When the Gas Fuse first landed on my desk I must admit I was very skeptical about the usefulness of this device, given the simplicity of its design. In the interest of fairness, we decided to put it to the test.
At first glance it seems like a good idea. The device promises 4 main functions:
- Automatic Shut off in the event of a major leak
- Leak Detection
- Gas Gauge
- Child Safety
The Gas Fuse is not a very expensive device and we have seen retail prices from R300 to around R500 depending on how much you shop around. The box claims that it is approved by the Australian Gas Association, and a quick search of the AGA appliance directory confirms the approval, however, crucially the device IS NOT approved by the Liquid Petroleum Gas Safety Association of South Africa. This does not necessarily mean that the device is unsafe, only that it has not been submitted for testing by the local distribution agent. No doubt the local distributors will neglect to mention that fitting any device to your gas installation, that has not been approved by LPGSA, renders your Certificate of Compliance void.
Installation is fairly straight forward and the colour, illustrated instructions are fairly easy to follow.
On to the features of the device.
Automatic Shut off
A device that automatically shuts off the gas supply at the cylinder when you have a gas leak seems like a great idea doesn’t it? The problem is that it’s not quite as simple as that. The Gas Fuse is fitted directly to your gas cylinder, and as such the only information ‘input’ it has to determine whether there is a leak or not is the gas pressure and flow rate. The difficulty with that, is that the Gas Fuse can not tell the difference between you using an appliance, and a small gas leak somewhere on your line. It can ONLY detect big, catastrophic failures of your gas line. In fact, when we tested the Gas Fuse, we had to quite literally cut the gas line off before the ’emergency’ shut off actually closed. It’s worth pointing out as well, that the shut-off could only be triggered by a complete and very sudden failure of the gas line. If we cut through the line slowly, the gas continued to flow through right up to the point where the line was completely open before the valve actually shut. In other tests with larger appliances, or multiple appliances on the same line, we also found that the Gas Fuse would shut off the gas supply even when there was no failure of the line.
The danger in this is that the Gas Fuse gives a false sense of security in that it convinces the user that it would protect against gas leaks, when in fact it can not do that. Luckily it does state such in the instructions, but if you don’t read them all, you could very easily think that the device will shut off your gas in the event of small gas leaks.
The leak detection function is a basic pressure test of the line. The idea being that you can place your gas line under normal operating pressure and then shut the valve. With the system under pressure you take note of the gauge reading and then leave the system pressurised for a period of a few minutes, then return to check the gauge again. If the system has not lost any pressure, then there are no leaks in the system. The theory is sound and we routinely use this method when checking new gas installations for leaks. The shortfall here is that the gauge used on the Gas Fuse is too vague. We pressurised a test line with the Gas Fuse in place and then deliberately caused a very small leak on one of the fittings. The leak was big enough to create small bubbles when soapy water is sprayed on the joint, but not so big that you could hear it hissing. Over a period of around 5 minutes, the gauge had not moved noticeably, which would indicate that there are no leaks, when clearly there was. We increased the size of the leak to the point where we could almost hear it and left it for another 5 minutes. After this time we did see the gauge move, but unfortunately for a device claiming to be a safety tool, this simply wouldn’t be good enough. We would need to be able to see, even a small leak, instantly, but the Gas Fuse simply isn’t accurate enough to use for leak detection.
I’m going to try very hard not to get too scientific here, but there are a few things that need to be understood in order for me to explain why the Gas Fuse does not work as a gas gauge. Firstly LPG is stored in liquid form in your gas cylinders. The cylinder is filled to about 80% of its liquid volume to leave room for expansion and a pocket of LPG vapour on top of the liquid. Your appliances require the vapour form of LPG and not the liquid – this is why your cylinders must always stand upright when being used. When the cylinder is filled and the pressure inside increases, the LPG starts to turn into a liquid when it reaches a threshold called the vapour pressure. This pressure will change with the temperature and the exact butane-to-propane ratio of the LPG being used, but for practicality we will say it’s around 550 – 600kPa at room temperature. This means that the vapour pocket in the top of your cylinder will ALWAYS be in that vapour pressure range provided there is at least some LPG still in liquid form inside your cylinder.
