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Obraik

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#311114 15-Dec-2023 11:04
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I recently moved into a new build house and one of the things we opted for was a ducted heat pump system, along with an ERV. For the most part it's been great - having cooled or heated air in every room of the house is a dream come true. However, one thing I've noticed in the 4 months that we've been moved in is that it seems the unit overshoots the temps that we set on the controller.

 

With summer here now, I've been trying to compensate for this by setting the set point higher than I would normally like but as an example, last night while it was in cooling only mode I had it set to 24c to try counter the overshooting. In the morning the house was quite chilly and the controller was saying that the room that it is in was 17, which felt true for the whole house (I had to put on some socks and a hoodie). Despite the controller displaying a temp of 17c, I could still hear and feel the unit actively blowing cold air through the vents and the outside unit was running.

 

This is my first ducted system though so before I go back to the heat pump/building company I thought I'd do a dummy check or see if this is just normal based on what others experience. The system is pretty basic in that there is no zone control and as far as I'm aware the only temperature sensor is from the controller itself, although from what I understand it likely also has temperature sensors on the intake air as well? In regards to the latter, I wonder if there is a conflict on temperature readings due to the ERV pulling warm air from outside as well so it thinks things are warmer than they are (although it's meant to be doing heat exchanging to match the outside air temp to the inside temp). During the brief winter period we've been here it also did the opposite with heating, where I would set the temp to 18c but the controller would be reading a room temp of 22-24.





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timmmay
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  #3172035 15-Dec-2023 12:10
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Does your ducted unit have individual room temperature sensors / control? If so is it build into the Daikin unit, or is it a third party system?

 

If you have no individual room temperature control then you probably have dampers with preset flow, and central temperature sensing / control. Temperatures will be all over the place. I had that in my first ducted unit, I had it removed partly because of that, partly because the brand I had was very loud. You can add a third party unit such as Airtouch5, will cost $4-6K I guess (I got mine a while ago) depending on outlets.

 

I wrote a ducted heatpump FAQ here. I'm not sure it will help with your question, but it may be interesting to read.


 
 
 

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jonathan18
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  #3172037 15-Dec-2023 12:14
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Just checking that you're 100% sure it's reading the sensor in the controller not the return? 

 

We had a similar problem with our Daikin ducted system a few years back; this system (no longer sold, for very good reason!) was a terrible design as its controller is an Android tablet, so no sensor built in! The installers didn't know this (or didn't care) so it was relying solely on the return sensor; with a 3m stud it was leading to stupidly wide range of temperatures (I think this is the page where I discussed this in a thread here on GZ: https://www.geekzone.co.nz/forums.asp?forumid=141&topicid=175823&page_no=4#1357553). 

 

This specific problem (one of many, as that thread shows!) was fixed when WE had to suggest to the installers that it needed a temp sensor 1. in a living space and 2. at a height where the temp was actually reflective of where humans reside!

 

Of course, this may not be related to your problem at all... 

 

 


Obraik

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  #3172038 15-Dec-2023 12:16
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timmmay:

 

Does your ducted unit have individual room temperature sensors / control? If so is it build into the Daikin unit, or is it a third party system?

 

If you have no individual room temperature control then you probably have dampers with preset flow, and central temperature sensing / control. Temperatures will be all over the place. I had that in my first ducted unit, I had it removed partly because of that, partly because the brand I had was very loud. You can add a third party unit such as Airtouch5, will cost $4-6K I guess (I got mine a while ago) depending on outlets.

 

I wrote a ducted heatpump FAQ here. I'm not sure it will help with your question, but it may be interesting to read.

 

 

No, there's no individual room temperature control but at the same time, it doesn't seem like it's struggling to keep the rooms at the same temperature. I've got a few basic thermometers that I've put in various rooms of the house to test with and they're all reading the same 17-18c temps that the controller is reading (despite the set point being 24). Even so, I would have thought the problem would be the opposite at this time of the year where some rooms would be feeling too hot compared to the room the controller is in.

