The Mystery of the ...
 
Notifications
Clear all

The Mystery of the Weather Compensation Curve

37 Posts
9 Users
19 Reactions
5,678 Views
Saz
 Saz
(@saz)
Reputable Member Member
943 kWhs
Joined: 3 years ago
Posts: 119
 

@derek-m It's in the hallway. I do have the Sensocomfort set to weather compensation (after months of persistence) but unfortunately many other issues remain to put a spanner in the works as it were. What is the point of the VRC700 then?


   
ReplyQuote
(@derek-m)
Illustrious Member Moderator
14051 kWhs
Veteran Expert
Joined: 3 years ago
Posts: 4210
 

Posted by: @saz

@derek-m It's in the hallway. I do have the Sensocomfort set to weather compensation (after months of persistence) but unfortunately many other issues remain to put a spanner in the works as it were. What is the point of the VRC700 then?

As far as I am aware they are both controllers, the SensoComfort I think being the more recent model. I'm afraid without going through the manuals in detail, which I don't have time to do, I cannot give details of any differences. Maybe someone else on the forum can help?

 


   
ReplyQuote
cathodeRay
(@cathoderay)
Famed Member Moderator
6919 kWhs
Joined: 2 years ago
Posts: 1391
Topic starter  

Posted by: @cathoderay

I'm pretty sure the Midea controller can have an external room temp sensor fitted, there is a line in the 'Operational Parameters' for it, Ta Room Temp, but it doesn't get fitted, display just shows --, and I don't know whether it just controls the heat pump via on/off, or whether it can be set up to adapt the curve, something I need to look into. 

A room temp sensor can be fitted, it connects to a PCB in the main outdoor unit, but it is not exactly clear what it can do...

From the Installation and owner's Manual:

About TEMP. TYPE SETTING

10.6.5 TEMP. TYPE SETTING

Go to MENU> FOR SERVICEMAN> 4.AUTO MODE
SETTING. Press OK, the following page will be displayed.

The TEMP. TYPE SETTING is used for selecting whether
the water flow temperature or room temperature is used
to control the ON/OFF of the heat pump.

When ROOM TEMP. is enabled, the target water flow
temperature will be calculated from climate-related curves
(refer to 10.1 "Climate related curves" ). 

There are two relevant TEMP. TYPE SETTINGs, Water Flow Temp and Room Temp. If the former is on, the unit targets a set LWT, if the latter is selected, what it actually does is use weather comp (which Midea call climate related curves) - see last paragraph above. There are a presets, and a ninth custom setting, which is where you set your chosen weather comp curve on a Midea unit. This custom 'curve' only has two set points, and the only input is outside (ambient) temp (T4) and the only output is the set LWT. No other variables are involved. Well, at least that is all nice and clear, when ROOM TEMP. is enabled, the unit uses ambient temp to set the LWT, according to the chosen weather comp curve...

Unless and until a room stat is enabled in another setting as MODE SET (honestly, I am not making this up). In this case, it looks like the room stat operates like a conventional fossil fuel on/off setup. From the wired controller operation manual:

5.2.2 Use the room thermostat to turn on or off the unit
for space heating or cooling.

① The room thermostat is set MODE SET (see ''ROOM
THERMOSTAT SETTING'' in ''Installation and owner's
manual ''). The unit operation mode and ON /OFF controlled
by room thermostat,press ON/OFF on the interface, the
following page will display:

Turning on or off cooling/
heating mode is controlled by
the room thermostat.
Please turn on or off cooling/
heating mode by the room
thermostat.  

Conclusion as far as I can see: if ROOM TEMP. is selected in TEMP. TYPE SETTING, the unit uses AMBIENT temp via a weather comp curve to control LWT. However, if a room stat is added and connected to the system, and ROOM THERMOSTAT is set to MODE SET, then the becomes a simple fossil fuel on/off set up. I've absolutely no idea how in those circumstances its sets the LWT, and frankly I'm not going chase down that rabbit hole, because simple on/off based on room stat is not what we want at all.

Bottom line appears to be you can't use the room stat to fine tune the weather comp curve. 

 

 

Midea 14kW (for now...) ASHP heating both building and DHW


   
ReplyQuote



(@derek-m)
Illustrious Member Moderator
14051 kWhs
Veteran Expert
Joined: 3 years ago
Posts: 4210
 

@cathoderay

Don't you speak Chinese? 🙄 


   
ReplyQuote
cathodeRay
(@cathoderay)
Famed Member Moderator
6919 kWhs
Joined: 2 years ago
Posts: 1391
Topic starter  

@derek-m - only in 'interesting times'.

