which pipes need upgrade for condensing boiler use?

measurement

I'm considering changing to a condensing boiler (gas) for my CH and water heating(cylinder). I understand it is more efficient, but I've heard some stories about piping requirements that I need to clarify before I upgrade things that don't need upgrading:eek:
1. A friend reported being told they need to upgrade the pipes to the radiators to cope with extra pressure. I wouldn't have thought the water pressure from the boiler to the radiators would be affected - any views from the experts welcome!
2. I saw on a UK (old) post to a board that someone needed to upgrade the gas supply to a condenser boiler to 22mm instead of 15mm. how do I measure? is it circumference or diameter (I suspect its the latter).
3. A plumber who is about to quote to replace my old radiators made some comment about newer ones cooling quicker because of the small bore on their pipes.
I haven't got the pricing yet, and would like to sound as if I know what I'm talking about - even more importantly, I'd like to understand what I'm being quoted for - all help much appreciated:)

yoshytoshy

Take your time ,get advice from whoever is pricing the job. Most condensing boilers need a 22mm gas pipe and good water pressure.
Depending on your current systems condition ,both might need some modification.

Theres a lot of technical stuff on the net that won't have any bearing on your own job ,better getting a couple of prices.

youtheman

I did exactly as you planned (3 or 4 years ago).

1. regarding the pressure, I assume your current system is an 'open' or 'vented' sysem and you are considering going for a 'closed' or 'unvented' system. If you do this then you are upping the operating pressure of your complete pipework system. Then you run the risk of causing a leak, and if this is under a concrete floor then you are talking major costs of repairs. So I elected to keep my system at the original pressure.

2. my old pipework had the correct pipe diameter, and I suspect that your's is o.k.

3. I didn't have to replace my radiators. I think if you are going to keep it as an 'open' system then there should be no need.

4. the only pipe 'addition' was a external drian for the condensate. This need to be 1 1/4" plastic.

In summary, the first 'major' choice you face is if you are going to go for a pressurised system. In 'theory' the pipework should be o.k (1 bar operating pressure, recommended pressure test to approx 3 bar). But you would be a very brave man (in my opinion) risking it.

yoshytoshy

youtheman wrote: »

2. my old pipework had the correct pipe diameter, and I suspect that your's is o.k.
.

A lot of standard gas installations need modification on the gas supply ,for condensing boilers. Regardless of whether the boiler is running an open system or not.

The boiler might work with smaller pipe ,but it's not safe and no good for your boiler.

I've personally had to change gas pipes ,where installers left long smaller pipes supplying condensing boilers. Boilers are not guaranteed if they don't get enough gas.

measurement

Thanks everyone for your comments.
They helped when I was talking to my regular boiler servicer, so that I understood what he was saying.
I don't have concrete, and the radiator pipes are copper, in ok condition, so don't need replacing. However the pressure at the boiler was marginal, so since I'm getting the floors up for other work, I'll replace them with the recommended size.

markaarkgas

the most important thing about a gas boiler is ensuring its getting enough gas at the right pressure.
if you can supply details , estimate but fairly accurate,
the following.
1 size of gas meter
2 number and type of appliances supplied// by meter.
3. the length of pipe run it will require and number of tees/ fittings to feed each individual apliances.
4. the size of each appliances in k/w ..

this is a complicated process , and not one to just guess at.
you are only allowed a 1 m/bar drop to each appliance, or its not up to spec.
there is a high tendency to do assume that 3/4 inch will cover everything , but more often than not (it doesnt.)


as there is nothing more dangerous than a gas appliance being undergassed

heinbloed

Markaarkgas wrote:

the most important thing about a gas boiler is ensuring its getting enough gas at the right pressure.

This is correct.
The boiler's manual will tell the details: minimum pressure, minimum volume.

