Ducted heatpump advice sought

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#1357553 3-Aug-2015 09:45

A couple of questions that I hope readers may be able to help with regarding the operation of the heatpump:

While the system's working well, I'm concerned at the variance in temperature it currently appears to tolerate. For example, we had it set to 21 on Saturday; occasionally it would reach as high as 23 before switching off, but more worryingly it could drop to 18 before it would start back up. The result is a too greater fluctuation in temperature - rather than cycle on and off more regularly in order to maintain a more stable temperature, it appears to wait too long to start up again meaning it has to belt it to get the room back up to temperature (and then can overshoot). The result was we'd get cold at one end of the 'cycle', and too hot at the other. Is there anything that we or the installers can do to solve this?

Second, the 'contoller' (ie Android tablet) appears to be fully functioning - by this I mean even stuff like the browser works. Does this introduce any security vulnerabilities, and is there anything I can do to reduce any risk?

Many thanks for your ideas.

Jase2985

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#1357612 3-Aug-2015 10:34

its called hysteresis, and its there so that the unit isnt always switching on and off again, if it had very little hysteresis, then it would get to 21 hit 22 and turn off get down to 20 and turn back on, this could be a very short period of time so it could cause undue ware on components. hence a generally larger than 1deg worth of hysteresis. Im not sure on the specs on your one, but our one at home is set to 20 degrees and it gets to about 23.5 inside and then just ramps the fan right down to bearly blowing. Its an older Toshiba wall mounted unit.

also remember temperature needs to stableise over the entire room not jsut where the controller/thermostat is.

jonathan18

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#1357635 3-Aug-2015 11:00

Jase2985: its called hysteresis, and its there so that the unit isnt always switching on and off again, if it had very little hysteresis, then it would get to 21 hit 22 and turn off get down to 20 and turn back on, this could be a very short period of time so it could cause undue ware on components. hence a generally larger than 1deg worth of hysteresis. Im not sure on the specs on your one, but our one at home is set to 20 degrees and it gets to about 23.5 inside and then just ramps the fan right down to bearly blowing. Its an older Toshiba wall mounted unit.

also remember temperature needs to stableise over the entire room not jsut where the controller/thermostat is.

Thanks for the reply, and the technical term for this! I'd assumed it was controlled for this purpose (ie, to stop constant cycling), but I wondered if there is the ability to control the degree of allowable variation. Part of the problem is that when it cycles off it appears to stop competely (as opposed to a very low fan speed), so the lack of any air flow means it feels like a near instant temperature drop. And when it cycles back on it it does so on what appears to be on the medium or fast fan speed, whereas I'd prefer it to switch back on more promptly with a slower fan. I guess I could force it to use the slowest fan speed, but such an override means if there was a big drop in temperature it would be pushed to circulate the necessary volume of air.

lapimate

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#1357636 3-Aug-2015 11:00

Jase2985: ... so that the unit isnt always switching on and off again, ... could cause undue [wear] on components. hence a generally larger than 1deg worth of hysteresis.....

Isn't the main point of "Inverter" heat pumps that they allow smooth changes of output? So that with decent thermostatic control systems the output is related not just to the current temperature, but also to the rate of change of temperature. This is a "well-known" engineering control theory problem and with modern controllers/software it would be reasonable to expect more acceptable performance than reported.

Kickinbac

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#1358025 3-Aug-2015 17:17

There's a setting that turns off indoor fan motor when in the deadband (close to set point), it's a stupid setting if you ask me as people always notice the fan switching on/off as opposed to a constant background noise. There should be a setting in the controller or dipswitches in the indoor control panel that changes the fan to continuous operation. You'll need your installer to change this. It may also help with better temperature control as system always circulating air through the house so giving a better average temp of the house.

Also sounds like you are getting stratification which is the hot air pooling near the roof which is affecting the temperature sensing (google search for info). A ducted system has a sensor in the return air, if the temperature is warm at ceiling level it thinks it's at setpoint and backs off. This setting can be changed to the wall controller only, return air only or an average of both. Daikin's usually sense from both wall controller and return air sensor to get the best of both worlds. Basically the hot and cold air need to be mixed better as hot air rises. Some controllers have a high ceiling setting that puts an offset in the temperature settings to allow for this. Basically fools the controller it thinking it's cooler than it is. This is where the Holyoake ECO-A diffusers work well as they jet the air down to the occupants when in heating.

gedc

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#1358141 3-Aug-2015 19:47

Jeeze..I feel for ya. I've been working with the installers for roughly 3 to 4 months to get my system working and half the house is now being removed as we were about to get divorced over the noise. Just look back for my previous post which also deals to a lot of stuff you are experiencing. Where we got to in the end.

