WiFi control of hot water cylinder: feasible?

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Fred99

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#1612402 16-Aug-2016 12:07

frankv:

timmmay:

Where else would you put a controller for the hot water cylinder?

At the water cylinder.

Absolutely, but IIRC @timmmay commented that in his case the HWC was in the ceiling space.

timmmay

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#1612403 16-Aug-2016 12:15

Jaxson:

The recommendation is that water temp reaches 60°C in the tank at least once per day.

The issue is that the in a water tank, the top can be warmer than the bottom, so the real objective is that the whole tank be raised to this temp.

http://www.stuff.co.nz/national/health/70285141/legionnaires-disease-from-hot-water-cylinder-results-in-amputations

It's a funny situation though, in that with tempering valves the water in the lines from the HWC are never at this high temp.

I guess it has been up to that temperature recently though, so as long as there's no source after the hot water cylinder it should be safe. Raising it to 60c at least once each day is really important though. I have hot water on a timer, heating 2am to 7am every day plus occasionally on days I know are heavy uses (washing day).

timmmay

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#1612404 16-Aug-2016 12:16

Fred99:

Absolutely, but IIRC @timmmay commented that in his case the HWC was in the ceiling space.

Remember I'm not the OP, not sure where their tank is. Putting it beside the tank seems reasonable enough, but putting it on the switchboard where it's out of the way and there's space might make more sense.

kiwigander

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#1612473 16-Aug-2016 13:42

The cottage is in the city on a regular urban water supply. Not in Havelock North, either.

The cylinder is in the attic.

The switchboard enclosure is plastic, not steel as I had thought, so a device mounted there should be able to communicate over WiFi.

If we had had the option I'd have gone for an LPG-fuelled califont, but that was not available in the cookie-cutter subdivision.

neb

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#1612830 16-Aug-2016 21:36

Jaxson:
Warm water is a nice breading ground for bacteria.

Specifically, read up on legionellosis before you start deciding to lower the temp of your cylinder for longer periods of time. Running it below 50 degrees makes it an ideal breeding ground for bacteria.

timmmay

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#1612961 17-Aug-2016 07:55

Anyone have any thoughts on heating only at night? So it gets cooler throughout the day (still pretty darn warm most days), then heated 2am - 7am? That means for a period of up to 12 hours we could have water below the recommended temperature. The recommendation is to heat it up at least once a day so we're doing what we're meant to I think. If we had anyone with a compromised immune system I'd just have it on at all times outside peak.

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pulsta

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#1612970 17-Aug-2016 08:29

timmmay:

Anyone have any thoughts on heating only at night? So it gets cooler throughout the day (still pretty darn warm most days), then heated 2am - 7am? That means for a period of up to 12 hours we could have water below the recommended temperature. The recommendation is to heat it up at least once a day so we're doing what we're meant to I think. If we had anyone with a compromised immune system I'd just have it on at all times outside peak.

Hi timmmay - this is from the other thread you OP'd and I had on my watch list - no idea how you would go about installing one though.

http://www.activeautomation.co.nz/aeon-heavey-duty-smart-switch

I take it you haven't installed anything yet? as I'm super keen to get something going too...

timmmay

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#1612981 17-Aug-2016 08:56

pulsta:

Hi timmmay - this is from the other thread you OP'd and I had on my watch list - no idea how you would go about installing one though.

http://www.activeautomation.co.nz/aeon-heavey-duty-smart-switch

I take it you haven't installed anything yet? as I'm super keen to get something going too...

I've had a digital timer in place for a few months. My electrician supplied it.

SumnerBoy

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#1612983 17-Aug-2016 08:56

timmmay:

Anyone have any thoughts on heating only at night? So it gets cooler throughout the day (still pretty darn warm most days), then heated 2am - 7am? That means for a period of up to 12 hours we could have water below the recommended temperature. The recommendation is to heat it up at least once a day so we're doing what we're meant to I think. If we had anyone with a compromised immune system I'd just have it on at all times outside peak.

This is exactly what I do. Heats from 4am - 7am (on cheap rates) up to 65 degrees. I do have solar H20 evacuated tubes however, so on sunny days the cylinder is also being boosted.

Here is a link to my monitoring dashboard for the HWC... https://snapshot.raintank.io/dashboard/snapshot/AVzbX6cIxHpA61geVK4beQo5cOOH1v7W

You can see the temp steadily increasing yesterday (since it was nice and sunny) and then the bottom of the cylinder start to cool as we use hot water in the evening. Then at 4am the electric boost starts (which is wired to the middle element of my HWC) and heats the top half of the cylinder back up to 65.

OldGeek

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#2548184 23-Aug-2020 13:29

Looking at an update from GZers on this. I am simply looking to ensure my electric cylinder is only on during low-cost electricity periods (I have TOD pricing). One such unit is this: https://www.turfrey.co.nz/shop/building-products/water-heating/bobbie-smart-hot-water-cylinder-controller/. Are there other less-expensive options?>

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timmmay

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#2548186 23-Aug-2020 13:41

I had my electrician put in a heavy duty timer. No wifi, works fine and we rarely need to change it, maybe twice a year. fitting will cost you an hour or two of electrician time as it's probably done at the switchboard.

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nickb800

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#2548195 23-Aug-2020 13:59

Cheapest way is to get two separate components - timer (or wifi controller) and contactor/relay. With the Bobbie, your paying a premium for smarts and high current relay in a single package.

Hot water cylinders are heavy power users, so you want some headroom between the rating of your element and rating of contactor/relay. If you have a 2000-2400w element, then could possibly get away with a small relay like the pdl 600RM which can be mounted with the cylinder switch (or hidden in the wall). For a bigger element you would be looking at a contactor, which is typically din mounted - so either in the switchboard or in a switchboard style enclosure in the hot water cupboard.

Can go for a commodity timer (din mount or otherwise) or basic wifi module e.g. Deta grid connect (assuming you haven't already got smart stuff from another brand around the house)

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