Now back to the Gas Fuse. Let’s remember the Gas Fuse is connected to the outside of your cylinder, and the ONLY information it has in order to ‘calculate’ how full the cylinder is, is the pressure. Unfortunately, because the vapour pressure of the gas is pretty much constant if the temperature doesn’t change, the Gas Fuse will ALWAYS tell you that the cylinder is full, right up to the point where it is virtually empty and the pressure starts to drop below the vapour pressure of 550kPa. In testing we connected the gas fuse to a full cylinder and placed the cylinder in the sun to start with. The gauge said the cylinder was full and in the green range. After moving the cylinder into the shade the cylinder was still in the green range but slightly lower. We then repeated the test with a 9kg cylinder filled with just under 4.5kg’s of LPG – so just under half full. In the sun the cylinder gave a green reading on the gauge, not very different from a completely full cylinder. However, when we moved the half full cylinder into the shade, the gauge dropped significantly, touching the red ‘refill’ zone of the gauge. For the final test we used a 9kg cylinder with only 1kg of gas in it. When placed in the sun the gauge was still in the green zone, indicating we had plenty of gas, even though we didn’t. When moved to the shade, the gauge eventually dropped into the red ‘refill’ zone.
It’s worth noting that the gas gauge feature can only be used while an appliance is running, and according to the instructions, it is better if the appliance has been running for about 10 minutes or more before taking the reading.
The Gas Fuse claims that it can be used as a safety device on unused cylinders. By screwing the device into an unused cylinder that still has gas in it, it will not allow gas through, should the child accidentally open the valve on the cylinder. Finally an advertised feature of this device that does actually work! If you screw the Gas Fuse into a gas cylinder and open the cylinder valve, nothing happens. The question becomes whether this isn’t a little redundant though? The same effect can be had by using a gas regulator with a piece of bent over hose, at less than half the cost of the Gas Fuse. Not only that, but surely if a child is strong enough to open your gas valve, they are strong and smart enough to unscrew the gas fuse from the cylinder?
We can not say that the Gas Fuse’s claims are false advertising, because it does do what it says on the box, BUT, and it is a very big but, it doesn’t do any of those things particularly well. Yes it will shut down automatically if your gas line is very suddenly cut or completely disconnected – in testing it also shut off when we were running multiple appliances or appliances with large gas consumption at start-up. However at the end of the day it was more an annoyance than a feature. Yes it can be used to detect leaks, but there are easier, more sensitive ways of doing that, besides which, you will smell LPG long before the Gas Fuse detects a leak on the system. Yes it can be used to gauge if your cylinders still have gas in them, but you have to take into account where your cylinder is (sun or shade), and even then the information is vague, at best. And yes the Gas Fuse can be used to make unused cylinders safer, but even if you really felt the need to, there are cheaper DIY ways of doing it.
Given the spectacular way in which the Gas Fuse failed all of our tests, we really can not see the point of this device. The idea is really good, but unfortunately they have tried to over-simplify the problem and produced a device that really serves no purpose. You also have to keep in mind the fact that it can render your Certificate of Compliance void. Let us not forget that without a valid Certificate of Compliance, your insurance will not pay out for ANY fire related claims, regardless of whether it was related to the gas installation or not.
There are just too many things on the negative side here and we really tried to find something that this device is good at, because a lot of our customers have asked about it. At the end of the day we would have to say there are better things you can spend your money on to make your gas installation safer, rather steer clear of this one… Eddlesgas certainly will.
Please note that the Gas Fuse used in our test was supplied as a consignment unit by an agent. The unit was brand new and boxed when it arrived and is the second unit of its type that Eddlesgas has tested with similar results. All tests were carried out by qualified LP Gas Practitioners under controlled conditions. Eddlesgas DOES NOT stock the Gas Fuse as it does not comply with LEGAL REQUIREMENTS of LPGSASA or SAQCC gas, and we refuse to stock any product that we would not use ourselves.