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Does anyone monitor collector water flow?

seekertom
seekertom Member Posts: 20
in Solar
I feel uncomfortable hearing pumps run without knowing they are pumping water. My grundfos supposedly pumps water up to my collector, and an erie motorized check valve is supposed to open and let the solar hot water pass back down to the top of my hwh tank. If the water doesn't flow, the grundfos just swirls the water, and the motor and surrounding pipes get hot. But the water isn't getting hot from the collector. Maybe the mcv isn't opening, or is restricted.



Does anyone use a sight-glass or something to monitor water flow? Is there any way to tell (by listening?) if water is flowing thru a pipe?



t
«1

Comments

  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    Quick flow test....

    Turn the system on. (preferably cold)



    Take a small soldering torch, light it and hold it in one spot on the circulated pipe for 5 seconds.



    Take torch off of pipe, and wait five seconds.



    CAREFULLY check the temperature of the pipe. If it is cool, you have circulation. If it is hot, you have NO circulation.



    If you are doing a drain back system, it is common to have a flow meter in the solar circuit, that also serves as a fluid level indicator for large drain back tanks. Otherwise, no, not common.



    You can also check for temperature differential between the supply and return during peak insolation. If the return is significantly hotter than the supply, it indicates flow.



    Lastly, if you have a ball valve in the circuit, with fluid moving, if you quickly close the ball valve, you should hear a hydraulic HISSSsss as the water is stopped. No noise, no or little flow.



    As Colonel Klink was wont to say, "Ve have Vays...."



    ME

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  • seekertom
    seekertom Member Posts: 20
    col klink says schetp twoo ist nexgts!

    Thanks, mark. I removed the clock-motor from the valve assy because the associated grundfos was running hot, yet no heat on the down-side pipes. The synchronous motor spins, but the gear doesn't. The gear box is a press-fit to the motor housing, so I can't open it. Do you know if the motor only is available for replacement? It seems like it ought to run about 25.00 or so, rather than 110.00 for the whole thing. Hate the extra work and cost of replacing a perfectly good valve, when only the motor is bad!
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    edited March 2011
    In all my years...

    I've never seen a motorized check valve...



    What you are describing to me is a zone valve, and they are not common in solar loops.



    Got pictures and or drawings?



    The motor is most probably a Synchron motor.



    Honeywell uses them, but if memory serves me correctly, it's cheaper to buy the whole valve then it is the valve in parts.



    Give us more information.



    ME

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  • seekertom
    seekertom Member Posts: 20
    motorized check valve

    Here is a jpg of the erie motorized check valve. It is located on the hot side of my collector, just above my hwh. The motor power is connected at my grundfos pump, and both are controlled by the goldline. When the controller says use solar, both motors actuate. The grundfos pumps water up to the collector and the erie motor opens the check valve.



    The mechanicals work like this: the motor is synchronous, which includes the feature that at stall, the hysteresis bucks the current and limits it. The motor drives a gear box to 5 rpms, and the output gear meshes with a 1/4 circle sector gear attached to the valve shaft. When there is solar, the motor runs, driving the valve open, but it continues to run, even at stall. When power is removed, a heavy spring returns the valve to closed.  Open and water flows, closed, siphoning is prevented.



    The whole valve assy runs more than 100.00. I'm hoping to find a replacement motor for under 25.00. The thing actually looks like an electric clock from the 'olden' days. ha.
  • Kevin_in_Denver_2
    Kevin_in_Denver_2 Member Posts: 588
    Collector loop is better off with a simple check valve

    You can replace the synchron motor only.   The wholesale price might be 40% of the cost of the entire valve.   Eries have a replaceable head nowadays that changes out in ten seconds plus wiring time.



