SIT 820 Nova Millivolt Valve Troubleshooting

The SIT 820 Nova mV is a millivolt gas valve for standing pilot gas fireplaces, log sets and space heaters. The pilot burns all the time and its thermopile powers the valve, so the fireplace works without house power. Your fireplace's parts list may give the valve under the fireplace maker's own number, so check both the SIT label and that list.

How to tell you have a SIT 820 Nova

The valve sits in the control compartment, usually behind the lower louver or door. On many Empire fireplaces, for example, you lower the bottom louver to reach it. Look for these features:

• The SIT name and a code that starts with 0.820. Our 30% turndown listings, for example, carry 0.820.652 (natural gas) and 0.820.651 (propane). Your fireplace's parts list may use its own number instead; Empire lists R7577 (natural gas) and R7578 (propane) for the valve in its DVD millivolt fireplaces.
• One control knob marked OFF, PILOT and ON. Many versions also have a second knob marked HI and LO for flame height.
• Three wire terminals on the main operator, marked TP, TP/TH (printed TPTH on some valves) and TH.
• On Millivolt Plus versions, a thermocouple nut threaded into the valve body, and often a piezo igniter mounted on a bracket on the valve.

SIT makes several versions: 820 mV ON/OFF, 820 mV Hi/Lo (manual flame knob), 829 mV (electrically modulated, used with the Proflame 1 remote) and 821 mV POD (pilot on demand, which shuts the pilot off after 7 days of no use). There are also three thermocouple setups:

• True Millivolt (B-vent): the thermopile powers both the main valve and the pilot safety.
• Millivolt Plus (direct vent): the thermopile powers the main valve and a thermocouple with an 11/32 in. nut holds the pilot safety.
• Vent-free: an oxygen depletion (ODS) pilot and an M8 thermocouple thread.

Not sure it is millivolt? See millivolt vs electronic ignition fireplaces, and find your model number before you order parts.

How the pilot, thermocouple and thermopile work together

The pilot flame heats the thermocouple (on True Millivolt valves, the thermopile), and that small current holds the safety magnet open. That is why you hold the knob in after lighting. The thermopile also feeds the TP and TP/TH terminals. When the wall switch, thermostat or remote receiver connects TH to TP/TH, that voltage opens the main operator and gas flows to the burner.

Safety devices such as limit switches are wired so they cut the current to the safety magnet. If one of them opens, the pilot and burner both go out, even when the thermocouple itself is fine.

Before you test: safety and tools

• SIT says installation, conversion and adjustment must be done by a qualified, certified gas technician. If you smell gas, do not light any appliance or touch any electrical switch, and call your gas supplier from a neighbor's phone (Empire's safety instructions).
• Use a meter on DC millivolts with a 0 to 1000 mV range.
• Never connect the valve to line voltage or jumper the valve coil terminals; SIT warns this damages the operator. The only jumper test here goes across the two switch wires.
• Give the pilot time. Empire says to hold the knob in 30 seconds to 1 minute after lighting, then let the pilot run 1 to 2 more minutes before turning to ON so the thermopile output builds.

Millivolt checks on the SIT 820 Nova

SIT's numbers are the minimum the valve needs. SIT says the appliance maker's instructions come first, and some makers set a higher bar, so if your owner's manual lists a value, use it. The Empire values below come from the manual for Empire's DVD series millivolt fireplaces (valve R7577 / R7578, which we sell as the SIT 820 0.820.652 / 0.820.651).

What the readings tell you

• Open circuit low: the thermopile is weak or the pilot flame is not on it. Clean and adjust the pilot, tighten the thermopile leads at the valve and make sure the thermopile is fully seated in the pilot bracket. If it still reads low, replace the thermopile or the pilot assembly.
• Open circuit good, closed circuit low: the switch, its wires or the remote receiver are losing the voltage. Do the jumper test below, and check the wire size. Empire calls for 18 gauge up to 10 ft, 16 gauge from 10 to 25 ft and 14 gauge from 25 to 35 ft.
• Closed circuit good but no burner: check the main burner orifice for a blockage (Empire). If it is clear, SIT says to replace the gas control.

For a step-by-step meter walkthrough, see how to test a fireplace thermocouple and thermopile.

Checking through a remote

Many 820 fireplaces have a REMOTE/OFF/ON switch. Empire's tip: if the remote stops working, flip that switch from REMOTE to ON. If the burner lights, the problem is the remote, its batteries or the receiver, not the valve. SIT built the Proflame 1 (GTM) remote for the modulating 829 Nova mV and for 820 valves converted with SIT's step-motor kit; see our SIT Proflame 1 troubleshooting guide.

