Heatmaker Model HW Units – Low Limit Control
Heatmaker is committed to providing you with information that can help you avoid mechanical malfunction before it becomes an issue.
These service issues relate to Low Limit control and its function.
The Low Limit control has two functions. First, it maintains minimum tank temperature for instant hot water use. Second, it provides domestic hot water (DHW) priority by temporarily cutting the 24-volt power on the thermostat (T-T) terminals during a domestic hot water draw.
Problems may result from improper positioning, venting or wiring; each allowing the unit to operate for domestic hot water but not enabling heating zones to operate.
If you are experiencing problems:
- Check to be sure that the Low Limit is properly mounted on the vertical section of the ¾” hot water supply coming out of the tank, close to the tank.
- If the positioning is correct and space heating still does not function, then release any air via the vent screw on top of DHW tank.
- Finally, check the wiring to ensure that it is correct.
Wiring sequence (wiring color of Low Limit connects to wiring color of unit):
HW+ (Plus)
Red (on Low Limit) to Red (on unit), Black to Gray, Brown to White
HW – M2 (Mark II)
Red to White/red stripe, Brown to Gray, Black to Red/Black stripe
If you have any questions, call Heatmaker’s technicians Monday-Friday, 5:00 a.m. – 7:00 p.m., EST; and Saturday 5:00 a.m. – 1:00 p.m., EST.
Extensive Inventory. Immediate Shipping.
781/961-1660
