Naturela NHC-H42-2 User manual

Electronic temperature regulator
for three-phase electrical water heaters,
with two heat exchangers and
a remote control option
NHC-H42-2
software version 2.3
User manual
NHC-H42 are a new generation built-in electronic temperature regulators, designed for
combined water heaters with up to three heat sources:
•An electrical heater;
•A solar collector;
•A boiler.
The controller has a contrast LCD display, four control buttons and a L D indication for the
electrical heater. NHC-H42 has a built-in electronic temperature regulator to control a mono-phase
or three-phase electrical heater with accuracy of the measured temperature up to 1%, and two
precise differential temperature regulators directly running the circulation pumps on 220VAC
The first one of the temperature regulators is specialized to work with a solar collector and the
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On/Off/Set
▲
▼
View/ nter
An indicator
for working
electrical heater

second one is for a boiler. The three built-in temperature regulators in one controller successfully
combine all the advantages of the different heat sources. Some of them are free and others are
always available. For example, if the sun hasn't been strong enough during the day, you can set up
the controller to use the electrical heater, so you will have hot water whenever you need it.
The controller's compact size allows it to be built-in in the water heater. This solution makes
the building of the external heating installations easier. All of the needed temperature sensors and
circulation pumps are directly plugged in to NHC-H42. No additional electrical boards and
complicate wiring are necessary. The information, displayed on the screen is clear and very useful.
Specific advantages of the temperature regulator NHC-H42
•New automatized software with less menus and easier parameters input. Work modes are
simplified, because the controller decides which heat source is best to be used.
•An option for a connection with a RF modem NRM-868/v5 for data transfer to a remote
monitoring and control system.
•Measures and displays the temperature of the water in the water heater at three points at the
same time: in the bottom section (beside the heater), in the middle (over the solar collector's
heat exchanger) and in the top (over the boiler's heat exchanger).
•Automatically turns on a work mode that prevents the overheating of the solar collector.
•Uses energy from the electrical heater if the temperature of the hot water, heated by the solar
collector is not high enough.
•Automatically uses energy from a boiler or a fireplace installation, if their temperature is
high enough.
•Automatically takes off the heat from the water heater to prevent the solar collector's
overheating on the next day.
•Prevents the freezing of the water heater or of the solar collector.
•Information about the condition of the anode protector.
•Information if higher than 30mA leakage from the electrical heater to the hull occurs and
automatically turns off the water heater when such a leakage is registered.
•Diagnostics of all used circuits.
•Three timers to set up to three intervals per day when more intensive work of the electrical
heater is allowed
•System time and date. Knowing what time it is while you are in the bathroom is really
convenient.
•Measures the consumed electricity in kWh and shows it in a digital view for two rates.
•Graphic view hour by hour for the current and the previous day with information about the
consumed electricity and the work time of the boiler's and the solar collector's circulation
pumps.
•Monitors the condition of the heater and shows a message if the water is not heated up for
the presumed time.
•An option for a connection with an UPS so the circulation pumps and the controller could
keep working if a failure in the mains power supply occurs.
•Two work modes for the boiler's circulation pump – CH Priority and DHW Priority. This is
an advantage if there is only one circulation pump in the building's heating installation and it
transfers the water from the boiler both to the water heater and to the heating radiators. In
this case, if no hot water has been consumed and the differential temperature goes below the
set limit, the circulation pump will stop transferring water not only to the water heater, but to
the heating installation, too. This means that the building is going to be heated only if there
is a consumption of hot water from the water heater. To avoid this inconvenience, CH
Priority mode might be used. Thus, the circulation pump's turnings on and off depend only
on the boiler's temperature. On this mode, if the boiler is hot enough, the building is heated,
regardless of the water heater's temperature.
