Thermostat + Timer
in [Design]
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From: Charlie E. on 15 Oct 2009 11:49 On Thu, 15 Oct 2009 08:01:37 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote: >I have recirculating hot water here... big loop around the house and >back to the water heater, pushed by a pump (Bosch). So you get >instant on hot water. And also big heat losses in the underground >loop. Since the water heater is well-insulated, I'm tempted to simply >turn off the pump (with a timer) in off hours. > > ...Jim Thompson Hi Jim, How about a flow sensor on the cold in side of the water heater that turns on the pump for five minutes. You want hot water, you turn the tap on, turn it off, and a few moments later you have hot water. That way the pump only runs when you need it. Charlie
From: baron on 15 Oct 2009 11:59 Jim Thompson Inscribed thus: > On Thu, 15 Oct 2009 15:52:50 +0100, baron > <baron.nospam(a)linuxmaniac.nospam.net> wrote: > >>don <don> Inscribed thus: >> >>> baron wrote: >>>> Hi Guys, >>>> >>>> I'm doing a hobby project to build a timer that can be used to turn >>>> on a relay at a pre-determined time and then turn it off after a >>>> delay. I also want to use a temperature sensor to override the >>>> relay but only during the time period that is programmed. >>>> >>>> The idea is to turn on a water heater for a pre-determined period >>>> but to use a thermostat to control the temperature during this >>>> period. >>>> >>>> I have suggested using a relay because the heater is rated at 3.5Kw >>>> 240/250 volts, 50hz AC. Low voltage relays are available that can >>>> handle this load with ease. The heater has a safety cutout built in >>>> that should prevent boiling dry. >>>> >>>> I am aware that I can buy programmable motor driven timers very >>>> cheaply, however they are limited in contact loading and I would >>>> still need a relay for thermostat control. >>>> >>>> I thought this might make a nice PIC project. (Ducking) :-) >>>> >>> >>> I have built and programmed a battery backed clock chip and a >>> PIC16F628, attached to a RS-232 serial port. >>> >>> I am sure this can be modified to add a relay driver. >>> >>> Let me get the docs together sometime this weekend. >>> >>> don >> >>Thanks. I'll take any help I can get. > > Doesn't the hot water heater already have its own thermostat? No ! Just an over temp non reseting cutout. > Thus all you would need would be ON/OFF. > > Has anyone tallied up power consumption for such an ON/OFF, > COOL-DOWN/WARM-UP type of operation? > > I have recirculating hot water here... big loop around the house and > back to the water heater, pushed by a pump (Bosch). So you get > instant on hot water. And also big heat losses in the underground > loop. Since the water heater is well-insulated, I'm tempted to simply > turn off the pump (with a timer) in off hours. > > ...Jim Thompson I would imagine the losses could be quite large unless the pipes are well insulated. -- Best Regards: Baron.
From: baron on 15 Oct 2009 12:07 Jan Panteltje Inscribed thus: > On a sunny day (Thu, 15 Oct 2009 13:46:48 +0100) it happened baron > <baron.nospam(a)linuxmaniac.nospam.net> wrote in > <hb75jp$pc8$1(a)news.eternal-september.org>: > >>Hi Guys, >> >>I'm doing a hobby project to build a timer that can be used to turn on >>a relay at a pre-determined time and then turn it off after a delay. >>I also want to use a temperature sensor to override the relay but only >>during the time period that is programmed. >> >>The idea is to turn on a water heater for a pre-determined period but >>to use a thermostat to control the temperature during this period. >> >>I have suggested using a relay because the heater is rated at 3.5Kw >>240/250 volts, 50hz AC. Low voltage relays are available that can >>handle this load with ease. The heater has a safety cutout built in >>that should prevent boiling dry. >> >>I am aware that I can buy programmable motor driven timers very >>cheaply, however they are limited in contact loading and I would still >>need a relay for thermostat control. >> >>I thought this might make a nice PIC project. (Ducking) :-) >> >>-- >>Best Regards: >> Baron. > > You can make a nice zero crossing power switch for 240 V with a > MOC3041, driving a TIC263M triac, that one can do 25 A continuous (use > heatink). The MOC3041 needs 15 mA, PIC can drive that, the MOC3042 > 10mA, and the MOC3043 needs only 5mA. Just did one last week. > What sort of temp sensor are planning to use? > Immersed in the water? Hi Jan, That heatsink would be live I guess ! I wouldn't want to compromise safety at all. The temperature sensor I was just going to clamp to the bath lip or I could clamp it to the heater fixing. -- Best Regards: Baron.
