INSECT DAMAGE TO BOSCH CONTINUOUS FLOW GAS HOT WATER HEATER HYDROPOWER 10H, 13H & 16H.
NOTE TO PLUMBERS AND PRACTICAL AMATEURS::
FIRST: You don’t want a flood, fire, or explosion. Turn off the gas: bottled or town. Turn off the water (good if there’s a stop-cock at the unit). Turn on your brain: this operation requires concentration and deftness, but no skill.
SECOND: The ‘owner’s’ manual is no use whatsoever.
Preamble: The drawback concerning gas hot-water systems is the inevitable invasion of insects, which will cause a total but fixable breakdown. Gas systems must have uninterrupted air supply: so insects also get in. Actually, insects could be screened, but for some reason are not. A design fault. Please explain.
GET STARTED: IF YOU HAVE ANY ABILITY WITH A SCREWDRIVER AND SPANNER, FIX IT YOURSELF; BUT BE GENTLE, ALL PARTS OF YOUR BOSCH ARE FRAGILE AND BEAUTIFULLY MINIMALISTIC, AND WILL LAST FOR A LIFETIME.
1) Approach your hot-water system. Remove the cover (two knurled nuts, bottom outside left and right).
2) REMOVE THE BURNER RACKS: 1st) Unscrew the ignition pilot; there are two screws in front of you, don’t lose them. Gently bend the pilot towards you slightly, whilst leaving it connected. 2nd) Unscrew the big brass nut behind the pilot, releasing the burners from the gas supply. Do not lose the plastic washer. 3rd) Gently manoevre the burner racks to the left and remove them.
3) ACCESS GAS JETS TO BURNER RACKS: 1st) Undo the eight black screws at the back of the burners, gently prise off the jet assembly: it’s a very snug fit. 2nd) Aha! You’ve got at the first half of your problem. Use a pricker to clean all twelve gas jets, though they are probably ok. Insect blockage of the burners? There’s soot everywhere! Hold the burners with the air/gas intakes downwards (so shit falls out, not in!), and with a wire, rake out all insect nests thoroughly. Spray the clean tubes with insect surface killer. 3rd) Re-assemble the burners and put safely to one side.
4) REMOVE THE WATER JACKET: 1st) At the top, remove the retainer with its two screws. 2nd) Remove the temperature sensor clipped onto the right-hand side. 3rd) Under the copper jacket, undo the retaining nuts for the inlet and outlet pipes, holding the unit so that it doesn’t fall. This is the most tricky part: just be slow and gentle. Ease the top of the unit out and down, and the two copper tubes out of their retaining sockets. The one on the right will bend forwards to allow you to release it. Two small tags on the metal frame at the back of the unit may need bending-out a bit to enable you to remove the jacket. It sounds difficult but do it once and it’s a doddle. TREAT THIS WATER-JACKET WITH CARE; IT IS FRAGILE.
5) CLEANING THE WATER JACKET: This is the second and final job. Due to the insect blockage of the gas jets below, the pipes, vanes, and insides of the jacket may be blocked with an accumulation of soot, due to inadequate gas-burning, and big smokey flames. This is the entire problem. This soot is extremely messy, so work in a suitable place. Stand the water-jacket on a slab of wood to keep the two protruding pipes off the ground, and remember how fragile and easily-bent it is. Prepare neat washing-up liquid and a soft brush of the dustpan type. Dip the brush in the liquid and work it into all the surfaces of sooty copper, from all sides, top and bottom: very messy. Hose off and inspect your work; it may take two or three cleanings to expose clean copper. Make sure no dirt gets into the outlet/inlet pipes. THAT’S IT. WHEN YOU’RE HAPPY THE WATER JACKET IS CLEAN, RE-ASSEMBLE ALL THE PARTS CAUTIOUSLY AND CAREFULLY, AND DON’T FORGET THE INSECT SPRAY AS YOU GO.
Note for the future: Though this is untried, place mothballs or similar products on the bottom shelf of your unit before you replace the cover, and renew these as they evaporate: you don’t want to go through all this again!