Electronic systems for renewable energy sources, home automation

WATTrouter FAQ

On this page you can find answers to most common questions about WATTrouter and self-consumption in general.

Is it a good idea to self-consume the energy produced from local PV-plants or wind plants?

Surely yes. You both save money because you save energy you would otherwise buy from public grid (this still depends on local regulations) and contribute to environmental protection - the energy is consumed locally without the need to be distributed in public grids accross distances (here we encourage you to connect only those loads to WATTrouter you really need). At the times where feed-in tariffs go inevitably lower and lower this is the only way how to give real purpose to your PV-plant.

Which PV-plants do you support?

We support only traditional grid-tied PV plants with classic DC/AC inverter, running parallel with a 230VAC/50 Hz grid, where electricity is typically measured with bidirectional (4-quadrant) meter. We do not support island PV plants. Moreover, WATTrouter self-consumption management cannot be combined with any other management system, which might be for example built into inverter etc. With some limitations it is possible to use WATTrouter with hybrid (battery equipped) inverters.

Which inverters is WATTrouter compatible with?

WATTrouter is compatible with any inverter of classic design, which runs parallel to the 230V / 50Hz electrical network and supplies power to this network. It is also possible to use hybrid inverters, which provide electrical storage using a built-in or external battery and which meet the above conditions. Hybrid inverters use their own energy management to control battery charging and discharging. Usually, the inverter uses its own electricity meter (smart meter), which performs a similar function as the WATTrouter measuring module. When combining this inverter with a WATTrouter, care must be taken to verify that these 2 control loops do not interact in a bad way. The issue of combining a hybrid inverter with a WATTrouter can be summarized in the following modes:

  • PV plant produces, battery charges without excess energy - only enough to charge the battery. The WATTrouter therefore does not detect any energy excesses and does not switch on the connected appliances, ie it does not apply at all.
  • PV plant produces, charging the battery with excesses - the excess energy is so large that some of it is used to charge the battery, some of it goes to the grid. In this case, the WATTrouter can easily be used to capture these energy overflows and utilize them in the connected appliances. Some inverters make it possible to completely disable these excesses, which is meant for a case where legal circumstances do not allow excesses to the grid. This function must of course be switched off for WATTrouter operation. Surplus into the grid must therefore be permitted in the inverter.
  • PV plant produces, the battery is fully charged, all excess energy goes into the grid. In this case, the WATTrouter can again be used without any problems to capture these energy overflows and utilize them in connected appliances. The system behaves like a classic inverter without a battery.
  • PV plant does not produce (or little), battery discharges - in this mode, the inverter tries to cover the consumption in the house from the battery. This control inevitably results in peak energy overflows that go into the grid (eg after the appliance has been switched off, the inverter supplies energy from the battery to the grid for a while before its own control loop, formed by an inverter-smart meter pair, responds and limits the battery output power). In this case, the WATTrouter can react to this peak and start switching the connected appliances. This causes positive feedback in the inverter control, which can be further increased until the WATTrouter has fully switched outputs corresponding to the maximum power of the inverter in the battery consumption mode. This will drain the battery very soon. However, this is usually not desirable, because we want to use battery power for appliances other than those connected to the WATTrouter.
  • PV plant does not produce, the battery is fully discharged - in this mode, the inverter is unable to supply any energy. WATTrouter switches off connected appliances. The system behaves like a classic inverter without a battery.

It is obvious that WATTrouter can therefore be combined with a hybrid inverter without any problems, except when the inverter covers the house consumption from the battery. So how the positive feedback during battery discharge mode can be avoided?

