09/17/2014
2
BI308
MODULATING STAGING CONTROL
This model series is factory equipped with a digital supply water sensor and a modulating controller. The
controller regulates the elements to maintain a preset operating temperature. The control board has a front panel
screwdriver adjustment (see Operational Tips section) for setting the operating temperature point.
ZONE CONTROLLER
If there are zones with capacities and flow less than this boiler’s total capacity, consideration should be given
towards installing a zone controller with the ability to cut off one element for small zones. Low cost multi-zone
interlock, EB-5415A, can provide this function. It also has its own 40VA transformer for powering zone valves.
SAFETY TEMPERATURE CONTROL
The hi-limits within this unit are for safety purposes only. The system installation must have a proper
responding slab or air sensing thermostat or zone controlling device to properly turn the boiler on and off. If the
water flow is greater than the nominal GPM specified, this boiler should not reach hi-limit and the hydronics
loop should continue to flow in the normal heating pattern until the operating slab stat is satisfied. If hi-limiting
is experienced prior to satisfying the operating slab stat, there is probably a water flow issue.
In addition to the built-in supply sensing point and electronic operating temperature control point, there is a 190°
automatic reset hi-limit and a 205° F top vessel manual reset hi-limit.
ROOM THERMOSTAT PLACEMENT – RADIANT FLOOR
Comfort and proper space heating response is a direct relationship to the room thermostat type and the
placement of the thermostat sensing bulb. Typically an under floor heating system can be broken down into two
categories.
Energy storage, water tubing is under the concrete or within the sand base
- The controlling
thermostat must have a remote bulb, and this remote bulb must sense the concrete slab temperature (slab
stat). Coordinated with the concrete pour, install a ¾” PVC, minimum bend radius of 7 inches, and
locate at approximately center (vertical) of the concrete slab. The thermostat sensing bulb can later be
pushed down this PVC conduit. If the slab is already poured without conduit for slab stat, use electronic
remote sensing thermostat such as Electro Industries’ ES-24-BR. This type of device only requires a
5/16” hole drilled in the concrete at some center wall location.
Quick response, hydronics tubing just under the concrete surface, no flooring material over the
concrete
– slab stat is still suggested and preferred, but a standard wall mount room thermostat can be
adequate. Mount room thermostat on an inside wall similar to most heating systems.
Comment: If the slab was poured without the conduit, Electro Industries can provide a remote
(wired) sensing slab stat with a remote sensor requiring only a 5/16” hole. If it is at an inside
wall, the 5/16” hole need only be 1” or 2” away from the plate. If it is an outside wall you
should go in about 24”. Simply insert the sensor about 2” and fill with basic silicone to keep
the sensor protected within the hole.
INFORMATION/WATER FLOW CALCULATIONS
Water flow, GPM, can easily be calculated if the temperature rise across the electric boiler can be measured.
The following formula can only be used when the temperature rise is stable and the boiler is not hi-limiting. In
other words, verify constant current draw and stable outlet temperatures for at least 15 minutes.
GPM=
Volts x Amps x 3.4
Example:
240 volts x 36 amps x 3.4
=
29376
= 5.8
gpm
500 x Temp. rise
500 x 10 degree rise
5000
INFORMATION/WATER FLOW CALCULATIONS – METRIC
L/min =
Volts x Amps x 3.587
Example:
240 volts x 36 amps x 3.587
=
30991.68
= 20.57
L/min
251.04 x Temp. rise ° C
251.04 x 6° C rise
1506.24