Every other aproach is like using deviner's guess work.
The boiler has to be comissioned, here it is the comissioner's duty to check the parameters and to sign the protocol. See manual !

markaarkgas

the amount of times have gone to check systems, very little attention been given to the gas supply line, mostly done by guess work , (installers hoping it ill work.)and very little attention be given to manufacturers instructions. and homeowners been not any the wiser,
untill they start having problems and call out someone to check the instalation out.

measurement

I certainly won't try to second-guess the experts. I trust the man who services my boiler, and his advice was useful. It now depends on whether his prices is much higher than the quote for the same work from the builder who is doing other work, and whether the builder's plumber is certified.
Thanks again everyone.:)

markaarkgas

your main concern should be , that the gas pipe suppling your boiler is of the correct diameter, and this should be your main concern.
ask both your plumber and builder if they can check this out for you.
and dont let them fob you off. with it should be alright.
if you need to know what the pipe sizing should be. supply the information requested above. (as sometimes trust is just not good enough.)

DoneDL

Dont the MI`s give the size of the supply pipework.

markaarkgas

mi will only tell you what kw the appliance is ,
burner pressure is on appliance ,and they assume you work out pipework to supply the appliance. with proper amount of gas at the appropriate pressure

example 1 gas meter(6 cbm) with 1/2 inch pipework total length pipework 10 meters away supplying cooker/ boiler , and supplying gas fire.
what would happen if person turned all appliances on.

example 2 gas meter (6 cbm)with 1/2 inch pipe total length pipework 45 meters also
supplying cooker/ boiler , and supplying gas fire.
what would happen if person turned all appliances on.

can you really guess, to see if appliance are undergassed.
thats why the supply gas pipework is so important. and to work out the drops in pressure along any given lenght of pipework. up to each branch pipe supplying individual appliances.

JohnnieK

markaarkgas wrote: »

as there is nothing more dangerous than a gas appliance being undergassed

I wouldn't totaly agree with this. For the likes of fires and cookers yes but not for new condensing boilers. A lot of new boilers will work comfortably down to 17mbar and the Viessmann will work as low as 13mbar (it's in the manual).

But at the end of the day the regs are the strongest and must be adhered to.

I wonder are all the cash kings out there worrying about this when there under cutting everyone:mad:.

markaarkgas

have to totally disagree with previous post ,
to much reliance on manuals and not enough knowledge on pipe work,

start of meter at 23 to 19 mb pressure.
3 appliance working of same meter.
reg state that 1 mb drop across the 3 appliance.

leaving that aside for 1 minute.
(as the above will even make it more complicated for readers to understand)

if you appliance is a 24 kw applicance reuires 2.23 cbm ofgas per hour
or thereabouts
supplying with a 15mm pipe and 6 meters of pipework excluding fittings can only supply 1.9 cbm of gas per hour , boiler is now undergassed .

now lets add on a cooker and that maybe has 8 kw thats another .74 cbm of gas
then a gas fire lets say 5kw thats another .46 cbm of gas
all from a pipe that can only supply ,1.9 and without any stretch of the imagination our appliance are using 3.43 cbm of gas. so how does that now leave the instalation.

you wont find any of that in manufacturers instruction,
but that is what ,you are expected to know.

you may be getting a little confused with burner pressure, and quantitys of gas a unit would expect to function on. safely.

markaarkgas

markaarkgas wrote: »

have to totally disagree with previous post ,
to much reliance on manuals and not enough knowledge on pipe work,
.

The kw output of the boiler drops so it will not use the volume of gas in your maths, but the point is the Viessmann is safe to a working pressure of 11 mbar all be it under gassed, not to standard and not right.
It is not a standard that determines the safe parameters of a appliance, But the manufactures who have tested it, a appliance can be safe but outside of gas regs.

By the way, welcome markaarkgas, I thought I get that in before I start bitching:)

JohnnieK

markaarkgas wrote: »

you wont find any of that in manufacturers instruction,
but that is what ,you are expected to know.

you may be getting a little confused with burner pressure, and quantitys of gas a unit would expect to function on. safely.

