Gradient syncFURNACE filter size depends on the model. The 05L, 08L, 06H, 10L, 12L and 10H take a
16 x 25 filter. The 16L, 15H and 20L take a 20 x 25. All of them are 14 inches high by 23 inches
deep. Any standard furnace filter fits, so you do not need a proprietary one. 180 Plumbing and
Heating services Gradient equipment across southeast Calgary. Call 403-404-9975.
The filter table
| Model size code | Filter size | Depth |
|---|---|---|
| 05L, 08L, 06H, 10L, 12L, 10H | 16 x 25 | 14 in high by 23 in deep |
| 16L, 15H, 20L | 20 x 25 | 14 in high by 23 in deep |
Where the model code is. On the rating plate on the unit, usually on the front or just inside
the access door. The code follows the model number, so a plate reading sFT-202 12L means a 12L, and
therefore a 16 x 25 filter.
Which brand. Any standard furnace filter is compatible. Gradient names Aerostar, Clean Comfort,
GeneralAire and Honeywell as examples. Buy on fit and on a sensible filtration rating rather than
on brand.
How often. Gradient recommends checking monthly and changing as required, which for most homes
works out to about four times a year. Pets, renovations and a dusty summer all shorten that.
Why a filter matters more on this unit than you would think
A restricted filter chokes airflow across the coil. On a conventional furnace that costs you
efficiency and comfort. On a combination unit it can also contribute to nuisance lockouts, because
the appliance is watching temperatures that airflow affects.
If your unit has been faulting intermittently and nobody has looked at the filter in a year, look
at the filter before you look at anything else. It is the cheapest possible first check.
Write the size on the unit. A permanent marker on the cabinet beside the filter slot saves
everyone in the house a trip back to the store, including us.
The service parts on a syncFURNACE
You do not need to know any of this to own one, but owners regularly ask what is actually in there,
and a technician quoting you should be able to name what they are replacing and why.
- Condensate trap. Internal, and the most frequent maintenance item on the platform. Blockage
here is the most common cause of a lockout in Calgary homes. Usually cleaned rather than replaced. - Igniter and flame sensor electrodes. Annual service items. They get cleaned every year and
replaced when they degrade. - Combustion blower. Involved in ALM 1 and ALM 2 faults. Often the fault is a blocked vent
rather than the blower itself. - Gas valve. Part of the ALM 4 and ALM 5 picture, along with pressure and ignition.
- Pressure and temperature sensors. Involved in high limit faults.
- Recirculation pump. Gradient specifies a Grundfos 15-78 non ferrous on the tankless models.
- Pressure relief valve. Internal, rated 150 psig on the tankless models.
- Safety switches. Water temperature high limit, condensate trap pressure switch, vent limit
switch. The vent limit switch is not resettable, must not be bypassed, and its opening means the
heat exchanger has to be replaced. - Heat exchanger. Stainless steel, dual pass, and covered by Gradient for ten years provided
maintenance has been carried out and documented.
Getting the right parts
We stock Gradient parts on the van. Filters, common service parts and the items that fail on
this platform travel with us, which is the difference between a job finished today and a job
finished when a part arrives.
Tell us your model number when you book and we bring what your unit needs. The model code is
the one thing we ask for on the phone.
If you are not sure what you have, photograph the rating plate and text it to 403-404-9975. We will
tell you the model, the filter size and roughly what it should be needing at its age.
Your filter and your warranty
Two things in Gradient’s warranty policy point straight at the filter, and almost no owner knows
either of them.
Air filters are an excluded component. The policy lists them alongside gaskets, O-rings and
fuses as items the warranty does not cover. That is normal for a consumable and it is not a
complaint.
Running without the correct filter is an exclusion. The policy excludes damage from operating
the unit “without a high-velocity filter installed on the return air duct as per the Product
manual(s)”. So the cheapest item on the appliance is also a condition of the most expensive part of
the coverage. See the warranty page.
While the filter is out, check these too
Three things take a minute and are all yours to do.
- Look at the outside vent terminations. In winter, clear any snow or ice. Gradient tells
owners to monitor and remove ice buildup from exterior pipes, and it is the most common cold
weather fault in Calgary. - Glance at the system pressure on the controller screen. What matters is that it is stable
over time, not the exact figure. - Look underneath and behind for water. A condensate drain that is starting to block often
shows itself before it faults.
Service, faults and warranty
- Annual service, and what Gradient actually requires:
service and maintenance - A red screen and a code: fault codes explained
- What your warranty covers and what it asks of you: warranty
- Everything an owner needs in one place: owner guide
Call 403-404-9975.
Frequently asked questions
What filter does a Gradient syncFURNACE take?
It depends on the model. The 05L, 08L, 06H, 10L, 12L and 10H take a 16×25. The 16L, 15H and 20L take a 20×25. All are 14 inches high by 23 inches deep. Any standard furnace filter fits, and Gradient names Aerostar, Clean Comfort, GeneralAire and Honeywell as compatible examples.
How often should I change the filter in a Gradient furnace?
Gradient recommends checking monthly and changing as required, which generally works out to about four times a year. Pets, renovation dust and a dry summer all shorten that interval.
Do I need a special Gradient filter?
No. Any standard furnace filter of the correct size fits. You should not be paying a premium for a proprietary filter on this appliance.
Where is the model number on a Gradient furnace?
On the rating plate, usually on the front of the unit or just inside the access door. It carries the model, such as sFT-202 or sFT-201, and a size code such as 12L or 06H. The size code determines the filter size.
Can a dirty filter cause my Gradient to lock out?
It can contribute. A restricted filter chokes airflow across the coil, and the appliance monitors temperatures that airflow affects. If your unit has been faulting intermittently and the filter has not been changed in a year, change the filter before doing anything else.
Written by Desmond Neufeld, Red Seal Journeyman Plumber and Certified Type B Gasfitter. Last updated 23 August 2026.