1. 24 site visits from the installers and fujitsu techs.
2. Me having to clamber into the loft to record / video the upstairs unit sounding like a cold diesel every night.
3. Me doing heaps of research online in NZ, in OZ, talking to various companies by email and asking them questions like " I'm really interested in product x but have heard these bad things - is that true ? "
4. Loved geekzone for all the help they pointed me at.
5. Half the house coming back out and replacing it with an 8kw floorstander in living room 1 and a hiwall in living room 2.

The issues

1. Temperature stratification in every room, particularly the back of the house - hallway and all the bedrooms and bathrooms - 38 at ceiling and 10 at floor on a 2.4 stud !!
2. Fans ramping up and down during use and every time the fan speed changed
3. Nobody at the company listening to my rants and suggestions from the good folks here until they tried everything else they could think of
4. Most nights, the air handler above the living room starts to sound like a drone and the ceiling magnifies it beautifully. Turn it off and on fixes it for a couple of hours.
5. Freezing cold hallway even with all bedroom doors opened and system running constantly - $37 power bill in 24 hours.
6. Shut a bedroom door and the room heats up in about 5 minutes. Open it and it cools down just as quick.
7. Roasting hot rooms and cool others
8. Temp overshooting on wall and unit thermostat.
9. About 8 hours to get the back of house to consistent temp.
10. Noisy / Loud upstairs units

The fixes

1. They kept insisting it was a balancing issue even when I supplied tons of data re temps, temp levels, heat up times. Eventually they removed the cores of the diffusers and the problems went away immediately. Rooms and hallway heated up quickly and conistently. Put cores back in and issues came back. We now have the bimetal strip diffuser cores that open and close based on air temp. They aren't as good as having no diffuser core but seem to do an okay job all being told - HEAPS better than the normal diffusers that just chuck air out sideways.

2. Turns out static pressure is a devil to ducted systems - particularly when the ducts are the big flexible types and not hard, straight runs of aluminimum etc. An unplanned bend or kink changes the static pressures that were designed on a CAD layout system etc. There was heaps of backpressure from poorly laid out ducts and also the air returns were undersized, hence the fans ramping to suck in more air etc.

3. Persistence and just keep telling them the same thing

4. Remove that part of system. Even with a video from 2 feet away showing it in its glory and the noise it makes that then disappears at power down and back on nobody was interested and kept saying things like - thats interesting. Fujitsu have had it for 5 weeks and made no comment as to why its doing it.

5. As with 1. Air was short circuiting along the roof without mixing with the cooler air at body and feet level. I had a hot head every time I walked under an internal door threshold. The hallway has no thermal gain i,e no windows or exposure to sunlight really. Its also 18 metres long. They eventually relented and put a small one above front door at one end. Did nothing. Eventually they located a larger outlet halfway up hallway opposite a large cold bathroom that has no heating. Success..Also be aware that the 43 to 45c heat pumping out the diffusers will be heating your bedrooms first and then the return air will heat the hallway. If your bedrooms are still at 14 to 15c then the return hallway air will not raise the temp in that area significantly. The only way to resolve this and not have to wait on bedrooms to heat up prior to the hallway THEN getting to temp - about 1 to 2 hours difference was to treat the hallway as standalone room. Once they did that and installed the 2 outlets - all is a lot better.

6. As with 1 and 5. Poor design and also showed them most of the hot air was being sucked straight back into the return vent in the hallway.

7. They tried to balance the system using the diffuser vents alone. Some were fully open while others were closed so much they whistled. Then the installer learned about inserting control dampers into the ductlines to controll airflow. Success.

8. Generally I find with the wall controller it will overshoot and undershoot a few times then eventually settles down. If we set the living room for 22, it can get to 26/27 at controller before the system then recycles the air without heating it. Then it drops to around 20, then heats then recycles around 24, then drops to 21 then seems to sit happilly around the 22 mark. Generally takes 1 to 2 hours for this to happen. If we put the thermostat settings on the upstairs unit then it just heats all the timea and room gets to suana temps.

9. They would turn up at 10am. Put the sytem on full blast, play with some stuff then by 6pm when I got home the house was warm. Problem solved I thought. What I didn't realise was it took about 7 hours to get to temp. The rooms were eventually heating slowly as the warm upper layers transferred some heat to the cooler lower layers through convection and not mixing. Hence the 7 hours + for this to happen.

