(206) 949-5683, Top Rated Plumber, Seattle
Page 2 of 4 FirstFirst 1234 LastLast
Results 16 to 30 of 50

Thread: Solar collector t&p valve excessive tripping

  1. #16
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
    Join Date
    Nov 2005
    Location
    Central Florida
    Posts
    2,687

    Default

    Quote Originally Posted by protech View Post
    There are a few things that will cause that condition to occur. I know of a plumber in central Florida that specializes in that sort of thing. You should give him a call. <whistling and twittles his thumbs>
    I might do that -- it's a local call... but I'm busily occupied getting ready for a long trip Up North for my <insert big number here>th High School Reunion, so it'll be a couple of weeks.

  2. #17

    Default

    10th, I bet...

  3. #18
    DIY Member flamefix's Avatar
    Join Date
    Sep 2009
    Location
    Exeter, England
    Posts
    71

    Default

    Quote Originally Posted by protech View Post
    I guess you are assuming it's an indirect system flamefix? There is such a thing as a direct system that uses potable water in the collector circuit. Also known as "open loop" system. Very common in central and south Florida as well as central America.
    Yes I did but I was questioning it.

    Why would you really want to use a potable loop it seems to me that it is cheaper perhaps? even in Greece and Cyprus (95%) solar energy heated sytems the indirect method is used.

    To have that loop direct to the tap with no regulation is that normal? Surely the supply side is regulated to the taps with a blender valve TMV set to 50c say?

    I'm beginning to see now why a TPR valve might be used as the cylinder is the pressurised vessel subject to temperature also so if it didn't blow on pressure the cylinder could reach stagnation itself possible?.

    Perhaps you could send me a link to read about the systems you are installing I'd like to read up on them, thanks.


    Perhaps make it a indirect circuit and fix a plate to plate heatexchanger between the tank and the collector and pump both sides triggered by the temp of the store and the flow from the collector.
    Gas, Oil, solar and renewable service and installation in Devon UK- Please note my advice is not based on USA regulations as I am UK resident. Therefore I will try to avoid posting where confusion may be caused or make that clear.
    http://www.flamefix.co.uk

  4. #19
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
    Join Date
    Nov 2005
    Location
    Central Florida
    Posts
    2,687

    Default

    Close, but no see-gar. Thank you, thank you.

  5. #20

    Default

    can't be 20 no sir...
    but then again, I got my teachers 31 years ago, lol. lordy, that is a long time.
    Last edited by Cookie; 09-06-2009 at 05:14 AM.

  6. #21

    Default

    See here: http://www.fsec.ucf.edu/en/industry/...terHeating.pdf

    Go to the section entitled "1. Active Direct Systems"

    Look at "Figure 2 Additional system components" to see a basic drawing of an active-direct system (A type of open loop system)

    Quote Originally Posted by flamefix View Post
    Yes I did but I was questioning it.

    Why would you really want to use a potable loop it seems to me that it is cheaper perhaps? even in Greece and Cyprus (95%) solar energy heated sytems the indirect method is used.

    To have that loop direct to the tap with no regulation is that normal? Surely the supply side is regulated to the taps with a blender valve TMV set to 50c say?

    I'm beginning to see now why a TPR valve might be used as the cylinder is the pressurised vessel subject to temperature also so if it didn't blow on pressure the cylinder could reach stagnation itself possible?.

    Perhaps you could send me a link to read about the systems you are installing I'd like to read up on them, thanks.


    Perhaps make it a indirect circuit and fix a plate to plate heatexchanger between the tank and the collector and pump both sides triggered by the temp of the store and the flow from the collector.

  7. #22

    Default

    You'll notice that a pressure only relief valve is used up on the panel while a T/P relief valve is used on the tank. This is FSEC here. These guys are at the for front of solar.

  8. #23
    DIY Member flamefix's Avatar
    Join Date
    Sep 2009
    Location
    Exeter, England
    Posts
    71

    Default

    So no Temperature relief valve on the collector then as all agreed to.

