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back2space
23-11-2016, 12:00 PM
Hello everyone

Our reception area has high ceilings of 5/6m we need to turn on the high ceiling mode as high fan speed alone is not enough to get warm air down to floor level.

The controller suggests that high ceiling mode is Mode number 13 (23) followed by first code 0 then we have second code numbers of 01 (normal <2.7m), 02 (high >2.7m) or 03 (extra high >3.0).

On our other floors setting option 03 actually reduces the fan output and you can hear the fan and airflow is less, setting it to 01 where you would expect it to be the least actually makes the fan speed up the fastest. Also on this controller there is an option for static pressure which is not available on the ducted units on the other floors so our reception ducted unit is clearly a diff unit.

The issue is on the reception unit we cannot hear the fan anyway due to the height of the ceiling and the noise level from the busy street so we need to know the correct settings as they do not seem to correspond to what its saying in the field settings. Even the engineers when they come out are confused by this and say that code 03 is high ceiling mode even though this slows the fan down even slower. As the FM for this site I am having to resolve this myself now due to the call out costs.

Anyone any idea on what is the correct settings? The system is about 6 years old now and is a big VRV system with some areas having localised controllers - the reception area included. The rest are controlled from itouch controllers in the riser cupboards.

The Viking
23-11-2016, 01:05 PM
OK,
I can't speak with authority on Daikin specific issues but generally...

The "High ceiling mode" is for use on cassettes (the square units visible in the ceiling), i.e. units with louvres built in to the AC unit itself. When high ceiling mode is enabled the unit will change the angle of the louvers and it might up the fan speed.

However, when it comes to ducted units the air distribution is via 3rd party ducts and grilles (hopefully) bespoke designed for the individual site. So if you got a ducted unit that's not providing the air circulation required the only real option is to look in to the design of the air distribution system. Upping the setting for external static pressure might help but if you want to throw the air further you will need higher velocity through the grilles.

In some cases I come across in the past similar to yours the only viable option, as hot air always rises, was to relocate the air supply grilles to low level.

:cool:

back2space
23-11-2016, 01:45 PM
The ducted units also have high ceiling mode in Daikin, if the option wasn't available it wouldn't show as changeable option on the controller. We also have static pressure also as an option to change whereas some of our smaller ducted units dont have this.

Slim R410a
23-11-2016, 01:51 PM
I would forget about the high ceiling mode if your ducted unit/supply grille is at 5-6m height its never going to get the warm air down.

I would look into a de-stratification fan(s) to push the warm air down or as above extending the supply air duct/grilles to a lower level, say 3m height, but that would be a much larger expense.

back2space
23-11-2016, 02:02 PM
If we could get more airflow we could at least try.

Even the high static pressure mode doesn't seem to do anything or increase the fan speed and there is no clear options to select.

The issue is that we have automatic reception doors and the are constantly opening/closing and all the heat that does build goes out the door. The landlord will not pay for door curtains.

back2space
23-11-2016, 02:10 PM
So for example in this video - https://www.youtube.com/watch?v=O8e138vrFmI

It gives various options 1-15 of various pressures... however the manual gives 3 options with the 2nd option being high static pressure and the 3rd option being low pressure. Whereas the video suggests that they go up from 1-15 each step higher pressure?

frank
23-11-2016, 07:39 PM
The Daikin cassette in not recommended for ceilings in excess of 3.4m height.

If you have them installed in ceilings 5-6m high I would suggest that you install sweep fans controlled by a thermostat which will act as destratification

back2space
23-11-2016, 09:25 PM
The Daikin cassette in not recommended for ceilings in excess of 3.4m height.

If you have them installed in ceilings 5-6m high I would suggest that you install sweep fans controlled by a thermostat which will act as destratification

They are ducted not cassette units. This is a contemporary reception fans would not suit it.

Neddy
24-11-2016, 08:24 AM
On some older Ducted units the static pressure is changed from at the PCB. Have you got a model number? Have you set the static pressure to the highest setting? Also the position of the return air thermistor is important as if its in the ducted unit it's measuring hot air 6 meters high which is no good. Have you a wall sensor or is the thermistor in the controller used?

back2space
24-11-2016, 08:34 AM
On some older Ducted units the static pressure is changed from at the PCB. Have you got a model number? Have you set the static pressure to the highest setting? Also the position of the return air thermistor is important as if its in the ducted unit it's measuring hot air 6 meters high which is no good. Have you a wall sensor or is the thermistor in the controller used?

yeah it's reading from the wall controller. Set point 30c room temp 16c - at ceiling level it is 26c. The units are about 6 years old.

