Heatmiser Plus Installation And Configuration

Heatmiser Plus Installation And Configuration

Photo Of Heatmiser Plus Controller

The Heatmiser Plus is totally adaptable to control both commercial plant rooms and high end domestic systems, where different types of zones need to be controlled centrally. The Heatmiser Plus is easy to use, the large illuminated screen provides easy viewing and relevant information is displayed at the push of a button. The Heatmiser Plus design is aesthetically pleasing and the well spaced keys are nice to operate, unlike some of those horrible membrane keypads on competitor products.

Before even taking the Heatmiser Plus out of the box, you really need to sit down and read the manual from cover to cover. It might not make sense just yet but it will when you start. Next make a note of your system components and write them down carefully. For example you have a boiler, hot water, radiator circuit and underfloor heating. Some of these may have pumps, valves and sensors so note these down as well.

One of the most asked questions we are asked is how to wire up the Heatmiser Plus. Because the controller is adaptable to multiple scenarios, it will tell you how to wire it when you program it. When you do this later on, write down all the relays and sensors the controller asks you to use.

Heatmiser Plus Base PCB

This is the rear PCB of the Heatmiser Plus that we will make all our connections to. Study the Heatmiser Plus PCB and look carefully at the PCB screen print for details of each of the terminals.

  • Mains Connection Block
  • 10 Relays – Change Over Type (C / NO / NC)
  • 10 Sensor Inputs – Heatmiser Commercial Sensors (Use Position B)
  • 10 Alarm Inputs – Low Voltage To Be Relay Or Switch Operated
  • Communications Connections – Link Controllers Together

When you read the screen print on the PCB, the top row corresponds to the lower (terminals closer to the board). The bottom row relates to the taller (terminals below the lower ones). For instance, the S printed on the sensor inputs is on the top row. Therefore the sensor S connection will be made to the lower terminal.

Install a fused electrical supply to the PCB, connect the ribbon cable between the PCB and the front panel and screw it back together. Power up the unit and after a few second wait the unit will enter Initial Configuration Mode. If you have used it before then you can force a restart from the Engineer Menu. Simply press program, enter the engineer code of 6343 and press ok. Select initial setup and confirm. Once you have configured the controller you are unable to add and remove zones just reconfigure them, so have the system well planned.

For this system we have:-

  • A basic oil fired commercial boiler with a control circuit (T1,T2)
  • A 230V single phase central heating pump

And we are going to add:-

  • A room sensor in the ground floor office
  • A boiler flow sensor
  • A sensor located outside on a shaded wall
  • A relay box to operate the pump

First the Heatmiser Plus will ask if you are going to control boilers on another Heatmiser Plus? We are not so we answer No.
Now we are asked if we are using a boiler flow sensor. We are so we answer yes.
Next we set how many boilers we have, we are using one.
Now we need to set how the controller will operate the boilers.

Hint. Look at how many pumps you have in your system. When you select a boiler mode, in the configuration page if you add a value to pump over run, the controller will automatically assign a relay to operate the boiler pump. If your system has a specific shunt pump (for example on a low loss header) then add a pump over run time here to get a pump relay assigned. If the boiler does not have a shunt pump then leave this as 0 so no pump relay is assigned. For a basic single pump system we can add the relay later.

Fixed mode has fixed parameters. If you have a hot water requirement then you will have to use fixed mode.
Select this mode and configure the options.
If you have a pump for the boiler zone then add a time, generally 20 minutes.
Set the fixed flow temperature required over the system.
Flow Frost enables frost protection for the Boiler Zone. If you have multiple boiler enable the lead lag option. The controller will then control boilers independently and drop some out as the flow rate is achieved. Boiler firing is rotated weekly so they all have equal firing.
You can set a boiler on and off delay if necessary. If the boilers are cycling often, consider adding a small delay in here.

In variable mode the Heatmiser Plus adjusts the temperature of the boiler flow depending on outside temperature. As it warms up outside flow temperature is lowered. As it cools down outside flow temperature is increased. As less energy is put into the building you save money on your fuel bill. You cant really use this mode if you have a hot water circuit.
If you have a pump for the boiler zone then add a time, generally 20 minutes.
Flow Frost enables frost protection for the Boiler Zone.
Compensation Slope sets the relationship between the outside temperature and the boiler flow temperature. The default compensation slope is 3 Degrees which is a good place to start. Every time the external temperature rises 1 Degree, the flow temperature would be lowered by 3 Degrees (compensation slope).
Set the minimum and maximum flow temperatures, or just leave them alone for a while. The defaults are a good place to start. As it suggests, boiler flow temperature will always remain between these two figures when in use. Auto lead and lag works the same as Fixed mode, see above.
Hysteresis controls when the boilers switch off to allow for heat loss entering the primary circuit for example. If you have a maximum flow temperature of 80 Degrees and a Hysteresis of 2, when the flow temperature reaches 82 Degrees the Boiler Zone will turn off.

For our simple installation we have no hot water to consider and our client wants to maintain a comfort level all year round. For us, the Variable mode works well. I have kept the default settings but changed pump over run to 0 as I don’t need a pump relay.

When you click OK the Heatmiser Plus will then give you a list of relays and sensors to use so write these down.

  • We were given Relay 1 for the boiler
  • We were given Sensor 1 for the boiler flow sensor
  • Hint, always connect the outside sensor to Sensor 10

That should now have the boilers set up and you have a note of where the connections will be made. We can’t control the boiler zone directly so we need to add some extra zones to control the boilers for us. So lets add the zones we need and look at how they work.

