+ Reply to Thread
Results 1 to 5 of 5
  1. #1
    Join Date
    Mar 2012
    Posts
    1

    Default Installing Electric Tankless Heater with Solar

    Hi all,

    First time here, first post. I tried searching before posting but did not find any relevant hits.

    I am seeking help/guidance. I am interested in installing an electric tankless heater, primarily powered by solar but also wired to my home's electrical system as a backup. This is to replace my oil burning furnace. Key Points: I am using well water, so I suspect perhaps around 65 degrees inlet. The home has 2 full baths, 1 kitchen. Heat is currently baseboard water radiators. The solar hookup is only needed to power the electric tankless heater, not the entire home. I'm not having any luck while researching products finding what I am looking for. I seek advice on brands to consider, 'gotchas' during installs, brand quality and reliability, etc. Please help. Any advice appreciated. Thanks in advance!

  2. #2
    Join Date
    Feb 2010
    Location
    South*East
    Posts
    1,210

    Default Re: Installing Electric Tankless Heater with Solar

    Quote Originally Posted by marsmann View Post
    Hi all,

    First time here, first post. I tried searching before posting but did not find any relevant hits.

    I am seeking help/guidance. I am interested in installing an electric tankless heater, primarily powered by solar but also wired to my home's electrical system as a backup. This is to replace my oil burning furnace. Key Points: I am using well water, so I suspect perhaps around 65 degrees inlet. The home has 2 full baths, 1 kitchen. Heat is currently baseboard water radiators. The solar hookup is only needed to power the electric tankless heater, not the entire home. I'm not having any luck while researching products finding what I am looking for. I seek advice on brands to consider, 'gotchas' during installs, brand quality and reliability, etc. Please help. Any advice appreciated. Thanks in advance!
    The best advice I could give you is stay away from electric tank less water heaters. To be large enough to supply the needs you have will require at least 60 amps. Even with that they have a flow restriction that is needed to allow the heater enough time to heat the water. This restriction will not give you enough water to supply to run your shower along with another fixture. If you have a hot water boiler for heating you would be far better off using a indirect water heater.

    http://www.amtrol.com/boilermate.htm

    John

  3. #3
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,738

    Default Re: Installing Electric Tankless Heater with Solar

    Electric tankless water heaters should be banned from the market. This is a case where a loophole exists that allow them to get an energy star rating when they do in fact use a lot more energy than the tank type. While the homeowner gets a break, the rest of us have to pay for the inefficiency of these.

    The inefficiency is due to the transformer that supplies power to the house. An electric tankless water heater uses 90+ amps, but its on only when there is a demand for hot water. If a regular residential transformer is hung on the pole outside your house, it is designed to supply about 60 amps.

    Now it can supply a lot more than this, but two things happen when it does, its efficiency goes down due to load losses. Load losses increase exponentially with the load. The output voltage goes down as well. It can go low enough to damage fluorescent lights (below 100 volts). In order to provide you with an ample supply of power, the utility would have to use a larger transformer. But a larger transformer would cost the utility a lot of money in increased no load losses, those are losses that keep the transformer energized when it is not in use but still connected to the power line.

    If the utility was allowed to put your watt meter on the primary side of your transformer, which is a common practice in industrial settings, then you would have to pay for these losses and then you would find out that the tankless water heater is no bargain. Your bill would go up.

    The cost to store hot water in a tank system is not that much if you get a well insulated tank. A well insulated tank will cost you about a dollar a month to store hot water. If you heat the water in the tank with a supplemental solar system, your storage costs will be a lot less.

    Also consider that you will be using hot water during the peak hours. You might check with your utility to see if they offer off peak rates and then put a timer on your hot water heater so that it only runs off peak. Also use the delay on your dishwasher so that it only runs in the middle of the night, off peak.

    Without tank storage, there is one more flaw to your plan, the solar panel will be generating hot water during the day when you will be least likely to use it, especially if everyone in the household is at work or school during the day. When you need the hot water, the sun will be down.

  4. #4
    Join Date
    Aug 2007
    Location
    Maryland
    Posts
    1,588

    Default Re: Installing Electric Tankless Heater with Solar

    I've only used electric tankless heaters for single sink applications, never a whole house. I think the other assesments about the use for a whole house are correct.
    I know of one company locally that uses a German made solar storage tank/electric or gas water heater. This is combined with roof mounted panel(s). The heater & controls are by Schuco & the local comany is Greenspring Energy on east coast. The one tank system uses the electric or gas for backup to the solar. The solar part of the system has a ciculating pump with glycol along with electronics for control.
    An owner wanted to use solar heating on a project & this system seemed to be a well made product although I have not seen it in use yet.

  5. #5
    Join Date
    Nov 2011
    Posts
    51

    Default Re: Installing Electric Tankless Heater with Solar

    I would certainly go with that Boilermate option that johnjh2o suggested. An electric tankless water heater is the worst by far.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •