Installer must be a trained, experienced service
After installation is complete, check out product
operation as provided in these instructions.
These boiler-mounted, immersion type controllers
operate in response to temperature changes in hydronic
Can cause serious injury, death or equipment
Disconnect the power supply before beginning
installation to prevent electrical shock or
L4006A breaks the circuit on a temperature rise to the
control setting. It is used for high limit or low limit control.
When used as a controller or as a low limit, a separate
high limit must be used.
Electrical Shock Hazard.
L4006B makes the circuit on a temperature rise. It is
used as a circulator controller, delaying circulator
operation when boiler water temperature is below the
Installing Immersion Well Models
L4006E,H includes a trip-free manual reset switch.
These models are designed to break the control circuit
whenever the temperature of the controlled medium
reaches the high limit setting. A reset button on the front
of the case must be pressed to re-establish the control
circuit. L4006H also includes bracket and clamp for
surface mounting on pipe or tank.
Obtain the best thermal response with a well
that snugly fits the sensing bulb. The bulb
should be inserted until it rests against the
bottom of the well. Use a well of correct length
and bend the tubing, if necessary, to provide
enough force to hold the bulb against the
bottom of the well. Do not make a sharp bend in
the tubing. A sharp bend can produce a break in
the tubing and cause a loss of fill. This condition
will cause the high and low limit controls to be
A plastic bag of heat-conductive compound is included
with the L4006A,B,E Aquastat® Controllers for use when
the sensing bulb is inserted into a well designed for a
large bulb than the one used on the L4006A,B,E. A
24904 Well Adapter, for use on old wells that do not fit
the L4006A,B,E immersion well clamp, can be ordered;
see form 68-0040, Wells and Fittings for Temperature
Controllers. A setting stop is included to prevent setting
above a desired temperature on limit.
If the well is not a snug fit on the bulb, use the
heat-conductive compound as follows. Fold the
plastic bag of compound lengthwise and twist
gently. Snip the end of the bag and insert into
the well. Slowly pull out the bag while squeezing
firmly to distribute the compound evenly in the
well. Insert the bulb into the well. Bend the
tubing, if necessary, to provide force to hold the
bulb against the bottom of the well and to hold
the out end of the bulb in firm contact with the
side of the well. Wipe off any excess compound.
If a well adapter or other accessories are needed, refer to
form 68-0040, Wells and Fittings for Temperature
Controllers, for part numbers and ordering information.
When Installing This Product…
Read these instructions carefully. Failure to follow
them could damage the product or cause a
Check the ratings given in the instructions and on
the product to make sure the product is suitable for
NOTE: Some models have an adjustable capillary
tubing length to 3 inches (76 mm). In these
models, pull out extra tubing from inside the
case, if needed.
Follow the boiler manufacturer instructions, if available;
otherwise, proceed as follows.