Neddy
24-11-2016, 08:56 AM
Some models will only allow the static pressure to be changed from the PCB. If the setting cannot be changed at the controller it is done from the PCB. If the setting can be changed at the controller the ducted unit will make the changes set at the controller. A model number would help to verify this.

The Viking
24-11-2016, 09:21 AM
OK, let my try to visualise the issue.

Imagine you are driving a car from London and you want to get to Paris, everything runs smoothly until you get just past Dover but as you arrive at the seafront your car will drop off the quay side and land 10 yards out in the sea. Now you could increase your speed and get the car to jump further, say up to 100 yards in to the sea, but you would still be nowhere near Paris, your destination.
What options have you got?
1) You could use the tunnel to go underneath the channel
2) You could take a ferry across the channel
3) You could have started in Calais
4) You could replace your car with an amphibious vehicle

So how does this relate to your AC unit?
You have a unit that, as far as we know, is working as it should (just like the car above does) but the air is not reaching its destination.
You could;
1) Use ductwork to route the air supply to where you want it to go
2) Use external fan(s) to deliver the air to where you want it to go
3) Move the unit closer to where you want the air to go
4) Replace the existing AC unit with something else, perhaps radiators or underfloor heating

:cool:

back2space
24-11-2016, 09:22 AM
Some models will only allow the static pressure to be changed from the PCB. If the setting cannot be changed at the controller it is done from the PCB. If the setting can be changed at the controller the ducted unit will make the changes set at the controller. A model number would help to verify this.

I will try and get hold of the model number but its difficult due to the ceiling height the unit then is installed another meter above the dropped ceiling so we have to use scaffold to access it.

Its quite possible the static pressure isn't changeable from the controller like you say as nothing happens when you change it. Shame the model number doesn't show up on the controller.

back2space
24-11-2016, 09:50 AM
OK, let my try to visualise the issue.

Imagine you are driving a car from London and you want to get to Paris, everything runs smoothly until you get just past Dover but as you arrive at the seafront your car will drop off the quay side and land 10 yards out in the sea. Now you could increase your speed and get the car to jump further, say up to 100 yards in to the sea, but you would still be nowhere near Paris, your destination.
What options have you got?
1) You could use the tunnel to go underneath the channel
2) You could take a ferry across the channel
3) You could have started in Calais
4) You could replace your car with an amphibious vehicle

So how does this relate to your AC unit?
You have a unit that, as far as we know, is working as it should (just like the car above does) but the air is not reaching its destination.
You could;
1) Use ductwork to route the air supply to where you want it to go
2) Use external fan(s) to deliver the air to where you want it to go
3) Move the unit closer to where you want the air to go
4) Replace the existing AC unit with something else, perhaps radiators or underfloor heating

:cool:

Totally get what your saying and thank you for your suggestions but this unit is a large capacity unit, it cools the space perfectly fine. The diffusers are massive there are 2 they are similar to the following: http://effectiv-hvac.com/product/ax6-adjustable-round-swirl-diffuser/

or

http://www.waterloo.co.uk/product-models/sdch-high-capacity-swirl-diffusers/ - I think these are the ones we have though.

There is large flexi duct connected to them and they are actuator controlled so in heating the blades move and point the air flow down and in cooling they reverse. At head height you can just about feel the air but its obviously rising too quickly and not coming out with enough force.

They are designed to heat spaces such as this and its not a massive area its just the ceiling height. I have measured the ceiling properly and its approx 5m in height. The unit is installed in the dropped ceiling at 6m though but from floor to diffuser its 5m approx.

The Viking
24-11-2016, 02:59 PM
OK,
Just remember, cold air drop down whilst hot air rises...
Also, in order to throw the air far away you need high velocity through the diffusers.

Large diffusers with low velocities are great during the summer when you want cooling and don't need to push the air down to floor level as cold air will fall on its own. Large diffusers creates less draft during cooling operation.
However, when you need to push hot air down to floor level you really need to get the velocity of that air as high as possible i.e. small diffusers, perhaps even venturi type ones.


