Potterton Flamingo Boiler Question

8 Nov 2010
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United Kingdom
Good morning,

I have what seems to be an incredibly old boiler in my house, and I’ve been tearing my hair out trying to figure out the best way to regulate my central heating.

The boiler is a Potterton Flamingo RS 20; I have TRV’s fitted to all the rads, but no other temperature control (i.e. wall mounted thermostat).

On the boiler itself is some form of temperature control, which from the user guide states the following:

The boiler thermostat enables you to control the temperature of the water as it leaves the boiler and it is also used for turning the boiler off and on. The thermostat knob can be set to 0 (OFF), Min, 1, 2, 3, 4 or Max. The graduations Min. to Max. correspond approximately to a temperature range of 55° to 82°C (130° to 180°F).
During the summer months when the boiler is only being used to supply domestic hot water and there is no independent hot water temperature control, the thermostat can be set to position 1 or 2 which will probably be hot enough for bathing or washing up requirements. For washing clothes, a higher setting may be necessary.
In winter months when central heating is required, the thermostat knob can be turned higher but it must be remembered that unless the temperature of the water in the domestic hot water tank is independently controlled the stored hot water could be at a temperature that could scald.

(I have what I think is an immersion heater upstairs to control the water and this is on a seperate timer to the one used to control the boiler)

So what I read from that is that the higher the setting, the hotter the water becomes before reaching the radiators? However, I would say the difference is minimal and I find the only difference between 1 and 4 is the amount of times the boiler ticks over and fires up whilst on. Is this how it should work?

So on to the TRV’s….I am confused about how these actually work? If you say set the TRV to 4, does the rads stay at this constant temperature whilst the heating is turned on? Or do the TRV’s work on the basis of the room temperature reaching level 4, and then cool/heat accordingly to maintain this temperature?

I ask the question because I have previously had all the trv’s set to MAX, and the temperature of every RAD stays constant whilst the heating is on. However, when I have then turned them all down to 4, I find that some radiators maintain a constant temperature and others seem to cool very quickly, heating up occasionally whilst the heating is switched on (generally when the boiler fires up, the rads get hot and then they cool down again).

What I would really like to know is, based on the rather outdated system I have, what would be the best way to use the system when the heating is on for long periods (e.g. on all day). Should the boiler temperature be set low and the TRV’s high? Should I keep the boiler temp on high and regulate the temperature through the TRV’s? Or would a combination of the 2 be better?

Any advice would be greatly appreciated.

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TRVs adjust the output of your radiators relative to the room temperature. They should begin to close, so the rad. begins to cool a bit, as the room temperature approaches the temperature selected on the TRV control knob. Set your TRVs to what you consider a comfortable room temperature, and they should automatically adjust the radiator output to maintain that temperature.

If set to Max, the TRV will stay fully open no matter what the room temperature is.

A poorly positioned TRV may just be sensing the air temperature immediately around the rad. rather than the general room temperature, and close before warming the whole room. You may be able to compensate by selecting a higher temperture on the errant TRV.

A good starting point would be to make sure the system is correctly balanced, so each rad. gets it's fair share of the boiler output, and the return temperature to the boiler is within the expected limits. There is information on balancing in the wiki / FAQs.

A correctly balanced system may be better able to take care of both your hot water and heating needs without resorting to the immersion heater.

Whether the boiler output should be high or low.... do you have your money on the tortoise or the hare in this particular race? As your boiler manual suggests, your hot water needs may become the governing factor with the limited controls fitted to your system.
Any advice would be greatly appreciated.
Get a room stat. You are tipping money down the drain without one.

You need a cylinder stat as well but it is unclear if you have one, or if you have a 3-port motorised valve to direct ther primary flow to the cylinder nd/or radiators.

Some photos of your controls and the pipes, cables and devices around your boiler and cylinder will help. There is a slim chance you have a cyltrol or tapstat heat-sensitive valve fitted on the return connection of your cylinder.

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