Help gratefully appreciated on 3mb drop

[mikimac]

Hi, I'm a new gas engineer & have a job where I've increased a pipe run as the old pipe was inadequate for the existing 31kw boiler & a new 12.95kw range. I did, as usual tape the ends of the 28mm pipe when taking them into the loft especially as this loft not only had rock wool but was full of vermiculite too.

After tightness i purged the boiler & the air/gas pressure exiting the open pipe seemed good ie no sound of blockage or struggle. The problem I have is this.. Working pressure at the meter is 22mb. Working at the boiler inlet is 19mb so this I would indicate as a blockage (working pressure on the range taken at the boiler is 22mb) but before I go cutting the pipework to check it all I wondered if it could be a filter on the gas valve before p1 (if that's where the filter is) any advice would be gratefully appreciated.

The pipe run is:
17m x 28mm & 4m x 22mm to boiler
6m x 15mm to range

 

[mikegas]

Check the manufacturers instructions for the boiler as some manufactures allow more loss due to restrictions before the test point on the gas valve

 

[mikimac]

Thanks mikegas, I spoke to Vaillant technical & did a flue gas analysis which was perfect. Valiant said they were looking for a minimum 17mb at the boiler & as I had 19mb & good co & co2 they were happy but it's been bugging away at me all weekend as to why the drop.

 

[arran197]

What is the meter out let? Same size as 22mm?

 

[mikimac]

Hi Arran197, yes it's 22mm.

 

[arran197]

Never a good thing as the volume of gas will always be restricted, even using 28mm. Could do with a bigger meter outlet, but I don't know if/where they are available from. Is it a long run and what was the drop before?

 

[mikimac]

Thanks arran197, I haven't heard of a bigger outlet on a meter. The run to the boiler is 17m x 28mm & 4m x 22mm. I didn't check the inlet pressure when I first looked at the job. All I did was tightness test on existing & as it was 14m x 22mm & 7m x 15mm I knew that it would be insufficient for the new range.

 

[SimonJohns]

Thanks mikegas, I spoke to Vaillant technical & did a flue gas analysis which was perfect. Valiant said they were looking for a minimum 17mb at the boiler & as I had 19mb & good co & co2 they were happy but it's been bugging away at me all weekend as to why the drop.

Only way to get a true working pressure at the appliance is to cut a test point in to gas pipe below boiler

There is a technical bulletin about vallants and their working pressures

 

[mikimac]

Hi SimonJohns, Thanks for your advice. I still don't understand why I'm getting a 3mb drop from meter to the appliance. Do you know if there is a filter on the gas valve before p1 that could be blocked & therefore show as a drop? I will check out the technical bulletin you mentioned.

 

[SimonJohns]

I'll try and fin the tb for you

It's mainly because of the small gas iso on entry to the appliance. And it is very fustrating but I think it's just poor design from the engineers. Your pipe work will be fine

 

[SimonJohns]

I'm on my phone but I think it's tb033

 

[mikimac]

@ SimonJohns, thanks a lot, it is TB033 but I can't seem to be able to open it on the GSR login page on the iPad but I will check later. I really appreciate all the input. I phoned Gas Safe Tech re this problem & was told that I 'had a rat in my pipework' & it must be blocked! He then pretty much hung up on me. Good to know the body we are supposed to turn to supports us in times of need.

 

[CMairiD]

Hmm, I was interested to see whether Valliant's TB was similar to Worcester Bosch's (TB 115). I couldn't find it, so had a wee look at the TB index and it appears that Valliant withdrew that TB 033 in Sept 10.

 

[mikimac]

Hi CMairiD, I also saw that it had been withdrawn but I wasnt sure whether that applied to models produced after that date. The boiler in question was a 2007 install. I will check this evening.

 

[mikimac]

*update* Seems like Technical Bulletin 033 has been removed without trace. At least I know there was some issue with gas valves & pressure loss on Vaillant Ecotec boilers up to 2010. I will investigate further & post any findings. Thanks again to all who posted.

 

[Ian10261]

Only way to get a true working pressure at the appliance is to cut a test point in to gas pipe below boiler

There is a technical bulletin about vallants and their working pressures

Had a Gasafe inspection a few weeks ago and the bloke said just call the boiler manufacturer and ask wot the permissible drop is through the gas valve.

 

[mikimac]

Thanks Ian10261. I will call Vaillant and check that. It still bothers me that Gas Safe Technical were so dismissive of what I was saying & were pretty much adamant that I had a blockage in my pipework & to get off the phone & sort it out. There is a letter in this months Registered Gas Engineer saying similar & their response is quite dismissive. I will definitely think twice before calling them for advice in the future.

 

[Ian10261]

my inspector came across as a decent bloke but gave the impression that you dont mess with him, having said that he was one of the most helpful blokes i've ever met, put you at ease, helped out etc was very enthusiastic in saying that if you EVER have any problems then dont hesitate to call us. Well, i'm yet to call them but in all honesty i'd call the local training school (who i have a really good relationship with) before i call anyone else. Having said that i do carry testing points in my van just in case the advice you get on the phone aint what you want to hear.

 

[stevetheplumber]

i think all boiler inlet cocks should have a test nipple on the inlet side all thiese diferent allowances from different manufacturers is lucicrous
water heaters used to have them

 

[SimonJohns]

i think all boiler inlet cocks should have a test nipple on the inlet side all thiese diferent allowances from different manufacturers is lucicrous
water heaters used to have them

I have the understanding that all the new ideal logic boilers use this setup and not a integral test point on the gas valve

 

[mikimac]

I have just got off the phone with Vaillant Technical & have been told that you could lose 3mb across the gas valve. Wish I had known this days ago..would have saved me a load of sleepless nights! Thanks again to all who posted & advised.

 

[Unregistered]

I fitted a ideal combi and have a standing pressure of 23mb i fire the boiler and get a drop down to 19mb i have checked the pipework tightness tested all fine cannot understand this large drop can anyone advise thks.

 

[ShaunCorbs]

are you gas safe if yes you should know not that hard, and if not naughty naughty and please register with the forum

 

[rpm]

are you gas safe if yes you should know not that hard, and if not naughty naughty and please register with the forum

....... and start your own thread as this is all but 4.5yrs old.

 

[ShaunCorbs]

....... and start your own thread as this is all but 4.5yrs old.

age is just a number tho

 

[Dotty]

As above.

Register first, then build your post count up to 10+, then ask how to join the private forum.

For you zer thread is over!