Edit:
Try and block off 1/3 of the gaps between the blades in your diffusers and see if it makes any difference.

Slim R410a
24-11-2016, 03:06 PM
If you can get the Daikin FCU model number, duct size and diffuser size we can work out the maxium air throw in meters available. Thats presuming the filter is clean.

Your saying its a 'large capacity unit' which in my book is 20kw or 25kw i.e 200 or 250?

Apart from this its so obvious you need an air curtain to stop cold air infiltration and output some additional heat where its needed at low level. I know you've said the landlord wont pay for air curtains but if there nothing you can do with the ducted a/c then they have no choice..

EDIT: If the system is only 6 years old can you get hold of an as fitted drawing or schematic to get the model number?

back2space
24-11-2016, 03:11 PM
OK,
Just remember, cold air drop down whilst hot air rises...
Also, in order to throw the air far away you need high velocity through the diffusers.

Large diffusers with low velocities are great during the summer when you want cooling and don't need to push the air down to floor level as cold air will fall on its own. Large diffusers creates less draft during cooling operation.
However, when you need to push hot air down to floor level you really need to get the velocity of that air as high as possible i.e. small diffusers, perhaps even venturi type ones.

Edit:
Try and block off 1/3 of the gaps between the blades in your diffusers and see if it makes any difference.

Thanks, yes we do need to get the air velocity through them, we have an engineer on site who is going to look into this and speak to Daikin tech.

back2space
24-11-2016, 03:16 PM
If you can get the Daikin FCU model number, duct size and diffuser size we can work out the maxium air throw in meters available. Thats presuming the filter is clean.

Your saying its a 'large capacity unit' which in my book is 20kw or 25kw i.e 200 or 250?

Apart from this its so obvious you need an air curtain to stop cold air infiltration and output some additional heat where its needed at low level. I know you've said the landlord wont pay for air curtains but if there nothing you can do with the ducted a/c then they have no choice..

EDIT: If the system is only 6 years old can you get hold of an as fitted drawing or schematic to get the model number?

An engineer is on site now as we have issues with a faulty compressor elsewhere in the building. This is a large VRF system but I am told the reception units (there are 2) have their own outdoor condenser and are not part of the VRF system even though they are are also present on the central controller.

No they wont give us air curtains due to cost so its down to trying to get the system working as best it can really. I dont think it was ever commissioned properly really as we found in other areas of the building. The engineer knows what model numbers are which and he said its a high static pressure unit.

niceman
24-11-2016, 04:00 PM
Has this system heated ok in previous winters? If it is a seperate system are all filters clean? If ok in previous years whats changed? Can you put heater behind reception desk to make it better for the receptionist?

back2space
24-11-2016, 04:05 PM
No its the same every winter but we now have a manned reception and security desk whereas before it was just an entrance so there are people in there working.

We have put a heater in but it only raises it to about 14C.

frank
24-11-2016, 08:13 PM
Same old chestnut....got a problem but no money available to fix it or the fix won't look right.

If you cant get the heat down to the 'Comfort Zone' i.e. 2m above floor level, then you will never be able to fix the problem with the equipment you have.

If you press the bottom left hand grey button on the controller once, the model size comes up in the display.

back2space
24-11-2016, 09:58 PM
Same old chestnut....got a problem but no money available to fix it or the fix won't look right.

If you cant get the heat down to the 'Comfort Zone' i.e. 2m above floor level, then you will never be able to fix the problem with the equipment you have.

If you press the bottom left hand grey button on the controller once, the model size comes up in the display.

Yeah apparently they have rang daikin and he's put the static pressure up on the controller but it's made no difference there is no tone increase in the motor.

The test button do you mean to press?

Neddy
25-11-2016, 08:00 AM
Models numbers can be obtained from the F gas records or the commissioning reports.

frank
25-11-2016, 05:20 PM
The test button do you mean to press?

Yes,just press it once

Slim R410a
01-12-2016, 04:40 PM
Any update on this?

back2space
01-12-2016, 04:43 PM
Hello, well the contact person from the landlord has gone off on leave now. The contractor came out and rang Daikin and apparently they told the receptionist "they have done it remotely" absolute rubbish! So I am going to meet with the landlord again when they are back from leave.

When I pressed the test button lots of different numbers were displayed before it went into test mode, nothing corresponded to a capacity as such.