Announcement

Collapse
No announcement yet.

Panel to Heater Direct

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Panel to Heater Direct

    I've been doing some reading online and have come across others saying you can power a 120/220v AC heater with DC power. While I know its not economical etc. I have extra panels and was considering wiring them up to an old baseboard heater. Thought that maybe during the day it may put off enough heat to keep my off grid cabin above freezing temps in the winter. It would be an experiment to see if it could. I'm not talking about using batteries etc, just straight from the panel to a breaker to the heater, it will only produce heat while its sunny. Is that doable or is the internet lying to me again?
    Thanks.

  • #2
    The problem as always is getting an impedance match between the panel and the heater. The ever
    changing available power makes it worse. There is also the issue that the thermostat can't handle
    breaking a DC current flow, though you might never get that warm.

    If you can come up with a reasonable voltage/current/resistance combination design for 100% and
    50% panel output, it might have some success. Below those power levels it probably doesn't
    matter anyway. Bruce Roe

    Comment


    • #3
      A friend gave me a little gadget he made to put a load on a panel for testing. It consists of a pair of MC connectors with a length of Nichrome wire coil taken from a little portable heater. I must say that when using it on, for example a 175 watt, 24 volt panel it would get really hot, really fast. I have no scientific data other than to say he took a multimeter and used it to find how long to make it by finding the point/lengtha certain amount of resistance was.I don't remember what that was though.

      Anyhow It does appear to work on DC. as to safety, I'll let other more knowledgeable members answer.
      2.2kw Suntech mono, Classic 200, NEW Trace SW4024

      Comment


      • #4
        Most heating elements are purely resistive, and therefor will work equally well on either AC or DC.

        BUT there are 2 problems

        1) initial resistance (cold) vs Hot. Some elements, if under powered, will start with a low resistance, and never heat up to normal (hot) resistance, like a Light Bulb
        2) Thermostats, are only made for AC, and DC will nearly instantly fry/ruin/start a fire

        and the 3rd goes without saying, if there is a fan, it's nearly certainly a shaded pole AC motor, which will burn up on DC
        Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
        || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
        || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

        solar: http://tinyurl.com/LMR-Solar
        gen: http://tinyurl.com/LMR-Lister

        Comment


        • #5
          I understand the no go on fans and thermostats. I was thinking a baseboard wired direct. When the panels produce power the heater works when they don't produce power the heater doesn't. i will likely rig it up at home and just test the output before ever installing at my cabin. I just thought it was neat that it might be capable of working. there was a output conversion i seen somewhere but cant recall the website now.

          Comment


          • #6
            A simple baseboard without a thermostat would work. I guess thats got a calrod element in a long oil filled tube ?
            First step is to turn it on for 20 min or so, disconnect it, and measure it's Resistance while it's still hot. Then again, when it's cold. Now you have a Resistance value you can balance against your PV's max power specs, and decide how many panels to wire to it. Remember, if you don't allow the PV to build up to it's Vmp setting, 6V at 4A is not much heating into your house, much better if you can get the voltage to be in the right ballpark.90V @ 4A gives you more heat
            Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
            || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
            || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

            solar: http://tinyurl.com/LMR-Solar
            gen: http://tinyurl.com/LMR-Lister

            Comment


            • #7
              I have 2 spare 300w 36volt 8 amp panels. I'll likely wire them in and see what happens. For measuring resistance why hot before cold? Wouldn't the other way work?

              Comment


              • #8
                Originally posted by Shane.R13 View Post
                ..... For measuring resistance why hot before cold? Wouldn't the other way work?
                Measuring either one first is fine.

                Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                solar: http://tinyurl.com/LMR-Solar
                gen: http://tinyurl.com/LMR-Lister

                Comment


                • #9
                  Hi,

                  Been lurking a while and registered to follow up on (revive) this thread.

                  It doesn't look like [USER="48979"]Shane.R13[/USER] has been on for a while, but if you see this, did you ever work anything out?

                  I have the same question as the OP:

                  I am in New Mexico (lots of sun). I have a room on the north side of my house that doesn't get any passive solar, and doesn't really have a heat source. It's a dining room that we don't use much, and when we do I light a fire and it's fine. However, it would be nice to figure out a simple solution to keeping it warmer. The house is adobe, so heat input when the sun shines does tend to warm up the mass and stick around for later (i.e., dinner time).

                  I rejected solar hydronic because of the complexity and maintenance. We heat the rest of the house with mini splits and my PV system maxes out what our POCO allows for residential (10KW).

                  So, I got thinking that if I could power a small baseboard with a few modules and avoid inverter, storage, etc. that might be a nice solution. Sophisticated controls aren't really necessary, as it could just be turned on in October and turned off in April (there is no way a baseboard of around 1,000 watts could overheat our house).

                  It seems like some type of MPPT controller, DC direct to the heating element, should be possible. But I am too far from being an EE to know how to go about it.

                  Does anyone have any thoughts?

