Allegedly insufficient gas supply

[Adsibob]

I think this is a load of regulatory bollox, but here goes:

 

Moved into newly refurbed house a year ago. All good with my new boiler, save that I always thought the boiler  engineer had oversized it. Per my calculations we needed around 24kW boiler, but the boiler installer laughed at that and told me to go bigger and so we went with a 32kW. Over winter I don’t think I ever saw the boiler output more than 25kW, so my calcs must have been about right.

 

A year later the installer calls me up and says: is it ok if I use your installation as part of my regulatory checks; meaning an inspector will come and check his work for his ongoing certification. I said yeah sure, thinking it’s always good to get extra peace of mind.

 

Today, inspector attended. He says everything is fine with his work, but the gas supply itself is faulty, as it is not supplying enough gas for the installation. He suspects the gas “Governor” might be faulty, but notes that this isn’t my installer’s responsibility and that it is Cadent’s responsibility as they own/manage the local gas supply.

 

Cadent turned up an hour ago, ask me to switch all my thermostats to max and to put my hot water on. We don’t have gas hobs. They check the gas supply and say it is within their range of (about) 19 to 25 (I think it was about 20). They speak to boiler installer who says that is not a reliable test because the cylinder is already hot (it was heated a couple hours earlier). And that the proper way is to put boiler in test mode (which is what the inspector has insisted on Earley in the day). This appears to be technically correct, given that with everything switched on boiler was modulating to about 21kw or so, whereas once in test mode, it shot up to 32kW.

 

In test mode it failed Cadent’s test, recording somewhere below the bottom range, not far below, but below. They installed a new Governor but this makes no difference . Conclusion: insufficient gas supply.

 

Cadent tell me they will pass on my details to the “works team” who will advise what needs to be done, but it could involve digging up and replacing the gas supply pipe. He reassured me that they will reinstate everything they have to disturb.  I don’t know the exact route of the pipe, but i think it  goes under some concrete planters, some very expensive external paving and a concrete platform and retaining wall that separates our bin storage area from part of the planters.
 

Even if they pay for all the works, am I obliged to do this? Can I just accept the allegedly inadequate gas supply, which in my view would never have been an issue if the installer went with my initial preference of a smaller boiler?

 

 

[SteamyTea]

Would it not be cheaper, and easier all round, to just change your boiler to a smaller one.

And give you a cheque for the inconvenience.

[Adsibob]

1 minute ago, SteamyTea said:

Would it not be cheaper, and easier all round, to just change your boiler to a smaller one.

And give you a cheque for the inconvenience.

But you are saying that from the land of common sense. I don’t think regulators and gas networks live there. 

[SimonD]

This sounds like a load of buck passing going on. We need figures here. What was the inlet pressure at the boiler? What was the operating pressure at the meter?

 

Technically, if the inlet pressure was too low, your installer should not have commisioned the boiler and should have raised the gas pressure issue at the time of commissioning. So in essence the view that his work was fine but the supply pressure is faulty doesn't entirely hold water if it means the boiler isn't getting sufficient gas.

 

I recently completed an install where the manufacturer had to attend due to an incorrect jet having been put in the boiler during manufacture. The inlet tests following repair showed a low gas pressure but one above the manufacturer's minimum - no problem at all. I've even had low pressure during a Gas Safe inspection (not my installation) but as it was above MI minimum the inspector said not a problem there too.

 

The key determinant is whether the boiler is receiving the minimum pressure allowed by the Manufacturer. If it is, then everything should be fine. Gas pressure across the whole system varies, as does supply pressure depending on network demand. This means that you can't necessarily rely on a single test on a single day to determine whether the supply pressure is okay or not. Most manufacturer's will permit a very low inlet pressure for a small period of time for this very reason. The other issue with pressure loss across a gas system is that the design figures are theoretical - you can design the pipework for a 1mbar drop but in reality it could be measured as almost zero, in some cases it could be 3mbar or so for instance.

 

From the perspective of the network provider, it needs to supply minimum of 19mbar but there can be a loss of up to 4mbar across the meter. This scenario obviously doesn't match the theoretical numbers and figures often bandied about - but it is uncommon.

 

Unforunately you're at the mercy of a collection of people who don't seem able to figure their way through these rather simple steps in a pragmatic way. Or maybe something is missing in the data provided?

[Mike]

Unless you have an obviously undersized incoming gas pipe, or an ultra-long garden / driveway, or a blockage, doesn't it seem unlikely that the size of the pipe in your garden is the problem?

 

Wouldn't it be more likely that the size of the gas main, or the pressure within it, is the problem?

[Adsibob]

57 minutes ago, SimonD said:

This sounds like a load of buck passing going on. We need figures here. What was the inlet pressure at the boiler? What was the operating pressure at the meter?

 

Technically, if the inlet pressure was too low, your installer should not have commisioned the boiler and should have raised the gas pressure issue at the time of commissioning. So in essence the view that his work was fine but the supply pressure is faulty doesn't entirely hold water if it means the boiler isn't getting sufficient gas.

