Weather Compensation Curve

[richo106]

Good Afternoon

 

As you can probably tell from some of my latest posts I am trying to set up my ASHP/UFH system correctly as this is the first winter in my house

 

I have been reading into it a lot and it seems general feeling is that the buffer tank temp is controlled on weather compensation curve

 

My next question is how do you correctly set up the temp on the compensation curve? I have just had my buffer set at 35 deg

 

In my ASHP (Panosonic Aquarea) manual it recommends 40 - 35, i know that is very generic so i was just seeing what are peoples set up likes so I have a starting point

 

I have currently set my downstairs thermostats to 22 deg and upstairs to 19deg, i am also interested to see what other people set their normal temperature to be?

 

Many Thanks

[JohnMo]

I would start at a lower temp than the 35 to 40

 

Something like 25 to 35 may be better. You need to wind your thermostats out the way, especially downstairs and fine tune the curve based on the house just being warm enough. Leave your house to stabilise 24 hrs before making adjustments. Not a fan of thermostats with WC as it's really designed to run 24/7 and drip feed energy into the house. If your stop starting, go with Panasonic recommendations.

[richo106]

Thanks @JohnMo

 

When you wind my thermostats out the way would you just set them all at 25 deg for example? Or set them at like 23 as a limiter?

My only concern with this is my expensive period 4pm - 7pm, I could just turn the ASHP & Set my thermostats low in this period? 

So my ufh pump would be constantly going and circling heated water around?

 

Thanks again for your help

[JohnMo]

28 minutes ago, richo106 said:

My only concern with this is my expensive period 4pm - 7pm, I could just turn the ASHP & Set my thermostats low in this period?

If you have zero intention to run during that period you should set your thermostats low to switch the HP off. Then you get a realistic operation and suitable WC curve.

 

If you start with them at 22.5 to 23, if you are hitting that temp move the low outside temp of the curve, down.

32 minutes ago, richo106 said:

So my ufh pump would be constantly going and circling heated water around

Basically except during the tea time period when you have no demand.

[richo106]

I have set my compensation curve to 35 deg to 25 deg, this was from 0 to 15 deg. I wasn't sure what to put for the outside temperature range though, are these figures suitable to start with?

 

I have set my ASHP controller up like below, this is to make use of the cheaper periods for hot water. There was also the option for compensation curve shift but I left this at 0

 

For my own sanity, my house is 250m2 total area (125m2 each floor). I am solely electric and my total usage for everything on Tuesday, Wednesday & today (3 coldest days which ranged from -5 to 2 during the whole period) has been on 55kWh (£11) does this seem reasonable? 

 

The 4 weeks prior to this i was averaging between 160 - 180kWh (£28) per week in total

 

Many Thanks again, really do appreciate your help

 

 

[PhilT]

4 minutes ago, richo106 said:

For my own sanity, my house is 250m2 total area (125m2 each floor). I am solely electric and my total usage for everything on Tuesday, Wednesday & today (3 coldest days which ranged from -5 to 2 during the whole period) has been on 55kWh (£11) does this seem reasonable? 

 

The 4 weeks prior to this i was averaging between 160 - 180kWh (£28) per week in total

 

I take it you mean 55kWh PER DAY (= 385kWh/week)? That sounds about right compared to 180kWh/week during the first half of November, which was around 10degC warmer. My usage has also more than doubled over the last 3 days compared to the first half of Nov.

[richo106]

31 minutes ago, PhilT said:

I take it you mean 55kWh PER DAY (= 385kWh/week)? That sounds about right compared to 180kWh/week during the first half of November, which was around 10degC warmer. My usage has also more than doubled over the last 3 days compared to the first half of Nov.

Ooops..yup definitely meant to put on AVERAGE its been 55kWh

[JohnMo]

59 minutes ago, richo106 said:

this was from 0 to 15 deg

Change the zero for your lowest outside design temperature.

 

 

[richo106]

I have no design details or anything, they had all the details of my build insulation etc etc and they specced a 12kw ASHP. The UFH was designed by the company who just supplied it

 

looking back this was very naive but I was non the wiser at the time and was just going with the flow🙈

[SuperJohnG]

1 hour ago, richo106 said:

) does this seem reasonable?

I'd say so. 

 

Here's my main consumption and my ASHP for the 20th November. Others skew it up to 23 quid cos of the Lazy spa...

 

[richo106]

@JohnMo actually I have just found this that was used to size my Ashp (I think) 

 

To be honest I have tried to make sense of this a few times and still not gotten anywhere with it. 

CombineReports_007400_001_2022-10-24_13-27-34.pdf

[richo106]

Thanks @SuperJohnG, those figures are almost identical to mine tbf even the ASHP usage was 39kWh and total 58kWh

[JohnMo]

9 hours ago, richo106 said:

I have no design details

Use -3 as you low outside temp then, you can always move it later

[richo106]

 

1 hour ago, JohnMo said:

Use -3 as you low outside temp then, you can always move it later

Will do

Edited November 22 by richo106

[Thorfun]

12 hours ago, SuperJohnG said:

I'd say so. 

 

Here's my main consumption and my ASHP for the 20th November. Others skew it up to 23 quid cos of the Lazy spa...

 

that's some pretty awesome looking data and visualisation you've got there! how do you accomplish that?

[richo106]

I ran 24/7 since 7pm last night using weather comp (35 deg 0 and below) my ground floor heated up lovely and hit 22.5 within 2 hours and kept hitting it and going off through the night...is this right?