    This active system I just don't like the idea of domestic cold water supply circulating around a panel into the tank and then on to my shower or tap personally. I can understand having the collector direct to the store but I'd rather have my hot water indirect. I think I would have a plate to plate heat exchanger connected top to bottom of the store with a pump. Triggered by a flow switch on the cold inlet side which when a hot tap is opened causes the heat from the store to heat the hot water. Or as I said earlier on the solar side, and keep the store as the tank of hot water. But I am digressing rather from the topic.

    you can see why I was confused by the words active..
    http://www.solar-trade.org.uk/solarenergy/howwork.htm

    What's the typical install cost of one of these active systems if I may ask?
    Last edited by flamefix; 09-06-2009 at 09:25 AM.
    Gas, Oil, solar and renewable service and installation in Devon UK- Please note my advice is not based on USA regulations as I am UK resident. Therefore I will try to avoid posting where confusion may be caused or make that clear.
    http://www.flamefix.co.uk

  9. #24

    Default

    About the lowest you can get one here before you get your rebates and incentives back is $3500 for the smallest system under the most ideal circumstances. Most people will end up paying in the mid 4 thousands for a system sized for 2-4 people installed on a single story shingle roof. Bigger systems, multiple stories and tile roofing all make the price go up. The high end of the spectrum would be $8000ish.

    This is of course for active-direct systems. Indirect systems cost even more and put out less heat (size for size). If you live south of Ocala Fl there is no need to have an indirect system unless you are both paranoid about freezing and like to spend extra money for no reason. If you do live north of that point, then I would recommend an indirect system.


    [QUOTE=flamefix;219528]So no Temperature relief valve on the collector then as all agreed to.

    This active system I just don't like the idea of domestic cold water supply circulating around a panel into the tank and then on to my shower or tap personally. I can understand having the collector direct to the store but I'd rather have my hot water indirect. I think I would have a plate to plate heat exchanger connected top to bottom of the store with a pump. Triggered by a flow switch on the cold inlet side which when a hot tap is opened causes the heat from the store to heat the hot water. Or as I said earlier on the solar side, and keep the store as the tank of hot water. But I am digressing rather from the topic.

    you can see why I was confused by the words active..
    http://www.solar-trade.org.uk/solarenergy/howwork.htm

    What's the typical install cost of one of these active systems if I may ask?[/QUOTE]

  10. #25
    DIY Junior Member Alphacarina's Avatar
    Join Date
    Sep 2009
    Location
    Biloxi, MS
    Posts
    26

    Default

    Quote Originally Posted by flamefix View Post
    Why would you really want to use a potable loop it seems to me that it is cheaper perhaps?
    Another good reason we use it is because it's more efficient . . . . we get more hot water

    So long as freezing isn't a problem (or can be dealt with) there's no real reason to use an indirect loop

    Don

  11. #26
    DIY Member flamefix's Avatar
    Join Date
    Sep 2009
    Location
    Exeter, England
    Posts
    71

    Default

    Quote Originally Posted by Alphacarina View Post
    Another good reason we use it is because it's more efficient . . . . we get more hot water

    So long as freezing isn't a problem (or can be dealt with) there's no real reason to use an indirect loop

    Don
    But in a southerly latitude efficiency is the least of your problems surely? and You can't get more hot water you can only get it quicker albeit if you draw it off and it reheats quicker you can get more but you are limiting your store temperature to 120F correct? With an indirect sealed system you could run the store higher and mix it down to 120F thereby increasing the amount of hot water you can draw off anyway.

    I can accept the no need to have an internal tank arrangement and have a system like this for example..
    I'll not link direct to them but you can work it out as I am not advocating their product just citing it as an example.

    The cost of something like that is far cheaper more in the region of $1500

    3*w.eliotsolar.com/solar_hot_water.htm
    Gas, Oil, solar and renewable service and installation in Devon UK- Please note my advice is not based on USA regulations as I am UK resident. Therefore I will try to avoid posting where confusion may be caused or make that clear.
    http://www.flamefix.co.uk

  12. #27
    DIY Junior Member Alphacarina's Avatar
    Join Date
    Sep 2009
    Location
    Biloxi, MS
    Posts
    26

    Default

    Quote Originally Posted by flamefix View Post
    You can't get more hot water you can only get it quicker albeit if you draw it off and it reheats quicker you can get more but you are limiting your store temperature to 120F correct? With an indirect sealed system you could run the store higher and mix it down to 120F thereby increasing the amount of hot water you can draw off anyway
    No - My tank temperature will go as high as 150 degrees on a really good day . . . . but 125 to 135 is more typical

    I have a single 4 by 10 AET panel feeding two Sears Best 55 gallon electric water heaters for storage. I have a T&P valve on each tank and one at the top of the collector

    For 9 or 10 months of the year, solar provides 100% of my hot water and only in the dead of winter is any electricity applied . . . . and even then, it's just to the top of the supply tank (the one with the thermal mixing valve on it) and only for 30 minutes in the morning before the sun comes up so that we have the normal temperature water for morning showers - The electricity is only used to raise the temp of the top half of the supply tank up to 120 degrees, which is what the mixing valve is adjusted for

    I like having 110 gallons of really hot water . . . . it doesn't cool off much overnight and we can take a half hour shower in the morning, knowing it's basically all FREE

    Don
    Last edited by Alphacarina; 09-07-2009 at 09:40 AM.