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Purposes and connection way of the controller NHC-H42
The controller is designed for combined water heaters with up to two heat exchangers and mono-
phase or three-phase electrical heater. The outer and accession dimensions of the controller comply
with the specifications of the water heaters produced by ldominvest (www.eldominvest.com). The
controller has one temperature regulator for an electrical heater and two differential temperature
regulators, adapted for a solar collector installation and a heating installation with a boiler or a
fireplace. The difference in the differential temperature regulators is in the safe modes: the solar
installation needs prevention from overheating and freezing, while the boiler doesn't. The controller
directly controls the circulation pumps of the external installations and turns on the three-phase
electrical heater via three relays.
Connection scheme of NHC-H42 to a three-phase water heater
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All of the necessary temperature sensors connect to the controller: three of them measure the
temperature of the water in the water heater, one in the solar collector and one in the boiler. The
temperature sensors should be mounted as described in table 1.
Table 1
Temperature
sensor
Temperature Mounting
Sensor 1 t1 In the bottom section of the water heater, beside the electrical heater
Sensor 2 t2 In the upper section of the water heater, above the boiler's serpentine
Sensor 3 t3 pt1000 – in the solar collector
Sensor 4 t4 NTC – in the boiler
Sensor 5 t5 In the middle section of the water heater, above the solar collector's
serpentine
If you want to remotely monitor and control your water heater's performance through your
computer, you can connect a radio modem NRM-868 to the controller to build a wireless network.
Information displayed on the main screen
The display has four main screen designs. They show different screen view for the main work
conditions of NHC-H42: Water Heater Off, Water Heater On, Settings and Graphics
1. Design I – Water Heater Off
When the water heater is off, the screen displays date, time, the current temperature of the water,
measured on the top section of the water heater, and the condition of the tank's anode protector. If
there is an error, the anode protector's indicator switches with the error message and there might be
a sound alarm too. When the water heater is off, the screen is darker.
If the time is not set, the clock blinks. The temperature regulator has a battery that keeps the time
settings if the mains power supply is off for short time. The battery keeps the time settings for
maximum 18 hours, after that the clock turns off and needs to be set again.
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System date
System time
Temperature of the water
in the top section of the
water heater
The anode protector's
condition or an error
message, if any

2. Design II – Water Heater On
When the water heater is on and ready to work, the display has the following look:
All of the important parameters about the water heater's and the additional heating installations'
performance are displayed on the screen. There is a clear and useful information about the measured
temperatures, the clock and a field with additional information.
If any of the heat sources is not activated from the menu System Setting, the relevant field for
measured temperature is displayed with an OFF sign.
When a pump is currently working, it is displayed with a spinning paddle
The field Water's temperature in the top section of the water heater shows the current
temperature of the water in the top section of the tank. Must have in mind, that if the temperature
sensor in the top section of the tank is damaged, the temperature measured by the temperature
sensor in the bottom section is displayed in this field. Since the hot water goes up to the top section
of the water heater and then to the pipes, it is possible that despite the low temperature measured
by the temperature regulator, the real temperature of the water to be much higher. This is a
restriction of the temperature measuring method and it is necessary to pay attention when using
only not cooled hot water.
3. Design III – Settings
While in Settings mode, the display has a similar view:
The parameter that is currently selected and is going to be edited, is blinking.
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Temperature of the boiler
Water's temperature in the
middle section of the
water heater
Temperature of
the solar collector
Information about the
electrical heater: On/Off
Water's temperature in the top
section of the water heater
System time
Measured or set parameters
Boiler installation's pump
Solar installation's pump
Title of the setting menu
ditable parameters

4. Design IV – Diagrams with information distributed hour by hour
The controller displays diagrams with information about the electrical heater's and heating
installation pump's performance. This is implemented with a full screen histogram. On the
horizontal axis of the coordinate system are the hours and on the vertical axis is the maximum
possible value for an hour in percentage. On the top of the screen is the date for the displayed
information and the bottom left field shows the summary information for the whole day.
This information remains on the screen for 30 seconds. After that the display goes back to its
previous view. Press the F button to see the next diagram.
Operation with NHC-H42
An easy and intuitive software manages the controller. It is specially designed to automatize the
water heater's control, so you don't have to take care for the hot water.