Midea 14kW (for now...) ASHP heating both building and DHW


   
ReplyQuote
(@bob77)
Trusted Member Member
292 kWhs
Joined: 2 years ago
Posts: 36
 

I'm confused, aren't the room stats supposed to be turning the flow on and off, while the weather compensation controls how hot the flow is?

It seems to me they should work together. The thermostat tells the heat pump if it needs to do any heating at all, and once it is on, the weather compensation adjusts the water temperature ideally to the minimum temperature that will maintain the right indoor temperature. But "thermostat" seems to be a dirty word on here for some reason!


   
ReplyQuote
(@derek-m)
Illustrious Member Moderator
14051 kWhs
Veteran Expert
Joined: 3 years ago
Posts: 4210
 

Posted by: @bob77

I'm confused, aren't the room stats supposed to be turning the flow on and off, while the weather compensation controls how hot the flow is?

It seems to me they should work together. The thermostat tells the heat pump if it needs to do any heating at all, and once it is on, the weather compensation adjusts the water temperature ideally to the minimum temperature that will maintain the right indoor temperature. But "thermostat" seems to be a dirty word on here for some reason!

From my control systems background, thermostat to me is an On - Off device. What some refer to as a 'thermostat' I would call a temperature sensor, since it continually monitors the temperature and can provide an actual measurement.

With a heat pump it is not always best to be stopping and starting it, since it could actually be using more energy, and it is often better to run the heat pump for longer periods at a lower LWT. This is one of the things that WC is designed to do.

 


   
SKD reacted
ReplyQuote
(@alec-morrow)
Honorable Member Contributor
1314 kWhs
Joined: 2 years ago
Posts: 209
 

it’s called weather compensation as you compensate for the weather, as that’s what causes heat loss! It was mandated in Germany in Boilers because it saves energy in 1986. 

It works because small loads (low temps) allow all plant to be operate with high efficiencies. Savings of c 10% on gas boilers and 20% on heat pumps

 

Weather comp has not entered easily into the U.K. This means the manufacturers don’t have to offer such comprehensive technical support, and they don’t have to train installers.And installers don’t have to be very knowledgable because everyone understands off saves energy!

 

UK is a lucrative market kept purposefully dumb with regulation writers in cahoots with manufacturers to fleece the public!

 

 

 

Professional installer


   
Derek M and mjr reacted
ReplyQuote
(@alec-morrow)
Honorable Member Contributor
1314 kWhs
Joined: 2 years ago
Posts: 209
 

@scrchngwsl 

 

This is classic! 

 

The heating industry is much bigger than people realise. Many people like comfort and  many other nations have demanding consumers. which don’t tolerate the poor heating systems the U.K. have.

 A heating system is a critical component of a building in most countries, but it’s been trivialised in the U.K. on the back of public indifference!

 

hence you thinking Nest is a good control!

 

Professional installer


   
ReplyQuote



(@alec-morrow)
Honorable Member Contributor
1314 kWhs
Joined: 2 years ago
Posts: 209
 

@cathoderay put simply, waiting for things to get cold means you have to generate excess heat to raise temperature room temp quickly. That’s water in the system, pipes and radiators etc!

 

couple with keeping something warm uses less energy, at a lower temperature enhancing efficiency!

 

 

Professional installer


   
ReplyQuote
(@kev-m)
Famed Member Moderator
5562 kWhs
Joined: 3 years ago
Posts: 1299
 

Posted by: @alec-morrow

@scrchngwsl 

 

This is classic! 

 

The heating industry is much bigger than people realise. Many people like comfort and  many other nations have demanding consumers. which don’t tolerate the poor heating systems the U.K. have.

 A heating system is a critical component of a building in most countries, but it’s been trivialised in the U.K. on the back of public indifference!

 

hence you thinking Nest is a good control!

 

It is but most CH is gas and gas was historically so cheap it didn't matter is the systems were poor.  It does now.

It's the same as cars in the USA; in the 1960s and 70s nobody cared about mpg as petrol was practically free.  They did in Europe because it wasn't.  

 

This post was modified 2 years ago by Kev M

   
ReplyQuote
(@alec-morrow)
Honorable Member Contributor
1314 kWhs
Joined: 2 years ago
Posts: 209
 

 

 

 

It always mattered, people didn’t  care, look at global warming!

 

Professional installer


   
Derek M, mjr and Morgan reacted
ReplyQuote
Page 2 / 4
Share:

Join Us!

Latest Posts

Heat Pump T-Shirts

Delta T Sounds Greek to Me

Members Online

x  Powerful Protection for WordPress, from Shield Security
This Site Is Protected By
Shield Security