Hot water venting over

[howy1]

Is it possible to check out wether a boiler stat is defunked before commiting to a new one , its on an oil boiler HRM wallstar and the symptoms are hot water out of vent into heating expansion tank .
Cheers

 

[Softus]

Turn down the stat to minimum - does it still happen?

Have you considered other possible causes, such as a [partial] blockage?

When was the most recent work carried out on the system?

Was a chemical corrosion inhibitor added?

 

[howy1]

Softus , thanks for replying , i have turned the stat down from 80c to 70c gradually and i dont think much has changed , could you explain further the partial blockadge theory as in where and how it affects the system.
thanks mark

 

[Softus]

When was the most recent work carried out on the system?

Was a chemical corrosion inhibitor added?

 

[howy1]

Its a friends system and to be honest i dont think its been worked on much apart from i think he changes the nozzle once a year as far as inhibitor goes i will have to ask him , do you think the system is getting sludged up ? cheers

 

[Softus]

do you think the system is getting sludged up ? cheers

If it started with cleanish water and was treated at the correct concentration, then I don't; otherwise I do.

 

[howy1]

So if that is the case the whole system would need a flush out , would this be a power flush or could we get away with less . thanks mark

 

[Softus]

I think you should post more information first - please read this.

 

[howy1]

Here goes ...
1) HRM Wallstar wallhung oil boiler
2) Hot water/steam coming out of vent to heating expansion tank , consequently out of overflow .
3)No
4)Approx 1.5 weeks - Water coming out of overflow
5)When heating / hot water system has been on a while
6) It is a Y plan system - not sure wether it is inhibited .
Cheers
mark

 

[Softus]

Well, I've have to assess the state of the water in the system, initially by looking into the F&E (feed and expansion) cistern (usually in the loft), but also by draining down and watching the colour of the water coming out.

Another barometer of what's going on is the amount of ferrous material deposited at or near the junction of the cold feed into the primary circuit. If you wander over the pipework near the pump and MZV with a strongish magnet, do you find anything?

Another sign of corrosion is the presence of cool areas at the bottom middle area of some radiators (usually downstairs ones).

Yet another is the need to regularly vent the radiators - the corrosive reaction generates Hydrogen, which people often think is air.

 

[howy1]

Turned stat down , still hot so new one on teusday .
Many thanks for your help softus i have also learnt more from your other info cheers