Gas pipe/Condensing Boiler question

[tiggerish]

Hello,

I'm after some advice before getting any quotes so I know what to ask.

I need to replace the very dead Potterton Lynx in my 1 bed ground floor flat. The flat is in a terrace and the meter is at the front of the flat, the boiler is in the kitchen at the back of the flat. The gas pipe currently runs under the concrete floor and the distance between the meter and the boiler is about a 12m run with about 4 elbows going under the sitting room, bedroom, corridor and kitchen.

I'm presuming I'll need a bigger gas pipe for a new condensing boiler. As it's a terrace there's no side return to run the gas pipe outside the building so does this mean my whole flat will have to have the solid floors removed and be dug up? (If the pipe runs above ground the distance would be even longer and involve going around chimney breasts, through fitted wardrobes, doorways etc with high ceilings and low ceilings along the way) I already know there is nowhere to put the boiler other than where it's positioned now in the kitchen.

Are there any options in this situation or should I just brace myself for the worst?

Thanks for any advice offered.

 

[oldplumber]

get in some rgis to give you proper quotes/estimates based on what they find and what you need. You cannt tell if you cannt see in a situation like this really.

 

[Billy Bob Bob]

agree with old plumb this needs a visit off a pro

 

[tiggerish]

Thank you anyway old plumb and gas man.

I know it seems a bit daft that I'm asking before getting anyone round - unfortunately I got badly stung by two 'recommended' engineers in quick succession a couple of years ago so I'm just really wary now.

 

[Blackcatgas]

why not just stick with another conventional boiler? (which needs a smaller gas pipe) and maybe upgrade the cylinder and to a y plan (if needed), combis are good but there not the be all and end all.

 

[Puddle]

why not just stick with another conventional boiler? (which needs a smaller gas pipe) and maybe upgrade the cylinder and to a y plan (if needed), combis are good but there not the be all and end all.

Thanks Blackcatgas,make us oldies free the pain ,a Potterton Lynx is a combi boiler or was,it is past its ell by date,still have a few I look after,what gas pipe size do you have tiggeris,would have thought 22mm to the lynx

 

[Blackcatgas]

Thanks Blackcatgas,make us oldies free the pain ,a Potterton Lynx is a combi boiler or was,it is past its ell by date,still have a few I look after,what gas pipe size do you have tiggeris,would have thought 22mm to the lynx

Funny thing is that i tried to be clever and edited my post after checking via google wether the lynx was a combi lol!.
Too many Strongbow.

 

[tiggerish]

Good point puddle. It looks like it's 22 from the meter then reappears as 15 coming out of the kitchen floor into the boiler. However I've seen the pipe under the concrete in the bedroom (during one of the previous engineers escapades) and it was 22. That's about 3m and an elbow from the boiler so maybe it's only the last little bit that's 15. Is it normal to get the new boiler put in with fingers crossed on the pressure being OK and then fit a bigger pipe afterwards if it isn't. If the flat has to be ripped up it doesn't make any difference in terms of disruption whether it's done before or after but it would be nice to avoid it.

On a separate note I have a bag of left over spares, some nearly new, stripped of a friend's Potterton Lynx - are second-hand spares worth anything generally or should I chuck them.

 

[Billy Bob Bob]

is the lynx the one were the pcb is bolted to the door and swivels out with it?

 

[Reg Man]

If you have 22mm copper gas all the way from the meter to where it comes up to the boiler, it should be ok, as long as its not a monster combi, ie more than 3.4m3/hr on max HW demand.

 

[metaldust9]

could go for a vokera pro combi 85he or 100he which uses a 15mm gas feed to it and long as its gas rated and comes within spec u should be ok or read reg man

 

[Reg Man]

The Vokera 28, may have a 15mm connection, but in relality you will probably have to take a minimum22mm copper pipe right up to the connection. I do not understand why manufacturer's don't put 22mm connections on there combi's. Reason being. You are allowed 1 mbar WP differential pressure between the WP @ meter & WP @ boiler inlet. A vokera 28 requires 2.96m3/h. Maxmium length of 15mm if you came straight off the meter outlet and allow your .5m for each elbow etc is less than 3m length. How many gas meters do you find directly next to the boiler. So say I run 22mm part of the way. I have to allow that I will get some pressure loss over the 22mm so I will have to allow this into my tiddly bit of 15mm as well. For example I design the pipe size so I get .5mbar differential on my 22mm so now I have to shorten my 15mm length, because I only have another .5mbar. so I am nearly up to the boiler.

 

[tamz]

One of my customers moved house recently and asked me to have a look at her boiler as it had poor hw compared to her old house.
Vokera 29 fitted far away side of loft, 15mm gas run over 20 METRES long without counting bends and a cooker branched off it. Fk me. Never even gas rated it. A look was enough. But when i thought about it it would have been interesting to know how much it could scrape.
Nice wee earner for me but it would have been good to find out what idiot fitted it.

As Reg said no matter what size valve is fitted it still needs the correct size pipe which should be worked out before fitting. Dont assume a 22mm will do a 30 kw boiler.

 

[metaldust9]

yes i agree what your saying reg man id do the same and make sure its 22mm to the boiler with maybe 2 metres from the boiler being 15m i personaly wouldnt put a boiler in 15mm and make sure ,if it was a 15mm connection it would be as short as possible but ive see it done loads of times with gsr people but usually people who,ve been registered for yrs which is why its vital you gas rate it and put other appliances on when the boiler fires up on hot water to see the flame picture

 

[Billy Bob Bob]

in the terraced houses i work in its not uncommon to have to run 28mm from the meter for 6-9 mtrs then reduce to 22mm

 

[metaldust9]

itsnt that dependent on the size of the boiler gas man and the lenegh of the pipe

 

[gasmarc]

yes the lynx is the one with the pcb on the door that costs £140, i usually will fit a like for like combi if there is any issue over pipe sizing, I have never done one wrong with any call back yet