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| Thread ID: 65705 | 2006-01-27 19:53:00 | Electrical/plumbing help please | Greg (193) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 424682 | 2006-01-27 19:53:00 | I just recently noticed the wording of a label on the hot water cylinder, and it's made me a bit confused. I mean, I can actually change the piston rings on a car, but when it comes to blumbing and electrics I get kinda shy. The label reads: "To the owner/maintenance If a temperature and a relief valve is fitted to this water heater, the valve easing gear must be operated every 6 months. Lift the lever, hold open for 2 - 3 seconds, and lower the lever to reset the valve. This will ensure that water is passed through the valve drain line to clear any obstructions. If water is not discharged from the drain line or water flows from the relief button on the back of the valve, have the valve and drain line checked by an authorised service provider or plumber." Images of the openy/closey things are linked below: www.imagef1.net.nz www.imagef1.net.nz So, is my cylinder fitted with a temperature and relief valve? And if so, precisely what do I do, with what? Thanks! |
Greg (193) | ||
| 424683 | 2006-01-27 21:43:00 | Excellent photos. I wouldn't touch it. I've done my own plumbing for a long time but it's all involved rural low pressure systems. Even if it costs you to find I'd get a plumber to have a look at it first. You can get in deep doos fiddling around with high pressure systems and valves and ajaxes if you don't know what you're doing. The plumber can tell you what you've got and what you need to do to maintain it. Never heard of anything quite like this. Be worth the (hopefully) one-off investment to get someone out to have a look The hot water system is worth it. :2cents: |
mark c (247) | ||
| 424684 | 2006-01-28 00:05:00 | My husband is a plumber and he says: This has been installed wrong. It has no cold water expansion valve, no suitable way to drain it easily, its been chnage to mains pressure from low pressure. To do that to comply with council regulations it should have a tempering valve at the top to feed hot water for hygiene purposes but a separate feed before the tempering valve can be piped directly to the kitchen and laundry. The tempering valve ensures the hot water does not exceed 55 degrees for hygiene purposes - shower, bath etc. Ignore the silly instructions on it because its in theory to blow bits of grit out and normally doing that will stuff it anyway. So leave it. More important is the idiot that installed this incorrectly. |
pctek (84) | ||
| 424685 | 2006-01-28 00:22:00 | My husband is a plumber and he says: This has been installed wrong. It has no cold water expansion valve, no suitable way to drain it easily, its been chnage to mains pressure from low pressure. To do that to comply with council regulations it should have a tempering valve at the top to feed hot water for hygiene purposes but a separate feed before the tempering valve can be piped directly to the kitchen and laundry. The tempering valve ensures the hot water does not exceed 55 degrees for hygiene purposes - shower, bath etc. Ignore the silly instructions on it because its in theory to blow bits of grit out and normally doing that will stuff it anyway. So leave it. More important is the idiot that installed this incorrectly.Wow - now I'm more than confused. This house seems to have been built to a really high standard with quaility fixtures and fittings - (two independent reports before we bought said so). Should I be calling in a plumber? |
Greg (193) | ||
| 424686 | 2006-01-28 00:24:00 | Looks like a high pressure cylinder to me . That 1120 kPa working pressure is about 160 psi . I don't think anyone would be foolish enough to put mains pressure on a traditional cylinder . More than once, anyway . That's a pressure relief valve in the first picture, with the exit pipe going down through the floor . Is this upstairs, Greg? It must have been approved by a building inspector . (Perhaps there's a tempering valve somewhere else, out of the picture) . Is it an actual requirement to have an easy way to drain the cylinder? It's certainly a good idea to have one . . . I don't think the instruction to operate the relief valve is "in theory to blow bits of grit out and normally doing that will stuff it anyway . " It's a safety valve on a pressure vessel . On steam boilers it's a requirement to operate the safety valve periodically . It's to ensure that it will open if it's needed . |
Graham L (2) | ||
| 424687 | 2006-01-28 00:49:00 | I don't think anyone would be foolish enough to put mains pressure on a traditional cylinder . I don't think the instruction to operate the relief valve is "in theory to blow bits of grit out and normally doing that will stuff it anyway . " It's a safety valve on a pressure vessel . On steam boilers it's a requirement to operate the safety valve periodically . It's to ensure that it will open if it's needed . You'd be surprised . Its not . This is not a STEAM BOILER . But obviously you are the plumber . . . . . . . . . . . . . . . |
pctek (84) | ||
| 424688 | 2006-01-28 01:10:00 | No, but I know what a pressure relief valve is for. It's so that if the pressure gets too high, it will be released safely. (A HW cylinder would probably just fail messily). It is compulsory to test the safety valve(s) on a steam boiler. This is to ensure that they will work if needed, because steam boilers fail dangerously. The manufacturers of the HW cylinder recommend that the pressure relief valve be tested, to ensure that it will work if needed. Any grit and swarf in the system which might "stuff" a pressure relief valve is probably the result of sloppy work by an incompetent plumber. (In fact, it would be most likely to just cause the valve to stay open, rather than wreck it. It could be dismantled and cleaned out). Are you saying that a plumber would connect a low pressure cylinder to mains pressure more than once? |
Graham L (2) | ||
