Navitron Renewable Energy and Sustainability Forum

General Renewable Topics => Inventions, Ideas, Innovation, Bodges etc => Topic started by: woodstove on March 15, 2017, 06:18:08 PM



Title: Hot water cylinder temperature gauge
Post by: woodstove on March 15, 2017, 06:18:08 PM
Can someone please suggest a suitable solution to this problem.

Now it's getting a bit warmer, our boiler wood stove is not needed until the evening. It supplies all our hot water and I get asked nearly every evening if there is enough hot water for a shower or bath etc.

So, I would like to fit a suitable gauge to the hot water cylinder that anyone in the family can view and determine how much hot water is available.

Thanks for reading.



Title: Re: Hot water cylinder temperature gauge
Post by: eabadger on March 15, 2017, 06:29:20 PM
bottom two show temp at bottom and top of cylinder
rest show wood boiler temp up pipe temt and ufh temp and rad flow return temps.


Title: Re: Hot water cylinder temperature gauge
Post by: woodstove on March 15, 2017, 07:01:38 PM
Thanks for your reply ...... I'd actually been looking at your system already, very nice.

Have considered building a copy of yours, but was holding off hoping for a simple 'off the shelf' solution...... but so far haven't found anything, so I started this thread.

It's hard to believe that there's still no simple way to read the amount of hot water that's stored in a simple hot water cylinder?




Title: Re: Hot water cylinder temperature gauge
Post by: AndrewE on March 15, 2017, 07:09:35 PM
I have a (lower) solar thermal coil in our cylinder and an upper coil fed from the gas boiler...  a hand on the house outlet flow pipe then on the (boiler) coil connectors tells you quickly how much hot water is available.  However by evening (or earlier if it's one of our regular "going out" evenings) the old gas boiler will have topped up the temperature in the top half if it thought it was necessary.  The only problem is if you want a bath mid-afternoon in the winter before the gas water heating has cut in, when you have to switch it on and wait a while...


Title: Re: Hot water cylinder temperature gauge
Post by: woodstove on March 15, 2017, 07:34:05 PM
Thanks Andrew ........ I have used the hand on pipe method, and but then a little while later I'm told the shower went cold or there wasn't enough water to fill the bath  :hysteria







Title: Re: Hot water cylinder temperature gauge
Post by: eabadger on March 15, 2017, 08:22:52 PM
i think they were 3 each and then the box to mount them on.
off the shelf can be making do as not all have same set up.
i am adding to mine now i have seen it woprks well, i use the outputs to bring on floor or rads as required.


Title: Re: Hot water cylinder temperature gauge
Post by: marcus on March 15, 2017, 09:08:53 PM
I have a single temp probe near the top of my small hot water tank; over time I've learned to interpret it's readings in combination with how the tank was heated:-

if using the Woodburning stove (normal winter), the coil on the bottom of the tank heats all the top evenly so any temp over 43C is enough for a warm bath; 48C for a hot bath.
if using the immersion slowly over the day (normal summer - dumping excess power into the top-down immersion), anything over 44C is OK for a modest warm bath. 48C for a hot bath. 52C for a generous hot bath.
if using the immersion on grid (a few minutes at a full 3kw input - I hardly ever do this), 55C will give a meagre hot bath or a modest warm bath but you must remember to turn off the water before it goes stone cold.


Title: Re: Hot water cylinder temperature gauge
Post by: woodstove on March 15, 2017, 10:05:41 PM
Thanks again ebadger ..... 3 is not a lot!, do you think they'll last?

Thanks Marcus ......... that's roughly how I see it working for us.

Just want something to indicate there's enough hot water, then simply check it again after each use.
What type of temperature sensor are you using?


Title: Re: Hot water cylinder temperature gauge
Post by: eabadger on March 16, 2017, 08:25:58 AM
will they last at 3? anyones guess but they look ok, i ordered double in case of issues.
250ltr main pressurized cylinder twin coil, lower main coil on the big wood boiler, top is a little 5kw oil boiler.
two temp pockets on the cylinder, on wood i aim at 60* + at top.
family like the display idea, they dont have to ask about showers now, but the two eldest hammer the 250ltr.

you could always use a infrared thermometer point at place on cylinder and read external temp, any sensor pockets?

steve


Title: Re: Hot water cylinder temperature gauge
Post by: mr_magicfingers on March 16, 2017, 10:03:06 AM
I have a similar system to eabadger, cheap 1.99 thermometers from eblag. I have the sensors in pockets that were put in when the cylinder was ordered - top, middle and bottom, plus two extra for the flow and return pipes from the woodburner. I used a piece of cat5 cable to extend the sensor wires and they're mounted in a plastic box that's in the room near to the woodburner. A quick glance tells me how much hot water is in the tank and whether I need to light the fire or give the immersion an hour's boost. Also tells me how much heat the pv diverter has been throwing into the tank on a sunny day.

Cost under 15 and a couple of hours of my time.


Title: Re: Hot water cylinder temperature gauge
Post by: marcus on March 16, 2017, 09:49:45 PM
I don't actually know what my temp sensor is - well, it's a newport digital pyrometer with GPIB/IEEE488 interface IIRC - i fished it out of the rubbish skip at the place I used to work many years ago and it was probably dreadfully expensive when it was new. If I were looking to buy one now I'd go for one of those cheap n cheerful chinese ones for something like this.


Title: Re: Hot water cylinder temperature gauge
Post by: Zaph on August 17, 2017, 11:28:59 AM
Hi
Badger, any clue where we can get some of those cheap thermometers pictured? More importantly, how long can you make the lead?


Title: Re: Hot water cylinder temperature gauge
Post by: mr_magicfingers on August 17, 2017, 01:20:48 PM
Hi
Badger, any clue where we can get some of those cheap thermometers pictured? More importantly, how long can you make the lead?

Not badger but mine are from ebay, similar to this, https://www.ebay.co.uk/p/Digital-Aquarium-Reptile-Thermometer-With-Probe-Freeze-UK-SELLER/1688591981?iid=111418097114

I cut the wire and extended with cat 5 cable in between, I have extended them about 5-6m.

Hope that helps.


Title: Re: Hot water cylinder temperature gauge
Post by: Zaph on August 17, 2017, 02:45:04 PM
Ah, OK thanks. These definitely appear to use the DS18B20 waterproofed 1-wire digital sensors, so yep should work up to 40 meters.
Added one to my weekend shopping list to try out. Still trying to work out where I want to mount the display. The basics will be to display the bottom of tank temperature, on the bathroom door I guess.


Title: Re: Hot water cylinder temperature gauge
Post by: Fionn on August 17, 2017, 03:07:18 PM
If you only have one sensor I think a mid tank measurement would be more useful, but for the cost I can't think of any reason not to have one at the top, middle and bottom!


Title: Re: Hot water cylinder temperature gauge
Post by: Zaph on August 17, 2017, 08:16:43 PM
Agree Fionn. 3 is better.
I intend hooking a logger up, and connect it to a tablet computer/browser display. And then have top, middle and bottom, but before all the wiring maze starts to starts, just a single display. The trouble is in summer the topmost temp is most usefull, but in winter, the back boiler feeds in at the top. so the bottom temp is more useful, so all 3 are going to be needed.
Eventually want to try monitor the back boiler inlet, and ensure that my pump does not rush cold water into it. Will probably take me ages, but winter is coming, so I better get cracking.


Title: Re: Hot water cylinder temperature gauge
Post by: mr_magicfingers on August 17, 2017, 09:39:35 PM
I'd be interested to know how you get on with the logging, I've not figured out how to do that easily. Having it available via a web interface would be very useful.


Title: Re: Hot water cylinder temperature gauge
Post by: regen on August 18, 2017, 06:37:24 AM
As per Mr. Magic fingers

I installed 16 of these 1.00 chinese jobbies over 2 years ago,extending the wires using Cat 5 by as much as 8 metres and simply twisting the ends together. They came with batteries and 15/16 are still working fine although some LEDS are getting a bit DIM. I doubt they are accurate to better than +- 3 degrees. For the tank I just put them into the probe pockets top and middle- actually its a thermal store. They also measure things like all the room temps and IN/OUT temps for the wood burner,oil boiler, under floor heating and rad heating circuits as well as attic temp and TS pipe to tank. Mostly they are taped to pipe under insulation.

