You don't think the HAH is a bargin?
1 February, 2012 - 00:56
I had to laugh at how much this unit costs ... I won't spoil the suprise.
http://www.automatedhome.co.uk/New-Products/Keene-Netswitch-Controls-Mai...
What are you waiting for? Keene are super keen to take your money :)
http://www.amazon.co.uk/gp/product/B006X11AFY
Brett
2 February, 2012 - 13:09
#2
Happy HAH Bunny now saving me MORE money
I have for a while thought about all the electricity i keep exporting and how i could make use of it..
My conclusion was why not heat my hot water using the immersion.
Lots of thought went into this and just for info i have a dual heater set up (very large tank)
each heater is 3Kw so both=6Kw in series thats 1.5Kw (still too much as it would hardly ever be on to be effective) i looked a pwm (puls width modulation) so it would feed the heaters aith just under avalible power but this was ridiculously expensive and would require some real specialist hardware and software to work.
the final soloutuion is as follows
SOftware a plugboard script tha monitors the solar generation AND the ligh on my electricity meter (which goes solid red when i am feeding grid) so if solar=1.9Kw+ and grid=feeding then switch relay 1 on, there is a 2minute "timer" as well so it does not switch on for 2 minutes after a change to stop oscillation. Thanks Alan i said i would use it properly in ernest
Hardware is an LDR (light dependant resistor) and a currrent cost digital board for the meter.
wired both imersions in series and then put 2 0.79p diodes also in series which brings the max draw to 750watts (ish) and used a proper mains relay to switch the heaters (the HAH relay is not up to the job of direct mains switching)
the outcome well look at my pachube feed, specifically grid1 (500=feeding) hot water tank and feed-the feed is from boiler so you can tell if boiler is heating it or the solar is. there is also an indicator for when the boiler is on. already i can see water getting hotter and the boiler is off :) Magic
https://pachube.com/feeds/15114
My house is oil fired and i estimate i use apx £150 on oil for heating during the summer (6months) so estimate my total to be £300. I am hoping to save 75%+ of this figure so HAH should now pay foritself in cold hard cash in apx 3-4 months!!
Yes i am a happy bunny!!!
Thanks Bret and Derek
2 February, 2012 - 13:19
#3
clarification
The 2 diodes are wired in series with the cct but in parallel with each other so they are running at 50% capacity.
Dean
2 February, 2012 - 13:36
#4
Hotw water sensor
Agree, this is project has wider horizons than my HoemVision at half the price - though the if then else logic is much easier than LUA;-)
Dean I was just wondering how you measure the hot water? I have a DS1820 stuffed down a hole I drilled in the insulation, but it seems very temperamental to the height.
Any better way of doing it?
Alan
2 February, 2012 - 14:07
#5
Height
Yes it is very temperamental to the height.
My immersion tank is huge and stands apx 5feet high, hence it has 2 immersion points top and bottom, the sensor that goes in the tank to switch it on/off when it reaces temperature-i removed the top one and stuffed a ds1820 in the pipe which means the temp displayed is near the top of the tank apx central.
I use the bottom one to decide when the water is really hot enough and the immersion can switch off.
the temp at the bottom of my tank compared to top depends on how much hot water i use and can differ by over 30degrees!
the other way would be to mount the sensor by tywrapping it very close to the pipe at the top this would then be probarly as good as it would be the temp that the water would come out at-hope the above makes sense, i did say i had been researching for a long time :)
2 February, 2012 - 15:02
#6
Hot water Temperature Profile
I have been monitoring my hot water tank for some time, originally with 3 dS18S20s, top, middle and bottom. The middle one is defunct now, but you can see the data at
https://pachube.com/feeds/2037, datastreams 1 top and 3 bottom. Probably best selcting a week view...
My CG/HW system is gas fired. I have an immersion heater but don't use it. The top sensor is tie-wrapped to the outlet on the top of the tank under a jacket, but insulated from the copper by tape. The bottom and middle are underneath the foam against the copper but again insulted by tape. The foam I (carefully) cut out has been replaced on top of the sensors..
My boiler is downstairs and the tank is in the loft. In simplified terms the actions are:-
Hot water heated in boiler rises through pipes to the coil in the tank heating the hot water, the hottest water is at the top (hot water rises)
As you use hot water it comes off the top of the tank, cold water replaces the consumed hot water in the system, the cold water is at the bottom of the tank, and the hot is at the top. The hot runs out once the cold reaches the top of the tank
If the boiler is on it will detect the cold water and heat it to replace the consumed hot water
So you need a sensor at the top to tell you how hot the water you use is, but you need one at the bottom to show you the process. You can see it at the top, but the data is damped by the effects of the mixing of the hot and cold water. If you have a tall tank or multiple heat sources then a sensor in the middle is worth having.
Unfortunately the separate graphs with different scales on the Pachube page don't show the results very well, You need them on the same graph to the same scale really but that is another thread... ;)
A word of caution about cutting away the foam on a tank, you will probably use a knife, you must take care not to score the copper of the tank which is really quite thin.......
My plan is to move this monitoring over to the HAH soon, when I do I will post some pictures
kevint
PS We ** know ** HAH is bargain! ;) , well done Brett and Derek
2 February, 2012 - 21:26
#7
Thanks KevinI had worked out
Thanks Kevin
I had worked out the temp variations I was seeing, I was more interested in the mounting methods.
The reason is that even with the temp sensor deep in the insulation and touching the tank, i am getting variations when the heating is on. This is caused by the heating effect of the airing cupboard as the pump and 3way valve is in there. I think this is real, but was keen to isolate the water temp from the temperature of the airing cupboard.
All useful stuff. I think I will start a new thread where we can share pics of sensor solutions.
Alan
3 February, 2012 - 00:24
#8
re-read my post and realised
re-read my post and realised it sounded like I was being less than complementary, trust me I'm not intending to sound like that, love mine still playing with it and planning sensors. Thanks Brett & Derek.
Did you use thermal compound? Tried a an 18s20 with & without on copper pipes, the heatsink compound made a difference, also it needs to be pressed against the surface. Strapping round the tank with a standoff pushing in (gently) is how they do it with commercial thermostats. I found wire / garden hose screw straps better than tie wrap on pipes.
Possibly a silly idea but rather than use a knife try a sharpened plastic tube for cutting the insulation its pretty soft (when I fitted a thermostat on the old tank I used a plastic scraper). Also its disolved by acetone a little messily (but don't use too much, think damp cotton buds) just to clean the copper (rememeber test on a small area first).
Seen multiple thermostats used on some designs so you can easily estimate how much hot water is left.
Brett
Never doubted it was darn good value for hobbyists and a fantasic achievement.
Theirs looks like a Siteplayer / Rabbit / PIC / AVR with some relays, not much expansion.
However HAH uses a recycled router value £25 - £50 retail, Case milling £10 and the HAH board £42 kit form. So if you wanted to build it from scratch HAH would cost about the same. Key thing is the openness and functionality.
A Raspberry PI plus an Arduino with an enclosure, usb mains relay & RF board would come in at £50 -100 for hobbyists.
The add ons are very cheap rf sockets & current cost so its complete HA for less than £500.
Personally I think the nearest equivalent is the Vera $299.
http://micasaverde.com/
This is zwave only so the cost of expansion is more.