10. There wasn't one hence its coming out. It might help to ask the installers NOT to install the upstairs unit directly above the living room seating areas. Ignore the marketing materials. You WILL hear it if they locate it above your head. I was told it would be silent. Cough Cough..little white lie there. It's fairly silent until you turn it on then it gets noisier. I don't mind the noise of normal heatpumps or indeed the noise of air blowing but this background droning just goes through everything.

What I learned.

1.For me, and looking at the systems I think ducted is still a relatively new product for NZ and some installers ( particularly ours who was fujitsu accredited ) just haven't done many prior. Turns out we were their first and they happily indicate they have " learned a lot" from my setup.

2. Don't give up and use facts and science to prove your arguements. All I kept hearing was " it should work"..I eventually said, stop thinking like that and understand and accept its not so you need to start changing things out one at at time until the problem is fixed.

3. Laws of physics are hard to break - irrespective of the lovely brochures and marketing materials. Hot air rises and stays at ceiling level unless its fired into the cold air and mixed well.

4. In OZ, they also use gas hot air systems that pump out at floor level and use their ducted systems for cooling - cold air drops down quickly.

5. Some manufactures seem to give a damn more than others.

6. The install company stood by their work and have done everything they could to put it right.

7. I wouldn't rush to install ducted again and also now know of two families ( touchline soccer) who had it and removed it - one a new build insulated house that just didn't heat and the other a retrofit into a new(ish) build.

8. Our units 'work' down to -15 degrees. At -5 outside they were struggling a lot and went into defrost mode every 40 minutes or so for about 12 minutes. So gave out jack all heat and lost their efficiency - fairly common with heatpumps though.

Sorry for the long post. I hope you get most of your issues sorted and some of the above rambling helps. It helped me :)

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Handle9

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#1358172 3-Aug-2015 20:33

I'd like to say that the problems described in this thread are surprising but they aren't. Ducted systems are an order of magnitude more sophisticated to design and set up than high wall or floor consoles. There are some competent guys doing residential systems but not many. Even in the commercial world there aren't that many. Saying that anyone who doesn't understand the difference between a diffuser and a balancing damper shouldn't be doing this kind of work. Unfortunately lots of residential heat pump installers are barely qualified or have no exposure to more classical HVAC solutions.

I've mentioned in a few threads that trying to control multiple zones from one heating/cooling source is always an excercise in compromise. Best case is you have a sensor in each zone and either do averaging or high/low select but unless they are properly balanced you will over heat one zone and under heat the other. If you don't have enough air velocity the rooms won't mix and you will get stratification. If you get too much you get dumping which is horrible as well. The diffusers also need to be properly designed so they don't push air directly onto the occupants.

Even if you put branch dampers in to isolate zones all that happens is that your solution gets unbalanced as the fan is generally speed controlled rather volume or pressure controlled.

There has been a load of crap pushed by heat pump companies that they are the perfect solution for every situation. They aren't and never will be. They work at their best in temperate or hot climates. They don't work any where near as well in cold climates, it's physically impossible for them to. There is a reason they don't get used in large installations but are generally used in more budget oriented situations.

Just my view, and to be fair my company doesn't do as well when a refrigerant based system is used, but if it was my house a I'd put multi head high wall units in rather than a single ducted system. Generally cheaper and much easier to make work.

jnimmo

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#1358241 3-Aug-2015 22:08

Interesting, about to put in building consent with a ducted Fujitsu 10kw but now reconsidering..

jonathan18

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#1358342 4-Aug-2015 08:59

Kickinbac:
There's a setting that turns off indoor fan motor when in the deadband (close to set point), it's a stupid setting if you ask me as people always notice the fan switching on/off as opposed to a constant background noise. There should be a setting in the controller or dipswitches in the indoor control panel that changes the fan to continuous operation. You'll need your installer to change this. It may also help with better temperature control as system always circulating air through the house so giving a better average temp of the house.

Weirdly it appears the unit was operating like this last night - not sure if this was due to me having changed a setting that ensured one zone was always in operation if the unit was on (to prevent damage if the unit's running but no zones are turned on). The internal fan went constantly, even when the outside unit was not functioning (ie, the outside unit's fans were not going at all). Is this how it works when the fan is set to continuous operation?

