Ferroli GFN8 boiler with Ferroli SUN P7 pellet burner. - problems and fixes - versiunea in romana
Problem with SUN P7 pellet burner
The problem that I had with SUN P7 pellet burner was that it was jamming all the time. The tube was getting filled with pellets and the burner would stop and switch on the fault light.
After some investigation I saw that the pellets were jamming somewhere in the metallic neck of the burner. But it was not a strong blockage. At the slightest movement the pellets would fall in the grille. Very strange. I tried to clean very well the tube and the metallic neck but to no avail. From about two attempts to start, one would fail.
SUN P7 presentation
SUN P7 has a minimum of automation:
- a fan – provides air for combustion (the boiler ash door must be completely closed).
- heating element – ignites the pellets.
- pressure sensor – the fan can blow with different pressures depending on the set power of the burner. If the fan blows stronger, the pellets will burn faster and the burner will generate more power.
- light sensor – photoresistance which detects the flame or lack of flame.
- 85°C sensor – mounted on the loading tube; it’s only for safety.
- temperature sensor (not in image) – is mounted inside the shell of the boiler (in the special place inside it’s walls).
- no sensor to detect when it’s stuck with pellets or other sensors.
- it can be programmed to function after a fixed daily schedule, but different schedule for each week day.
When it get’s stuck, the light from the flame can not reach the light sensor anymore. In this way it detects, indirectly, the blockage.
The burner has 3 menus.
The first menu is accessed by holding down the M button (5 seconds) until the first parameter blinks on the screen. Due to the strange display, the first parameter u01, with value 80 will be displayed like so: u 80 01.
To advance to the next parameter, press P.
To modify the value of the current parameter press + or –
After you have modified a value, you must wait 3 seconds for it to be saved! If you scroll to next parameter too quick, the value will not be saved. (in conclusion you must check that the value was actually saved – annoying).
To exit the menu, hold button M pressed until the clock appears again.
|Parameter||Description||Allowed values||Factory settings|
|u01||Delivery setpoint adjustment||30 – 80°C||80°C|
|u02||Power level setting||1 – 5||3|
|u03||Burner operation method||0 – 2||0|
The burner has 5 power settings(u02). For each setting you can set the pressure/speed of the fan and how many seconds to load pellets during one burning cycle.
For each setting you can set any power level, from minimum to maximum. In other words, setting 1 can be set to have a low power level or a high power level. I recommend to set them in increasing power level, from setting 1 to setting 5. If you use the modulation function (the burner can automatically switch from one power level to another, depending on the needs) then it’s mandatory to set the power levels like this.
If you will use only one power level (recommended until you get used with the burner) then it is necessary only to set the used power setting.
The burner has 3 methods of operation (u03):
- 0 – the burner will start only when the ignition is requested by the thermostat or by a switch (manual). The weekly schedule is ignored.
- 1 – the burner will start when the weekly schedule requests it or when the thermostat requests it or when the manual switch is pressed. It’s very important to understand the „or” in this text. This means that the burner will start when any of the above conditions are met. Usually this method is used when you want a weekly schedule and additionally you want to start it manually. The thermostat and the manual switch are tied together so they will be active one or the other (not both at the same time).
- 2 – the burner starts when the weekly schedule requests it and the thermostat also requests it (or the manual switch). For example, if you set it to function only one hour during the day, the burner will start only in that hour and only if the temperature is bellow the thermostat set temperature (or the manual switch is pressed).
I recommend functioning method 0, with a thermostat, just like a gas burner.
The second menu is accessed by holding down P button (10 seconds – it’s good they didn’t make it 10 minutes…).
The parameters are modified in the same way like on the first menu: P will advance to next parameter, + and – will modify the value.
After you modified a value, you must wait 3 seconds so that it it’s saved. If you jump to quickly to next parameter, the value will not be saved (you must come back and check that the value was saved – annoying).
To quit the menu, hold P until the clock appears again(10 seconds).