  13. #28

    Default

    I have a similar setup as Alphacarina. I have a 4'x10' flat plate collector and an 80 gallon 5 port solar tank with 3 dip tubes. I installed a kilowatt hour meter on my old electric 40 gallon tank for a year before I installed my solar setup. it was costing me $55 and some change every month to feed electricity into that heater and that was back when rates were at $0.12 per KWA. I've had the solar setup on the same meter now for about 2 years and it's running at 95% solar fraction. That also includes the energy used to circulate the water. I've cut my water heating costs by 95%.

  14. #29
    DIY Member flamefix's Avatar
    Join Date
    Sep 2009
    Location
    Exeter, England
    Posts
    71

    Default

    Quote Originally Posted by Alphacarina View Post
    No - My tank temperature will go as high as 150 degrees on a really good day . . . . but 125 to 135 is more typical

    I like having 110 gallons of really hot water . . . . it doesn't cool off much overnight and we can take a half hour shower in the morning, knowing it's basically all FREE

    Don
    But Don you'll easily acheive that with an indirect system. In fact the systems I install can reach 80 -85c before limits cut in those limits can cut in at 60c or 50c what ever you wish.

    However Jimbo from this site informed me the following in a separate post "perhaps the other thing which weighs heavliy on our procedures is the well know law firm of Dewey, Cheatham, and Howe. ALL water heater manufacturers, and many of our plumbing codes, SPECIFY that water heaters should NOT be set higher than 120F ( about 50C) for the reason that if someone gets scalded, the plumber and the manufacturer will get sued." that doesn't sit with solar systems achieving higher temps than this.
    However as Long as you have a thermostatic blending valve then upper store temps don't matter within reason.

    I'm not trying to Diss your installation or your system or antagonise you, I just don't follow your logic for having a system soley based on efficiency, and then not to store the heat at higher upper temperatures than you currently do possible with a fully stratified store and have it direct connected to your cold water mains supply. This side of the pond we simply would not be allowed to.

    Given your solar radiation levels at your latitudes then the efficiencies you may gain from a direct system is to me fractions if at all over the indirect system.

    Plus I suspect that an evacuated tube design would provide you more hot water in your winter season also.
    Gas, Oil, solar and renewable service and installation in Devon UK- Please note my advice is not based on USA regulations as I am UK resident. Therefore I will try to avoid posting where confusion may be caused or make that clear.
    http://www.flamefix.co.uk

  15. #30

    Default

    It very simple. Per dollar invested an indirect system puts out less heat than a direct system. If I install a 40 square foot collector ran direct and you install the same size collector indirect with both tanks containing the same volume and dimensions, my system will put out about 10% more heat than yours will. It also does not require the heat transfer fluid to be replaced every 4-5 years. In short, if you live in an area that rarely freezes, it makes good economic sense to install a direct system. I know from talking with the folks on the navitron forums that to get the same output over in the UK you end up spending more than twice what we do in Florida. Some of that is due to exchange rates and some due to our southern latitude, but it's also because we run direct flat plates and you tend to run vac tubes indirect.

    Quote Originally Posted by flamefix View Post
    But Don you'll easily acheive that with an indirect system. In fact the systems I install can reach 80 -85c before limits cut in those limits can cut in at 60c or 50c what ever you wish.

    However Jimbo from this site informed me the following in a separate post "perhaps the other thing which weighs heavliy on our procedures is the well know law firm of Dewey, Cheatham, and Howe. ALL water heater manufacturers, and many of our plumbing codes, SPECIFY that water heaters should NOT be set higher than 120F ( about 50C) for the reason that if someone gets scalded, the plumber and the manufacturer will get sued." that doesn't sit with solar systems achieving higher temps than this.
    However as Long as you have a thermostatic blending valve then upper store temps don't matter within reason.

    I'm not trying to Diss your installation or your system or antagonise you, I just don't follow your logic for having a system soley based on efficiency, and then not to store the heat at higher upper temperatures than you currently do possible with a fully stratified store and have it direct connected to your cold water mains supply. This side of the pond we simply would not be allowed to.

    Given your solar radiation levels at your latitudes then the efficiencies you may gain from a direct system is to me fractions if at all over the indirect system.

    Plus I suspect that an evacuated tube design would provide you more hot water in your winter season also.

Bookmarks

Posting Permissions

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