The Heating System

The controller unit is mounted inside the left-hand cupboard above the sink in the laundry. This provides the continuous control of the 3-way valve according to its programming.

The unit has 3 sections for its programming and a display of its current control status.

The indoor thermocouple with comfort dial is mounted on the North lounge room wall.

It has a red LED light that is on when the indoor temperature is below current target, and off when it is above.

The target can be varied with the control dial to "a little bit" lower or higher temperature; the full swing is roughly -4C to +2C relative to the programming of the control unit. In principle this setting just adds to the controller unit’s middle control dial (the level of the curve).

The motor controlled 3-way valve is found outside by the West wall, to the left of the heater, and usually covered by a plexi-glass hood.

The control handle leans right when closed and left when opened. The 3-way valve has the hot inlet at the top, the cool return inlet at the left, and its mixed outlet at the bottom.

The circulation pump is mounted on the radiator return flow to the left of the 3-way valve.

The pump has an airing screw covering the rotation axis (the West oriented face) and a speed setting dial on the left side. The settings are "low", "medium" and "high", and the current setup is designed for and tuned to the middle (medium) setting.

For maximum service life, the circulation pump is best left on at all times since the circulating water lubricates it and keeps corrosion at bay. If needs be, the pump may be turned off by the heater switch (together with the heater control system). The pump power cable is fixed inside the switch while the heater is via a power plug.

The outdoor thermocouple is in a box that is mounted on the West wall above the shed roof and shaded by the rain water down-pipe.

It’s important to keep it clear of leaves so it can capture a true air temperature.

The forward flow thermocouple is hidden in the pipe insulation.

There is no maintenance needed for this apart from making sure that the lead, which hangs loose from the controller unit cable outlet, is undisturbed.

The hot water airing nipple sits to the right at the back of the heater.

This is only used when the system is refilled with water, to ensure that there is no trapped air in that part of the piping.

Each radiator has an airing nipple at its left or right top end, typically straight above its control valve.

These are used (opened) when the system is refilled, to release any trapped air accumulated in the radiator. A radiator with trapped air is cooler at the top than in the middle, and it may also have a "bubbly" sound.

The heater airing nipple is found behind the heater door on the protruding water pipe to the right.

This is only used when the system is refilled with water, to ensure that there is no air trapped in the heater tank.

Each radiator has a balancing valve which is a screw covered by a screw-on lid.

The balancing valves are used so as to achive a flow balance among all the radiators, and avoid that the heated water flows too fast through some radiators while not at all through other. Balancing is a slow procedure that involves adjusting one of those that seem too open or too closed by half a turn, then wait an hour or so to check again that all radiators feel just right: a functioning just right radiator should feel cool at the bottom and warm at the top, transitioning rougly in the middle.

Each radiator has a control valve opposite to the balancing valve, and these are either thermostat valves or manual valves.

A thermostat valve opens and closes the valve automatically depending on whether the local temperature for the valve is below or above its setting, determined by the position to which it is turned. The lowest setting is about 12 degrees, and the highest setting is 22 degrees (or more accurately, as "physically programmed" into the valve knob by releasing the the metal lock pin, then twisting the dial as appropriate, and then push back the lock pin)

Each radiator has a control valve opposite to the balancing valve, and these are either manual valves or thermostat valves.

A manual valve is opened or closed manually and it stays as set.

The gas valve is found to the left at the back of the heater.

It is open when the "wings" are vertical and closed when the wings are horizontal.

The gas control knob is inside of the heater door, and to the left, on the gas control house in the middle behind the heater door.

This is pressed and turned slightly to allow the flow of gas, firstly a limited flow for lighting the pilot flame and secondly the main gas flow for the heating. It must be held pressed down while operating the ignition button for starting the pilot flame, and then be slowly released until it stays without pressure, enabling the main gas to flow and be ignited by the pilot flame.

The knob remains down while the heater is operating, although the heater will turn off and on the main flame as needed according to its own thermocople. The heater operation is programmed with the heater temperature dial.

The heater ignition button is inside of the heater door, mounted on the gas pipe below the gas control house in the middle behind the heater door.