 

The idea was to add zone control later as the build budget was already ballooning at the time 





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Obraik

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  #3172040 15-Dec-2023 12:19
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jonathan18:

 

Just checking that you're 100% sure it's reading the sensor in the controller not the return? 

 

We had a similar problem with our Daikin ducted system a few years back; this system (no longer sold, for very good reason!) was a terrible design as its controller is an Android tablet, so no sensor built in! The installers didn't know this (or didn't care) so it was relying solely on the return sensor; with a 3m stud it was leading to stupidly wide range of temperatures (I think this is the page where I discussed this in a thread here on GZ: https://www.geekzone.co.nz/forums.asp?forumid=141&topicid=175823&page_no=4)

 

This specific problem (one of many, as that thread shows!) was fixed when WE had to suggest to the installers that it needed a temp sensor 1. in a living space and 2. at a height where the temp was actually reflective of where humans reside!

 

Of course, this may not be related to your problem at all... 

 

 

 

 

That's the thing, it seems like it's not so you might be right and it's only using the return sensor, which is kind of where my theory comes in that it's getting confused by the air temps from the ERV. The controller is a BRC1H62W which does have a built in temp sensor and it does display that on the screen but yeah, there's no certainty that it's actually using that sensor.





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timmmay
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  #3172133 15-Dec-2023 16:05
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There's a sensor inside the heat pump roof unit, in the return vent somewhere, it may be using. You're probably best getting the installer out to have a look. If they can't solve it go for the zone system.


jonathan18
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  #3172143 15-Dec-2023 16:30
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timmmay:

 

There's a sensor inside the heat pump roof unit, in the return vent somewhere, it may be using. You're probably best getting the installer out to have a look. If they can't solve it go for the zone system.

 

 

Umm, isn't this exactly what I suggested earlier?!

 

Just checking that you're 100% sure it's reading the sensor in the controller not the return?


timmmay
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  #3172144 15-Dec-2023 16:32
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Yeah I was saying the same thing, agreeing with you 🙂



Obraik

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  #3172145 15-Dec-2023 16:32
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So I had a look in the installers manual for my controller and found how to get into the menu that shows what sensor it's using and as suggested, it was set to use the intake sensor rather than the controller. I've changed it over now so I'll see if that makes a difference.





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Kickinbac
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  #3172146 15-Dec-2023 16:37
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There could be several problems.

 

The dead band for these ducted systems is about +/- 2°C so if the setpoint is 22°C it will be somewhere between until 20°C - 24°C. The compressor will be varying output speed to suit the load so slowing down as its closer to the setpoint. 

 

If the ERV is fed into the return plenum then the return air sensor is not a true measure of the conditioned space which could be the problem as this is mixed air so it that case the sensing location needs to be set to the wall controller. There is a setting in the installer/field settings of the wall controller where the temperature is measured can be changed, basically says use or not use the wall sensor. 

 

There is an option to install a remote sensor which unplugs the return air sensor and replaces it with a temperature sensor on a long lead which can be located anywhere in the house. Wherever the sensor is, that is the location the system is trying to achieve the setpoint. Sometimes this is used to put the sensor just above the return grille and before the air is mixed in the plenum.

 

The return air temperature is just an average of the whole house. Do you close the bedroom doors at night? The system needs the air in these rooms to return back to the return grille unrestricted. Ideally each room would have a return grille but most homes have one or two in the hallway. Undercutting doors about 20mm is one way to allow return air back when the door is closed.

 

Another thing worth checking is that there are no broken or detached ducts in the roof. You could be sucking in roof air or wasting supply air to the roof space and wasting energy and getting poor control. A good professional installer will use an air balancing hood to properly commission the system but this is rare in the residential industry. This will check the airflow at each grille so it can be balanced and look for airflow problems like no airflow. 

 

Also recommend don't use Auto mode, set the unit in 'cooling mode' when you want cooling and 'heating mode' when you want heating.

 

 

 

'Edit' I was writing this and see you have replied that you have changed the sensor location to the wall controller. See how you go here. 


jonathan18
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  #3172151 15-Dec-2023 16:49
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Ah, given the symptoms were so similar to ours, and what a difference not using the return sensor made to our situation, I'd be very surprised if that didn't go a long way to fixing that problem.