Optimiser Zone Setup
Optimiser control turns the boiler on early on cold days and later on warm days to save energy.
Optimiser zones can turn the boiler zone on and off. If you need a call for heat then set this option first.
Set a pump over run value here if your zone has its own pump.
Preheat Time adjusts how many hours early the boiler can be turned on. 3 hours is a good place to start.
Rate of change gets updated as the controller self learns. This is how long it takes to warm up by 1 Degree. Default is a good value.
Hot water boost enables the hot water output if required.
Apply Summer will disable the zone if the summer input is made. Useful for a summer / winter switch on commercial panels.
Over Ride limit sets the maximum time a user can over ride the zone for.
Over Ride input will activate the zone when the over ride input is activated. Useful for a mechanical count down timer on commercial panels.
External Off disables (or turns off) this zone when the outside temperature exceeds the figure you put here. Our occupancy temperature for this zone will be 21 Degree so we set this to 22 Degree just as a place to start. We think if it’s 22 Degree outside then the inside temperature should be warm enough.
Average sensor lets you have two internal sensors for a large room for example. Set this here to get two sensor inputs.

When we confirm the settings we get assigned :-

  • We were given Relay 2 for the pump
  • We were given Sensor 2 for the zone space sensor.
  • We were given Relay 3 for the zone control valve.

Compensating (With / Without Internal Sensor)
A compensating zone generally has a 3-port valve to mix cooler boiler return water with hot boiler flow water to adjust flow temperature
It opens and closes the valve in pulses to set the required mixing rates
Most of the settings have been covered above so I wont repeat them again. You did read it all right?
Pulse Time sets the amount of time the Open and Close relays for the zone pump are operated for. If the valve opens and closes quickly, set a low time here. For large commercial valves extend the time as needed. Work on the settings during testing to reduce the valve hunting (opening and closing continually to reach flow temperature).
Delay Time adds a delay between pulses to help slow the valve down further.
If you use the option to have an internal sensor, the zone can be turned on and off when comfort level is reached. If you don’t use an internal sensor the zone will operate continually when required.

Timer Zone
Lets you have a simple on and off zone ideal for hot water.
Options are easy and as above.

Vent Zone
Allow for control of ventilation following options as above.

Wiring Up
Sensor wires need to be run in a good quality Belden or equivalent. We use a 2-Core data cable with individual foil screen and a drain wire. You must use the correct cable as the sensors wont work properly without it. Use a small cut of earth sleeve to cover the drain wire or screen and connect back to S on the Heatmiser Plus PCB. All the S connections are linked together and you can connect to an external block but shield from the mains earth. The + connection on the sensor should be connected to + on the PCB. The – connection on the sensor connects to the sensor input on the PCB. We cant stress enough about installing the data cable well, making off the ends neatly and routing away from Cat II cables where possible.

For our installation we wired our boiler flow sensor into 1, room sensor into 2 and the external sensor to 10.
Wire all your sensors back to the Heatmiser Plus main PCB and terminate at the actual sensors.

Picture of a strap on pipe thermostat

Boiler Flow Sensor

Heatmiser Plus Space Sensor

Space Sensor

The new oil fired boiler we just installed requires a permanent electricity feed so we provided a spur for this. It has a 2-wire control circuit to turn the boiler on and off. We simply wired the control circuit to Relay 1 Common and Normally Open.

For our pump we installed a Relay underneath the Heatmiser Plus as the relays inside the controller are unable to handle high current loads. We took a jumper from the Mains Live In terminal to to Relay 2 Common. From the Normally Open terminal we then had a mains feed to operate the 230v relay. We used an additional spur to protect and isolate the pump supply.

If you have mains powered valves then you can use the Common Terminals on the relay to loop to other relays to make the live wiring a little easier.
If you prefer to have a spur for every device on the system, take a wire from the spur Live Out to the Relay Common terminal(s) in question and then take the NO terminal back down to operate the valve. If you need a valve open and valve close signal, you can still use a single Live and use the two Common connections to form a link inside the controller.

If you have low voltage actuators such as 24 volt which is common in a commercial application, use a separate relay or contactor. This could be mains operated or even low voltage operated by using a low voltage supply switched through the Relay terminals. Never mix mains and low voltage on the same Relay.

Heatmiser Plus Installation


You can go back into any of the zone settings from the Heatmiser Plus programming menu using the engineer code of 6343. It’s useful to go in and name the zones other than zone 1, zone 2 etc to Radiators, Underfloor Bedroom, Hot Water etc. Will make the next step much easier.

Now to get things working you need to add some comfort levels to tell the Heatmiser Plus when to operate. Press program and this time enter the user code of 0000. Select Comfort Levels.
A list of zones is displayed and each needs to be programmed individually. Go into each zone and set the on and off times as and when required. Each day has 4 switching times available. Set the temperature required in here as well where applicable. When you save the settings, any zones that need heat will immediately call the boilers.

The copy button works well in here and is easy to figure out. Push it and see what happens!

When you are back in display mode, push the < and > buttons to scroll through the zones and see whats going on. In the above picture it shows our Heating Zone has reached 21 Degrees, the Set Point is 21 Degrees and the pump and boiler is off.

Check everything works and change settings as required to prove that all the zone valves turn on and off and that the zones call for heat as required.

We hope that the above article has offered some help in you installing and configuring the Heatmiser Plus controller.

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Download The Heatmiser Plus Engineer Manual

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