  • By setting a sufficient delay for switching the WATTrouter. This can be done simply by assigning an unconnected relay output to the first priority. We set the minimum possible surplus (0.04 kW) and a sufficient switching delay (eg 10 s). Then the WATTrouter will not react to any energy spikes. Attention this method is without guarantee! It must be verified for the specific inverter type!
  • By experimenting with power offset. The more negative the power offset we set, the higher the surplus into the network will be ignored by WATTrouter. This can also force the WATTrouter to ignore energy spikes produced by the inverter when discharging the battery. Please note that this method is again without warranty! It must be verified for the specific inverter type!
  • By combining the two previous methods. This can force the WATTrouter to ignore large energy peaks without having to set too large negative power offset.
  • By connecting the WATTrouter and all appliances switched by it outside the control loop of the inverter, ie outside the control range of the smart meter of the inverter. This connection is shown here (picture below). When looked from the electricity meter to the rest of the house, first connect the current sensing module of the WATTrouter, then the circuit breakers of appliances switched by the WATTrouter, then the smart meter of the inverter and then anything else. With this method of connecting the smart meter, the inverter will not register the consumption of the appliances connected to the WATTrouter, so whatever the WATTrouter does with them, the battery discharge will not be affected. This solution is 100% protection against accidental discharge of the battery by WATTrouter. The disadvantage of this connection, however, is that it may be difficult to implement in existing buildings.

Can I use WATTrouter in single phase environment?

Yes, in such case you only need one small current transformer and there is no need to use the 3phase current sensing module. You can use even two-phase connection with two CTs. In these cases, connect only IL1 input (or IL1 + IL2) and leave the other measuring IL-inputs unconnected.

Is there possible to optimize when I have a fixed feed-in tariff?

This depends on local regulations. If you have the possibility to self-consume certain amount of energy and you would like to increase it, then WATTrouter device is the right choice for you. In CZ, for example if you get fixed feed-in tariff you have 2 electricity meters - one for PV-plant and the other for your house. In such models it is impossible to self-consume.

I already self-consume high percent of produced energy. What to do?

It always depends on the distribution of consumption time and PV-production time. If you mainly consume electricity from grid at night (heatings, hot water preparation, etc.) then yes, WATTrouter should be able to help you. But if there is steady consumption at daytime (many computers, machines etc.) it might be difficult for WATTrouter to find any surplus energy to "route" it somewhere else.

I don't have boilers, immersion heaters, electric heatings, etc. What to do?

In such cases there is no suitable load to connect to WATTrouter, perhaps except for expensive battery equipment. If you use gas or oil heating you can consider to buy a high-capacity (1m3) water tank where WATTrouter will be able to put the surplus energy. You can use accumulated hot water from this tank even for more days when the sun is not shining.

I only have boiler/immersion heater and this is hot in 3 hours in summer. Where to put the other surplus energy?

WATTrouter controllers have 6/8 outputs. It is possible to connect up to 6/8 loads. But if you have neither swimming pool to heat and filter its water, nor wet rooms to dry in summer, nor an air-conditioner, just sell the surplus energy as usual. WATTrouter will pay itself in 2-4 years horizon even with the boiler (this depends on local regulations).

Why does WATTrouter not measure current flowing through individual outputs and does not know whether the load is really connected or disconnected?

It is not generally possible to recognize the disconnection (or re-connection) of an appliance connected to the WATTrouter output by an external element (thermostat) from the measured powers in the individual phases. It is therefore necessary to measure directly the current flowing through the appliance circuit. Only our latest Mx model supports this measurement for up to 4 outputs. To make it work, it is necessary to purchase external compatible current transformers (or another current sensing module) supplied by us, connect them to the controller ANDI inputs and measure the circuit current of the connected appliance with them. Corresponding ANDI inputs also need to be set correctly in WATTconfig, see the User's Guide.

The above measurement slightly improves the overall control behavior by not physically disconnected outputs being included in it, and only the actually measured energy delivered, not just the assumed (i.e. calculated by the controller) is included in the statistics for the respective outputs.

In any case, however, it is appropriate to have enough space (a large storage tank) where energy can be stored without frequent disconnecting of the appliance by its thermostat.

What are the influences of WATTrouter on public grid and the 4-quadrant meter?

Triacs and SSR are switched on synchronously. By omitting certain amount of sinus halfwaves we modulate the ohmic load's output power. The switching mechanism complies with EN 61000-3-2 a EN 61000-3-3. Designed synchronous control counts with internal integration times and filter time constants of the electricity meters. Thus there is no increase of consumption from grid when this special control is running.

