Arduino powered servo arm for Hot Water service

[RobRoySyd]

Originally Posted by gtc

... which brings me back to my earlier general question about these sealed time switches: who resets them after blackouts?

Digging deep into the memory banks I recall these kind of devices having an option to use a clockwork backup mechanism. There was some very ingenious devices in the days before everything was done in silicon.

When I worked for Muzak we used them to switch the music on and off in 15min segments to match the content with the audience. I never recall us having to reset the clocks.

Looking at the photo of the clock in detail I did see it was rated to switch 50A so I was wrong, one clock probably could be used to control five water heaters.

[gtc]

Originally Posted by RobRoySyd

Digging deep into the memory banks I recall these kind of devices having an option to use a clockwork backup mechanism. There was some very ingenious devices in the days before everything was done in silicon.

When I worked for Muzak we used them to switch the music on and off in 15min segments to match the content with the audience. I never recall us having to reset the clocks.

Looking at the photo of the clock in detail I did see it was rated to switch 50A so I was wrong, one clock probably could be used to control five water heaters.

I've never encountered clockwork backup, but I guess that would be the only feasible way of providing backup to a unit like that.

I also saw the 50A switch rating but figured that each heater would be at least 2400 watt, and that 50 amps, being right on the total for 5 of them would not provide sufficient "headroom" for contact longevity. For that setup I would expect the time switch to operate a decent size contactor to switch the heaters themselves.

(Then again, maybe the heaters in those off peak tanks had lower wattage heaters for a long slow heat cycle. I do recall that our gravity tank not only gave poor pressure but also the hottest water ran out quickly and it was little better than tepid thereafter.)

From what Icarus has said more recently, I think his apartment may be the only one on that meter and switch.

[Icarus]

Originally Posted by gtc

Icarus, can you confirm that you have actually seen your HWS meter running at all hours of the day and night, not just those timeswitch-on periods of 0000 to 0700 and 1330 to 1830.

From what Icarus has said more recently, I think his apartment may be the only one on that meter and switch.

Our hot water does have its own meter (as shown in the photos) and the switch the servo turns on and off only controls our hot water. The timer is shared though.

I'd have to power the system on outside of those times to see as I was told by a plumber it should only be on between 2300 and 0700, so when I saw it going at 2ish in the arvo I presumed something was wrong, but as you've noted, the timer does power on from 1330 to 1830.

Originally Posted by sbadman

I will also go with the stuck time switch, as your photo shows it set at 1:15pm, but the Exif data says you took the photo just after midnight....

I think the Exif data got scrapped when I resized the image. The original Exif says 4:21pm.. So the timer is wrong, by 3 hours.

I believe I'm only a couple of days away from getting this quarters power bill, the first since the servo was installed, so we'll be able see how much of a difference its made.

[gtc]

Originally Posted by Icarus

I'd have to power the system on outside of those times to see as I was told by a plumber it should only be on between 2300 and 0700, so when I saw it going at 2ish in the arvo I presumed something was wrong, but as you've noted, the timer does power on from 1330 to 1830.

If the time switch is turning (albeit 3 hours behind AEST) and its two sets of on/off contacts are operating correctly, then it's looking more and more as though it's a jammed-on thermostat causing your heater to run every day for the full 12 hours per day that the off-peak timer provides, and that would certainly run up a big bill, albeit at the off-peak tariff.

And it could certainly boil the water and cause the pressure relief valve to open and stay open, venting boiling water to the outside of the building or a drain (and probably creating a very steamy atmosphere in the roof space as somebody mentioned earlier). Pressure relief valves are designed for intermittent use, and I've experienced consequential pressure valve failure following a failed thermostat on my Rheem mains pressure HWS, necessitating two repairs.

[RobRoySyd]

Originally Posted by gtc

If the time switch is turning (albeit 3 hours behind AEST) and its two sets of on/off contacts are operating correctly, then it's looking more and more as though it's a jammed-on thermostat causing your heater to run every day for the full 12 hours per day that the off-peak timer provides, and that would certainly run up a big bill, albeit at the off-peak tariff.

And it could certainly boil the water and cause the pressure relief valve to open and stay open, venting boiling water to the outside of the building or a drain (and probably creating a very steamy atmosphere in the roof space as somebody mentioned earlier). Pressure relief valves are designed for intermittent use, and I've experienced consequential pressure valve failure following a failed thermostat on my Rheem mains pressure HWS, necessitating two repairs.