When the water heater is on, it chooses the best heat source. With major priority are the solar
collector and the boiler. If the differential temperatures ∆t1 and ∆t2 are above the limits, set from the
menu Dif Temp 1 / 2 line Pump On, the relevant circulation pump turns on to transfer the heat to
the water heater. The differential temperatures are calculated as follows:
•∆t1 = t3 – t5 – for the solar installation
•∆t2 = t4 – t2 – for the boiler installation.
When the pumps are on and the differential temperatures ∆t1 and ∆t2 go below the limits, set
from the menu Dif Temp 1 / 2 line Pump Off, the relevant circulation pump turns off.
To help the outer heat sources when their heat energy is not enough, the water heater could use
its electrical heater. Its work is controlled by a method which main purpose is to use the electricity
only when no other heat sources are available. This way, with as low expenses as possible, you can
be sure that you will always have hot water, no matter if your boiler works, or if the sun light is
enough, or if there is any sun light at all.
To restrict the use of the electrical heater, there are two specific solutions in NHC-H42:
•The heater turns on when the temperature, measured by the middle temperature sensor
(Sensor 5) goes below the set limit, and turns off when the bottom temperature sensor
(Sensor 1) reaches the needed temperature. Because of this, if a small amount of hot water
has been used, the temperature in the bottom section could get lower, but in the middle
section it will still be higher. Meanwhile, if the solar installation works, it will continue
heating the water up and the electrical heater might not be used at all.
•Beside the temperature that should be reached while using electricity, there is a temperature
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A diagram for
the measured parameter
Summarized information
about the measured parameter
Hours of the day: 00-23
% of the maximum possible
value for one hour

below which the heater turns on. This gives an additional tolerance for the hot and cold
water to mix in the middle of the water heater and only after the water is really cooled, the
electrical heater turns on. This earns more time for the solar installation to heat up the water
if there is enough energy.
Turning the water heater on
When the water heater is off and the controller's screen is in Design I view, by pressing the F button
(On/Off/Set) the water heater turns on, the screen's brightness gets increased and the screen view
goes to Design II.
If the requirements for heating up the water heater are implemented, all of the allowed heat sources
will be activated (see Configuration of the allowed for use heat sources). The requirements for
heating up are as follows:
•For the solar collector's installation: the solar collector's circulation pump turns on if ∆t1 or
the temperature of the collector (t3) is higher than the temperature in the middle of the water
heater (t5) with as many degrees as it is set in the menu Dif Temp 1, line Pump On. The
pump works until ∆t1 gets less or equal to the degrees set in the menu Dif Temp 1, line Pump
Off. While this installation is working, an animated spinning of the solar installation's
circulation pump (the upper one) appears on the display.
•For the boiler's installation:
•DHW priority mode – boiler's circulation pump turns on if ∆t2 or the temperature of the
boiler t4 has to be higher than the temperature in the top section of the water heater t2
with as many degrees as it is set in the menu Dif Temp 2, line Pump On. The pump works
until ∆t2 gets less or equal to the degrees set in the menu Dif Temp 2, line Pump Off.
While this installation works, an animated spinning of the boiler installation's circulation
pump (the bottom one) appears on the screen;
•CH priority mode – boiler's circulation pump turns on if its temperature (t4) gets higher
than the temperature set in the menu CH Setup, line Pump On. The pump turns off when
t4 gets lower than the temperature set in the menu CH Setup, line Pump Off. While this
installation is working, an animated spinning of the boiler's installation circulation pump
(the bottom one) appears on the display.
•For the electrical heater:
•the electrical heater turns on when the temperature t5 in the middle of the water
heater gets below the limit set in the menu EL Eco Settin s, line Heater On and turns
off when the temperature t1 in the bottom section of the water heater gets equal or
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Information about
the solar installation
Information about
the boiler installation
Information about the
heater's work mode and
the following turning On/Off
Moving bubbles indicate
the working heater

higher than the limit set in the menu EL Eco Settin s, line Heater Off.
•if the electrical heater is off, because the temperature in the middle section of the
water heater is above the set temperature in Heater On, pressing and holding the
button ▲ for more than 2 seconds turns the heater on. It turns off when the the
Heater Off conditions are implemented.