Is the bidirectional (4-quadrant) electricity meter in my house compatible with WATTrouter?

WATTrouter can be connected to be compatible with any 4-quadrant electricity meter that complies with EN 62053. WATTrouter has been tested with electricity meters installed in Czech republic and Slovakia.

Is WATTrouter compatible with normal electricity meter?

Older rotating wheel meters are mostly compatible with WATTrouter. During active regulation, the wheel stops or slightly vibrates. Newer electronic meters can count surplus energy as consumption from utility grid. Such meters are NOT compatible with WATTrouter's proportional control of heating elements. Generally you should not have such meter when using photovoltaics. If so, you still can decrease the amount of surplus energy (which is counted as consumption) by using relay outputs or by controlling inverter air conditioners or heat pumps proportionally as described below.

Can WATTrouter be used even when 4-quadrant electricity meter examines each phase wire independently?

Yes. These meters are programmed to evaluate the produced and consumed energy in each phase separately. These meters try to avoid assymetric energy flows and are used in some countries. You should ask your electricity provider about your meter's configuration. Even if you don't get answer, it is a good idea to configure WATTrouter to control each phase independently. Only in this mode the energy flow is the so called "phase zero", where there is physically no flow of energy to and from your house when WATTrouter does its work. In this mode there is no way to optimize self-consumption for phase wires without installed PV-inverters. If you have only a single phase PV-plant, you can optimize only in that phase. As such, you should connect all suitable loads to that phase wire and let other loads (such as lights, TV, etc.) occupy other phase wires.

How to find out my 4-quadrant electricity meter configuration?

You can test it in your house. You can let the PV-plant to supply into one phase wire and at the same time you can consume from another phase wire. If the meter measures each phase separately both production and consumption counters will increase.

Your electricity provider should be able to tell you the configuration as well.

How exactly is the reaction of 4-quadrant meter to such synchronous control WATTrouter is using?

WATTrouter uses a special proportional control to modulate the power of the loads using power triacs or solid state relays (SSR). This control is synchronous where in some AC voltage half-waves the load is swiched on and in some of them not. Only full half-waves are switched on or omitted (zero switching SSRs must be used).

When using this control, one might deduct that for half-waves where the load is switched on there is consumption from the grid (because in this state the switched load has higher nominal input power than the PV-inverter output power) and in omitted half-waves the PV-inverter output power is being fed into the grid.

Digital meters use specialized integrated circuits to achieve very accurate measurement and compute instantenous and effective values of voltages and currents in all three phases. For the purpose of WATTrouter control the effective active power values apply. Because the calculation of the active power effective value requires about 900 ms of filtering in those ICs, it is possible to use synchronous control to modulate the power of the load and many succesive half-waves may be omitted. The filters in electicity meter react to this with corresponding delay. There is small ripple at the output of active power filter which slightly affects the active energy sign and both energy counters (consumption + production). Even at low load modulation levels there is almost no consumption from the grid when half-waves are fully switched on and, similarly, there is almost no surplus energy fed to the grid when half-waves are omitted. In addition, WATTrouter devices contain the so called power offset setting to reduce consumption from the grid at the expense of low amount of surplus energy (by default set to 100W) being fed back to grid.

What about an influence on other electronic devices, lights etc.?

There is possible to encounter a flicker sensation at light bulbs, even when WATTrouter is installed properly. See next point how to reduce or eliminate this.

Reducing flicker when switching power loads

If you are sensitive to light disturbances (flicker) you can encounter disturbances when WATTrouter proportional control (triac and SSR outputs) is active, even when the device is compliant to EU regulations. The switching control mechanism reduces these effects as much as possible, but they cannot be fully eliminated. There are 2 reasons why these effects should not be crucial. First, the proportional control is active only at daytime, where possibly there is mostly little reason to use a light bulb, except for some dark rooms. Second, there can be a phase wire selected, where the load is so small that these effect will approximate to zero. On that phase wire the light bulbs should be connected.

