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14-10-2010, 01:44   #1
sector_000
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Vokera gas boiler - low pressure

I barely understand gas boilers and how they are plumbed in... so bear with my question! Apologies for the length!

My Vokera Mynute boiler pressure guage has always been low - in fact close to 0 bar (around 0.1~0.2 bar). Red zone for this boiler is 0 to 0.5 bar!
I had it checked & serviced today and the RGI technician said the boiler was fine but that the water pressure should really be ~0.75bar (out of the red zone). He looked in my hot press and opened/closed some valve in
a pipe running alongside the hot tank. He says this is the valve that fills up the radiator system from the attic tank. He was surprised not to hear any sound of water travelling thru the pipe... and suggested I get a plumber to look at the valve. He suspected that the valve was blocked or the pipe air-locked.

Questions:
Any ideas what is causing the boiler low pressure?
Is it harmful?
What do you recommend?
Should this hotpress "fill-up" valve be open all the time?


I traced the pipe with the fill-up valve and it does indeed go between the smaller of my 2 attic tanks... and something big pipe at the bottom of my hot tank. There are actually 3 valves on this pipe.... highest was an old wheel handle one, middle was the one the RGI man twiddled, bottom is another similar to middle but only operated by screwdriver.
I unscrewed the flex pipe below the middle valve... and then could confirm/check that water could come thru the other 2 valves just fine.

If I turn off the valve, the boiler doesn't like it and shuts down, with lots of gurgling sounds. When I turn the value on, the boiler comes on... but got lots of gurgling in the radiators - I then bled some air out of one the rads.

I notice that with the fill-up valve open... that that pipe that goes up into the attic is quite hot.
Question
: Does this mean hot water is being pushed all the way up into the attic water tank?

I very much appreciate any help/tips!
Thank in advance.
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14-10-2010, 09:27   #2
heinbloed
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re.

You might have the wrong systems combined. The boiler MIGHT not be suitable for a vented/open circulation system.
Check this.

About hot pipes leading into unheated/unused space: these do indeed waste thermal energy, money.

Looking at the chance that a.)the systems are are not compatible and b.) the unwanted thermal loss of the system is to be reduced you could go for a pressurised CH system. Without tank in the attic, no pipework going there. And an insulated hot press. Or freed space when demolishing the hot press.
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18-10-2010, 19:55   #3
foxinsox
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I also have a Vokera boiler..not sure if it's the same model as yours though... I checked mine is a Vokera Mynute 14SE

I am no expert... just telling you my own experience...

My house was built around 14 years ago... I reckon the boiler was thrown in...literally..

I have to fill the tank (the fill valve thing) with a plyers every 2 days when I am using the heating..

I did leave the valve open once...... Disaster ... it was not a good idea

Water leaking out of every single rad..

There are about 100 houses here and every one of them have to manually fill the tank every few days.. and it is a pain..

Mine probably needs a major over haul, but once it keeps working I just bleed the rads, have a cup under the drippy rads as I reckon it will cost me a fortune to get it all done properly!!!


Sounds like you need a professional to check it..

Last edited by foxinsox; 18-10-2010 at 20:17.
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18-10-2010, 20:25   #4
sector_000
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Quote:
Originally Posted by heinbloed View Post
You might have the wrong systems combined. The boiler MIGHT not be suitable for a vented/open circulation system.
Check this.

About hot pipes leading into unheated/unused space: these do indeed waste thermal energy, money.

Looking at the chance that a.)the systems are are not compatible and b.) the unwanted thermal loss of the system is to be reduced you could go for a pressurised CH system. Without tank in the attic, no pipework going there. And an insulated hot press. Or freed space when demolishing the hot press.
I looked in the Vokera manual and it describes how it is to be connected to a "filling point". It says it should be connected thru an approved non-return valve and stopcock for isolation purposed". I don't know enough to be able to identify/recognise what is used in my house .
However, when the boiler is on, I can feel that this fillup pipe gets hot... and this pipe gets warm right up to the water tank in the attic - 3 metres above it.

Sounds like I need a plumber to look at this and give a professional analysis.
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18-10-2010, 20:29   #5
sector_000
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Quote:
Originally Posted by foxinsox View Post
I also have a Vokera boiler..not sure if it's the same model as yours though... I checked mine is a Vokera Mynute 14SE

I am no expert... just telling you my own experience...

My house was built around 14 years ago... I reckon the boiler was thrown in...literally..

I have to fill the tank (the fill valve thing) with a plyers every 2 days when I am using the heating..

I did leave the valve open once...... Disaster ... it was not a good idea

Water leaking out of every single rad..

There are about 100 houses here and every one of them have to manually fill the tank every few days.. and it is a pain..

Mine probably needs a major over haul, but once it keeps working I just bleed the rads, have a cup under the drippy rads as I reckon it will cost me a fortune to get it all done properly!!!


Sounds like you need a professional to check it..
mine is model "28e".

I have no problems (no leaks) when I leave the fill valve open... except that I seem to be loosing some heat up into the attic thru the fill-up pipe connecting to the attic water tank 3metres above it.
Maybe I am missing some (lot!) understanding here, but I don't understand how my boiler (with some ultra low pressure.... close to zero bar) can push hot water up 3 metres into the attic.
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18-10-2010, 20:43   #6
foxinsox
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Quote:
Originally Posted by sector_000 View Post
mine is model "28e".

I have no problems (no leaks) when I leave the fill valve open... except that I seem to be loosing some heat up into the attic thru the fill-up pipe connecting to the attic water tank 3metres above it.
Maybe I am missing some (lot!) understanding here, but I don't understand how my boiler (with some ultra low pressure.... close to zero bar) can push hot water up 3 metres into the attic.
Completely amateur girly advice to follow:

would all the water pushing in from the mains (fill valve open) be pushing the it up..hence your pressure so low????

Have you tried it with the fill valve closed, but first making sure it is full to the correct water level???

I haven't a clue to be honest
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15-11-2010, 23:27   #7
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Solution

I had a plumber look at it - he put a non-return valve between the hot tank and the filler/header tank in the attic. Pressure in the boiler crept up to around 0.5bar....
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16-11-2010, 18:59   #8
heinbloed
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Plumber-check

Well done, sector_000 !

0.5 pressure bar pressure in the system means with an open(vented) system around 5 meters diffference in height between the pressure meter and the water level of the tank. Does that sound right? Any problems since ?

This non-return valve will safe a bit on the fuel bill as well, stopping the thermosyphoning losses for a good deal. Make sure the pipe between the non-return valve and the tank is insulated anyhow, now it draws less heat the exposed parts of it might freeze easier.

Last edited by heinbloed; 16-11-2010 at 19:04. Reason: recommended pipe insulation
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16-11-2010, 20:28   #9
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Update

Heinbloed:

yep... it's about 5metres.
I had to google "water pressure bar" to see where you figured that out from!

I'm happy to report that the NRV now stops heat leaking up into the attic.
I already had the pipe between the NRV and the filler tank insulated.

Heating system seems to be working nicely now - just in time for winter.

Thanks for all your helpful suggestions.

Last edited by sector_000; 16-11-2010 at 20:29. Reason: typos
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