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.