Recommendations to minimize flicker sensation:

  • Use loads <= 2kW, optimum is 1-1,5kW, e.g. 3-phase heat elements should be splitted into 3 WATTrouter outputs. where on each phase only one output can be switched in proportional mode at a time.
  • Do not set the Maximum power field in WATTconfig to lower value than the Connected power field unless you have to. When there is enough surplus energy this output should be switched on fully to avoid flicker sensation. This is the precaution.
  • Connect bigger loads to a thick wire and nearby of the point where the cable from utility grid enters your house. Thicker wires decrease the line impedance and flicker sensation is proportional to line impedance.
  • Connect bigger loads to phase wire where there are no light bulbs in frequently used rooms.
  • You can set one phase wire apart from proportional control and connect all light bulbs to it.
  • Use LED lights - these are resistant to frequent voltage changes, save the most energy and have the longest endurance.
  • If you cannot use LED lights and still have problem with flicker sensation then you must use only relay function for all respective outputs.
  • If a higher network impedance (L + N) than the normalized 0.47 Ohms is measured at the connection point, it will be necessary to reduce the rated power of the proportionally controlled ohmic loads (0.47 Ohms = max. 2kW, 0.94 Ohms = max. 1kW, etc.) in most cases. Or again use the triac / SSR output in relay mode so that feedback effects on the public grid do not exceed the normalized limits. On the other hand, with a lower impedance of the power line, it is possible to connect bigger loads. So here applies an inverse relationship.

Can there be connected any warm water boiler?

Yes. If there is no electronic control in that device, just heating element with mechanic (or electromechanic) thermal fuse, then you can connect this to triac and SSR and take benefits from the accurate proportional control. Otherwise you have to use relay (or proportional output in relay mode).

Can there be connected a freezer or ice-box?

If this load is connected to a separated line in your house (not just wall outlet) then it is basically possible. WATTrouter can optimize the time when the freezer can run and with CombiWATT mode it can switch it even if there is little surplus energy. But we don't recommend this. Because of ensuring the quality of stored meals the temperature should vary as little as possible. Additionally, in case of malfunction of WATTrouter due to some unpredictable events the freezer contents might melt down.

Can there be connected some floor heating element?

Yes but you have to observe existing connection to some dedicated control system. The WATTrouter output can be connected in serial with the existing system's switching element or in parallel. Use serial connection if you don't want to heat more than necessary (activate CombiWATT in that case to allow the dedicated heating regulator to switch on even if there is no surplus energy). Use parallel connection if you want both systems to be run independently. Polarity and correctness of phase wire must be observed to avoid short circuit here!

Can there be connected a three phase heating element?

Yes but this element has to be connected in Y mode and the neutral line must be also used. It means this element must be used such as 3 independent heating elements connected between phase wire and neutral wire.

Can there be connected a three phase load which just has to be connected as three phase load?

Yes but only using a relay output. For electricity meters configured to evaluate each phase separately (see above) this might not be good idea because that load can be switched on even if there is not enough surplus energy in other phase wires.

Can there be connected an electric heating?

Yes. The same applies as for boilers / immersion heaters. No electronic control - you can connect to triac or SSR and benefit the accurate proportional control. Otherwise connect to relay.

Can there be connected a load with variable power input?

Yes. Because these loads have variable power input, we have to use it in combination with a proportional triac or SSR output where a heating element is connected.

Example: Mark the load with variable power input A and the heating element B. Connect load A to relay 1, set the highest possible power to the Connected power field and assign it 2nd priority. Further set Prepend before triacs/SSRs to 1. Connect load B to triac 1, set nominal power to the Connected power field (as usual according to user manual) and assign it 1st priority with proportional control mode.

This configuration has following impacts: First the surplus energy flows into load B. At the point where the steady modulated power of load B achieves the highest possible power of load A relay 1 is switched on and the load A gets active. WATTrouter will register that and decreases the power of load B to maintain "phase zero" or "virtual zero" according to choosen control mode.

Can there be connected a battery charger?