 

However my upstairs is really struggling to heat up when the doors are shut to the bedrooms (e.g my daughers bedroom didnt get above 16.5 deg) but now its at 20 deg ish with all the doors open

My gut feeling is that my upstairs UFH is just undersized/ineffective especially when its cold outside

 

Currently I can't change the individual flow temps to the upstairs and downstairs UFH as they are off a common buffer temp but one options i thought down the line was to run my buffer at a higher temp and then blend the d/s UFH to reduce temp?

 

Any ideas at all what to try next to try and improve my upstairs heating level? as when waking up this morning it felt cold getting out of bed (with temp ranging from 16.5 - 18) especially with the heating running all night and has been on 24/7 since Tuesday morning (apart from 4pm - 7pm daily)

 

My set points are 22.5 downstairs and 20 deg upstairs, do these seem ok?

Edited November 22 by richo106

[JohnMo]

6 minutes ago, richo106 said:

Currently I can't change the individual flow temps

To change the energy diverted by the floor, you adjust the flow rate to the loops. The flow meter is on the manifold, so increase heat output you increase flow rate. Increase the bedroom loops 1 l/m and see what changes. We found our bedrooms UFH is also rubbish, mainly due to carpets. If we want the bedrooms warm we just open the doors.

 

8 minutes ago, richo106 said:

hit 22.5 within 2 hours and kept hitting it and going off through the night...is this right?

Your flow temp is too high. Extending the curve to -3, from 0, will lower the flow temperature generally. But the 35 degs looks way to hot. Try leaving it with the -3 change, then tomorrow if still bouncing of the thermostat drop the 35 to 33. Then reassess.

 

[richo106]

39 minutes ago, JohnMo said:

To change the energy diverted by the floor, you adjust the flow rate to the loops. The flow meter is on the manifold, so increase heat output you increase flow rate. Increase the bedroom loops 1 l/m and see what changes. We found our bedrooms UFH is also rubbish, mainly due to carpets. If we want the bedrooms warm we just open the doors.

 

Your flow temp is too high. Extending the curve to -3, from 0, will lower the flow temperature generally. But the 35 degs looks way to hot. Try leaving it with the -3 change, then tomorrow if still bouncing of the thermostat drop the 35 to 33. Then reassess.

 

Thanks again @JohnMo I will try both of these later when I get home

 

I know when I looked yesterday my flow rate of my upstairs manifold was around 2L/m

[JohnMo]

1 minute ago, richo106 said:

2L/m

Increase to 3

[SuperJohnG]

On 22/11/2024 at 11:56, Thorfun said:

that's some pretty awesome looking data and visualisation you've got there! how do you accomplish that?

Shelly EM basic clamp units, cloud connected. I've had zero reliability issues...I would highly recommend them. Think it was like 50 or 80 quid for the Shelly meter and two clamps which were 100A and a 20A.

[Thorfun]

8 minutes ago, SuperJohnG said:

Shelly EM basic clamp units, cloud connected. I've had zero reliability issues...I would highly recommend them. Think it was like 50 or 80 quid for the Shelly meter and two clamps which were 100A and a 20A.

nice. thank you. I got an email from Shelly about Black Friday deals. I might take a more in-depth look and see what deals are to be had.

[Mike]

18 minutes ago, Thorfun said:

I got an email from Shelly about Black Friday deals. I might take a more in-depth look and see what deals are to be had.

It's not connected yet, but I've got the Shelly Shelly Pro 3EM - maybe the same one that @SuperJohnG has. In particular I'll be using it to detect when the power to my UFCH Willis heaters is cut by my load sheader*, so that the operating hours of the heaters is extended to make up for the outage.

 

*It temporarily cuts the power to the heating & hot water if the overall electrical load approaches the 45A maximum permitted by the electric meter, to ensure that there's plenty of power for everything else.

[richo106]

Hi All

 

I have been away for a few days so now back at looking at my heating

 

I tried to increase my flow rate on my UFH heating but only managed to increase it slightly to just over 2 in the end (embarrassingly my mrs loved it when I unscrewed it too far without thinking and I got a nice splash in the face!)

 

One thing I am still tweaking is my weather compensation curve, its currently on 35 deg -5 to 25 deg 15 deg. But in error I set my downstairs thermostats to 22.5 and with a 1 deg hysteresis it was bouncing off it which I am guessing this is something we want to avoid.

 

I have now changed all my house thermostats to 23.5, just confirming that the aim of using the weather compensation is that the UFH runs 24/7 and keeps the house a nice temperature - hopefully around 22.5/23 ish

 

Is this how you guys run UFH with ASHP?

 

Thanks again

[JohnMo]

11 minutes ago, richo106 said:

22.5 and with a 1 deg hysteresis it was bouncing off it

That would indicate you are getting up to 23.5 degs. Looks like you trim the the curve down little.

 

I would change the 35 deg to 34 Deg on your WC curve.

[PhilT]

1 hour ago, richo106 said:

Hi All

 

I have been away for a few days so now back at looking at my heating

 

I tried to increase my flow rate on my UFH heating but only managed to increase it slightly to just over 2 in the end (embarrassingly my mrs loved it when I unscrewed it too far without thinking and I got a nice splash in the face!)

 

One thing I am still tweaking is my weather compensation curve, its currently on 35 deg -5 to 25 deg 15 deg. But in error I set my downstairs thermostats to 22.5 and with a 1 deg hysteresis it was bouncing off it which I am guessing this is something we want to avoid.

 

I have now changed all my house thermostats to 23.5, just confirming that the aim of using the weather compensation is that the UFH runs 24/7 and keeps the house a nice temperature - hopefully around 22.5/23 ish

 

Is this how you guys run UFH with ASHP?

 

Thanks again

Yes but with straight WC if you have a lot of south facing glass there may still be some "bounce" on sunny days, not really a big deal though