If you own a Gradient syncFURNACE, this page covers what you actually need to know as an owner: how
to identify your model, what filter it takes, what the screen is telling you, how often it needs
servicing, how to shut the water off before a holiday, and what you can safely do yourself. It is
written by Desmond Neufeld, Red Seal Journeyman Plumber and Certified Type B Gasfitter, in Calgary,
and every instruction traces to Gradient’s own documentation.
Identify your model
Everything else on this page depends on knowing which unit you have.
Find the rating plate. It is on the unit, usually on the front or just inside the access door.
It carries the manufacturer name, the model number and the serial number.
The model number tells you the generation.
- sFT-202 is a current V5 syncFURNACE Tankless with 24 volt ignition.
- sFT-201 is a current V5 syncFURNACE Tankless with 120 volt ignition.
- mOD-200 is the previous generation V4. It still works, parts are still available, and there
is no reason to replace a working one.
The size code matters too. You will see a size such as 8L, 12L, 16L or 20L on standard duct
models, or 06H or 10H on high velocity models. That code is what determines your filter size.
If you cannot find it, photograph the unit and text it to 403-404-9975. We will tell you what
you have.
Your filter size
This is the single most useful fact on this page, and it is buried in a manual almost nobody has
read.
| Model size code | Filter size |
|---|---|
| 05L, 08L, 06H, 10L, 12L, 10H | 16 x 25 |
| 16L, 15H, 20L | 20 x 25 |
All of them are 14 inches high by 23 inches deep.
Any standard furnace filter fits. Gradient names Aerostar, Clean Comfort, GeneralAire and Honeywell
as examples. You do not need a proprietary filter and you should not be paying for one.
How often. Gradient recommends checking the filter monthly and changing as required, which
generally works out to about four times a year. A restricted filter chokes airflow, and restricted
airflow is a common cause of nuisance lockouts.
Buy the right one and keep a spare: parts and filters.
What the screen is telling you
The controller screen turns red when the unit has locked out on a fault, and it will show a
code: ALM 1 through ALM 6, or NO FLOW, or LOW PRES.
Write the code down before you do anything else. It tells a technician where to start and it
saves you diagnostic time.
Every code, what it means, which ones clear themselves and what you can safely check yourself is on
the fault code page.
One rule worth learning now: if the unit keeps locking out and resetting, stop resetting it.
ALM 2, ALM 3 and ALM 4 auto reset after an hour, up to three attempts a day. A unit cycling through
that is not fixing itself, it is hitting the same fault repeatedly, and each reset buys an hour
instead of a solution.
System pressure
Your syncFURNACE has a water side, and it runs at a pressure. Learning to glance at it once a month
is worth the thirty seconds.
Where to look. The controller display shows system pressure. On a normal residential system you
are looking for a stable reading in the range the unit was commissioned at, and the important word
is stable.
What matters is change, not the exact number. A slow drop over weeks means the system is losing
water somewhere, and the cause is worth finding rather than topping up repeatedly. A pressure low
enough to fault will show as NO FLOW or LOW PRES, and the unit will not restart until it has been
refilled and re-pressurised properly.
Do not keep refilling it. Repeated top ups introduce fresh oxygenated water, which is harder on
the system than the original fill, and they hide a leak that is going to need finding anyway.
Servicing: what has to happen and how often
Gradient’s schedule, from their manual and their homeowner guidance:
| Task | Frequency | Who |
|---|---|---|
| Filter check | Monthly | You |
| Filter change | About quarterly | You |
| Clear ice and snow from outside vent terminations | As needed in winter | You |
| Condensate trap inspection | Quarterly | Technician |
| Condensate line and trap clean | Semi annually | Technician |
| Burner and combustion chamber clean | Annually | Technician |
| Flue, air intake, igniter, flame sensor, flame check | Annually | Technician |
| Full vent system leak inspection | Annually | Technician |
| Water system flush and descale | Annually | Technician |
Full detail on the annual service page, including why the
water system flush is the item most often skipped.
Going away? How to shut the water off properly
This is Gradient’s own procedure and it is worth doing correctly, because closing the wrong valve
in the wrong order on a combination appliance is a bad idea.
To turn the water off:
- Make sure no water is running anywhere in the house and the thermostat is not calling for heat.