Menu P parameters:
- t01 – the burner has no sensor to detect if pellets are falling through the tube or not (the sensor mounted on the tube is a temperature sensor). The burner will just power the auger for x seconds and hope that pellets will fall. Because of this, before you start the burner for the first time you must power only the auger first, until it will be filled with pellets. To do this set this parameter to 1. The auger will spin for 5 minutes (remove the tube from the burner first). After 5 minutes the parameter is reset to 0 automatically. You can set it to 1 again if the auger is not yet filled with pellets. You can do this 3 times. After that you must disconnect the power and reconnect it for 3 more tries.
- t02 – if enabled the burner will stop when temperature will be close to 100°C. The temperature sensor is inside the boilers walls.
- t03 – air pressure (fan speed) during ignition phase (don’t modify).
- t04 – defines what quantity of pellets will be loaded first, before ignition phase. Take care when setting this parameter: the value on the screen must be multiplied by 4. For example, 8 on the screen means it will power the auger for 8 x 4 = 32 seconds.
- t05 – it’s used when the burner power modulation is activated (t18 = 1). Burner will switch from one power level to another depending on demand. For example, if this parameter is set to 5 (5 seconds) then every 5 seconds the burner will modify current power level settings to be closer to next power level setting.
- t06 – defines how long it take to switch from one power level to next power level (only if t18 = 1). I’m not 100% sure.
- t07 – defines the length of a burning cycle (after ignition phase): time to wait for pellets to burn + time to load pellets.
- t08 – t17 – each power level has 2 parameters: air pressure and how long is the period in which auger is powered and pellets are loaded. Pellets loading time is set in tens of seconds (53 means 5.3 seconds).
- t18 – if it’s set to 0 the burner will use only one power level (the one selected by u02); if it’s set to 1 the burner will automatically switch between different power levels (not recommended until you get used with the burner; all power levels must be properly set).
- t19 – post ventilation duration. How long, in tens of a second, the fan will continue to blow after the burner decided it will stop. During this period the remaining pellets are burned and ash is blown away from the grille. Recommended to be a big value, because in this way the grille will not have to be manually cleaned too often.
- t20 – photoresistance voltage ??? 🙂
How SUN P7 pellets burner works
When the burner starts, first it will ventilate the boiler for some time. During this time only the fan works.
After ventilation period, the burner will load pellets for some time (set with parameter t04). The purpose is to have enough pellets in the grille so that the heating element is covered.
After this, the heating element is powered and the fan will blow slowly until the pellets ignite. Ignition is detected by the light sensor.
From this moment on, the burner will enter a cycle. In the first part of the cycle it will not load pellets, in the second it will load pellets. And then it repeats. The duration of the cycle is set with parameter t07. The duration of the period in which it loads pellets is set with parameters t09, t11, t13, t15, t17 depending on the power level in which the burner functions (only one parameter per level). For example, if t07 is 15 seconds, and t09 is 5 seconds, then the burner will wait 10 seconds for the pellets to burn and 5 seconds will load pellets and then it will repeat.
Immediately after ignition, the duration of a cycle is equal with the value set by t07 but the auger will load less pellets than defined by t09, t11, t13, t15, t17 parameters. This is because, initially, it loads a lot of pellets and they need time to burn. That’s why the duration of the loading period is small after ignition but it will increase until it reaches the value set.
The burner was getting blocked all the time because the initial quantity of pellets (before ignition) was too big. So big, that the burner was blocked from the very beginning. The pellets filled the grille and almost all the metal neck. The culprit was parameter t04 which was too big: 8 x 4 = 32 seconds during which pellets were loaded. I reduced in half this parameter and the strange blockages disappeared. This is the only thing you have to modify from the factory settings or the settings that were set during installation.
It is possible that this parameter will not create any problems if you have very good quality pellets.
