Honeywell Aquastat Relay L8148E Wiring Diagram

Honeywell Aquastat Relay L8148E Wiring Diagram

Honeywell Aquastat Relay L8148E Wiring Diagram

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L8148E connections

Thermostat, 24 V gas valve, circulator and power; below, the internal schematic in gray.

L8148E connections
THERMOSTAT24 VL8148EHIGHLIMITTRTHTHTRLOW VOLTAGEGAS VALVE(e.g., VR8300)L8148E INTERNAL SCHEMATICGL1L21K2BRZW1KTTVB1B2C1C21K1TVTB1B2L1L1(HOT)L2L2GC1C2CIRCULATORWZJUMPERBRTHERMOSTAT24 VL8148EHIGHLIMITTRTHTHTRLOW VOLTAGEGAS VALVE(e.g., VR8300)L8148E INTERNAL SCHEMATICGL1L21K2BRZW1KTTVB1B2C1C21K1TVTWRBL6006LOW LIMITCONTROLLERB1B2L1L1(HOT)L2L2GC1C2CIRCULATORWZJUMPER REMOVEDBR

Terminals and components · 8

  • Thermostat
  • Jumper
  • High limit
  • Burner
  • Circulator
  • L1
  • L2
  • Ground

About This Diagram

These diagrams are redrawn from pages 8–11 of the Honeywell Aquastat Relay L8148E manual, and we offer them completely free and in English. We have also categorized it in the Capacitors, Contactors & Relays (HVAC & Water Heating) section on Diagramverse, and it has been rated by 1 user with an average rating of 5.0. If you have any specific questions about the Honeywell Aquastat Relay L8148E Wiring Diagram, we suggest checking the Frequently Asked Questions (FAQs) section.

Printable Honeywell Aquastat Relay L8148E Wiring Diagrams

Complete · Z–W jumper

1 / 8
Honeywell Aquastat Relay L8148E Wiring Diagram – Complete · Z–W jumper
Honeywell Aquastat Relay L8148E Wiring Diagram – Complete · With L6006 low limit
Honeywell Aquastat Relay L8148E Wiring Diagram – Zone valves
Honeywell Aquastat Relay L8148E Wiring Diagram – R845 relays · One pump per zone
Honeywell Aquastat Relay L8148E Wiring Diagram – R845 relays · Switched circulator
Honeywell Aquastat Relay L8148E Wiring Diagram – R882C relays
Honeywell Aquastat Relay L8148E Wiring Diagram – Vent damper · With S8610 module
Honeywell Aquastat Relay L8148E Wiring Diagram – Vent damper · Direct to the L8148E

Wiring Instructions

Before you start

First, pick the Honeywell Aquastat Relay L8148E tab that matches your system. Use Complete for a single-zone boiler controlled by one 24 V thermostat. Inside it, choose the With L6006 low limit variant only if you are adding an L6006 low limit controller. Use Zone valves for V8043F valve zoning. Use R845 relays when each zone has its own pump (One pump per zone) or when an R845A switches the circulator (Switched circulator). Use R882C relays when R882C relays switch the zone circulators. Use Vent damper when a D892/M892 damper is fitted, either through an S8610 module or plugged straight into the L8148E.

Gather an insulated flat-blade screwdriver, a wire stripper, a non-contact voltage tester and a multimeter that reads AC volts and continuity. Do not use a push-type ratchet screwdriver. Use copper wire only, because the terminals are approved for copper and accept wrap-around connections only. If a wire lands on the 1/4 in. tab of terminal B1, use 18 to 22 gauge wire with a fully insulated flag receptacle connector. Size the 120 V conductors for the branch circuit and the circulator according to local code. The circulator contact is rated 7.4 A full load and 44.4 A locked rotor at 120 V, so check the pump nameplate against those figures.

Shut off power at the boiler disconnect, lock or tag it, and confirm with your tester that L1, L2, C1 and C2 are dead before you remove the cover. Confirm that the boiler has a pressure relief valve: this control must not be used without one. The installer should be a trained, experienced service technician. Work on boilers, gas valves and line voltage usually requires a licensed professional, and often a permit, so check your local rules.

If you are replacing an old control, tag every lead before you disconnect it, using the old control's cover insert as a guide. Add up the 24 V load. It must not exceed 1.4 A, or 1.2 A if the boiler room is warmer than 77°F. The burner circuit itself is limited to 0.8 A at 24 V AC.