Yes, but the charger must have externally controllable charging power (eg. through a 0-10VDC signal, then WATTrouter PWM mode should be usable) or at least be externally switchable (relay function applicable only in this case). WATTrouter does not control discharging of batteries, here different control system has to be used. Generally, we do not have experience here because we do not recommend installing battery chargers, especially in houses equipped with stable mains connection. It is much better to consume electricity directly and/or accumulate it into heat or cold than to save it to expensive batteries with additional losses, just to use it later.

Can there be connected an electric vehicle charger?

Yes, but the vehicle charger (or wallbox) must have externally controllable charging power (eg. through a 0-10 VDC signal, then WATTrouter PWM mode should be usable) or at least be externally switchable (relay function applicable only in this case).

For variable charging through the 0-10 VDC signal the electric vehicle can be charged with variable power, i.e. only with the PV power that is currently available. It is known that all electric vehicles have lowest charging current set to 6 A and their charging current can be increased to 10, 16, 20 or 32 A according to IEC 61851.

For that, our control mode built originally for heat pumps can be used. Ask for a wallbox that has 0-10V control input and is (or can be) programmed as follows:

  • 0 - 1 V = vehicle charging at maximum current, depending on the wallbox settings.
  • 1 - 9 V = the charging increases linearly from 6A to the upper limit and vice versa.
  • 9 V = vehicle charging at minimum current 6 A.
  • 9 - 9,3 V = hysteresis for turning on/off.
  • 9,3 - 10 V = vehicle charging turned off.

This setting allows charging with the maximum charging current when the 0-10V control signal is disconnected from the wallbox/charger.

Note: We cooperate with several Czech companies that provide such control signal and corresponding settings in their charging cables or wallboxes. Of course you might find a wallbox with different settings but in that case you might have to set WATTrouter differently. We consider the above settings as a standard.

If you have such vehicle charger (wallbox) then connect its 0-10V control input to any SSR output of WATTrouter:

  • Either directly to SSR4-6 of Mx type (these SSR outputs provide 0-10V signal).
  • Or via our PWM/0-10V converter to any other SSR output (other SSR outputs provide PWM signal). We recommend this because our PWM/0-10V converter provides additional galvanic isolation.

Then select the SSR output in WATTconfig as follows (for 1-phase charger, assuming you use control mode set to "Sum of all phases"):

  • Set PWM function.
  • Set first priority.
  • Set Minimum power to 1,4 kW (corresponds to 6 A).
  • Set Connected and Maximum power to maximum charging power (eg. 3,7 kW which corresponds to 16 A).
  • Set PWM-I parameter according to the dynamic reaction of your charger. The value is always experimental and we recommend using values 30 to 99.
  • Keep default values for PWM range (0-100%).
  • Check inverted option, it must be checked.
  • Set other parameters as needed.

For 3-phase charger, set Minimum power to 3x 1,4 kW = 4,2 kW (as 6 A limit is per phase). Connected and Maximum power 3x 3,7 kW ~ 11 kW (for 3x 16A max. charging current). Again we assume you're using "Sum of all phases" control mode.

Note: It is not possible to use surplus energy below 6 A (0-1,4 kW) for vehicle charging (when using only PV power for that). Because of the 6A minimum charging current. If you want to use this surplus power you need another load, eg. a heating (eg. 1,5 kW). Connect it to another SSR output with second priority. This load will be active until there is 1,4 kW surplus power availabe to start vehicle charging.

What electricity meters can I choose for FB/ANDI inputs?

They should have optically isolated impulse output (S0 output). Typically they have an open collector output (NPN transistor + some shunt resistor). Suitable types can be found among Carlo Gavazzi EM series, Applied Meters AMT series, Maneler 99 series, etc.

What about wireless control of some loads connected to wall outlets?

Yes it is possible with WATTrouter Mx and ECO via our extension SC-Gateway module and wireless sockets. Or you can use any third party wireless systems (transmitters and wall outlet receivers) which support external relay signal connection. In such case you connect transmitter to relay output(s) of WATTrouter.

What digital temperature sensors can be connected to WATTrouter Mx?

