We have a another autopsy victim on the table this time it is a burner and gas valve assembly from a instantaneous water heater this one came out of a large Bosch instant water heater this is one of three that I scrapped a while ago one of them was an ever Dewar type and there were two boss units the ever Dewar one I quickly opened up or separated the brass valve and found that the diaphragm was blown and this one here no idea but we’re going to do a full autopsy on it instead of just breaking it in half these work off of flow of water when you turn the hot tap on water flows through the valve body pushing a diaphragm up diaphragm opens the gas valve pilot light up here ignites the gas coming out of these burners and there’s a copper coil a finned copper coil a large heat exchanger which you’d see in the previous video.
I’ll try and find the link to that one put in the description the heat exchanger has the water flowing through it and you get instant hot water by the time it reaches the end of the coil that’s basic design behind it it’s a nice design you do lose a bit of water during the heat up period but once you’re running it just runs continuously not like the storage type tanks which constantly reheat and less efficient but I think you just get hot water a little bit quicker that’s about the only advantage I guess it’s a little piezo igniter on it and there are settings I think that’s off low and high and that’s about it there’s not really much else to it and that’s for the igniter I don’t think the ignited even in there.
I know there it is yeah but anyway I’ll open this thing up and have a look at it starting with I think the water valve oh no sorry we’ll get the burner rack off and have a look at that the burner acts pretty straightforward the nest Inlet screen and just draught tight Inlet for the pilot light and see up there a little housing near which acts as a air inlet draught tube then there’s a wax statue type thermocouple which is actually blown open I guess that would explain the failure of this unit a little firmer couple there is blown open or the stat where does he go that’s electronic actually it’s not a is it actually there’s an electrical sensor there and there’s also you might have to pull him out to find out but let’s definitely it a whole blown it that’s not normal and that dog next door sounds like.
It’s having a buddy seizure it does that from time to time yeah I’d say that blown couple is the problem looks like there’s a lot of corrosion there as well it might be leaking although that’s gas though that’s not water there’s condensation damage there yeah I’ll be willing to bet that’s the only thing that failed on it but a roadside finds a roadside finds who’s going to complain so yeah let’s I’ll break this into three pieces we’ll have a look at the gas body butter in a rack and the valve how about that there’s a lot of little bits on this thing and I don’t want a thirty minute video to try and upload so let’s keep it simple and straight to the point okay well that breaks down into some pretty easy component groups gas Inlet hot the gas burner rack nice little jets and everything on it I like to connect that straight up to a gas bottle and see what kind of flame each we can make one day.
I won’t destroy that we’ve got the valve body that the burner rack screws on to at the top here gas comes in through there and with water valve which actuates the gas gas body it’s also adjustable by the looks of it so yes we shall start from top to bottom with the burner rack which is pretty straightforward you’ve got the gas coming in through there under pressure the jets fire into the center of each of those our mixer tubes and well when you inject a jet of air into the center of a tube the high pressure discharge creates low pressure behind it and that draws air in behind it so it’s actually drawing air in from underneath that’s all the holes are about and mixing the gasses goes through the tube so you’re not getting straight gas.
You’re getting a mixture of air and gas which then comes out through the slits in the top and burns off so that’s the point of even in common barbecue your gas grill if you look at the way the burners are set up you’ve got a gas jet aiming into the center of big open tube and that jet of gas creates a low-pressure behind it which draws air in it’s also the same principle behind the Lewis machine guns cooling jacket it looks like a big fat water cooling jacket but it’s actually a air cooling jacket with long heatsink fins along the barrel and as the bullet leaves the barrel that blasted gas coming out of the muzzle creates a low pressure behind it and draws the air from the back of the jacket all the way through so it’s actually creating the same effect it’s a really neat design it’s bulky and ugly but it works so yeah if you it’s like an air vacuum you stick the end of an air nozzle down a tube and discharge.
It like a large diameter tube you’ll actually get a larger volume of air coming out the other end then you’re putting in with the air gun for the same reason that’s how air vacuums work and this thing’s doing the exact same thing so there’s a little bit on your average gas burner rack and that can be applied to pretty much all of them whether it’s a big I suppose you’d say industrial sized heater or your average water heater in the home or a gas grill a barbecue same deal they all use the same principle mix air high pressure jet of gas air drawn in mixed and burnt as it comes up through the burner tube they’re really nice so let’s move on to the gas body.