Never take anything for granted

[glenn1340]

I`ve got a problem with two Airdale units (apart from the one mentioned on a previous post) both tripping on HP. I can actually see the pressure rise until they trip on these ones. They are ducted heat pump ones.
Checked the usual stuff: condensors, ducting filters and evaporators; all ok.
The air flow didn`t seem quite right so climbed up into the roof void which was so tight the builders had to cut notches out of the roof trusses to fit over the ducting. After struggling to get the fan inspection cover off I found the reason for the tripping: the ducting manufacturers had fitted the fan upside down in the fan box so that the gap for the air to the fan is 1/2" this along with the filters and sound attenuation is the the cause of the tripping.
The client said they`d had problems for years. His previous aircon guy had linked out the Hp switch on one unit resulting in the compressor failing TWICE.
Now all I`ve got to do is cut the ducting out and turn it over!! after cutting the roof trusses away.
Here`s a pic. the ratchet is a 3/8 drive to give scale

[karl957]

Looks like fun, glad I am not involved. It can get quite hot and cramped working in ceilings.

[sedgy]

hi glenn
are the fan motors 3ph , is the direction right? I ,m sure its worth testing first,

[marc5180]

As above post says, it could be wired wrong causing it to run backwards.

[Grizzly]

Well done Glen.
Doesn't it feel good when you are able to resolve a problem that is "historic".
Good engineering practises reward all in the end.
Meaning those that ask why as well as what needs replacing!
Once again well done.
Sounds like a job for the apprentice!!!
(usually the only 1 slim enough to fit in tight spots!!)
Grizzly

[glenn1340]

Hi grizzly,
Went back today to finnish the job, found the problem wasn`t the fan upside down but the AV mountings supporting the fan box had given way (incorrectly fitted) allowing the fan to fall directly onto the ducting stopping the air flow.I fitted new mounts and checked the air velocity into the outdoor grill, it was 1.18 m/sec before the repair and
3 m/sec after. The HP is now steady at 220 psi before it was 450 and tripping out.

Smug, self satsfied Glenn signing out;-)

[Brian_UK]

Smug, self satisfied Glenn signing out;-)

and why not, well done Glen.