Hot water heating up in several stages.

[NowWhyisThat?]

Anyone who can answer me this one? Recently had my Annual boiler service. I have a conventional boiler ( a Worcester Greenstar Ri). Since then I have noticed that the hot water in my hot water cistern is now heating up in 2 or 3 separate stages of “burn” from the boiler, rather than in one sustained “burn” from the boiler, which was the case prior to the service. The water is indeed reaching the required 60c temperature as set on the cylinder stat, and the boiler then shuts off as per usual. I’m just curious to know what has been done by the servicing engineer to cause the hot water to now heat up in several stages. Do I have a “dodgy” cylinder stat? Or what?

 

[picasso]

What are the boiler and cylinder stat set at ?

 

[NowWhyisThat?]

Boiler set at number 4. Cylinder stat set at 60c.

 

[picasso]

I have no idea what 4 equates to in terms of degrees c so I can only suggest you turn up the boiler stat and see if that improves the burn time.

 

[NowWhyisThat?]

Thanks for your input my friend. Much appreciated. Number 4 on the boiler is certainly hotter than 60c. Number 6 is “hottest” (sorry for using layman’s terms). Is it normal for the HW to reach required temperature in several “stages” of burn from the boiler (especially after a service). I’m just trying to figure out in my head what exactly is going on. It seems that the boiler is taking a short 3 minute break between “burns” while perhaps the cylinder stat is sorting itself out. That’s why I wonder if the cylinder stat is slightly faulty. Each “burn” lasts slightly shorter in time from the previous one (that’s after the initial 20-25 minute burn immediately after someone has a long shower). The second “burn” lasts for around 5 minutes and then the third “burn” for around 3 minutes, and then the final burn for no more than 2 minutes. The Central heating doesn’t do this (have checked that). I just wonder what is going on to cause this.

 

[fixitflav]

Is it normal for the HW to reach required temperature in several “stages” of burn from the boiler (especially after a service).

I don't think there's a problem. If the boiler control-stat is reduced, that temperature is reached and the flame stops (pump keeps running) before the cylinder stat temperature is reached. Then it re-fires after the water cools a bit. Mine does same thing in 4-5 stages, it's an old cylinder and probably plenty of scale on the outside of the coil. Sounds like the service guy left it with the control-stat lower than it had been. If it's a problem to you, turn the control-stat up, as picasso suggested.

 

[Hugh Jaleak]

The Boiler has it's own stat, which switches the burner off when the water within the boiler reaches set temperature. The Pump will be moving that heated water around the system, but until sufficient heat is dissipated into the stored water in the cylinder, (or the radiators or both), and the returning cooler water to the boiler then lowers the internal temperature of the water, (within the boiler), then the boiler will not fire again.


Possibly the service has made the boiler more efficient, so it is getting the heat into the water quicker, thus is taking longer to dissipate that heat.

 

[NowWhyisThat?]

Gentlemen.Thank you so much for taking the time.