•if there is a time interval, activated from the menu EL Boost Timer, the heater turns
on in this interval if the temperature, measured by t1 is lower than the set temperature
in the menu EL Eco Settin s, line Heater Off – 5 de rees. In this case, the water heater
turns on sooner, because the turning on temperature might get higher than the set
temperature in Heater Off and moreover, it is measured in the bottom section of the
water heater, where the water gets cooler easier.
When a time interval is activated, in the field Information about the heater's work is
displayed the upcoming action (ON/OFF) and the time for it.
When the electrical heater is on, there are animated moving bubbles above its icon on the
screen and the controller's red LED is on, too.
If the electrical heater hasn't been activated from the menu System Setting, in the field
Information about the heater's work appears an OFF sign.
If only the electrical heater is activated from the menu System Setting, its turning on and
off depends on the temperature in the bottom section of the water heater, measured by
Sensor 1.
When changing the differential temperatures for turning the circulation pumps on and off, it is good
to have in mind the following:
•Pump Off is good to be greater than 3 degrees, because if the difference is smaller, the
pump would work for too long, since the heat exchangers start giving out their heat less
effectively. Besides, there might be some losses and temperature decreasing from the
sensor's spot in the solar collector to the water heater, which additionally decreases the
differential with the heat exchanger.
•Pump On should have to recoup the heat losses between the solar collector and the heat
exchanger, and has to be enough greater than Pump Off.
When using energy from the solar installation, the temperature restriction for heating up the water
heater is up to 88 degrees, measured by Sensor 1. When using energy from the boiler, the restriction
for heating up the water heater is up to 85 degrees, measured by Sensor 2. After this limit the
circulation pumps turn off and stop transferring heat to the water heater.
Turning the water heater off
When the water heater is on and the screen has the Design II view, pressing the F (On/Off/Set)
button turns the water heater off, the screen's brightness gets decreased and the screen gets the
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Design I view.
If the water heater is off, the electrical heater and the boiler's circulation pump don't turn on. The
solar installation keeps working normally to avoid overheating of the solar collector. Safe modes
also function normally: preventing the freezing of the tank and the solar collector and preventing
the overheating of the solar collector by automatically turning on the Holiday mode.
Changing the information from Measured or set parameters field
In all work modes this field shows information about the measured values, that are not displayed on
the main screen, as well as about some of the set parameters for the water heater's control. By
pressing the View/Enter button all the possible data appears successively in the following order:
Set temperature for heating with the electrical heater.
Temperature measured in the bottom section of the water heater
Differential temperature for turning on/off the solar collector's
circulation pump
Differential temperature for turning on/off the boiler's circulation
pump
Date
Anode protector's condition indicator
Consumed electricity on day rate
Consumed electricity on night rate
(the view is below) ** diagrams for the consumed electricity and for the pump's work
Day rate start time to calculate the consumed electricity
Night rate start time to calculate the consumed electricity
* Start of the first interval (timer) that allows the heater's work
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Anode protector's
condition

* nd of the first interval (timer) that allows the heater's work
* Start of the second interval (timer) that allows the heater's work
* nd of the second interval (timer) that allows the heater's work
* Start of the third interval (timer) that allows the heater's work
* nd of the third interval (timer) that allows the heater's work
rror messages
* If no intervals that allow the heater's work are activated, pressing the View/Enter button skips
this information.
Possible error messages
■No Errors – No registered errors
■Anode Low – Reduced size of the anode protector. A check is required.
■Leakage – A leakage from the electrical heater to the water heater's hull is
registered. In this case it turns off and the next turning on is possible only after
turning it off from the electrical power panel.
■No heat – The heater is on, but the temperature in the water heater is not increasing
■S1 E1 – A breakdown in the temperature sensor in the bottom section of the water
heater. It is broken or disconnected.
■S1 E2 – A breakdown in the temperature sensor in the bottom section of the water
heater. It is on short circuit.
