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 support neither hybrid nor 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.

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 outputs. It is possible to connect up to 6 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 split core 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 disconnection of the appliance by the thermostat.

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

Triacs and SSR are switched on synchronously. 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 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 if WATTrouter does its work. In this mode there is no way how to optimize self-consumption for phase wires without PV-inverters. If you have only a single phase PV-plant, you can optimize only in that phase. As such, you should connect all corresponding 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. This control is synchronous where some half-waves are swiched on and some omitted. One might deduct that in swiched half-waves there is consumption from the grid (because the switched load has some higher nominal power) and in omitted half-waves there is surplus energy 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 stabile effective value of active power requires about 900 ms of filtering, there is possible to use synchronous control to modulate the power of the load and there can be even more succesive half-waves 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 in similar there is almost no surplus energy fed to the grid in omitted half-waves. 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 <= 2,3kW, 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.

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 battery charger?

Yes. Because these chargers have variable power according to battery status, we have to use it in combination with a proportional triac or SSR output where a heating element is connected. We speak about chargers whose power cannot be externally controlled.

Example: Mark the charger 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 (tr./SSR) to 1 (firmware 2.2 and newer). 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 charger gets active. WATTrouter knows that and decreases the power of load B instantly to maintain "phase zero" or "virtual zero" according to choosen control mode.

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.

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.

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 dedicated mobile applications. Dedicated apps are only available for the most popular mobile Android OS (for the Mx model even for iOS), and others are not available and will not be available. For these devices, you can only operate the device with a 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.

I bought the device and wish other functions.

Please send us an e-mail with your ideas. We evaluate them and possibly create a firmware update when there is more people with the same idea. This update will be created without additional costs for you.