Point of use water heater

[Terry Hayden]

It seems that darkroom construction if booming - at least within this
august group ( hmm, august in january - how does that work?).

Anyway, does anyone have any opinions on point of use water heaters
for the darkroom?

My plans call for the new darkroom to be in an outbuilding that has power
and cold water service only. I've read adds for undersink units, but
the ones that run on 110v don't seem to have much capacity. One
brand in particular does go up to 8 gallons per hour, but I don't know
if that is enough.

Our water hear is not all that cold in the winter, but it does go down to
somewhere in the 40's ( f ).

Any suggestions?

Thanks
Terry

 

[Lee L]

Not to discourage you, but a word of warning. My plumber advises against the gas heated on demand heaters with a manifold because of a very high calcium content in the water where I live. The smaller manifold tubes are quickly clogged and the whole heater is gone in a couple of years in average household use. A regular large batch water heater is typically destroyed in 10 years by the same mechanism here.

So if you have a high calcium content, I'd advise against that specific kind of heater. This warning wouldn't apply with a non-manifold batch heater or with better water quality.

Lee

 

[Bob F.]

I use a 3kW on-demand electric water heater (no water tank - it heats the water as required). It works fine in London where the air temperature rarely falls much below zero degrees Celsius. If you want a greater flow rate, units designed to use for a shower are available, but at 5kW and above will require a separate electrical circuit to the fuse box (here in the UK, a 3kW unit can be connected to the normal ring-main).

Good luck, Bob.

P.S. Just did a quick check, water is currently coming out of the ground at around 7 degrees C (air temp 1C) and I am getting 3 litres/minute at 20C from the heater and 1.2 l/min at 40C (it just scrapes up to 41C before the flow rate is too low and the safety cut-out kicks in and switches the heater off).

 

[Photo Engineer]

We had an on-demand water heater for our house when I was growing up. It lasted over 30 years from what I have been told, as my grandparents used it before we lived there. It was still going strong when we moved out.

The biggest problem was that the slower you ran the water, the hotter it got until you could actually get steam coming out. Back then there was not as much concern for safety I guess.

Anyhow, I did my first color processes (E1 and E2) when I was a teen using that water heater to control the temperature at the proper value.

PE

 

[msage]

Terry
At work, a color and BxW lab, we have a gas on demand tank less water heater. It is great for 100 degree water ( at 3-5 l/m flow) for the E-6, but terrible for 68 degree water ( 1-2 l/m ) for BxW. Its great for a lot of HOT water, not so great for lower flows of 68 degree water.
I am currently building a darkroom in an out building and am going with a small electric tank water heater. Hope to have some input soon ( sheetrock is up, taping and mudding now).

Michael

 

[Terry Hayden]

point of use water heater clarification

Thanks for the quick response folks.

As a slight matter of clarification - I am limited to an electric unit.

One of the questions that I have is whether the 110v units will
be functional in a darkroom application.

Yes, we have very hard water here - so the comments about the
effect on the unit are taken under advisement. I appreciate the
comment.

Is it true that in the UK you are running 220v circuits as normal
power? If so, your experience may not apply to our 110v standard
situation. Still, thanks for the feedback.

Terry

 

[Dave Parker]

I looked at the hot water on demand units for my darkroom, which I live in a very high mineral content area and draw off of a well located on the property, but after looking at the cost to flow as well as maintenence, I am going with a 10 gallon 220V electric tank system, I can get one of these for just about the same cost as the electric on demand system and it has a 10 year warrantee on the tank, I have already wired the shop for 220v service and when it is all said and done, based on number crunching over a 10 year period of time the cost of the equipment the electrical costs and such will be much less with the 220v electric tank system, I am also installing in an outbuilding..and our temps are very low in the winter around here, we went to 37 below zero in December, so had to make some adjustments to keep room temps in the range required, but still cheaper and longer lasting.

Dave

 

[Dave Miller]

Terry,
The standard European domestic voltage is 230 volt, but it is the wattage that is the important measure in this instance, so Bob’s remarks regarding a 3Kw heaters performance will be equally valid for a 110volt on demand electric water heater. Having said that a 3Kw heater on 110v will require a 30 amp circuit, and a corresponding large supply cable size which may cause you problems in other directions. Consider getting local professional advice.