■S1 Frost – On turning on the power, the temperature of the water in the water heater
is negative and it is possible to be frozen. Must check the tank's wholeness before
turning on the power again.
■S2 E1 – A breakdown in the temperature sensor in the top section of the water heater.
It is broken or disconnected.
■S2 E2 – A breakdown in the temperature sensor in the top section of the water heater.
It is on short circuit.
■S2 Frost – The temperature sensor in the top section of the water heater registers
negative temperature.
■S3 E1 – A breakdown in the temperature sensor of the collector. It is broken or
disconnected. Only modes with electrical heating and boiler heating will work. In
this case the solar installation's circulation pump works constantly to avoid
overheating of the solar collector!!!
■S3 E2 – A breakdown in the temperature sensor of the collector. It is on short circuit.
Only modes with electrical heating and boiler heating will work. In this case the
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solar installation's circulation pump works constantly to avoid overheating of the
solar collector!!!
■S3 Frost – The collector's temperature sensor has registered temperature lower than
the set critical minimum temperature and it is possible the fluid to be frozen. Only
modes with electrical heating and boiler heating will work. Must check the system
wholeness, before turning it on again.
■S4 E1 – A breakdown in the boiler's temperature sensor. It is broken or disconnected.
Only modes with electrical heating and solar heating will work.
■S4 E2 – A breakdown in the boiler's temperature sensor. It is on short circuit. Only
modes with electrical heating and solar heating will work.
■S4 Frost – The boiler's temperature sensor has registered temperature lower than the
set critical minimum temperature and it is possible the fluid to be frozen. Only modes
with electrical heating and solar heating will work. Must check the system wholeness
before turning it on again.
■S5 E1 – A breakdown in the water heater's middle temperature sensor. It is broken or
disconnected.
■S5 E2 – A breakdown in the water heater's middle temperature sensor. It is on short
circuit.
■S5 Frost – On turning on the power supply the temperature of the water in the water
heater is below zero and it is possible to be frozen. Must check the wholeness of the
tank before turning the power supply on again.
** diagrams for the consumed electricity and pumps performance
A diagram for the consumed electricity, divided by hours for the
current day. 50% for one hour means that the electrical heater
has been working on its full power for 30 minutes out of 60
possible.
A diagram for the active hours of the solar collector's circulation
pump, divided by hours for the current day. 50% for one hour
means that the pump has been working for 30 minutes out of 60
possible.
A diagram for the active hours of the boiler's circulation pump,
divided by hours for the current day. 50% for one hour means
that the pump has been working for 30 minutes out of 60
possible.
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A diagram for the consumed electricity, divided by hours for the
previous day.
A diagram for the active hours of the solar collector's circulation
pump, divided by hours for the previous day.
A diagram for the active hours of the boiler's circulation pump,
divided by hours for the previous day.
Note:
If the Measured or set parameters field is currently showing the consumed day or night
electricity, pressing and holding the View/Enter button for more than 1.5 seconds, resets the
parameter.
Set temperature for heating with the electrical heater*
When the water heater is on, pressing any of the buttons ▲ or ▼ activates screen for
Changing the set temperature. Further pressing any of the same buttons changes the set
temperature in the relevant direction. The View/Enter button saves the new settings and the screen
goes back to its previous view. If no buttons have been pressed for 5 seconds, the display goes back
to its previous state, but the changes won't be saved. If any of the buttons ▲ or ▼ is pressed and
held for more than 0.8 seconds, the value automatically increases or decreases with 3 digits per
second.
This sets the temperature only for heating with the electrical heater!!!
The temperature limits are between 20 and 75°С.
The menu EL Eco Setting is more appropriate for setting the temperature, because it allows
regulating not only the temperature for turning the heater on, but also for turning it off.
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Work parameters settings
The controller has options for settings for most of the preset parameters. While the screen is in
Design II and the water heater is on, press and hold the F button for more than 1.5 seconds to enter
the settings mode. The only exception of the requirement for the water heater to be on is when the
time and date are blinking, i.e. they haven't been set yet. In this case you can enter the time setting
mode even if the water heater is off. While in settings mode the screen has the Design III view.
