paul_h
08-09-2010, 01:03 PM
I haven't worked on a fuji ducted for ages.
This is an old one for me, I replaced the compressor 2 years ago in summer.
Anyway, I'm called back again in winter 2 years later, they say airflow is bad now certain areas not heating (but worked fine last winter after I was last there).
I check everything, it all seems fine, filter a bit blocked, as well as that, it is a small unit not big enough for a whole house. Unfortunately the installers put two switches in for zone control, 1 for bedrooms, one for living areas, instead of a single day/night switch, so they tend to try run both zones.
But a closer look at how the system is running shows a few things not quite normal.
They had the system set to fan high, HEAT, and 30C setpoint, and run it all day.
So it had been running flat out for a few hours when I got there in the afternoon, ambient 16C, inside temp 20C at the return (common area between the living and bedrooms).
I noticed the outdoor fan spending most of it's time cycled off, so air out of the indoor was only 34C.
Suction service valve was 85C which seemed high to me and probably why the indoor coil sensor was hot and cycling the outdoor fan off.
With the outdoor fan on, HP went up to 2200kPa, LP was 360kPa, liquid line return was 31C.
With the outdoor fan off, HP down to 1700kPa, LP down to 200Kpa, SSV 79C, liquid line 29C.
So to me temps and pressures high, differential across the indoor low, and I've never seen one of these have the outdoor fan cycle off so much when the indoor return only 20C.
But first question is anyone know what size return air duct these should have?
It's got a single run of 400 diam flex 6m long, off a 350mm x 900mm filter.
I just want to make sure it's getting enough air before I start scratching my head about the temps and pressure.
This is an old one for me, I replaced the compressor 2 years ago in summer.
Anyway, I'm called back again in winter 2 years later, they say airflow is bad now certain areas not heating (but worked fine last winter after I was last there).
I check everything, it all seems fine, filter a bit blocked, as well as that, it is a small unit not big enough for a whole house. Unfortunately the installers put two switches in for zone control, 1 for bedrooms, one for living areas, instead of a single day/night switch, so they tend to try run both zones.
But a closer look at how the system is running shows a few things not quite normal.
They had the system set to fan high, HEAT, and 30C setpoint, and run it all day.
So it had been running flat out for a few hours when I got there in the afternoon, ambient 16C, inside temp 20C at the return (common area between the living and bedrooms).
I noticed the outdoor fan spending most of it's time cycled off, so air out of the indoor was only 34C.
Suction service valve was 85C which seemed high to me and probably why the indoor coil sensor was hot and cycling the outdoor fan off.
With the outdoor fan on, HP went up to 2200kPa, LP was 360kPa, liquid line return was 31C.
With the outdoor fan off, HP down to 1700kPa, LP down to 200Kpa, SSV 79C, liquid line 29C.
So to me temps and pressures high, differential across the indoor low, and I've never seen one of these have the outdoor fan cycle off so much when the indoor return only 20C.
But first question is anyone know what size return air duct these should have?
It's got a single run of 400 diam flex 6m long, off a 350mm x 900mm filter.
I just want to make sure it's getting enough air before I start scratching my head about the temps and pressure.