Is anyone having problems with recent Daikin heat pumps?

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#3264654 26-Jul-2024 12:35

tweake: my guess here without knowing model numbers, is a major factor is its well oversized for the room.

It's a 2.5kW which was pretty much the smallest they could get. They have the same problem in their office which is quite a bit larger, maybe 3.5 x 5m.

tweake

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#3264671 26-Jul-2024 13:07

neb:

tweake: my guess here without knowing model numbers, is a major factor is its well oversized for the room.

It's a 2.5kW which was pretty much the smallest they could get. They have the same problem in their office which is quite a bit larger, maybe 3.5 x 5m.

if its the same model as another person has mentioned, then you can get one size smaller.

one of the issues is how they rate them. that model has a max heat output of 5.4kw. you could heat a whole small house with that heat pump. even the larger office, it could do double that. (of course this is guessing a bit because of lack of info). the graphs show it gets the air temps up super quick. its really blasting air around that small space.

with nz small rooms its hard to get small enough heat pumps. it makes it worse when people size by the average size instead of the peak sizes. eg my Panasonic has lower heat output for the same size machine.

k1w1k1d

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#3264720 26-Jul-2024 16:14

The Daikin guy fixing our heat pump today had not heard of this problem.

We haven't had the problem with either of our Daikins, but we don't run them for hours as we only use them as a backup to our log burner.

tweake

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#3264735 26-Jul-2024 17:13

k1w1k1d:

The Daikin guy fixing our heat pump today had not heard of this problem.

thats probably due to most people not having temp gauges to check what the actual temp of the room is. so they never complain about it so the tech never hears about it.

neb

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#3264740 26-Jul-2024 17:27

tweake: thats probably due to most people not having temp gauges to check what the actual temp of the room is. so they never complain about it so the tech never hears about it.

Or they think "gee, it's a bit warm in here, better turn the heat pump off for awhile". Which is exactly what my neighbour, who has a Daikin, has been doing. Wouldn't be surprised, if I put a temperature logger in their living room, that they have this problem too.

Handle9

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#3264779 26-Jul-2024 20:33

neb:

tweake: thats probably due to most people not having temp gauges to check what the actual temp of the room is. so they never complain about it so the tech never hears about it.

Or they think "gee, it's a bit warm in here, better turn the heat pump off for awhile". Which is exactly what my neighbour, who has a Daikin, has been doing. Wouldn't be surprised, if I put a temperature logger in their living room, that they have this problem too.

A strong majority of people have no idea that the point of a thermostat is to set it and leave it the hell alone. They think that having a setpoint of 35 degrees or 18 degrees will get the room to a sensible setpoint faster.

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#3264783 26-Jul-2024 20:53

Handle9: A strong majority of people have no idea that the point of a thermostat is to set it and leave it the hell alone.

Agreed.

Handle9: They think that having a setpoint of 35 degrees or 18 degrees will get the room to a sensible setpoint faster.

Depends on the particular heat pump and how it is programmed. Some will vary the compressor power based on the difference between the set point and initial room temperature. If it's a small delta then the compressor is run at a lower power setting (presumably more economical and/or less wear and tear, less noise) until the setpoint is reached then it settles in to the normal hysteresis. If there is a higher difference then it runs at a higher power in order to reach the set point quicker before hitting hysteresis.

In terms of actual data on a Panasonic unit I checked it would heat at approx 2.5 degrees/hour if the intial difference was less than about 4 degrees. If the initial difference was greater than that then it ran at a higher setting. The hot air stream was noticably hotter and would result in about 6 degrees/hour room temp increase.

So while it can seem counter-intuitive, some heat pumps will get to a sensible setpoint faster if the setpoint is temporarily increased (or decresased) to the maximum (minimum) level. In comparison to a basic thermostatically controlled device like a water heater or oven that only has one power setting, heat pumps can and do reduce the power to less than maximum.

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#3264785 26-Jul-2024 20:57

RunningMan:

Handle9: They think that having a setpoint of 35 degrees or 18 degrees will get the room to a sensible setpoint faster.

Depends on the particular heat pump and how it is programmed. Some will vary the compressor power based on the difference between the set point and initial room temperature. If it's a small delta then the compressor is run at a lower power setting (presumably more economical and/or less wear and tear, less noise) until the setpoint is reached then it settles in to the normal hysteresis. If there is a higher difference then it runs at a higher power in order to reach the set point quicker before hitting hysteresis.

If you are running a unit at maximum power you are going to significantly overshoot setpoint. The whole point of PI (you don't use D in HVAC room control) is to come to a nice smooth room temperature, modulating down as you come closer to setpoint with minimal overshoot.