The pellets that I had were of poor quality which means that although they ignited, they didn’t burn very fast. Immediately after ignition the burner would start to load more pellets, trying to reach a normal working cycle. But, as the burner was almost blocked, the newly loaded pellets jammed it even harder. After it loaded pellets for a few times, it became completely jammed and the light from the fire would not reach the light sensor anymore. At this moment the burner would think that the fire went out (not enough pellets in the grille?) and it would start a new ignition which meant it would load pellets for 32 more seconds! And so, little by little, the loading tube was filled with pellets. After a few ignition attempts, the burner would stop and turn on the error light…
Interestingly, after this moment, the pellets would slowly burn almost completely from the grille. That’s why when I would check to see what is the cause of the blockage all I could see was an empty grille. And, even stranger, at the slightest movement the pellets that were jammed on the tube would start to fall down in the grille, sometimes while I was opening the door.
To find this problem took a lot of time also because in the paper manual that we received from ferroli.ro it was stated to never modify this parameter (?).
The quality of pellets is important. The pellets of poor quality are easy to identify: if when you clean the grille you find large chunks of glass-like waste (see pictures) then the pellets contain sand. The problem is that sand will not generate any heat and chunks of glass will form in the grille so that you have to clean it more often (the fan will blow away any ash but not the chunks of glass).
The pellets must be kept in nylon bags because otherwise they will absorb moisture from air and it will be like trying to burn green wood.
Pellets of good quality have pretty large chunks of wood inside them (you can see this when you break them). The poor quality ones are more dusty. I recommend you to buy good quality pellets because any savings that you will get from poor quality pellets will be canceled by the fact that sand will not generate any heat and also, the sand is quite heavy.
The burner SUN P7 from Ferroli has a minimum of automation, which means that is has no extra sensors apart from was is strictly necessary to function and for safety. There are burners that can measure the exhaust gases for example. For SUN P7 these are measured only after the installation and anyway, theoretically, if you change your pellets you have to measure them again and fine tune the burner.
The burner has some annoying things like:
- the screen is to little and too crowded.
- the fact that you must press the menu buttons for 5 or 10 seconds (why not 5 seconds for both menus? 10 seconds is too long).
- the weird way in which parameters are displayed: u01 with value 80 will be displayed like so u 80 01.
- after changing one parameter you have to wait for 3 seconds until the value is saved, without any indication that the value was saved.
- the fact that the burner is working is showed by only one segment of an 8 digit.
- the grille is fixed with a screw to the cylinder in which it sits so you have to take it down every time you want to clean the grille (luckily it’s easy to replace it with a stud).
- the boiler door is closed with a nut. So every time you have to clean the boiler you need a wrench. At other boilers the door is closed with a nut with handle. Much easier to use.
- the boiler does not show what it tries to do: pre-ventilation, ignition, normal working cycle, post-ventilation etc. but maybe I want too much 🙂
- the burner door can be mounted without taking down the original boiler door. One has hinges on the left, the other one on the right. This means that you can quickly switch from pellets to wood when you need to: just open one door and close the other.
- in order to be able to open the boiler door easily, do not let the workers cut the electric cables too tight or to fix them on the boiler. The cables must be long enough so you can fully open the door because you need to clean not only the burner but also the boiler (door must be able to open 180 degrees). In the same way, the loading tube must be longer.
- in order for the door to open 180 degrees, the pellet hopper must be placed behind the front line of the boiler.
- the boiler should be placed high above the floor so that you can easily take out the ash and also to be able to clean under it.
- the hopper must be placed high enough so that the level difference between the auger head and the top of the metal neck from the burner to be at least 60cm.
- the pipes behind the boiler should be connected in such a way that they allow easy access to chimney for cleaning.
- the advantage of a pellet burner is that you can use wood (pellets) to heat your house but in the same time you can set your room temperature with a thermostat. And you don’t have to load wood every 4 hours like with a regular wood boiler.
- however you are still burning wood which means that you will have the same quantity of ash and dust and that you will have to periodically clean the burner and the boiler (that’s why you should organize everything so that the cleaning is easy).
Even with the shown defects, SUN P7 is a great burner that works very well once you set it up.