Boiler gas inlet

[JimBiscuit]

Hi I'm in the process of getting quotes for a combi-boiler to replace my current antique Ferroli Hawk. I'd settled on a Vaillant Ecotec Plus, and asked for quotes to install the 831 model, as the previous boiler didn't seem quite powerful enough for the size of the house.

Both plumbers I've had to view and quote said that the current 22mm gas inlet pipe is too small for the 831, but the Vaillant specs say 22mm is correct. Who is right, and what are the potential pitfalls of getting the 831 installed with a pipe that's too narrow?

The boiler is at the back of the house and the gas meter at the front, with the pipe running down the whole of one side of the house and it's fairly inaccesible. One plumber suggested extending a wider diameter pipe from the meter for about six metres into the house (the most accessible part); the other suggested rerouting the pipe all the way around the other side of the house on the outside. Are either of these solutions a good/workable idea, or should I just hope that the 824 will be an improvement on my knackered old Hawk?

Any light shed gratefully received.

 

[DP]

There is no point in guessing pipe size. It has to calculated once route has been established. It will be counterproductive to undersize gas line. 22mm inlet is minimum size- it could even be 28 if pipe is going to have many bends in it. With boiler outputs rising, now RGIs are required to instal even 35mm should the need arise.

Having said this, it could well be 15mm if gas meter is next to the boiler. To recap, get it right first time and no guesses

 

[Legion]

Seeing as an RGI is going to fit it, I would suggest you take notice of what he recommends. It depends on how many appliances you have in your property, the length of the gas run from your boiler to your meter. The MIs probably state that the inlet to your boiler should be 22mm not the size of the pipe feeding it.

 

[JimBiscuit]

Thanks both of you for the swift and informative replies. I now understand better what they were telling me earlier. It's quite reassuring that both guys identified it as an issue, hopefully the third quoter will too.

Thanks again.

 

[namsag]

What sort of distance is it from meter to boiler

 

[JimBiscuit]

Somewhere between 9m and 10m. The meter is on the front of a porch wall, pipe leads through porch, boxed in at ground level, takes two short turns inside the front door (also boxed off), runs under stairs (open and accessible, then through the kitchen behind a wall of fitted units, through a wall to the boiler room.

Obviously 9m is also about the length of the house, which is two stories, (plus a badly built loft conversion) and one bathroom. The house has been quite cold in the past couple of winters, even after installing cavity wall insulation, but this could easily be down to the Hawk not operating well and/or the system being clogged. But in the future we will probably want to redo the loft extension (which is very very cold in winter with only one small radiator), and extend the kitchen by another two metres or so, so I was looking at the 831 with expandability in mind. The boiler is currently the only gas appliance, but when we renovate the kitchen we'll probably want to switch to a gas cooker.

 

[sooey]

Without sitting doing calculations, if I was doing that job I'd want to stick a couple of lengths of 28 mm in from the meter.

 

[Legion]

Without sitting doing calculations, if I was doing that job I'd want to stick a couple of lengths of 28 mm in from the meter.

Brilliant, good input.Well done. Point?

 

[sooey]

The point was that I believe a couple of lengths of 28 mm would see it alright, so I was basically agreeing with the two guys who've seen the job, and who the op is now questioning. I thought I'd made that clear. What was your point again bamber, apart from trying to be a smartarze of course.

 

[JimBiscuit]

Just for the record I'm not questioning the professionalism of the blokes who quoted, just trying to understand a bit more background so I can make a decision about what my options are. I'm not going to try to twist anyone's arm to do work that goes against their best judgment.

But again, thanks for all the input, it's genuinely helped. This wasn't a snag that I was anticipating and getting some more info will help me decide what to do and who should do it more easily and quickly.

 

[Legion]

The point was that I believe a couple of lengths of 28 mm would see it alright, so I was basically agreeing with the two guys who've seen the job,

Good , he can now do job with the knowledge that you concur. (agree) God knows what he would have done if you hadn`t posted.
By slagging me off as Bamber won`t get me removed mate. I`m not Bamber, tough luck.

 

[sooey]

Good , he can now do job with the knowledge that you concur. (agree) God knows what he would have done if you hadn`t posted.

Yeah, that seems to be the gist of his last post, and the reason for his first one. You got a problem with that?
I wasn't slagging you off bamber, much. I wasn't trying to get you removed either, I like reading all your sh1te.

 

[Legion]

I like reading all your sh1te.

Post some of my xxxx and I`d be impressed instead of inferring it.

Post some , scouse lad or button it. All mouth n trousers.

 

[bengasman]

Just for the record I'm not questioning the professionalism of the blokes who quoted, just trying to understand a bit more background so I can make a decision about what my options are...

To simplify things, a gaspipe can not be too big. If you decide to gamble and it turns out it was too small, you will have to chuck the pipe and redo at least part.
Another factor is that cooker, fire or anything else on gas that comes off the same pipe would make a 22 rather risky.

Don't pay too much attention to the clown posting under the name legion, he likes to pretend, but is a householder,not a RGI, and knows nothing about gas.

 

[Agile]

To explain the situation clearly to Jim !

There are regulations relating to gas pipe resistance. The pressure at the meter is a nominal 21 mB and the supply to the boiler ( with the hob/cooker and any fires on ) must not fall below 20 mB thus losing a MAXIMUN of 1.0 mB in the pipe.

Thats a BS standard and regarded as normal good practice.

Every installation is different and every bend increases the resistance to flow. A 9m run is typically about 14 m in effective length when the bends have been taken into account. Typically about half of that and ideally most of the bends will need to be at 28 mm to meet that requirement.

It can be calculated but the difference between calculated and measured results usually mean that the measured loss is higher.

An experienced engineer will have a good idea of what is likely to be needed.

I am pleased to hear that both your quoters have pointed out the requirement to upgrade the gas supply pipe.

Now did they measure the water supply pressure and flow rate ???

Tony