Kickinbac:
Also sounds like you are getting stratification which is the hot air pooling near the roof which is affecting the temperature sensing (google search for info). A ducted system has a sensor in the return air, if the temperature is warm at ceiling level it thinks it's at setpoint and backs off. This setting can be changed to the wall controller only, return air only or an average of both. Daikin's usually sense from both wall controller and return air sensor to get the best of both worlds. Basically the hot and cold air need to be mixed better as hot air rises. Some controllers have a high ceiling setting that puts an offset in the temperature settings to allow for this. Basically fools the controller it thinking it's cooler than it is. This is where the Holyoake ECO-A diffusers work well as they jet the air down to the occupants when in heating.

Yeah, that's what I'd been led to believe, but unfortunately it's not the case with this particular unit. Given the tight-@rses at Daikin have not developed a bespoke controller for this, but just relied on a bog-standard Android tablet, there's no temperature sensor in the controller! Had this been pointed out to me prior to selecting this unit, it would have been one more reason to not choose it. Do you think it would be worth investigating the cost of having an additional sensor put in? And if so whereabouts would it be best located? In the second zone, ie in the different zone to the returns? The controller allows one to select the sensor being used, so I'd imagine I could use different sensors for different heating purposes (eg, if heating only one zone, would it make sense to be using a sensor not even within that zone?).

bfginger

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#1358401 4-Aug-2015 10:09

Daikin does have bespoke controllers with a thermostat sensor. The Android tablet was the local Australian subsidiary's idea.

Click on Controller

http://www.daikin.co.nz/home-solutions/ducted-air-conditioning

http://www.daikinac.com/content/residential/residential-wired-controllers/daikin-envi-intelligent-thermostat/

https://www.youtube.com/watch?v=MWk0GMfQlhM

https://www.youtube.com/watch?v=9_Vk0_sru6E

jonathan18

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#1358423 4-Aug-2015 10:30

bfginger: Daikin does have bespoke controllers with a thermostat sensor. The Android tablet was the local Australian subsidiary's idea.

Click on Controller
http://www.daikin.co.nz/home-solutions/ducted-air-conditioning
http://www.daikinac.com/content/residential/residential-wired-controllers/daikin-envi-intelligent-thermostat/
https://www.youtube.com/watch?v=MWk0GMfQlhM
https://www.youtube.com/watch?v=9_Vk0_sru6E

Interesting. Clearly, though, the first link isn't available in NZ, going by what's listed on the second link.

There are some weird limitations on the Android-based controller, which I'm not sure if are specific to this model or apply across the range, eg:

* while the 7-day timers can be set to the nearest 10 minutes (still relatively crude in my book), the quick timers can only be set to the nearest hour (even half-hour periods - which is what the manual claims it provides - would be better than this)

* the 7-day timers don't allow the fan speed to be selected, so it'll just use whatever it was last set to. This is frustrating for us as we'd prefer to have the fan forced to 'low' at night to keep the noise down, but ramp up or set to 'auto' when the timer for the other zone comes on (so it'll warm it more quickly and we don't need to start it as early).

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Kickinbac

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#1358591 4-Aug-2015 12:10

Here's some information about the temp sensors available with the zone controllers from the zone controller installation manual.
I would put temp sensors in the rooms (zones) you use the most - say lounge and master bedroom as that is what they will control to when you select them. They shouldn't cost a lot to install only issue is getting the wires down the wall but electrician can usually fish them down with light switch wiring.

You have a choice of 5 temperature sensors.

1.) Indoor Sens – Temperature sensor located in the

indoor unit.

2.) Master RC - Master controller sensor (probably not as it's wireless)

3.) Sub RC - When using option BRCSZC Sub controller.

4.) Sens 1 - When using option KRCSO1-1

5.) Sens 2 - When using option KRCSO1-1

 Only the indoor sensor will be activated

(factory set) all other sensors must be activated by

the field set codes, once activated sensor selection

can be achieved by pressing the SEL SENSOR

button on the remote controller.

cantonascollar

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#1358646 4-Aug-2015 12:50

These problems are making me reconsider my install. We are having an extension and renovation done soon and I had planned on installing a Daikin ducted system (18.kW). I had planned to run the ducting under the floor and have the outlets at floor level, partly to protect my tin ceilings but also to generate better mixing of air. Will the floor installation be better? Is there an inherent problem with these systems or is there just a lack of knowledge when it comes to the installation?