The screen has a similar view for all of the setting mode menus. Pressing the buttons ▲ or
▼ changes the value of the currently blinking parameter. Press the View/Enter button to select the
next editable value of the same screen. Press the F button to save the changes made on this
parameter and to proceed to the next settings menu, if any. If there are no more settings, the display
goes back to the main screen view. If no buttons have been pressed for awhile, the controller leaves
the setting mode without saving the changes made on the current parameter. Setting menus appear
in the following order:
1 Setting the temperature for turning on and off the electrical
heater, if it has been activated.
•It turns on when the temperature, measured by Sensor 5
(if the solar installation is activated) or measured by
sensor 1 (if the solar installation is deactivated), is lower
than Heater On.
•It turns off when the temperature, measured by Sensor 1
is higher than Heater Off
2 Setting the time intervals that allow using the electrical heater if
the temperature of the water, measured by Sensor 1 is lower
than Heater Off–5°C. The rest of the time the electrical heater
turns on if the temperature of the water, measured by Sensor 5,
is lower than Heater On
3 Setting start time for the day and night electricity rates. An
important information for correctly reporting the consumed
electricity.
4 Setting the differential temperatures between the solar collector
and the water heater for turning the pump on and off. If the
temperature difference between the collector and the water
heater is more than Pump On, the pump turns on and works
until the difference is less than Pump Off.
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Title of the menu
Parameter's value

5 Work mode of the boiler's circulation pump.
6 Set the differential temperatures between the boiler (the second
heat source) and the water heater for turning the pump on and
off for DHW Priority mode. If the temperature difference
between the boiler and the water heater is more than Pump On,
the pump turns on and works until the difference is less than
Pump Off.
7 Set the temperature for turning on and off the boiler's
circulation pump in CH Priority mode. The pump turns on
when the temperature sensor in the boiler (t4) measures higher
or equal to Pump On temperature. The pump turns off when
this temperature goes below the one in line Pump Off.
8 Setting the time interval when the pump can turn on to transfer
the heat energy to the solar collector on Holiday mode. This
interval must be during the night, for this mode to make sense!
9 Turns on/off the anti-frost safe mode for the solar collector. The
solar installation's circulation pump turns on if the temperature
is lower than 4°C!
10 Time setting
11 Setting the date in format dd-mm-yyyy
12 Setting the display's contrast. If the display is too light, or if it is
streaked, you can try to improve its appearance by changing the
contrast.
Caution:
•Using the electrical power panel for turning on and off the water heater, doesn't change the
set temperature and the water heater's last work mode before the turning off. If the water
heater was on, after turning it off and then on again, it will be on the same mode with the
same set temperature.
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•When you are not using hot water for a long time and the sun is strong in this period, do not
turn the water heater off from the electrical power panel. This might damage the collector.
The water heater automatically switches to Holiday mode during the night to transfer the
heat and therefore, it could take the heat energy again on the next day which automatically
protects the whole solar installation from overheating.
•The water heater's clock is run by a lithium battery even if the water heater is off from the
electrical power panel or failure of the power supply network occurs (no electricity). For
the battery not to run down if the water heater is off for long time, when there is no power
supply for more than 18 hours, the clock stops and on the next turning on, the time won't be
correct. This case is indicated by blinking time and date. A new time setting is required!
Configuring the heat sources – System Settings.
If you still have no boiler or solar installations, you can deactivate them. Moreover, if you don't
want the water heater to use electricity for the electrical heater, you can disable it too. To do so the
water heater must be off and the screen view – in Design I. Then press and hold for more than 2
seconds the F button to enter the Settings mode. Then press the F button three more times to go
through the first three setting menus.
To deactivate any of the heat sources, uncheck the box on the relevant line, using the buttons ▲ or
▼. Of course, if you need to activate them again, you should have to check the box again. Switch to
the next line by using the View/Enter button. To save the changes and exit the setting menu, press
F.
If the clock is blinking, i.e. it is not set, you would have to do this first and proceed to System
Setting after that.