                  I did come upon this: Solar Space Heating SysEducational Project Idea

                  Thank you - this is a great resource.

                  edit: I recognize that the solution may have to do with the resistance. I am hoping to use a random selection of used modules from craigslist, but recognize that may complicate things.
                  Last edited by SantaFeTrailer; 08-19-2019, 08:41 AM.

                  Comment


                  • #10
                    Originally posted by SantaFeTrailer
                    We heat the rest of the house with mini splits and my PV system maxes out what our POCO allows for residential (10KW).

                    So, I got thinking that if I could power a small baseboard with a few modules and avoid inverter, storage, etc. that might be a nice solution. Sophisticated controls aren't really necessary, as it could just be turned on in October and turned off in April (there is no way a baseboard of around 1,000 watts could overheat our house).

                    It seems like some type of MPPT controller, DC direct to the heating element, should be possible. But I am too far from being an EE to know how to go about it.
                    For openers your mini splits will supply heat at 4 times the efficiency of any resistance
                    heater. That, within their operating temp range. Mine are rated well below zero, how
                    do yours match your needs?

                    Running minis direct off additional panels can be done with certain models. There is a
                    whole list of problems trying to run resistance air or water heaters directly off panel DC,
                    which may not work, may not work safely, or may be extremely inefficient. Bruce Roe
                    Last edited by bcroe; 08-19-2019, 02:36 PM.

                    Comment


                    • #11
                      Just random panels in series could be a problem if the currents don't match closely. I've done the old style oil finned radiator and run it off 60V of PV thru a power point controller. I certainly don't know how you could put 1500W into one of these unless the room was below freezing. At 350W it wasn't safe to put your hands on. I'm trying it again this year for end of season heating at the camp. Never got any results last year. I'd have it running all day only to find my wife would open the window for fresh air. In NM I can imagine you can do things with solar not possible here. Solar panels are current devices. With fixed resistance if the current drops in half the voltage drops in half. So, a little loss in light gives you 1/4 of the power you had. It is definitely worth having a heating controller that keeps the panels close to the power point. Probably not $250 worth for the techluc. They can be built really cheap and surprised there isn't a cheap one from china for about $40.

                      Comment


                      • #12


                        [I]For openers your mini splits will supply heat at 4 times the efficiency of any resistance
                        heater. That, within their operating temp range. Mine are rated well below zero, how
                        do yours match your needs?[/I]

                        [B]They do match our needs/design temp well. My original plan was to install one more small one in the dining room. I may still do that, but as it is we are pretty well balance on production and usage and I don't want to tip the balance in favor of the POCO.[/B]

                        [I]Running minis direct off additional panels can be done with certain models. [/I]

                        [B]This is intriguing, do you know where I could find more information on it?[/B]

                        [I]There is a whole list of problems trying to run resistance air or water heaters directly off panel DC,
                        which may not work, may not work safely, or may be extremely inefficient. Bruce Roe[/I]

                        [B]Got it, thank you for the input.[/B]

                        Comment


                        • #13
                          Originally posted by PNPmacnab View Post
                          Just random panels in series could be a problem if the currents don't match closely. I've done the old style oil finned radiator and run it off 60V of PV thru a power point controller. I certainly don't know how you could put 1500W into one of these unless the room was below freezing. At 350W it wasn't safe to put your hands on. I'm trying it again this year for end of season heating at the camp. Never got any results last year. I'd have it running all day only to find my wife would open the window for fresh air. In NM I can imagine you can do things with solar not possible here. Solar panels are current devices. With fixed resistance if the current drops in half the voltage drops in half. So, a little loss in light gives you 1/4 of the power you had. It is definitely worth having a heating controller that keeps the panels close to the power point. Probably not $250 worth for the techluc. They can be built really cheap and surprised there isn't a cheap one from china for about $40.
                          Thank you. I will be interested to see how your experiment goes. Any pointer to plans for a controller? It seems like there is inevitably a cheaper Chinese version of everything eventually!
                          Last edited by SantaFeTrailer; 08-26-2019, 12:40 PM.

                          Comment


                          • #14
                            Originally posted by SantaFeTrailer View Post

                            [I]Running minis direct off additional panels can be done with certain models. [/I]

                            [B]This is intriguing, do you know where I could find more information on it?[/B]
                            Being entirely committed to net metering here, I have not done the research. But there
                            would be interest in someone presenting that researched info. I have seen video & specs
                            on partially panel powered AC, there may also be 48VDC versions. Important points are
                            1. The price and efficiency of equipment varies greatly.
                            2. The effective temp range of equipment varies greatly.
                            3. There are single and multiple inside distribution point types, of varying capacity.
                            4. Typically such units have ability to fall back on PoCo input for insufficient solar input.

                            Bruce Roe

                            Comment


                            • #15
                              I did find this, but I am not interested at this price point:

                              http://www.cyboenergy.com/products/c..._overview.html

                              https://www.continuousresources.com/...-water-heaters

                              Comment

                              Working...
                              X