| 424689 | 2006-01-28 01:10:00 | I guess the plumbers in NZ don't see these things too often . . but over here we call them plain ol' safety blow-offs . There is a version that is called a T&P Valve, to keep the temperature below a set value and not allow the pressure to go over a certain amount too . Water at high temperature and pressure is recombinant in nature when vented off to atmospheric pressures and temperatures . Flash and percussion waves are generated at high enough temps/pressures and it can leave a crater where the heater once stood . But . . and here's the reason I think it's just a pressure blow-off . . . you have an electric water heater, and they are not like a fuel-fired water heater in that if a fired type goes over pressure, they can explode with a lot of energy . . . not quite as bad on an electric type in over-firing the tank . I would believe that in NZ the codes would have a melt-down fuseable link in any electrical heated water tank just like here . That way, the element would melt and the possibility of overheating is very unlikely . Our California codes allow a cumulative total of 180 degrees (not temperature, but angular degrees) in the total run of the relief pipe . That means, two 90-degree turns in the whole run . If you use three 90's, then that's 90 degrees too much . The exhaust must exit outside the living area and is not to be send under the house . There are to be no upturns on the run of the pipe either . The exhaust pipe must not be reduced in diameter in it's total length . "Bell" or "Street"-type fittings are not to be used as they impede the flow radically . Most of our T&P Valves are factory set to blow at 180 degrees F and about 125 lbs pressure . There are some variances by locale and state on installation . Our street presure from the water utilities are not supposed to exceed 100 lbs of pressure . It is recommended to "pop" them yearly, if not more often to insure freedom of action and that it can hold pressure when released . If it leaks after popping it, replace it . If it dribbles or in any way leaks, replace it . If it gets corroded, replace it . They are cheap . A semi-skilled chimpanzee can replace them . Use teflon tape on all joints, and make sure there aren't too many angles in the exhaust pipe . As far as hygiene is concerned, this is a potable water supply and not required to have a vacuum breaker . If this was a multi-level housing water system, then maybe . This relief valve is not set up to be a system drain according to the way it looks here . The valve being at the top of the tank is not drawing from the bottom of the tank, and besides that would negate the value of it's purpose to rapidly dump pressure anyway . Caution, not fear is a good thing here . . . this is not a sophisticated thermo-nuclear device, but certain rules and regulations must be observed . There might also be a pressure relief valve located at the street inlet to the home, so this valve is also a little redundant, but a good idea at the same time . There is nothing wrong with extra measures of safety . As far as a drain for the tank, I don't see one here in the pixs, and that's a shame . Most hot water tanks rust out from debris and formations in the bottom of the tank . Hopefully the tank is ceramic lined to get you a few extra years . This appears to be a very neat and well-qualified installation with three exceptions 1) the final outlet (where does it go?) 2) there is no floor pan to capture the eventual leakage when the tank does fail . It will allow the floor to be soaked and ruin whatever is below it . That is not in code here in the US . 3) there is no tank drain to service the tank . :2cents: |
SurferJoe46 (51) | ||
| 424690 | 2006-01-28 03:59:00 | All theory aside, I have two of those on my Rheem cylinder (about 18 years old), one on the hot side and one on the cold. The hot one vents outside and the original instructions said to operate it every six months or so I think, to ensure that it was not gummed up. I understood the purpose of the first valve to be to relieve the pressure generated by expansion as cold water was heated, but since this could never exceed the pressure of the supply, I couldn't understand why it was needed unless there is a one-way valve somewhere else in the system. Even if there was, that is taken care of by the second pressure relief valve on the cold water input so I am still in the dark. This shares the same drain vent at the hot water output. Not only were they to be operated at regular intervals, they were also supposed to be replaced every 4-5 years. I replaced the hot water one in 1991 but haven't bothered since. I didn't even notice the cold water relief valve until quite recently and it has never been replaced or even tested. Must add the earthquake strap as well one day, though I don't think the one picture will hold much back, it looks like it is secured with a single woodscrew. Hopefully we have a plumber here who can enlighten me as to what they are really there for. Cheers Billy 8-{) :confused: |
Billy T (70) | ||
| 424691 | 2006-01-28 04:56:00 | While we are on the subject can someone enlighten us as to the present day practice of using "sacrificial anodes" on modern ceramic coated steel high pressure hot water cylinders? Are they used these days, if so should they be replaced periodically? What is the design life of a mains pressure cylinder? Some years ago, when I had an allied involvement there were sacrificial anodes to be replaced 5 yearly, giving a cylinder life of about ~10 years before they rust through and leak. Most owners had no idea the requirement was there in those days and cylinders probably corroded quite early (I know some did). Personally I prefer the "medium pressure" design which has most of the advantages of the mains pressure system, but with the life similar to a low pressure cylinder. But most people seem never to heard of it. The low pressure copper cylinder replaced here a few years back was 50 years old. |
godfather (25) | ||
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