After a couple of years most are no longer even looked at but did help when system was first used. However those on the Store are used daily, particularly in summer and if the sun aint shining then the oil boiler can be flicked on manually.

For about 50 in total its been a good investment and no complaints about the Chinese jobbies.

Regen


Title: Re: Hot water cylinder temperature gauge
Post by: TheFairway on August 18, 2017, 11:16:34 AM
...I doubt they are accurate to better than +- 3 degrees.
Odd as if they are the Maxim single wire probes, they should be accurate to about +/- 0.5C even at the lowest resolution - the sensor supplies the temperature reading so the host just needs to read it. I had 5 in parallel linked to a Arduino test board and they all sat within 1C of each other.

I guess its how they are mounted. My final intention for the 5 above is for the tank (probably supply, bottom, mid, top, draw off) and was thnking of drilling out a hole in the tank insulation, filling with heat sink compound then pushing probe in until it hopefully touches, probe end on with the tank. Wonder how well this may work.

Yes, just checked -
https://datasheets.maximintegrated.com/en/ds/DS18B20.pdf
or
https://datasheets.maximintegrated.com/en/ds/DS18S20.pdf



Title: Re: Hot water cylinder temperature gauge
Post by: Zaph on August 18, 2017, 01:24:56 PM
Yep. A winter project, which will probably only be working in time for winter of 2019.
I'm trying to find the lazy way, because, I have some programming skills, some electronics skills, but not much cash, to buy a Hive, Alexa or a Philips solution. And enjoy building stuff - based on many people on the webs sharing their Raspberry Pi builds, want to copy ideas from the PiMon system, without paying for sensors and boards that I might not need initially. If you browse my website link in profile www.softcircuitry.blogspot.com , you can see I have built basic Arduino setups in the distant past when I had more time. The DIY needs of the new old house have been an immense drain on my hobby time.
I will defo paste some pics once we get some temperature readings, since that will encourage me and others to keep optimising our power consumption. My system still will rely on a 3KW immersion heater, which I hope to relegate to emergency use only. My biggest power use at the moment is running 3 computers, I have 2 teenage computer-gamer pros, so they will be one of the first things to try cut down.

(https://s12.postimg.org/d85ctnhi1/C_At_Ha_W0_AIrud_S.jpg) (https://postimg.org/image/d85ctnhi1/)


Title: Re: Hot water cylinder temperature gauge
Post by: regen on August 19, 2017, 06:30:11 AM
uote from: regen on August 18, 2017, 06:37:24 AM
...I doubt they are accurate to better than +- 3 degrees.
Odd as if they are the Maxim single wire probes, they should be accurate to about +/- 0.5C even at the lowest resolution - the sensor supplies the temperature reading so the host just needs to read it. I had 5 in parallel linked to a Arduino test board and they all sat within 1C of each other.


I suspect my perceived inaccuracies are due moe to differing wire lengths,poor joining connections and differing contact with the pipe under insulation etc rather than inbuilt inaccuracies in the units themselves. However exact measurements were not important to me only replication.

Regen


Title: Re: Hot water cylinder temperature gauge
Post by: eabadger on August 19, 2017, 11:25:24 AM
my chinese ones nearly a year on still working, i use the type with the relay and use this to switch (via a proper relay) different circuits in and out.
i have extended all leads and see no change of accuracy, biggest issue is fitting in the sensor pockets, i pack with fibreglass.
i think mine cost about 3 each but very worthwhile, you could in therory use one display and switch the sensor to view each.
 


Title: Re: Hot water cylinder temperature gauge
Post by: biff on August 19, 2017, 11:49:31 AM
That is impressive Steve,
                          Biff


Title: Re: Hot water cylinder temperature gauge
Post by: eabadger on August 19, 2017, 12:03:09 PM
have tidied up since then, they check gravity flow and return temp then bring on pumps, added a priority switch now so floor or rads get heat first after dhw.
they check floor and rad flow and return temps and dhw cylinder top and bottom.
you can set these sensors to switch on low or high temp, they dont make that clear when selling, but knowing it is a plus point.
all simple to do but does the job well, this is in what will be a cupboard in the dining room, currently we are using as the living room whilst what is to be the livingroom is my workshop, so i can sit and watch the numbers whilst watching telly, a bit addictive, sadly.

steve