I suppose if it is a problem with installation, then maybe we need to generate a list of experienced and recommended installers? Does anyone have any experience of Dunedin based companies that can successfully do these installs?

jonathan18

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#1358701 4-Aug-2015 14:07

cantonascollar: These problems are making me reconsider my install. We are having an extension and renovation done soon and I had planned on installing a Daikin ducted system (18.kW). I had planned to run the ducting under the floor and have the outlets at floor level, partly to protect my tin ceilings but also to generate better mixing of air. Will the floor installation be better? Is there an inherent problem with these systems or is there just a lack of knowledge when it comes to the installation?

I suppose if it is a problem with installation, then maybe we need to generate a list of experienced and recommended installers? Does anyone have any experience of Dunedin based companies that can successfully do these installs?

We were actually drawn to the idea of ducted heating from our direct experience of two installs (my in-laws and some friends of ours). The key differences between theirs and our installs were both of theirs have it installed under the house with floor-mounted vents.

Installers seem to really stay away from these if they can as I guess installation is more tricky due to less/dirtier space, but it made sense in the other cases as my inlaws had ducting in place as they were replacing a dead gas-fired central heating system, and our friends' house is an old two-storied one, so not possible to ceiling-mount.

Based on the three experiences, I think they were lucky to have theirs under-floor-mounted, as neither seem to have had the issues we've had with airflow etc. (That said, both installs took a while to get completely right). Many will argue that floor vents are more logical for heating (of course not the reps doing the quotes!), and while ceiling-mounted for heating may be ok, it appears there are so many more stars that need to be properly alligned for it to perform as intended. If I'd had the option I'd have def. gone under-floor, but was limited by a relatively low crawl space under the house.

A clearly highly knowledgeable poster above says he's he'd go with multiple indoor units rather than a ducted system (I assume using a single large outdoor unit, or perhaps multiple outdoor units?), but personally this wouldn't address our needs, which is guaranteed warmth in every room. I'm thinking we'd have needed six wall- or floor-mounted units - one in each bedroom, one in the lounge and one in the kitchen/dining - to have acheived the same coverage. Plus I prefer the more dissipated heat one gets with a ducted system - I just don't like the direct and often intense air flow from the standard units.

If you do go Daikin (and generally I've heard positive things about the brand), I suggest staying away from the Android-based touch-screen interface (known as the Premium Inverter Plus). These appear to just be the "Premium Inverter" range with a wifi controller bolted on and that sh!te tablet instead of a dedicated controller (see my earlier comments re lack of sensor in the controller).

Kickinbac

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#1358754 4-Aug-2015 15:06

cantonascollar: These problems are making me reconsider my install. We are having an extension and renovation done soon and I had planned on installing a Daikin ducted system (18.kW). I had planned to run the ducting under the floor and have the outlets at floor level, partly to protect my tin ceilings but also to generate better mixing of air. Will the floor installation be better? Is there an inherent problem with these systems or is there just a lack of knowledge when it comes to the installation?

I suppose if it is a problem with installation, then maybe we need to generate a list of experienced and recommended installers? Does anyone have any experience of Dunedin based companies that can successfully do these installs?

Heat pumps supplied through the floor grilles can be very good as you are putting in the heated air at low level where you need it. But spend your money first on insulation and stopping draughts. Old houses that leak air, have high ceilings etc can be difficult to heat by any method. There is always a compromise, type of system, control, physical constraints of the building etc.

Find out how much flexible duct they plan on using and how it will be supported under the house. Solid sheet metal insulated duct is better but more expensive and harder to install in an existing house. Upgrade the insulation on the duct, most installers use R0.6, but you can get R1.0 and R1.5 to retain the heat better. It shouldn't cost a lot more.

Daikins are good and work well 99.9% of the time. Generally it's the design/installation where there are issues and that can be with any brand. The good installs don't get talked about much on forums. There are always a few that don't work as well as expected which can be for any number of reasons.

There are a few people out there that give heat pump installers a bad name. Use a reputable experienced business, preferably HVAC or refrigeration engineers (not your local electrician or plumber!) shop around, ask for recommendations, ask for references of installs they have done, particularly in similar age/style of house. Stick with well known brands such as Daikin & Mitsubishi Electric etc. There's some good advice on the consumer website.

Also expect to give a heat pump time to heat a house especially in a cold climate, it takes a while to warm up a building, initially you heat up the air then that heat gets absorbed by the structure. Sometimes it's best to leave the heat pump on a low setting (say 17-18 degrees) while you're out as this will maintain the base heat without costing a fortune which comes back to insulation...

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