Oil Bubble stove – it’s all in the trim
WHEN we bought our narrowboat in November 2015, we didn’t have a clue what an oil Bubble stove was. We’d never heard of the Bubble brand either. It didn’t take long to find out because in November 2015 a fairly cold winter was in the offing.
At purchase, heating systems had been indicated to us and briefly discussed, including reams of other stuff which made it difficult to prioritise what was important and what wasn’t. However – and because of our thin southern hemisphere blood – we both remembered something about a Webasto in the engine room, and a Bubble stove in the saloon.
After the onset of the 2016 winter proper (and everyone said it was a mild one!) it didn’t take long for us to realise just how important heating on a narrowboat is. But first the Bubble. They aren’t fitted with gimbles and if not level it’s probably the most temperamental piece of heating equipment I’ve ever come across. Our Bubble is a 35kg corner model, specifically designed to fit snugly into a narrowboat corner. It’s situated in the saloon, as you enter the boat from the cratch.
The Bubble brand is a diesel oil-fed heating system. And when it works, it works well. The longest we’ve left it burning has been a month (never unattended). However, the relationship with our Bubble hasn’t always been a success story.
It worked perfectly from November 2015 until late 2019, and thereafter it started to annoy and confuse us. Throughout 2020, it worked in stops and starts and seemed to be developing a moody persona of its own. And then, during early 2021 the fuel flow stopped altogether.
Despairing, I spent hours on the internet trying to read up all I could about the Bubble brand on narrowboat forums. We even had our diesel ‘polished’ for £150. Frustratingly too we couldn’t find any technicians in our part of the world who’re trained in Bubble maintenance. Those who came aboard and did a bit of tinkering and tuning, all had their own theories as to why the Bubble was misbehaving. Fuel starvation seemed the accepted cause. Sadly, and despite these various visitations by engineers, the Bubble continued with its refusal to function correctly.
Our boat, Sabi Star, has bookshelves behind glass, in the saloon, along her starboard side and they quickly filled up. Almost to bursting point. I also dabble in art, and in the dinette art material and sketch books also gradually piled up. So much so, the boat soon took on a slight, but hardly noticeable list to the starboard side. The fact the boat’s list – and the Bubble’s sudden refusal to function – more or less coincided was lost on us.
A friend of ours, Andy, who is also an extremely astute engineer visited one evening and we told him our Bubble sob story. He was sitting on the saloon entry steps, alongside the non-functioning Bubble. I harped on about one theory being due to fuel starvation. He thought maybe not and asked if he could take the stove manufacturer’s technical brochure away with him. We obliged. He also asked me to purchase a metre or two of 8mm clear plastic tubing, which I did.
A few days later Andy returned with a fitting he’d made for one end of the plastic tubing. He attached this to the fuel feed on the stove, and then stood up holding the opposite end of the transparent tube above his head. Diesel flowed through strongly, which immediately ruled out fuel starvation. The fuel feed for the Bubble is from our main diesel tank in the stern.
He then explained to us how the Toby valve works. It has a ‘float’ in it similar to a motor car carburettor, or it could also be likened to the ball-valve concept on a livestock drinking trough. On the Bubble the Toby valve controls, or inhibits, the diesel flow into the burner pot. If the stove isn’t level no fuel flows into the burner pot.
Andy had noticed our boat’s slight list to the starboard. Putting two and two together, he then asked me if I had a spirit level and a ruler, which I did. Using them he showed how much our boat was out of trim by nearly three inches. He then suggested we try and sort the list out and opined that once we’d done that, he was sure the Bubble would function correctly.
We did a quick reshuffle of our furniture layout, and got rid of a lot of stuff (including weighty books) and soon had our boat back to level. When we tried the Bubble out the oil flowed energetically into the burner pot and we soon had it lit and performing perfectly, which goes to show just how important trim is if you opt to use a Bubble.
With regards trim, the manufacturer’s installation manual states Bubble stoves must not be fitted if the maximum angle of trim exceeds 0.75 degrees forward to aft, or port to starboard. They advise levelling the stove in both directions when the vessel is midway between its maximum and minimum trim conditions.
In addition, they emphasise a minimum pressure head of 10in is required. This head is measured from the base of the oil tank to the top of the oil control valve. In conclusion, we wouldn’t dream of changing our oil-burning Bubble for a solid fuel stove because it’s clean and economical.