- Close the hot and cold isolation valves on top of the syncFURNACE. Closed valves sit horizontal.
- Close the main water shut off for the house.
To turn it back on:
- Open the main shut off.
- Open the cold and hot isolation valves on top of the syncFURNACE. Open valves sit vertical.
- Slowly turn on a few taps to release trapped air.
Leave the heating on while you are away. A house at 15C is a house whose pipes are not freezing.
What you can safely do yourself
- Check and change the filter.
- Clear snow and ice from the outside vent terminations. Gradient tells owners directly to monitor
and remove ice buildup from exterior pipes, and it is the most common winter fault in this city. - Glance at the system pressure once a month.
- Keep the area around the unit clear, both for airflow and so a technician can actually work.
- Write down any fault code you see, with the date.
- Shut the water off correctly before a holiday.
What you must not do
- Do not open the burner door. The burner door and combustion chamber insulation contain
refractory ceramic fibres, which Gradient identifies as a potential carcinogen requiring
protective equipment. - Do not bypass a safety switch. Gradient says this explicitly, and the switches are the reason
a fault stays a fault instead of becoming an incident. - Do not work on the gas train, the venting or the condensate system. These are licensed work
and Gradient requires a qualified licensed technician. - Do not put the unit on carpet. The manual states the product cannot be installed on
carpeting. If yours is, get it corrected. - Do not store anything against it. A mechanical closet is not a cupboard.
Where the official documents are
Gradient publishes the manuals, brochures and installation drawings for every product under Guides
and Manuals on gradientthermal.com. If you want the full installation and operation manual for your
model, that is where it lives, and reading the maintenance section is a good way to check whether
the service you are being sold matches what the manufacturer asks for.
Two practical notes. Gradient’s own shortcut link to product registration is currently broken and
returns a 404. The working path is through the product registration page. And registration only
extends your parts coverage if it was done within sixty days of installation, so if your unit is
older than that, registering now will not add coverage. It is still worth knowing whether it was
ever done. See the warranty page.
When to call us
- The screen is red and you have written down the code.
- It has been more than a year since it was properly serviced, or you have no record of one.
- You have no hot water.
- System pressure is dropping and you do not know why.
- Another company has told you they cannot service it because of the closet.
- You are not sure whether it has ever been registered.
180 Plumbing and Heating, southeast Calgary. Call 403-404-9975. A Gradient warranty
check is free: we confirm the model, tell you when your first documented service was due, register
the unit if it has not been, and leave you the manufacturer’s record form.
Frequently asked questions
What filter does my 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 examples. The model code is on the rating plate.
How do I find out which Gradient model I have?
Look for the rating plate on the unit, usually on the front or inside the access door. It carries the model number: sFT-202 and sFT-201 are current V5 units, and mOD-200 is the previous V4 generation. The size code, such as 12L or 06H, is what determines your filter size.
How do I turn the water off to my syncFURNACE before a holiday?
Gradient’s procedure: with no water running and no call for heat, close the hot and cold isolation valves on top of the unit, which sit horizontal when closed, then close the main house shut off. To restore, open the main shut off, open both isolation valves so they sit vertical, then run a few taps slowly to release trapped air.
What should the pressure be on my Gradient furnace?
The reading itself is set at commissioning for your system, so what matters is that it stays stable. A slow drop over weeks means water is being lost somewhere and the cause needs finding rather than topping up repeatedly. A pressure low enough to fault will show as NO FLOW or LOW PRES.
Can I service my Gradient syncFURNACE myself?
You can change the filter, clear ice from the outside vent terminations, check the pressure, and keep the area clear. You cannot open the burner door, work on the gas train, the venting or the condensate system, or bypass a safety. The insulation contains refractory ceramic fibres, the high limit safeties are on a 115 volt line, and Gradient requires a qualified licensed technician.
Where can I find the Gradient syncFURNACE manual?
Gradient publishes manuals, brochures and installation drawings under Guides and Manuals on gradientthermal.com. The maintenance section is worth reading, because it sets out exactly what an annual service is supposed to include.
Written by Desmond Neufeld, Red Seal Journeyman Plumber and Certified Type B Gasfitter. Last updated 23 August 2026.
