Demand For Domestic Hot Water; Dhw Storage With Bulb And Strap-On Sensor; Dhw Mode 1 - Lochinvar EFW 85 Installation, Commissioning, User And Maintenance Instructions

Demand for Domestic Hot water

14.9.1 DHW S
TORAGE WITH BULB AND STRAP
Only use DHW mode 1 for a standalone water heater and for a Cascade water heater. Do not use another DHW
mode because the water heater will not work properly. Also, the heater must be programmed as managing
heater and a system sensor is needed next to a DHW sensor. The system sensor is a strap-on sensor connected to
the supply pipe close to the storage vessel and the DHW sensor is an adhesive sensor or bulb on or in the storage
tank.
When installing the water heater always check what the local water hardness is. Default the water heater is set
for a water hardness between 4 and 11 °dH (between 5 and 14 °Clark); the temperature difference between flow
and return of the heater should be maximum 16.5 °C.
For the water heater a modulating pump is available, which will modulate on a delta T setpoint of 16.5⁰C. This
feature gives the water heater extra efficiency because the water heater stays in the condensing zone of the
heat-exchanger, if the setpoint of the storage tank is below 65⁰C.
Principles to design the water heater system:
•
If the water hardness is between 4 and 11 °dH (between 5 and 14 °Clark) the temperature difference
between flow and return of the heater should be maximum 16.5 °C
•
If the water hardness is between 11 and 14 °dH (between 14 and 17 °Clark) the temperature difference
between flow and return should be maximum 12.5 °C
•
If the water hardness is above 14 °dH (17 °Clark) use a water softener . Also above 11 °dH (14 °Clark) a
water softener could be considered, since an installation at 12.5 °C temperature difference will need
bigger pipes and pumps. After softening, the water hardness should be minimum 4 °dH (5 °Clark).
It is possible to check if the flow over the heat-exchanger is according to this principles:
1. This can be done by changing parameter (136) "Mod. Pump Mode" from "Modulating" to "Fixed 100%"
the pump will run now at 100% speed.
2. Open a tapping point for hot water and be sure that the heater is running at 100% power, now the delta T
should be 16.5 °C or lower for water hardness below 11 °dH and 12.5 °C or lower for above 11 °dH. For
determining the delta T read out in the Information menu by selecting heater status now check the "Flow
temperature" minus the "Return Temperature".
3. If the delta T is within limits change back parameter 136 to "Modulating" if it is not within limits replace
the pump by a bigger pump or check if there are any obstructions between the water heater and the stor-
age tank. Or use a water softener when having a water hardness above 11 °dH (14 °Clark).
4. When using a delta T below 12.5 °C also change parameter (133) "Mod. Pump dT" from 16°C to 12°C. Also
change parameter (137) "Mod. Pump Min Pwr" from 45% to 75%.
5. Check if the water heater is working correctly by opening a tapping point on large and small amount of
water.
6. When using a DHW_Store_Setpoint above 70°C use a fixed setpoint for the pump because the water
heater will not condensate at high temperatures. Repeat point 1 and 2 and lower the % until your above
16.5°C or 12.5°C now increase the fixed setpoint by one step (10%). The delta T should be 16.5°C or 12.5°C
or smaller depending on water hardness below or above 11°dH (14 °Clark)
Warning: the warranty will be void if these design requirements are not met.
DHW Mode 1 is also used for cascading water heaters. Set the cascade parameters according to chapter
"16 cascade". Connect the depending water heaters and the managing water heater. Attach the strap on sensor
(system sensor) to the combined supply of the water heaters and connect this to the managing water heater, also
connect the DHW sensor which measures the temperature in the tank to the managing heater.
The DHW temperature in the tank is measured with sensor T_Store and set with parameter DHW_Store_Set-
point. When this sensor drops below DHW_Store_Setpoint minus DHW_Tank_Hyst_Down the control detects a
demand for the store and starts the DHW circulator.
84
- ; DHW 1
ON SENSOR MODE
E93.1804.014