Mind that if you deactivate the solar collector, this disables its safe modes for freezing and
overheating too!
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The electrical heater
is disabled
The solar installation
is activated
The boiler installation
is activated

Error messages
When the water heater is on, if there are any registered errors, a blinking Error sign appears in the
bottom section of the screen, above the field Measured and set parameters. You can see the
information about the error from the field Measured and set parameters. To do so, press the
View/Enter button as many times as needed to get to the error message. If there are more than one
errors at the same time, they appear successively when pressing the View/Enter button.
Clearing the errors
The controller has a diagnostic mechanism for the temperature sensors, the anode protector,
alternating current leakage to the water and heater's performance. Some of the error messages
disappear when the relevant problem is solved, but some of them need to be cleared manually to see
if the problem is solved. To do so, turn off the water heater. When the screen view is in Design I,
press and hold for more than 2 seconds the F button to enter Settings mode, menu Clear Errors. By
pressing the ▲ button select line Yes and press F again to save your choice and go back to the main
screen in Design I.
NHC-H42 safe modes
Safe modes are designed to protect the boiler's and solar collector's installations and the water
heater if extremal work conditions occur. Doesn't matter if the water heater is on or off, or which
work mode is currently activate, the temperature regulator always monitors the temperature of the
water in the tank and of the solar collector. If necessary, it activates any of the following safe
modes:
•Preventing the solar collector's freezing. This safe mode transfers the heat from the water
heater to the solar collector to protect its installation from freezing. It activates if the
collector's temperature is below 4°C.
•Preventing the tank's freezing. The electrical heater turns on if the temperature in the water
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Information about
the problem
rror sign

heater gets below 3°C.
•Automatic Holiday mode for taking off the accumulated heat energy from the water heater.
If the temperature of the water in the water heater is more than 85°C during the time interval
set in Holiday Mode menu, the temperature regulator activates this mode. Its purpose is to
transfer the heat energy from the water heater to the solar collector by turning the circulation
pump on. Due to the energy losses on the fluid's way while circulating and the energy losses
in the solar collector, when there is no sun light, the water in the water heater cools down.
Therefore, on the next day, the water heater can take heat energy again by taking it off from
the solar collector. The pump works until the temperature in the water heater gets below
30°C or until the temperature in the collector is 5 degrees lower than the one in the water
heater. This mode is indicated by a blinking COOL sign on the screen.
If there is a chance for the temperature to get too low or for the solar collector to overheat, it is
recommended not to turn the water heater off from the mains power supply!
Water heater's initial settings
The temperature regulators NHC-H42 are designed for different types of water heaters. The
necessary personalization is not made in the factory and after you instal your water heater it is
required to enter some information about the heater's power and whether there is an anode protector
(if the water heater is made of stainless steal it has no anode protector). By default the set
parameters are for a water heater with 3kW heating element and anode protector. If your water
heater is the same, no additional personalization is needed.
To enter the Initial settings mode press and hold F and ↵ buttons at the same time for more
than 4 seconds when the water heater is off (Design I). This operation is easier if you press the
button ↵ first and then F. After the button combination is recognized a screen with the controller's
software version appears:
The following pressing the F button enters a menu for manual control of the solar collector's
and boiler's circulation pumps. By pressing the buttons ▲ or ▼ check or uncheck the check box,
which turns the pump on or off:
NHC-H42-2 Reference Manual ver 1.6 стр. 17 / 18
Temperature regulator's
version
Software version
If the box is checked,
the solar installation's
pump works
If the box is checked,
the boiler installation's
pump works

Pressing the F button one more time enters the Initial settings menu:
To change the initial settings, use the following instructions:
•the field which is going to be changed is blinking
•process to the next field of the same parameter by pressing ↵ button and it will start
blinking
•increase the value of the blinking field by pressing the button ▲ and decrease it by
pressing the button ▼
•pressing the F button saves the changes and forwards to the next parameter, if any, or
to “Water heater Off” mode.
NHC-H42-2 Reference Manual ver 1.6 стр. 18 / 18
Heater's power
Presence of
an anode protector