If it's the kind of hot water heater I and others are thinking of then it has no pressure relief valve. It doesn't need one as the tank is vented to the air and cannot become pressurised. So if the thermostat fails On then the water will just boil off with little overflow and lots of steam going into the roof space.
If the valve in the cistern jams or the washer fails then the tank's overflow pipe saves the day but you loose a lot of water and waste a far amount of energy however if that was the problem the water in the tank would soon cool down from the cold water running into it all the time.

[gtc]

Originally Posted by RobRoySyd

If it's the kind of hot water heater I and others are thinking of then it has no pressure relief valve. It doesn't need one as the tank is vented to the air and cannot become pressurised. So if the thermostat fails On then the water will just boil off with little overflow and lots of steam going into the roof space.

Yes, of course, it being gravity feed it wouldn't need to be pressurized.

Odd that there's apparently no manhole access -- unless it's in another apartment ... if there is another apartment on the top floor.

[Icarus]

Hey, so out of curiosity I measured the water temperature straight out of the tap (the HWS was on overnight).

I tested the water from the tap 6 times (putting it into a mug). The top temperature recorded was 79.75^o. The lowest was 77.22^o.

The average of all 6 readings was 78.3^o.

What sort of temperature should I expect?

Also, update from the LL. A plumber and sparky are coming tomorrow to cut a manhole to gain access to inspect the current system and look at how/where a replacement could be installed.

[gtc]

Originally Posted by Icarus

Hey, so out of curiosity I measured the water temperature straight out of the tap (the HWS was on overnight).

I tested the water from the tap 6 times (putting it into a mug). The top temperature recorded was 79.75^o. The lowest was 77.22^o.

The average of all 6 readings was 78.3^o.

What sort of temperature should I expect?

The maximum temperature depends on what the thermostat is set to cut out on. On our mains pressure unit I have it set to 50 degrees which is plenty hot enough, however I read today where there's a legionella bacteria risk with tank style heaters unless it's 60 degrees or above:

http://www.theaustralian.com.au/news...-1226015191157

Also, update from the LL. A plumber and sparky are coming tomorrow to cut a manhole to gain access to inspect the current system and look at how/where a replacement could be installed.

Suddenly the landlord is interested? Maybe he reads this forum, LOL!

I'm still amazed that there is no manhole. Perhaps the ceiling has been replaced at some time or other.

[Icarus]

Originally Posted by gtc

I'm still amazed that there is no manhole. Perhaps the ceiling has been replaced at some time or other.

Yeah, he asked to come around and ended up doing 4 or 5 laps of the unit and looking in the cupboards over and over cos he couldn't believe there was no access either

[Icarus]

'k so this quarter's powerbill came today.

Prev bill | Aug - Nov 2010 Off-Peak: 2560 kWh.

After a full month of only powering on the hot water every 3 days.

Dec - Mar Off-Peak: 445 kWh.

Instantly $200 saved.

Also, they cut into the ceiling today to gain access to the HWS... and they found that that thermostat was set too... well the dial goes up to 100 and it was a couple of notches past that. Freaking insane.. It's been turned down now.

Best guess as to what happened (having learned a little more about the repair bills the LL has received over the last 7 months or so)

• The heating element started to die June-ish last year (first time I complained about the hot water.. it was a little over lukewarm). Plumber came out and 'fixed' it. No parts on repair bill.

• September, it went cold again. Plumber came out and this time charged for a replacement element.

We can only presume the first time the plumber came out, he just cranked the thermostat up in an effort to bring up the temperature, then when the element was replaced in September, it wasn't turned down again...

Anyway I'll leave the HWS on for a couple of days and keep an eye on the kWh usage.

[gtc]

Originally Posted by Icarus

We can only presume the first time the plumber came out, he just cranked the thermostat up in an effort to bring up the temperature, then when the element was replaced in September, it wasn't turned down again...

Sounds feasible. And he must've gained access by lifting tiles?

[stealthmatt]

so to the op did u comfirm if ur hotwater heater is spinning the elec 24/7?

[Sam_Q]

if the hot water system is defective isn't it your legal right to have the landlord fix it?

[gtc]

Originally Posted by Sam_Q

if the hot water system is defective isn't it your legal right to have the landlord fix it?

Yes, the landlord is responsible for such things, but the OP was dealing with a difficult one.

[Sam_Q]

irrelevant? push the legal rights, just because the landlord doesn't want to doesn't mean he can avoid it

How about an industry ombudsman of some kind?