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Fintan
09-10-2008, 03:43 AM
Iíve seen a nice dishwarmer for sale in Silverprint and am thinking of getting one. My darkíshedí can get quite cold and keeping lith developer up to temp is a real pain.

Iíve a (probably silly) question to ask about the use of a dishwarmer. As its an electrical device, working close to water/liquid, is there a danger of an electric shock from it? Should it be used with a RCB?

Fintan

Martin Reed
09-10-2008, 03:57 AM
Iíve seen a nice dishwarmer for sale in Silverprint and am thinking of getting one. My darkíshedí can get quite cold and keeping lith developer up to temp is a real pain.

Iíve a (probably silly) question to ask about the use of a dishwarmer. As its an electrical device, working close to water/liquid, is there a danger of an electric shock from it? Should it be used with a RCB?

Fintan

Well, it's an earthed device, which provides a high level of protection as long as your wiring is in order. But an isolation device would be a good extra precaution. Truly abused ones in community darkrooms have given up the ghost, however in 3 decades of selling these, and similar ones we've never had a case of anybody experiencing a shock.

The best arrangement is probably to keep it on duckboards raised away from the bottom of the sink, and give it a good wipedown after use.

nemo999
09-10-2008, 04:11 AM
I’ve seen a nice dishwarmer for sale in Silverprint and am thinking of getting one. My dark’shed’ can get quite cold and keeping lith developer up to temp is a real pain.

I’ve a (probably silly) question to ask about the use of a dishwarmer. As its an electrical device, working close to water/liquid, is there a danger of an electric shock from it? Should it be used with a RCB?

Fintan

The only dishwarmer I have used is the Paterson type, of which I have 4 or 5 examples. Essentially it is a rectangular box with a flanged top, the flange of which reaches down the side about 15 mm. This provides protection against splashes but I would not put one of these warmers anywhere near a sink, only on a benchtop where all spillages drain away rapidly. To place the warmer anywhere where it could accidentally get flooded would be far too risky - flooding would ruin the warmer (which is not sealed) and create a lethal shock hazard (an RCD would provide some safety against shock, but flooding would still ruin the device).

Bob F.
09-10-2008, 04:12 AM
Short answer: yes, use a residual current device...

Preferably have the whole shed on one. Don't know how you take power to the shed but you can get RCDs that fit on the wall to isolate the whole circuit with one RCD. Look for RCD FCU (fused connection unit) or RCD Spur if you use the same terminology in Ireland as in the UK.

Good luck, Bob.

Fintan
09-10-2008, 04:23 AM
Thanks for the reply Martin, I'll order one this week. I'll get an electrician to check my setup and use it in a raised position on the draining board part of my Browns sink.

nemo999
09-10-2008, 04:27 AM
Thanks for the reply Martin, I'll order one this week. I'll get an electrician to check my setup and use it in a raised position on the draining board part of my Browns sink.

Note that the interaction of electricity and water is closely defined by IP numbers:
http://en.wikipedia.org/wiki/IP_Code
Every electrical product should have an IP number, which states very clearly what you can and cannot expect it to do.

Fintan
09-10-2008, 05:03 AM
Thanks for that info, super useful :)

Dan Henderson
09-10-2008, 05:56 AM
In the US at least, the electrical code requires that any electrical outlet within 6 feet of a sink must be equipped with a ground fault circuit interrupter. It trips the circuit at a lower current than that which could electrocute you. An old electrician told me once that GFCI's on each outlet are safer than a remote one protecting several outlets because they act quicker, but I don't know if that is fact. Given my aversion for becoming part of an electrical circuit, I took his advice. I plug in a thermostatically controlled tank sitting in the darkroom sink that keeps my developer at the proper temp in cold weather, and it occasionally trips the GFCI, which is annoying but lets know know it is doing its job.

rwyoung
09-10-2008, 08:24 AM
One GFCI at breaker box vs one at each outlet won't make much difference as far as reaction speed goes. Yes, you could probably get a faster reaction by 2 times wire-distance times 75% the speed of light. But frankly this works out to about 800ns per 100 meters of wiring... Not very much difference.

But what might make a difference is the current leakage threshold detectable by an outlet central device vs a panel device. However I haven't convinced myself there is any real difference.

But if you have NO GFCI outlets, installing a GFCI breaker at the panel is a good idea and is potentially a simpler project than replacing a bunch of outlets in say a kitchen or darkroom. Could also be cheaper if you have three or four outlets on the same branch that need GFCI-ing.

All GFCI breakers require that the HOT/NEUTRAL/GROUND configuration be properly wired or they won't work correctly. This is because they detect current greater than a milliamp or two flowing in the ground lead (a bad thing). If you have older residential wiring that does not use a dedicated ground lead or at least use metal conduit (properly configured as ground) then you cannot install a GFCI outlet or breaker without upgrading the wiring.

bobwysiwyg
09-10-2008, 08:26 AM
I live in an older home and back when it was built they couldn't spell GFCI :) so there are many older homes without them. Definately have one properly installed per the codes suggested if you have not had any home additions or modifcations that would have required code updates.

greybeard
09-10-2008, 08:44 PM
All GFCI breakers require that the HOT/NEUTRAL/GROUND configuration be properly wired or they won't work correctly. This is because they detect current greater than a milliamp or two flowing in the ground lead (a bad thing). If you have older residential wiring that does not use a dedicated ground lead or at least use metal conduit (properly configured as ground) then you cannot install a GFCI outlet or breaker without upgrading the wiring.


This may be slightly oversimplified---a GFCI which monitored the ground lead would be oblivious to current flowing from the hot lead to earth ground (cold water pipe?) through someone's body.

The GFCIs that I have installed require only hot ("line" in electrical terminology) and neutral leads. The neutral is which is where the return current from the hot lead is supposed to flow. The circuitry compares what is going out (hot lead) and what is coming back on the neutral, and if the difference exceeds about six milliamperes, the hot lead is opened, shutting off the power. It doesn't matter whether the leakage is to the grounding conductor or to "earth", and in fact GFCIs work in ungrounded systems. What is important is that all current return on the neutral, instead of through some other path, and failure of this condition is what the GFCI detects.

The purpose of the ground is two-fold: it keeps things that are supposed to be non-energized (such as the housing of an appliance or tool) from going "hot" if there is an internal fault, and it causes such a fault to draw enough current to immediately trip the circuit breaker. If you have anything electrical in use, near water or otherwise, you really should have grounded wiring, and the next best thing is GFCI protection. The very best thing, of course, is to have both.

rwyoung
09-11-2008, 08:22 AM
graybeard is correct, I over simplified when I stated the above. The imbalance is between line and neutral. However I still stand by the upgrading of wiring before installing GFCIs.