms have no heating in at the moment, so colder than they would usually be.

 

UFH downstairs I wired a thermostat to each zone, so calls for heat as and when needed. 

[sirpatchuk]

5 minutes ago, crooksey said:

 

My radiators in the bedroom are calling for heat on a timer, I have them on constant between 5pm and 7am, got two young children so have the house heated all night. Especially when we are -5C here. And we are mid-refurb, the rooms below the kids rooms have no heating in at the moment, so colder than they would usually be.

 

UFH downstairs I wired a thermostat to each zone, so calls for heat as and when needed. 

What temp have you set them too and what kWh are you using?

[JohnMo]

1 hour ago, ReedRichards said:

preaches a very hard core style of weather compensation

Nothing wrong with that, but they don't preach to bin all the thermostats, they do say to set your thermostats above your target temperature as limit stops though.  Not really sure that's hardcore.  They do say to limit the amount of zones you have, for a heat pump that keeps a large capacity of water available for the flow rates a heat pump needs and helps stop short cycling when heat demand is low. 

 

Limiting zone and using thermostats or Trvs at above the target temp are both things are exactly what what my Atag boiler manual says if running WC.

[ReedRichards]

I used to have an Atag gas boiler in my old house (now I don't have mains gas).  I really liked it and it was way ahead of its time when I got my first one in 1998.  However since it did both Load Compensation and Weather Compensation there was no need to set the room thermostat at anything other than the temperature you wanted because it would modulate the output to maintain that temperature very precisely.  It was not thrown by TRVs elsewhere in the house.

 

Using a thermostat as a "limit stop" is effectively abandoning the use of the thermostat and to me that is hard core.  I use my thermostat to gradually increase the house temperature during the day and then set it back overnight, something difficult to do unless you have a controller that allows you to program multiple changes to the Weather Compensation settings (which few of us do).  This may cost me slightly more than the thermostat-free Weather Compensation advocated by Heat Geeks, although I'm not sure it does.    

 

 

Edited December 12, 2022 by ReedRichards

[markocosic]

Most of the heat pumps those guys use have curve shift etc built into the heat pump controls.

 

(i.e. you can offset the entire weather comp curve up or down to effect night setback or holiday setback)

 

They also have load comp too mind. TRVs as limit stops is more for bedrooms outside the main zone.

[ReedRichards]

My LG heat pump lets you manually move the weather compensation curve up and down by 5 degrees either way but this is a manual adjustment, it's not programmable.  AFAIK only a small minority of heat pumps would let you program a change to the weather compensation settings at particular times.    

[crooksey]

21 hours ago, sirpatchuk said:

What temp have you set them too and what kWh are you using?

 

An average day, I use about 40-50kw a day for heating and hot water. My wife is home all day, and kids have baths with heating on all night, so it uses a fair bit. Upstairs we still have traditional steel radiators, which again we will replace with aluminium ones, but haven't got round too yet, again next year this should help and reduce my flow temps further.

 

This is a 5 bedroom house and we are "mid" renovation, so some rooms have no ceilings/heating, so this should be reduced when we are finished.

 

We don't have any mains gas in our village, so this heat pump replaced an old LPG tank and boiler, so considerably cheaper than buying LPG.

 

I am hoping to have solar next year, which should help quite a bit.

[sirpatchuk]

I think I have a combination of issues and not sure where to start first.

 

think my Honeywell Evohome talking to the grant heat pump controller may be causing the pump to operate more than necessary 

 

 

[crooksey]

How many kwh per day are you using and what are your issue?

 

The honeywell home should just be calling for heat.

 

Usually the hot water is wired direct to the heatpump controller, most heat pump installs I have seen/come across simply heat the tank automatically when it drops below a certain temperature, its not like a traditional system boiler when you run it at certain times of the day.

 

Log burners are additional heat sources, I rarely need to use mine, but when we have an outside air temp of -6, even if you had traditional gas boiler, its going to be warmer inside with the use of a log burner. Keeping your flow temp as low as possible will use less electricity and be much easier for the heat pump to work at temperature with the low outside air temps.

[sirpatchuk]

We are using anywhere between 40 and 70 and we are not getting above 16 degrees downstairs.

Upstairs radiators fine.

Downstairs UFH takes AGES to heat up and if I leave it on all day that is when the usage is incredibly high and it doesn’t seem to make a difference to the ambient temperature.

[ReedRichards]

Is your system smart enough to reduce the flow temperature when the UFH is calling for heat but the radiators upstairs are not?

[sirpatchuk]

11 minutes ago, ReedRichards said:

Is your system smart enough to reduce the flow temperature when the UFH is calling for heat but the radiators upstairs are not?

no

 

appears same flow rate for radiators and ufh 

[crooksey]

That is very strange, it would usually be the UFH works but rads dont get warm.

 

Have you checked your manifold, is each port opening when you are calling for UFH?

 

Is your UFH pump kicking in when you are calling for UFH?

 

What UFH do you have, what insulation do you have beneath it and what is your pipe spacing?

[ReedRichards]

UFH is always slow to respond so you will need to keep it on most of the time.  If it follows the same timings as your rads then it may not be on long enough and that is why its not getting the rooms warm enough.  But if you make it stay on for longer you won't get the economic benefits of running the UFH at a lower flow temperature because that flow temperature has to be whatever your rads need.