Step-by-step wiring

  1. Mount the control on its immersion well. Push the bulb in until it bottoms, use heat-conductive compound if the bulb fits loosely, and center the loop of excess capillary tubing so it cannot touch any electrical part.
  2. For every screw terminal, strip 7/16 in. of insulation, wrap the wire at least three quarters of the way around the screw, tighten until snug, then give it another half turn.
  3. Connect the equipment ground to the case using the grounding screw provided.
  4. Run 120 V AC from a disconnect with overload protection: hot to L1 and neutral to L2. Bring the cable through the 1/2 in. conduit knockouts.
  5. Wire the circulator to C1 and C2. In the zoning tabs, C1 feeds the relay contacts instead: R845 terminal 3 in Switched circulator, or the lower N.O. contact of each R882C.
  6. Wire the burner circuit. On a standard 24 V gas valve, B1 goes to TR and B2 goes to TH. In the Vent damper tab, B1 goes to TH-W on the S8610 (or 24V on the S8600) and B2 goes to 24V GND.
  7. Wire the heat call to T and TV. This can be the room thermostat, the valve end switches in parallel, R845 contacts 5-6 in parallel, or the upper R882C contacts (N.O. to TV, COM. to T). Set the thermostat's heat anticipator to 0.2 A.
  8. Leave the Z–W jumper in place unless you are installing an L6006. In that case, remove the jumper and connect the L6006 W to W, R to Z, and B to the high limit B.
  9. For zone valves, power no more than two V8043 valves from W, add the TH jumper on each valve, and give any further valves their own transformer. For R882C zoning, power no more than three relays from the L8148E.
  10. For a vent damper, remove the plug-in that jumpers pins 2 and 3 only when you are actually connecting the damper, then seat the 197516A cable or the S8610 damper plug fully.
  11. Set the high limit dial to the boiler manufacturer's recommendation, then refit the cover.

Testing and start-up

Restore power and measure about 120 V AC between L1 and L2. With the thermostat satisfied, nothing should run. Raise the thermostat setting. You should hear the relay pull in, the circulator should start, and the gas valve should receive roughly 24 V AC across TR and TH so that the burner lights, provided the boiler water is below the high limit. Next, turn the high limit dial below the current boiler temperature: the burner should stop while the circulator keeps running. Return the dial to its setting afterward. Test each zone on its own, then watch the system through at least one complete heating cycle. With a vent damper, the burner should fire only after the damper has opened.

Safety notes

  • L1, L2, C1 and C2 carry 120 V in the same case as the 24 V terminals. Keep low voltage conductors routed away from line voltage conductors.
  • Never jumper or short B1 and B2: doing so burns out the internal transformer.
  • Connecting a vent damper to the L8148E permanently blows an internal fuse on the first call for heat. Do this only when the damper is a permanent part of the system.
  • Do not exceed the ratings above, and never run the boiler without a working pressure relief valve.

Troubleshooting

Symptom Probable Cause What to Check
Nothing happens when the thermostat calls for heat; no relay click No 120 V supply, Z–W jumper missing, or thermostat leads not on T and TV Measure 120 V AC between L1 and L2. Confirm that the Z–W jumper is in place, or that the L6006 is wired in its place. Check that the thermostat wires are tight on T and TV.
The control went dead right after work on the burner wiring B1 and B2 were shorted or jumpered, burning out the transformer Inspect the burner wiring for a short between the B1 and B2 leads or at the gas valve. A burned-out transformer means replacing the control.
The pump runs but the burner never lights B1 or B2 is loose or on the wrong valve terminal, the boiler is above the high limit, or the tab connector on B1 is not seated During a call, measure about 24 V AC across TR and TH on the gas valve. Confirm B1 goes to TR and B2 to TH, the flag connector is fully pushed onto B1, and the high limit dial is above the boiler temperature.
The burner fires but the circulator never starts Loose C1 or C2, missing neutral to the pump, or C1 not routed through the relay contacts in zoned systems During a call, measure 120 V AC across the circulator leads. In Switched circulator, check C1 to R845 terminal 3. With R882C relays, check C1 to the N.O. contacts and the return to C2.
The burner or pumps run constantly even with all thermostats satisfied Shorted thermostat cable, or end switches or relay contacts wired across the wrong terminals Lift the wire from T. If everything stops, the fault is external: check the thermostat cable, the end switches, R845 contacts 5-6 and the R882C N.O. and COM. connections.
The boiler stopped working once the vent damper was unplugged The internal fuse blew on the first call after the damper was connected, which is by design Reconnect the D892/M892 and make sure the 197516A cable, or the S8610 damper plug, is fully seated at both ends. From then on, the system works only with the damper connected.
Zone valves open slowly or not at all, and the control runs hot Too many valves on the internal transformer Power no more than two V8043 valves from W, or one if the room is above 77°F. Move the extra valves to their own transformer, with a maximum of two per transformer.
One zone's valve opens but the boiler never fires for that zone Missing TH jumper on that valve, or its end switch not wired in parallel to T and TV Add the jumper from TH to the end switch, then check continuity across that valve's end switch leads at T and TV with the valve open.
The L6006 is installed but has no effect on boiler temperature Z–W jumper left in place, or L6006 leads swapped Remove the Z–W jumper. Verify L6006 W to W, R to Z and B to the high limit B.
Room temperature overshoots or the burner short-cycles Thermostat anticipator set wrong, or bulb not bottomed in the well Set the anticipator to 0.2 A. Reseat the bulb against the bottom of the well, using heat-conductive compound if it fits loosely.
Wires work loose or terminals show scorch marks Non-copper wire, wire wrapped the wrong way or too little, or terminals undertightened Use copper only. Strip 7/16 in., wrap at least three quarters around the screw, tighten until snug, then add a half turn with a hand screwdriver.
You feel a tingle from the case or the boiler controls behave erratically Case ground missing or loose With power off, check continuity between the grounding screw and the equipment ground. You should read near 0 ohms.