Sensors containing original chips DS18B20 or DS18S20 from Maxim Integrated Products (originally Dallas Semiconductors). For recommended types see here. We warn against very cheap sensors sold typically at various Chinese eshops. These sensors may not contain the original chips and may not work with WATTrouter. An example is MK00241, which does not comply with the original chip specifications for the communication bus voltage levels and does not work with the WATTrouter (the same applies for our Heating Control device). However, eg. this sensor works according to the information of our customers.

What analog temperature sensors can be connected to WATTrouter Mx?

NTC type sensors with 10kOhm at 25°C (B25/85=3977) or PT1000 sensors. For recommended types see here.

Why is the regulator separated from current sensing module?

Because installation is easier in many cases. There is often not enough place in existing house wirings and the module is small enough to fit into it. Regulator can be placed even 15 meters away from the module (with appropriate shielded cable). There is also possible to connect more modules to one regulator, where the secondary currents of the modules just add to each other (see user manual). There has to be always wire between regulator and the module, wireless communication is not possible.

What to do if I have dual tariff but no low tariff (LT) signal available?

The low tariff (LT) logic in our devices assumes there is always an external signal that informs about LT presence. And can be connected to the controller via its LT input, as shown in the UM schemes. This is always the case in CZ, SK, and other countries. In case you don’t have such signal and you only know the LT switching times, then there are 3 options:

  • Use an external timer with a relay output. The relay of this timer then activates the LT input, just like the aux. relay described in the manuals (for most devices it means connecting LT input to GND).
  • Use built-in time schedules to switch relevant output at the LT times. In this case the LT logic of the controller is not used (bypassed), which means Combiwatt cannot be used and there is no LT share information in the statistics.
  • Use built-in time schedules to artificially build LT signal and route it back to controller, at the LT times. In this case you must sacrifice one built-in relay output for this. And this relay then activates the LT input just like the aux. relay described in the manuals (for most devices it means connecting LT input to GND).

Note: It is strongly recommended to connect the LT input with the switching signal from the electricity meter switchboard. This way you will not have to constantly check whether your distributor has changed these times, and, moreover, in case of accidental time changes in the controller, the low tariff functions will remain safe.

Note: For WATTrouter ECO and M, the weekday settings are not yet available in the schedules. These settings may be necessary for low tariff configuration. For both products, we plan to update the schedules to have the same functionality as the latest WATTrouter Mx, except for temperature conditions.

No display in WATTrouter?

WATTrouter is designed without display. One reason is to maintain low price of this device. Another reason is the way this controller gets configured. Expecially WATTrouter models with Ethernet interface are usually connected to Ethernet network and can be monitored and configured from PC, smartphone, tablet etc. Function is indicated with several LEDs and the computer based setup is very comfortable.

I would like to incorporate WATTrouter to my intelligent house system. Is it possible?

Yes if you have this system with integrated Ethernet interface. WATTrouters with Ethernet interface support XML data exchange which is described in the user manual.

For models with just USB interface it is not easily possible (it would be necessary to have an USB-HOST interface and a software capable to run FTDIchip drivers).

Can WATTrouter be monitored over Internet?

If you have Ethernet network in the place where regulator is installed then yes. The models with Ethernet interface support direct Ethernet connection, for models with just USB interface a suitable USB/Ethernet converter is needed, e.g. Silex SX-3000GB or Silex SX-DS-3000U1. However, these converters support only local networks, as far as we know.

Can WATTrouter be monitored over Wifi?

The models with Ethernet interface can be but you need additional Wifi router or switch.

Can WATTrouter be monitored from mobile devices?

For Ethernet models, this can be done using a web interface and/or special mobile applications. Mobile apps are only available for the most popular mobile OSes Android and iOS. Apps for other OSes are not available and will not be available. For these devices, you can only operate the device via built in web interface.

Can WATTrouter control power of air conditioner or heat pump according to available surplus energy?