Totally agree with you. I i'm not getting confused between burner pressures or quantity of gas for a unit to function proparly. I can asure you that any installations I have done have been sized correctly. I am talking about existing ones that dont comply. Say a cooker is taken of first and it's happy then you go to the boiler and it's down 3 to 4 mbar and you can see straight away that it's undersized. If the manufacturers manual states that the boiler is safe working at this pressure you dont have to shut down, a cert of non-conformance should be issued, either way the boiler is still operating safely.

markaarkgas

all very well if you are only operating a boiler in isolation ,with plenty off in built safety features ,
but more often than not, are used in conjunction with other appliances. ie cooker with no fsd fitted( and how many have we seen out there) , person puts on burner + oven ,pops out to awnser door talks to neighbour 15 mins etc , meanwhile boiler timeclock creates demand.
boiler on , cooker ring goes out , boiler reaches temp , heat demand satisfied, boiler goes to stanby, un lit ring still open gas flows , and we all know what happens next. all for the sake of not insuring proper pipe sizing. in the first place.
and how many do you see check that, while out on a busy day.

by the way interesting discussion

markaarkgas

thanks gary , love to have a bit of a bitch myself. its either that or take it out on my jack russell, because the wife only gets the better of me on most occasions

markaarkgas

markaarkgas wrote: »

all very well if you are only operating a boiler in isolation ,with plenty off in built safety features ,
but more often than not, are used in conjunction with other appliances. ie cooker with no fsd fitted

It's you as a gas fitter who determines the safety of the installation and appliances, but if you go with a cooker at 19 mbar working, with everything turned to max and the boiler at 16mbar which the manufactures are happy that the boiler is safe at that working pressure, then to say it's dangerous and cap it is a bit OTT,you have to put it in to context, a installation should only have a 1 mbar drop between the meter and the furthest appliance with all appliances turned to max, thats what i want to see when i look at a installation/appliance, if it's not right then i will be checking to see if the installation Matches your description or mine and take action depending on what i find, it's not always the case that i cap the appliance, i agree with what you have posted except low pressure is not always dangerous.
I asked RGII to clarify their position on low working pressure a few months ago, but they must be very busy as they have not got back to me:eek:.

markaarkgas wrote: »

and how many do you see check that, while out on a busy day.

Now your talking about a RGII skill set which is another can of worms, maybe you could start a tread *warning not all RGII are gasman*:D

markaarkgas

w/s/b pressures are a whole area for discussion even in their own right.


and m.i. will vary from one manufacture to the next.
some will state one thing and another will state something else.
but you really need to be able to stick to the specific mi for every differing type of boiler , you can come across on any given day..


what i am discussing above is pipe sizing and undergassing,( as per the original posting ) and the relationship numerous appliances will have if pipe sizing is not thought out fully on any alteration to any existing instalation,. (or for that matter any new instalation)...

you are given a tolerance (both above and below) on gas rating on any given appliance,
and if outside the range . it does raise a cause for concern. and should be looked into in more detail.
thats why we have tolerances to operate with.
how you want to proceed with that concern / result ,
is usually the individuals on the day responsibility ,
if it doesnt effect safety on any appliances normally classified as not to standard.
( but that can be 1 person opinion and another may look at it slightly differently) the what if senario may kick in etc.
but if it effects flame stability on any other appliance on that premises,
it becomes dangerous or at risk as mininum. and more often than not can be, and is often overlooked ..
and should be either sorted or capped....
no other way of looking at it in my opinion , but thats only my opinion.

markaarkgas

I agree with everything you have posted, if we were down the pub I'd have a sore neck from nodding, gasmans paranoia is the most important tool in the Toolbox, the thing I'm not with you on is:

markaarkgas wrote: »

as there is nothing more dangerous than a gas appliance being undergassed

You see it as a hazard, I see as a Potential hazard dependant on the installation, either way it not right and should be put to bed.

Sorry op for hijacking your tread:)

markaarkgas

gary ,shall have to disagree with you on this one,
but good discussion. none the less.
talk again soon.