 

We've got wall sensors in a couple of places, as per the photo below (the dumb installers hadn't even thought about ensuring there was a sensor in each zone, as what's the point of only being able to measure temperature in a zone that may not even be being warmed?!). And while you could install one in a central location (noting you don't have zones), hopefully the placement of the controller is representative enough of the wider house.

 

 

 

 

 


Kickinbac
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  #3172164 15-Dec-2023 17:13
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jonathan18:

Ah, given the symptoms were so similar to ours, and what a difference not using the return sensor made to our situation, I'd be very surprised if that didn't go a long way to fixing that problem.


We've got wall sensors in a couple of places, as per the photo below (the dumb installers hadn't even thought about ensuring there was a sensor in each zone, as what's the point of only being able to measure temperature in a zone that may not even be being warmed?!). And while you could install one in a central location (noting you don't have zones), hopefully the placement of the controller is representative enough of the wider house.


 


 




This is one solution I was mentioning in my previous reply.
Do you have zone control?
Because if you have two remote sensors on one ducted indoor they can only be averaging as they have to plug into the return sensor plug. This is done by wiring four thermistors in series/parallel so they read the right resistance. I have a wiring diagram of how it’s done at work.

tweake
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  #3172182 15-Dec-2023 19:51
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Obraik:

 

I recently moved into a new build house and one of the things we opted for was a ducted heat pump system, along with an ERV. For the most part it's been great - having cooled or heated air in every room of the house is a dream come true. However, one thing I've noticed in the 4 months that we've been moved in is that it seems the unit overshoots the temps that we set on the controller.

 

With summer here now, I've been trying to compensate for this by setting the set point higher than I would normally like but as an example, last night while it was in cooling only mode I had it set to 24c to try counter the overshooting. In the morning the house was quite chilly and the controller was saying that the room that it is in was 17, which felt true for the whole house (I had to put on some socks and a hoodie). Despite the controller displaying a temp of 17c, I could still hear and feel the unit actively blowing cold air through the vents and the outside unit was running.

 

This is my first ducted system though so before I go back to the heat pump/building company I thought I'd do a dummy check or see if this is just normal based on what others experience. The system is pretty basic in that there is no zone control and as far as I'm aware the only temperature sensor is from the controller itself, although from what I understand it likely also has temperature sensors on the intake air as well? In regards to the latter, I wonder if there is a conflict on temperature readings due to the ERV pulling warm air from outside as well so it thinks things are warmer than they are (although it's meant to be doing heat exchanging to match the outside air temp to the inside temp). During the brief winter period we've been here it also did the opposite with heating, where I would set the temp to 18c but the controller would be reading a room temp of 22-24.

 

 

can you find what model it is and a few pics of the install.

 

also how is the erv done?


Obraik

2007 posts

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  #3172192 15-Dec-2023 21:18
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tweake:

 

can you find what model it is and a few pics of the install.

 

also how is the erv done?

 

 

Sure,

 

 

Heatpump: FDYAN125AV1
ERV: VAM350HVE
Controller: BRC1H62W

 

What about the ERV are you interested in? I don't have any photos of it as it was installed in the roof unfortunately.

 





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  #3172196 15-Dec-2023 21:54
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a diagram of how its laid out, and how all the ducking is run


Obraik

2007 posts

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  #3172316 16-Dec-2023 12:00
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It mostly followed the plans, the only difference is that the ERVs return vent is in the hallway rather than the kitchen/dining area as it is on the above plan.

 

The evening and this morning were much improved after changing it to use the controllers sensor yesterday afternoon. I set it to 22 overnight this time and when we got up this morning the controller was showing the room was 21 - no hoody or socks required this time. I also changed the fan behaviour for cooling mode - it was set to run the fan at the set speed when it wasn't actively cooling so I've set it to the setting that puts it into low-low mode. The fan for heating mode was set to turn off when it wasn't actively heating, so I didn't need to adjust that.





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