Frequently Asked Questions (FAQs)


What is the difference between the L8148A, L8148E and L8148J?
The difference is the burner circuit each one switches. The L8148A switches a line voltage burner. The L8148E switches a 24 V burner circuit and adds terminals for zone valve wiring, with versions that have a plug for D892/M892 vent dampers. The L8148J handles low voltage or millivoltage burners and adds TP and B3 terminals. All three use a 24 V thermostat and switch a 120 V circulator.

Can the L8148E control a line voltage oil burner?
No. The L8148E switches only a low voltage burner circuit, rated 0.8 A maximum at 24 V AC, such as a 24 V gas valve or an ignition module input. To switch a line voltage burner relay or gas valve directly, use the L8148A. Connecting 120 V to B1 and B2 would destroy the control.

How many zone valves can the L8148E power?
The L8148E can power two V8043 zone valves, or only one if the ambient temperature exceeds 77°F. The total 24 V load must stay at or below 1.4 A, or 1.2 A in a hot boiler room. For more zones, add a separate 24 V transformer for each group of up to two valves. Their end switches still all go to T and TV in parallel.

How many R882C relays can I run from one L8148E?
You can power up to three R882C relays from the L8148E. Any additional relays go in groups of no more than three, each group with its own transformer. Whatever the number of zones, every relay's upper contact is wired in parallel to TV and T so that any zone can call the boiler.

What thermostat do I need and how do I set its anticipator?
Use a 24 V AC heating thermostat wired to T and TV, and set its heat anticipator to 0.2 A. A two-wire heat-only thermostat or the T87F shown in the zoning diagrams works. Do not connect a line voltage thermostat or a millivolt thermostat to T and TV, because they are not designed for this 24 V relay circuit.

When should I remove the Z–W jumper?
Remove the Z–W jumper only when you are adding an L6006 low limit controller, which takes its place. In every other layout, keep the jumper: single zone, zone valves, R845 or R882C relays, and vent damper systems. In the zone valve and R882C layouts, the jumper is also what supplies the 24 V that powers the thermostats, valves or relay coils.

What happens when I plug a vent damper into the L8148E?
Once the damper is plugged in, an internal fuse blows the first time the thermostat closes, and from then on the L8148E works only with the damper connected. This is intentional: it stops the boiler from firing without the damper. Remove the plug-in that jumpers pins 2 and 3 only if you are installing a damper permanently. With an S8610, the fuse is in the ignition module instead.

Does the circulator keep running when the high limit is reached?
Yes. When the boiler water exceeds the high limit setting, only the burner circuit opens. The circulator keeps running as long as the thermostat is calling for heat, which moves the hot water out to the system. When the water cools below the limit and the call is still active, the burner restarts automatically.

My old aquastat had a screw terminal for B1. Can I still use the L8148E?
Yes. On the L8148E, B1 is a 1/4 in. tab terminal. If your old control used a screw terminal, fit a tab-to-screw terminal adapter onto the B1 tab and reuse your existing wrap-around wire end. If the old control already had a tab, reuse the existing harness connector. For new tab connections, use 18 to 22 gauge wire with a fully insulated flag receptacle.

Can I use aluminum or stranded wire on the terminals?
Use copper wire only, because the terminals are approved only for copper. They are wrap-around screw terminals, so the wire must loop at least three quarters of the way around the screw. Solid copper wraps most reliably. If you use stranded copper, twist the strands tightly so none escape the screw. Aluminum is not acceptable here.

Can I use the L8148E with a SmartValve SV9500 or SV9600?
Yes, but only the version with the plug and the 50 VA transformer is intended for the SV9500 and SV9600 SmartValve system control. When it is used that way, the L8148E cannot power any zone valves or relays. Supply those from a separate transformer. Check the model label on your unit to confirm which version you have.

What temperature range does the L8148E high limit cover?
The standard L8148E scale runs from 180°F to 240°F, and some versions cover 140°F to 240°F. The differential is not adjustable. Set the dial to the boiler manufacturer's recommendation. If the dial will not reach your setting, the adjustable high limit stop may be blocking it: pry the stop up with a small screwdriver, turn the dial, and let the stop rest flat again.

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