Why why why?

[Dmuggy]

I'm a total novice so please bear with me. I've just had my annual boiler check from my gas supplier (inc as part of my tariff), and i'm a bit confused. I have a worcester cd24i boiler fitted, it's about 14 years old and so far has only ever needed the pump replacing. The engineer has issued me with a warning notice on the boiler as he said that there is no water discharge pipework from the boiler, and that it has been capped. He said that it would leak if the system was to be over pressurised, and although should be safe to use, it needed fixing immediately. He tried to pressurise the system, which has been on zero since it was installed (as far as i can remember), but although there was a hissing noise the guage didn't register a change. This is the third annual inspection in as many years, and the prvious two engineers tried but failed to increase the pressure, and left knowing that the boiler works. He said that if pipework were fitted correctly, and poss. replacement of pressure guage, the system would work correctly. Currently i can only get hot water if i turn the tap right down to slow, this has always been the case. Anyway, my question is, why would anyone fit a combi boiler, not pressurise it, and not include any pipework should the system need to overflow? Is the engineer wrong, and the system doesn't need pressure? Thankyou in advance for any advice.

 

[bonzo1974]

I suspect that the boiler is pressurised, just to mains pressure at 3.5 Bar or whatever it is where you are, and that the gauge is faulty. A combi normally cuts out if the pressure isn't high enough to protect itself against firing the burner with no water in the heat exchanger which might well damage the system.

If the radiators bleed out when you open the bleed vents then there's pressure in the system - probably not the right pressure, but pressure anyway.

The engineer was quite right in warning you about the safety valve which should have an exit in case the system overpressures above 3 Bar, also to protect the boiler and C/H system. It MUST be sorted as soon as possible as it is a safety device. Why someone would cap a pressure relief valve terminal is crazy in the first place - whoever did it should be shot at dawn!

I wouldn't be surprised if the gauge were replaced you'd see pressure in the system, but the PRV must be sorted asap mate.

As to the hot water, a combi will give you hotter water if the flowrate is lower as it sends more time in the heat exchanger getting hot in simplest terms so this could be normal, but might need looking at if it's just a dribble!!

Hope that helps, sorry if I have been teaching you to suck eggs!!

 

[Dmuggy]

Hi, thanks for replying but i think i've got an answer from a different forum...

Seems that i have an unusual boiler set up. My boiler is open vent, and has a tank in the loft.

 

[kay-jay]

nowt unusual about that

 

[Dmuggy]

nowt unusual about that

Unusual enough for a scottish power engineer to issue a warning notice, and report the problem as needing immediate attention.

 

[snowhead]

Sitting here sniggering at all the people over the years trying to pressurise this open vent system.:smilielol5:

 

[SimonG]

.....Delilah!

Couldn't resist 🙂 🙂 🙂

 

[Millsy 82]

Sitting here sniggering at all the people over the years trying to pressurise this open vent system.:smilielol5:

I spent ages once looking for the filling loop and then noticed an extra pipe and it suddenly hit me I was an idiot.

 

[tamz]

Unusual enough for a scottish power engineer to issue a warning notice, and report the problem as needing immediate attention.

That is because he is thick as mince

 

[kay-jay]

Unusual enough for a scottish power engineer to issue a warning notice, and report the problem as needing immediate attention.

lol i meant nothing unusual about a system that has tanks in loft :wink5:

 

[REDSAW]

hang on!

why is there a pressure gauge then?

 

[tamz]

Because it was fitted when the boiler was made.
Just because your car has a sunroof doesn't mean you need to use it :smile:

 

[TomLane]

And how we're they actually trying to pressurise the system if it's open? Surely it fills from F&E alone? The mind boggles sometimes.

 

[mountainman]

Because it was fitted when the boiler was made.
Just because your car has a sunroof doesn't mean you need to use it :smile:

Har Har, 🙂🙂🙂

 

[tamz]

The old cdi's came with an expansion vessel, prv, and a built in filling link (much the same as the new ones only a bigger key).
You could convert them to open vented by removing the auto air vent and fitting the open vent kit.
Someone trying to fill it would push water into the FE tank and out the overflow.

Anyone with half a brain would have looked up and seen the pipe coming off the top left hand corner and at the very least wondered what it was.

 

[theanalyst]

The old cdi's came with an expansion vessel, prv, and a built in filling link (much the same as the new ones only a bigger key).
You could convert them to open vented by removing the auto air vent and fitting the open vent kit.
Someone trying to fill it would push water into the FE tank and out the overflow.

Anyone with half a brain would have looked up and seen the pipe coming off the top left hand corner and at the very least wondered
what it was.

makes much more sense!!! hilarious story though

 

[TomLane]

Yes, thank you Tamz. Makes perfect sense now. Like you say though, surely a quick visual check would point out the obvious!!

 

[plumb_know]

can someone explain to me why you would have a combi boiler with all the safety devices fitted to it then convert it to a open vented system for the CH, what are the advantages of this?? why would the engineer not just install it as a pressurised heating system as it wouldn't of cost more if it has the expansion vessel and safety devices already fitted in the boiler and remove the old cistern to reduce chance of pipework in loft freezing and bursting??

may be a stupid question, just trying to establish the advantages of keeping it a open vented system??

 

[Ray Stafford]

If it was a boiler replacement going on an existing system, perhaps they didn't have faith in the existing pipework holding up under pressure?

 

[plumb_know]

yeah makes sense cheers for replying 🙂