 

I recently completed an install where the manufacturer had to attend due to an incorrect jet having been put in the boiler during manufacture. The inlet tests following repair showed a low gas pressure but one above the manufacturer's minimum - no problem at all. I've even had low pressure during a Gas Safe inspection (not my installation) but as it was above MI minimum the inspector said not a problem there too.

 

The key determinant is whether the boiler is receiving the minimum pressure allowed by the Manufacturer. If it is, then everything should be fine. Gas pressure across the whole system varies, as does supply pressure depending on network demand. This means that you can't necessarily rely on a single test on a single day to determine whether the supply pressure is okay or not. Most manufacturer's will permit a very low inlet pressure for a small period of time for this very reason. The other issue with pressure loss across a gas system is that the design figures are theoretical - you can design the pipework for a 1mbar drop but in reality it could be measured as almost zero, in some cases it could be 3mbar or so for instance.

 

From the perspective of the network provider, it needs to supply minimum of 19mbar but there can be a loss of up to 4mbar across the meter. This scenario obviously doesn't match the theoretical numbers and figures often bandied about - but it is uncommon.

 

Unforunately you're at the mercy of a collection of people who don't seem able to figure their way through these rather simple steps in a pragmatic way. Or maybe something is missing in the data provided?

Thanks @SimonD, very helpful. But given from a performance point of view, I’m not noticing any issues, do I have to do anything about this, or can I just tell Cadent I’m not interested in any work that needs to be done on my property, because it will be too disruptive? Appreciate this is ultimately a legal question, but given you are in the industry, I wondered if you had any real life experience of a situation where a gas board wants to rectify something but the owner of the property doesn’t want them to enter his land to do it.

[SteamyTea]

1 hour ago, Adsibob said:

But you are saying that from the land of common sense. I don’t think regulators and gas networks live there. 

I have no sense, nor am I common.

Try suggesting it to them, there may be someone who is a bit of a realist.

[SimonD]

1 hour ago, Adsibob said:

Thanks @SimonD, very helpful. But given from a performance point of view, I’m not noticing any issues, do I have to do anything about this, or can I just tell Cadent I’m not interested in any work that needs to be done on my property, because it will be too disruptive? Appreciate this is ultimately a legal question, but given you are in the industry, I wondered if you had any real life experience of a situation where a gas board wants to rectify something but the owner of the property doesn’t want them to enter his land to do it.

 

Cadent holds a lot of statutory power to enter property where it deems it necessary - but only with good reason. So it firstly depends on how the problem has been classified, if at all. Did you, or do you expect to, receive a warning notice from either Cadent or your installer? This will tell you what you need to know in terms of rights to rectify the problem. If it is deemed to be merely "At Risk" there is more flexibility as some At Risk installations can just be left as they are accompanied with just a warning notice, others need intervention. If it is deemed "Immediately Dangerous," then your boiler/installation would need to be capped off by your installer and rectified before going back on and is the kind of situation where Cadent can take action it deems necessary.

 

If they haven't turned off your boiler and told you not to use it, nor isolated the gas supply, I'd just wait for someone from Cadent to get in touch and have an adult conversation with them. I'm sure they'll do their own risk assessment too.

 

Unfortunately, the training in this area is not set up to encourage independent thinking but instead a fairly rigid binary mentality which some in the industry don't seem to be able to shake even after real world experience.

[SimonD]

3 hours ago, SteamyTea said:

Would it not be cheaper, and easier all round, to just change your boiler to a smaller one.

 

The problem is that this might not resolve the issue. If these peeps have deemed the problem to be "insufficient gas," (which actually isn't particularly meaningful) it may just be down to a supply pressure problem rather than a gas flow problem. In this case, if they still see too low pressure at the meter test point, they could still 'fail' it - e.g. a 24kW boiler still needs 19-23mbar at the meter same as a 32kW one. This is really why gas rate together with inlet and operating pressure should be taken and used as part of the overall risk assessment. And they need to make sure they're referring to the Manufacter's specifications as to what the boiler needs at its inlet.

[Adsibob]

26 minutes ago, SimonD said:

This is really why gas rate together with inlet and operating pressure should be taken and used as part of the overall risk assessment. And they need to make sure they're referring to the Manufacter's specifications as to what the boiler needs at its inlet.

Thanks. I will ask for figures once Cadent gets in touch.

[Adsibob]

34 minutes ago, SimonD said:

they haven't turned off your boiler and told you not to use it, nor isolated the gas supply

No, nothing dangerous so everything continuing as it was. I shall wait and see what happens. Hopefully get an answer soon as we were due to fill the planters with soil and new plants next week.

[Temp]

Can you fit smaller jets in the existing boiler? I had this done on an oil boiler. Reduced the output by about 7% as I recall.

[Adsibob]

2 hours ago, Temp said:

Can you fit smaller jets in the existing boiler? I had this done on an oil boiler. Reduced the output by about 7% as I recall.