Pilot will not light or will not stay lit

Work through these in order:

1. Use the full lighting procedure. Turn the knob to OFF and wait at least 5 minutes (Empire says 10). Turn to PILOT, press the knob all the way in, light the pilot, and keep holding for at least 30 seconds (Empire says about a minute). On first lighting, air in the line can take a few minutes to purge.
2. No spark: check for spark at the electrode. If there is none and the wire is connected, the igniter needs replacing.
3. Pilot goes out when you let go of the knob: on Millivolt Plus valves this is usually the thermocouple. Make sure the pilot flame hits the thermocouple, and that the thermocouple nut is hand tight plus a quarter turn with a wrench. Test it: under 15 mV, replace the thermocouple. If it reads more than 15 mV and the pilot still drops out, Empire says the valve is at fault. On True Millivolt valves, test the thermopile instead.
4. Look for an open safety switch. SIT requires safety cut-off devices, such as a limit thermostat, to be wired into the safety magnet circuit, so an open one puts the pilot out. Your fireplace's wiring diagram shows whether one is fitted. A safety switch that keeps opening is a job for a technician.
5. Frequent outages: a pilot flame that is too high, too low or blowing lets the safety drop out. Clean and adjust it so the flame covers the thermocouple and thermopile tips. If the whole fireplace shuts down, Empire also lists leaking vent pipe, loose glass and a badly pitched horizontal vent.

If the knob does not pop back up when released, or will not turn by hand, stop. Do not force it; call a qualified technician. More causes are in gas fireplace pilot light won't stay lit.

Pilot lit, main burner will not come on

1. Confirm the knob is at ON, not PILOT, and that the switch, thermostat or remote is calling for heat. Give the pilot 1 to 2 minutes after lighting.
2. Measure TP/TH to TP with the switch on. SIT's minimum is 100 mV closed circuit (325 mV open circuit).
3. Jumper test: place a jumper across the switch terminals. If the burner comes on, replace the switch. If not, jumper the switch wires at the gas valve. If the burner comes on now, the wires or their connections are bad.
4. If the open circuit reading is low, fix the thermopile side first (see above).
5. Check the main burner orifice for a blockage.
6. If the valve gets the right voltage and still will not open, replace it. SIT says the 820 Nova is not field serviceable and has no replaceable parts, so do not take it apart. See how to replace a gas fireplace gas valve.

Flame height and the HI/LO knob

With the main knob at ON, the HI/LO knob sets burner pressure. SIT says maximum flow is with the knob fully counterclockwise; follow the HI and LO marks on yours. 820 valves are sold in more than one turndown (our listings include 30% and 50%) for natural gas or propane, so order the same part number your fireplace uses. Fuel conversions use a SIT regulator kit or, on convertible versions, a flipped screw (red o-ring showing means propane), plus matching pilot and burner orifices. Leave conversions to a qualified technician.

Thermocouple port position when you replace the valve

On a valve swap, check which thermocouple port lines up with your lead before you connect it. SIT's Millivolt Plus valves have a main thermocouple connection and an alternative connection point, and SIT's instructions say to connect the thermocouple to whichever upper or lower port is convenient, hand tight and then a quarter turn with a wrench. Pick the port that lines up with your existing thermocouple lead. Do not mix thread types: vented Millivolt Plus valves take an 11/32 in. thermocouple, while vent-free valves use an M8 thread. SIT also warns never to use a vented valve on a vent-free appliance or the other way around.

Common SIT 820 part numbers and OEM versions

These cross-references come from our product listings, not from each fireplace maker's parts list, so match the number in your own parts list before you order.

Parts for the SIT 820 Nova

Find your symptom, check the usual cause, then the part. Confirm the part number in your owner's manual or parts list before ordering. Most parts come in natural gas (NG) and propane (LP) versions, and vented and vent-free valves are not interchangeable.

Find parts for your fireplace: Enviro EG31 parts · Empire fireplace parts · all SIT gas valves and controls.

FAQ

What is SIT 0.820.652?

It is the SIT code on our 820 Nova millivolt valve for natural gas with 30% turndown, for vented fireplaces that use both a thermopile and a thermocouple (not for vent-free). The propane version we list is 0.820.651. We sell them as R7577 and R7578, the numbers Empire's DVD millivolt parts list gives for its natural gas and propane valves.

How many millivolts does a SIT 820 thermopile need?

SIT's minimum at the TP/TH and TP terminals is 325 mV with the switch off and 100 mV with the switch on. Some fireplace makers ask for more; Empire's DVD series manual calls for 350 mV and more than 200 mV.

Can I put a vented SIT 820 on a vent-free fireplace?

No. SIT warns against using a vented valve on a vent-free appliance or a vent-free valve on a vented one. Vent-free versions use an ODS pilot and a different thermocouple thread.

Where is the SIT 820 Nova manual?

SIT publishes the North American use and installation instructions on its own site: SIT 820 Nova mV instruction manual.

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