From: Jim Thompson on 15 Oct 2009 12:31 On Thu, 15 Oct 2009 16:59:41 +0100, baron <baron.nospam(a)linuxmaniac.nospam.net> wrote: >Jim Thompson Inscribed thus: > >> On Thu, 15 Oct 2009 15:52:50 +0100, baron >> <baron.nospam(a)linuxmaniac.nospam.net> wrote: >> >>>don <don> Inscribed thus: >>> >>>> baron wrote: >>>>> Hi Guys, >>>>> >>>>> I'm doing a hobby project to build a timer that can be used to turn >>>>> on a relay at a pre-determined time and then turn it off after a >>>>> delay. I also want to use a temperature sensor to override the >>>>> relay but only during the time period that is programmed. >>>>> >>>>> The idea is to turn on a water heater for a pre-determined period >>>>> but to use a thermostat to control the temperature during this >>>>> period. >>>>> >>>>> I have suggested using a relay because the heater is rated at 3.5Kw >>>>> 240/250 volts, 50hz AC. Low voltage relays are available that can >>>>> handle this load with ease. The heater has a safety cutout built in >>>>> that should prevent boiling dry. >>>>> >>>>> I am aware that I can buy programmable motor driven timers very >>>>> cheaply, however they are limited in contact loading and I would >>>>> still need a relay for thermostat control. >>>>> >>>>> I thought this might make a nice PIC project. (Ducking) :-) >>>>> >>>> >>>> I have built and programmed a battery backed clock chip and a >>>> PIC16F628, attached to a RS-232 serial port. >>>> >>>> I am sure this can be modified to add a relay driver. >>>> >>>> Let me get the docs together sometime this weekend. >>>> >>>> don >>> >>>Thanks. I'll take any help I can get. >> >> Doesn't the hot water heater already have its own thermostat? > >No ! Just an over temp non reseting cutout. > >> Thus all you would need would be ON/OFF. >> >> Has anyone tallied up power consumption for such an ON/OFF, >> COOL-DOWN/WARM-UP type of operation? >> >> I have recirculating hot water here... big loop around the house and >> back to the water heater, pushed by a pump (Bosch). So you get >> instant on hot water. And also big heat losses in the underground >> loop. Since the water heater is well-insulated, I'm tempted to simply >> turn off the pump (with a timer) in off hours. >> >> ...Jim Thompson > >I would imagine the losses could be quite large unless the pipes are >well insulated. They're not insulated at all :-( At some point in time I should re-tile the house and, in the process, re-pipe will suitable insulation and containment (for easier repair). ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: Jan Panteltje on 15 Oct 2009 13:12
On a sunny day (Thu, 15 Oct 2009 17:07:29 +0100) it happened baron <baron.nospam(a)linuxmaniac.nospam.net> wrote in <hb7hc1$k6i$3(a)news.eternal-september.org>: >Jan Panteltje Inscribed thus: > >> On a sunny day (Thu, 15 Oct 2009 13:46:48 +0100) it happened baron >> <baron.nospam(a)linuxmaniac.nospam.net> wrote in >> <hb75jp$pc8$1(a)news.eternal-september.org>: >> >>>Hi Guys, >>> >>>I'm doing a hobby project to build a timer that can be used to turn on >>>a relay at a pre-determined time and then turn it off after a delay. >>>I also want to use a temperature sensor to override the relay but only >>>during the time period that is programmed. >>> >>>The idea is to turn on a water heater for a pre-determined period but >>>to use a thermostat to control the temperature during this period. >>> >>>I have suggested using a relay because the heater is rated at 3.5Kw >>>240/250 volts, 50hz AC. Low voltage relays are available that can >>>handle this load with ease. The heater has a safety cutout built in >>>that should prevent boiling dry. >>> >>>I am aware that I can buy programmable motor driven timers very >>>cheaply, however they are limited in contact loading and I would still >>>need a relay for thermostat control. >>> >>>I thought this might make a nice PIC project. (Ducking) :-) >>> >>>-- >>>Best Regards: >>> Baron. >> >> You can make a nice zero crossing power switch for 240 V with a >> MOC3041, driving a TIC263M triac, that one can do 25 A continuous (use >> heatink). The MOC3041 needs 15 mA, PIC can drive that, the MOC3042 >> 10mA, and the MOC3043 needs only 5mA. Just did one last week. >> What sort of temp sensor are planning to use? >> Immersed in the water? > >Hi Jan, >That heatsink would be live I guess ! I wouldn't want to compromise >safety at all. The temperature sensor I was just going to clamp to the >bath lip or I could clamp it to the heater fixing. > >-- >Best Regards: > Baron. Well I hope you mount the heatsink in some double isolated housing. You could use temp_pic: http://panteltje.com/panteltje/pic/temp_pic/ as a temprature sensor if you keep it dry, and drive the opto triac from it. And you can monitor temperature on the PC if you want. Only an 8 pin PIC... You will need a 5 V supply too. Could all be a very small box. I use temp_pic as room thermostat at the moment. 1 PIC 12F629 1 opto triac MOC 3041 1 power triac TIC263M 1 78L05 5V regulator some resistors, some capacitors, a small met heatsing, and a poly box. You could even feed it with a series C+R+bridge, and do optional RS232 out with an optocoupler, no transformer needed. |