I guess that’s a possibility. Will do nothing for the time being. Who knows, the gas board people might be reasonable!

[TonyT]

Can the boiler not be range rated to reduce the output, I can’t remember which boiler you had think it was a viesmann?

[Adsibob]

On 09/06/2023 at 11:35, Mike said:

 

Unless you have an obviously undersized incoming gas pipe, or an ultra-long garden / driveway

 

The distance from the street to the boiler is about 12.5m as the crow flies, or about 18m once you take into account the actual type of the pipe, which has to travel diagonally downwards (fall of about 1m down and run of 5m across) then up to get into the ceiling, then down again once in the boiler room. This isn’t that different to the original location of the boiler when we bought the house, but that was a much smaller boiler, serving a smaller 3 bed house. We are now a 5 bed house with a bigger water tank (300L vs older 180L).
 

 Does the pipe length I’m describing, as well as the fact it has to go down diagonally, then has a few right angles, raise any warning signs? 

[Adsibob]

7 hours ago, TonyT said:

Can the boiler not be range rated to reduce the output,

 

No idea

 

7 hours ago, TonyT said:

I can’t remember which boiler you had think it was a viesmann?

yes, Viessmann Vitodens 200w system boiler, 32kW.

[TonyT]

So it can modulate down to 1:17 so your only burning what you need so that’s good

[Adsibob]

41 minutes ago, TonyT said:

So it can modulate down to 1:17 so your only burning what you need so that’s good

Yes, this was the main reason I went for this boiler. I was advised that if I had this boiler, I definitely wouldn’t need a buffer tank, and that’s proven to be correct (we also have a low loss header), even when we are heating just a very small zone of our UFH.

[Mike]

44 minutes ago, Adsibob said:

The distance from the street to the boiler is about 12.5m as the crow flies, or about 18m once you take into account the actual type of the pipe

Does the pipe length I’m describing, as well as the fact it has to go down diagonally, then has a few right angles, raise any warning signs?

I'm not a gas expert, but I've found an interesting toy on the internet that may give some insights - a Gas Pipe Calculator.

 

If you type in 32 kWgross as the consumption, 18m length and 22mm copper pipe (guessing that may be what you have?), it calculates a pressure drop of 1.36mb (millibars). Add in 6 x 90° elbows and the pressure drop becomes 1.64, which isn't a dramatic worsening (the calculator indicates that that's equivalent to 21.6 m of straight pipe). Compared to somewhere just below 19 millibars that Cadent told you.

 

Then, if you upgrade the pipe to 32mm PE in the calculator, the pressure drop becomes 0.37. In other words, you would gain 1.27bar (1.64-0.37), which may push you over the 20 millibar limit. But that's a lot of work for around an extra 15% pressure difference.

 

However if you currently have a 15mm copper pipe, then upgrading to 22mm makes a big difference.

 

 

[TonyT]

28mm would be the next size up, mine is run in 28mm to supply boiler and range and then drops down to 22mm at each appliance 

 

[TomoD]

Hi there,

Once Cadent know about an issue it needs a resolution. If you don’t want an upsized service you can sign a waiver so no work will proceed. It sounds like you need a larger diameter service. There are many reasons why you existing service might be inadequate duelled with next door , old steel , inserted or not enough capacity in the main. Your new boiler requires a large amount of gas on startup which your gas service is struggling to provide this is very common fault now.  

[Adsibob]

12 hours ago, TomoD said:

Hi there,

Once Cadent know about an issue it needs a resolution. If you don’t want an upsized service you can sign a waiver so no work will proceed. It sounds like you need a larger diameter service. There are many reasons why you existing service might be inadequate duelled with next door , old steel , inserted or not enough capacity in the main. Your new boiler requires a large amount of gas on startup which your gas service is struggling to provide this is very common fault now.  

Sorry, i never updated this. They did the work in the summer and then I had to duel with Cadent telephone operatives for them to come back and clean up the mess they left. 

It is working just as well as it did before the "upgrade". I haven't spotted any difference. I guess now is winter time, there is greater gas use in our street, but I don't recall having any issues last year. Ultimately, I think our boiler is massively oversized. With the hot water tank being heated at the same time as half the heating is on, the boiler rarely modulates to more than 45%. I think the most i've seen is 50%, when we also had a couple of towel heaters running.

[Lofty718]

I think oversizing is less of an issue with your boiler since Viessmann 200 modulates to 1.9kw, I don't think theres much difference if you got a smaller Viesssmann

 

 

[Adsibob]

7 hours ago, Lofty718 said:

I think oversizing is less of an issue with your boiler since Viessmann 200 modulates to 1.9kw, I don't think theres much difference if you got a smaller Viesssmann

 

 

Yes, I agree. I could have saved £200 on a smaller boiler, and also saved a bit of space in my utility room as I think the smaller one is 5cm less in one of the dimensions, can’t remember which now, but all things considered, it’s not the end of the world.

Edited October 31, 2023 by Adsibob