This is a piezo-electric igniter for the heater’s pilot flame, and it is pushed, maybe repeatedly, while holding down the gas control knob for igniting the pilot flame.

The pilot flame inspection hole lid is found inside of the heater door, further down just above the burner unit and slightly behind the main gas flow pipe.

The lid gets hot and should be closed when the heater operates. When opened one can look down into the burning chamber to see the pilot flame nipple and the flame itself, if any. Obviously useful when turning on the flame, but the lid should be closed otherwise.

The presure sense bypass is seen inside the heater door, in the middle and slightly below the gas control housing.

The bypass is done by the ad-hoc connection of the two cables instead of connecting them to the low-pressure sensor, which aged and became faulty. Instead one must keep a light eye on the system to avoid the heater running without tank water, since if it were to run without tank water the temperature sensor may fail to detect enough heat to turn off the burner before there is other damage to the unit.

"Monitoring" the system usually means to just notice that the house is cosy as per normal, and it only requires action when that’s not the case. Then: check that there is water pressure above 0.5 [kg/cm²] that the pilot flame is burning, then that the 3-way valve operates and that the circulation pump works. (Refer to "Temperature and pressure gauge" below)

For me it has been only to find that the pilot-flame has gone out, which may happen due to a very strong wind, or twice in late summer when I reduced the tank heat level too much (which seemingly for some reason led to the pilot-flame exhausting as it got cooler outside).

The heater switch is mounted on the West wall to the right of the heater.

This turns off the electricity to the heater via the plugged in cord. It powers control logic including the relay valve for the main gas flow but it doesn’t control the pilot flame.

The circulation pump also gets its power from the heater switch via the separate cable from inside the switch.

The combined temperature and pressure gauge is found inside the heater door, high up to the left.

The larger dial shows the temperature of the heater tank water, which typically varies between about 50 degrees and about 80 degrees. The smaller dial shows the water pressure in the tank, in bar, where "1" indicates a 10 m water pillar.

When the system is filled, the tank pressure should show at least 0.5 since that’s the height difference between the water tank and the top of the upstairs radiators. When heated the pressure may rise above 1, depending on how much air there is in the system.

The heater temperature control dial is found inside the heater door, high up to the right.

Although it has numbers there is no strong correlation between those numbers and actual tank water temperature. It does however serve to control roughly where the temperature interval is, although there is generally no need to change that at all.

The outlet valve is found inside the heater door, at the very bottom.

This valve is opened for emptying the water from the system. Make sure the heater is off, eg by turning off the gas valve, before emptying. The system holds about 100 litres of water.

The water inlet valve is found straight behind the heater, accessible from the right.

This is actually a pressure-difference valve with a manual open/close setting. When closed it doesn’t let water through and when opened it lets water through until its outlet side reaches the programmed pressure. It is programmed by adjusting the pressure spring at the opposite side from the valve grip.

The water inlet valve pressure spring is found straight behind the heater, accessible from the left.

The spring is loosened or tightened with a screwdriver. It should be adjusted such that the valve closes when the heater tank pressure is 0.6.

In normal operation, "turning off" means only to switch the controller unit mode to "off" and leave all else running as per normal. Setting the control unit to "off" mode causes it to close the 3-way valve, which stops any hot water from being consumed. Otherwise:

"Normal operation" can only be verified when the outdoor temperature is a few degrees below the desired indoor temperature. Basicaly the daily maintenance observation is merely to confirm that it’s a cosy 22 degrees (thereabouts) inside regardless of outside temperature.

In more detail, the radiators should be radiating heat and ideally be warm at the top and cool at the bottom. By sliding a hand from bottom and up, the warmth should be first felt close to the vertical middle of the radiator.

The radiator’s balancing valve may be used to adjust it; opening it will lower the cold-warm line and closing it will raise the cold-warm line of that radiator. Note however that such a change actually affects the flow through all radiators, and that system balancing needs to be done slowly, incrediby slowly, by changing one valve at a time by only half a turn with an hour or so in between successive valve changes.