If you are a long way away from setpoint you run at 100%. Making the setpoint stupidly high or low doesn't giver you anymore than 100%.

Edit: It's probably worth mentioning that the P band in room control is typically 2K - i.e. if you are 2 degrees away from setpoint you're running at 100% heating or cooling. It's only going to modulate down if you're within 2 degrees of setpoint and even then I will take care of pushing it up a bit if you aren't getting to setpoint.

neb

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#3264801 26-Jul-2024 21:20

RunningMan: So while it can seem counter-intuitive, some heat pumps will get to a sensible setpoint faster if the setpoint is temporarily increased (or decresased) to the maximum (minimum) level. In comparison to a basic thermostatically controlled device like a water heater or oven that only has one power setting, heat pumps can and do reduce the power to less than maximum.

Daikins at least have a turbo mode where you can tell it to heat (or cool) a lot harder for a bit in order to get a room closer to the setpoint quicker than normal. So the manufacturers have recognised the user overcompensation problem and adapted their devices for it.

tweake

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#3264805 26-Jul-2024 21:26

RunningMan:

In terms of actual data on a Panasonic unit I checked it would heat at approx 2.5 degrees/hour if the intial difference was less than about 4 degrees. If the initial difference was greater than that then it ran at a higher setting. The hot air stream was noticably hotter and would result in about 6 degrees/hour room temp increase.

panasonics run 100% speed until 2c before set point, then slow down. according to their book. that may vary with model of course. they go flat out to get close, then slow down and creep up to target. power mode makes them run full speed until set point. one thing i do notice is they tend to do a quick blast at full speed, stop for a minute, then continue. like its checking room temp.

however i think one issue with these daikins is that are hitting the set points in 5 minutes (which is insanely quick), stopping, then going straight into on/off mode. it actually overshoots a bit, but then lets the temps come down and hit set point. but then slowly increases its max temp and creeps the set point up. it does that right from when it first goes into stop start. i have no idea why.

what might be interesting is if its left alone for long enough, will it adjust itself and stop doing that.

Handle9

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#3264905 26-Jul-2024 21:39

tweake:

RunningMan:

In terms of actual data on a Panasonic unit I checked it would heat at approx 2.5 degrees/hour if the intial difference was less than about 4 degrees. If the initial difference was greater than that then it ran at a higher setting. The hot air stream was noticably hotter and would result in about 6 degrees/hour room temp increase.

panasonics run 100% speed until 2c before set point, then slow down. according to their book.

2K is industry standard and it's pretty unusual to go away from that with room control. You'd need a really twitchy room to go wider and you normally wouldn't go narrower unless you can live with overshoots through deadband or have a wider than normal deadband.

neb

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#3268355 5-Aug-2024 14:55

Looks like it's solved, there's a problem with one of the modes it operates in, if you disable that it behaves as expected, when you enable it it goes into neverending-heating mode after a few hours use. It's the one where it directs warm air downwards onto the floor, which may be called "Comfort Mode", I'm still waiting to get more details.

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#3268376 5-Aug-2024 17:04

neb:

Looks like it's solved, there's a problem with one of the modes it operates in, if you disable that it behaves as expected, when you enable it it goes into neverending-heating mode after a few hours use. It's the one where it directs warm air downwards onto the floor, which may be called "Comfort Mode", I'm still waiting to get more details.

So you are saying you think it tied strictly to Comfort Mode? I have a Daikin Zena Vogue FTXJ50TVMAW that is 2 years old and seems to behave just fine, but I don't use comfort mode.

I have a different and super annoying other problem though with their iOS app update from last December where that has completely broken programming and scheduling so I have to manually downgrade back to the old app to keep it working. Have been going round and round with Daikin on this for 8 months with no resolution yet.

tweake

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#3268379 5-Aug-2024 17:08

neb:

Looks like it's solved, there's a problem with one of the modes it operates in, if you disable that it behaves as expected, when you enable it it goes into neverending-heating mode after a few hours use. It's the one where it directs warm air downwards onto the floor, which may be called "Comfort Mode", I'm still waiting to get more details.

do you get the same issue if the vanes are manually pointed down to the floor?

neb

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#3268380 5-Aug-2024 17:08

spacedog: So you are saying you think it tied strictly to Comfort Mode?

It happens when you use the mode that directs the heat flow across the floor, which on my one is labelled Comfort Mode. Turning that off results in correct operation. There may be different names for it, I'm still waiting to get all the details.

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