Weissmann boiler problems

[Dc]

My brother has a maison secondaire with a Weissmann fioul boiler. Whenever he switches it on it always heats the domestic hotwater first before the radiators come on. Is this normal here as when he is not using the house he wants to heat it when it is cold but obviously won't need domestic hot water.

Also the boiler has a frost sensor outside but when its really cold the boiler keeps firing and in a cold spell is on permanently and as there is no internal thermostat it just drinks the oil. Any help/advice greatly appreciated.

regards

dc

[Gluestick]

From your description, what is perhaps needed is the following:

1.    A room thermostat to regulate the internal temp, plus Thermostatic Radiator Valves if not already fitted:

2.    A modern programmer which allows the choice of DHW and CH or DHW only, or CH only. (DHW=Domestic Hot Water: CH=Central Heating).

3.    Motorised "Demand" valve/s to  control and regulate DHW and CH functions.

The programmer will allow the regulation of hot water to a Nil state, via the motorised valve.

A frost stat will keep the boiler working, unless it is interrupted by another control device (e.g. room stat), if the external temp drops beneath the "on" value of the frost stat. The idea is to prevent pipework inside from freezing up, during a cold snap. If there is no internal stat, however, then control of the boiler is predicated by the frost stat, only: and as long as it's cold outside, then the boiler will simply keep going!

There should be a boiler stat inside the boiler housing. Try turning this down. If one of those awful French plumber's delights is fitted which regulates (or is meant to!) water flow and temperature of water returning to the boiler ( Vannes melangeuses 3 ou 4 voles) try adjusting this or better, bin it and fit the motorised valves!

 

[Gyn_Paul]

[quote user="Dc"]

My brother has a maison secondaire with a Weissmann fioul boiler. Whenever he switches it on it always heats the domestic hotwater first before the radiators come on. Is this normal here as when he is not using the house he wants to heat it when it is cold but obviously won't need domestic hot water.

Also the boiler has a frost sensor outside but when its really cold the boiler keeps firing and in a cold spell is on permanently and as there is no internal thermostat it just drinks the oil. Any help/advice greatly appreciated.

regards

dc

[/quote]

How exactly does it "always heat the DHW" first ? Does it have a 3-port motorised valve? If so, it's wired to supply the demand ("call") for the hot water first.  In all likelihood it also has a thermostat on the HW tank. He simply needs to turn this right down when he leaves the house (or better yet fit an override switch) Thus the cylinder won't be able to call for heat for the DHW.

Agree with Gluestick:  internal room thermostat is an absolute must, otherwise in cold weather, the boiler is attempting to raise the temperature of the air round the external sensor, by heating the external walls until they glow! 

p