Yes (for WATTrouter ECO you just need to buy the PWM control SW feature. You need a suitable inverter air conditioner or heat pump. This unit has to be equipped with the external control input which allows to control the inverter's/compressor's input power. For example, Fujitsu and Mitsubishi inverter units have that option through a 0-10VDC control signal, with appropriate accessories (control boards). Then, WATTrouter output is set to PWM mode and connected through a PWM/0-10V interface to the control board of the inverter unit. So far, we have done this connection and tested on a Fujitsu unit.

Accessories according the picture:

  • Air conditioner or heat pump inverter unit from Fujitsu.
  • Control unit UTI-INV-XX – it is produced and sold by the Czech company Impromat www.impromat-klima.cz. To order proper control unit and/or consult the technical aspects of integration into the Fujitsu outdoor unit please directly ask representatives of Impromat.
  • PWM signal (TTL levels) to 0-10VDC converter - we sell already our own.

WATTrouter configuration:

Any SSR output is set to PWM mode and additional parameters like Connected power, PWM-I, Minimum power and time delay must be configured:

  • Parameter Connected power is set on nominal value of input power of the inverter unit, it is the same as for regular heating elements. In PWM mode, this value does not specify the parameters of regulation but is used only for calculation of expected power supply to the load. Regulation parameters are given by PWM-I input field. Even here, we can reduce the power output by specifying Maximum power, in case you need this.
  • Parameter PWM-I specifies the regulation speed. Because of slow reaction of the inverter unit, which is much slower than that of a regular heating element, it is needed to set this parameter to low value. We recommend to use value between 20 and 30.
  • Parameter Minimum power specifies the minimum surplus power, which needs to be reached to start the inverter. Usually the inverter unit does not work under 1/3 of its nominal power (except inrun phases). For inverter unit with nominal power of 3kW, we will set this parameter to 0,8kW to 1kW. In PWM signal levels, this Minimum power value corresponds to a 10% duty and Connected power value to 100% duty (fully switched output). Before the inverter is started up, it is possible to consume overflowing energy in heating elements connected to outputs with lower priorities.
  • Parameter Delay specifies the time required to delay the moment where the inverter unit is switched off, when there is no more enough surplus energy to run it. It is used to eliminate frequent starts of inverter unit as this has negative influence on its life time. This delay will cause the inverter unit to draw energy from utility grid for some period, even when the inverter unit runs at its minimum power through this period. Optimum value is about 20 to 30 minutes, so in seconds 1200 to 1800s.

Important notice: As mentioned above, AC or heat pump inverter units react on input power changes very slowly, almost 2 orders slower than regular heating elements, so it is necessary to count with higher consumption from utility grid during the day. This is not just because of the Delay parameter. Inverter units can increase or decrease their input power for some time when their internal control algorithm requires this (e.g. needs of higher lubrication, pressure balancing etc.). Even that, proportional regulation of inverter units brings more effective usage of surplus energy than in cases we switch them to full power in ON/OFF mode. Moreover, thanks to the COP factor, surplus energy gets consumed much more effectively on these inverter units than on regular heating elements.

Should I use single phase or three phase air conditioner or heat pump?

This depends on many circumstances. Mainly on nominal power of your PV system, what electricity meter is installed and how the heat pump is going to be used.

In case you have a 4-quadrant electricity meter, which measures each phase separately (this is the case in CZ), than it is suitable to use three one phase inverters (e.g. split A/C units). WATTrouter Mx and ECO can control all 3 of them with PWM mode, WATTrouter M just 2 of them.

In case of 4-quadrant meters which take vector sum from all phases or regular power meters we can take advantage of the "sum of all phases" control mode. Then you can use and control even one three phase AC unit by one external output from WATTrouter. We always set nominal power input of the three phase AC unit as Connected power and activate the "sum of all phases" control mode.

The big advantage of the proportional regulation of inverter units is the compatibility with any kind of electricity meter. You do not need to deal with situations where the electricity meter counts surplus energy as consumption from utility grid. This situation may occur only at the moment once inverter unit does not react fast enough on sudden increase of surplus power. According to our latest tests, these states will usually endure couple minutes only.