    But I'm guessing that your valve is just to prevent tank heat loss at night due to thermosyphon flow.   That problem is better solved with a swing check valve for even less money, and less chance of failure.

    http://www.google.com/products/catalog?hl=&q=flapper+check+valve&rlz=1B3GGGL_enUS314US314&um=1&ie=UTF-8&cid=11127270903025638656&sa=X&ei=tw-UTcjoBcmB0QHgyO30Cw&ved=0CDQQ8wIwAg#



    But it's just a guess, so you need to know how your system works before changing the design.

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  • hot_rod
    hot_rod Member Posts: 23,242
    zone valves on solar

    are becoming common when used as a 3 port for diverting flow. Solar heats up the first load, then the valve toggles to the second load. I's best to install them on the return (cooler) side of the piping.



    We actually offer a 3 way ZV kit that attaches to the solar pump stations. It has a 120V ZV to connect right into the solar controller.



    I probably have some of those Erie motors kicking around, I'd be glad to send you one to try.



    Heat kills those motors, if in fact you need a motorized valve in the loop, move it to the return side. We also have solar temperature rated spring checks if you do just need a check valve.



    hr
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    Leave to the marketing department to "develop" a new product....

    As I said, what you're describing is a zone valve. Contrary to what the literature states, it IS a zone valve.



    I agree with Kevin. Depending upon your system design (got schematic?), it could probably be replaced with either a spring or swing check valve.



    Crazy....



    ME

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  • hot_rod
    hot_rod Member Posts: 23,242
    flow meters

    you have a number of choices for flow meters. The plastic Blue White or a number of different flow meters from a simple float type, circuit setter, rotary meter, or the Grundfos vortex sensors.



    hr
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • seekertom
    seekertom Member Posts: 20
    my hw system

    Hope my sketching is adequate for showing what my system looks like. The original equipment came with the house (blt 1990) over 10 yrs ago, and worked well until Jan freeze burst a collector pipe. Probably good thing because that's how I discovered 8/10 pipes were packed shut with scale.



    I redid collector as one loop of 1/2" copper instead of parallel lines fed from manifolds. 1" copper was too expensive for me. Added new water heater also due to crud inside.



    After assembly, I noticed P2 was hot, but down pipes weren't. I connected a hose just above 'mcv' and got full water flow and motor temp went down, so I assumed mcv not functioning. I removed the clock-motor and the gear wasn't turning, and the motor was hot. I am able to move the valve lever manually, but need to verify flow thru it.



    This one part of the system has me puzzled: the recirc pump, P1, for the house loop connects to the top 'H' port and to the bottom of the tank at the drain port. I assume the flow is out of the top and INTO the bottom of the tank.



    But when solar is operating, water flows OUT of the bottom drain port and up to the collector, seemingly to conflict with the house loop trying to run water INTO the bottom of the tank. Maybe when solor runs, all the water, both OUT of the bottom of the tank and OUT of the house loop, runs up to the collector. Does this seem right?



    Other thing I'm missing is, P1 has a temp sensing control attached to the pipe between the pump and the tank .  Does the pump turn on or off when the pipe is hot? Seems to me, for ever, this pump has always been running. Exactly what is the idea behind this recirc pump system?



    Sure appreciate any help you can offer.



    t
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    Oh Lordy...

    Looks like you've got yourself a "direct" DHW heating system. I do hope you are located in an area that sees little to no deep freezing conditions... (Obviously, it does get cold where you are)



    P1 is a DHW recirculation return pump. It's only function is to make DHW readily available at the furthest points of use. It should be on a timer, to keep it off during periods of non DHW use, and the control should turn the pump off if the returning water is adequately hot, like say around 100 degrees F.



    Providing freeze protection for your open loop system is extremely critical, and I am not sure if your controller is capable of doing so. Really, the only means of freeze protection that you MIGHT have, would be to circulate hot water out of the tank and back to the collectors, which makes no sense to me, but have seen worse.



    You might want to consider converting the system to a closed loop system with heat exchangers and glycol to avoid freezing conditions.



    As for lime scale, look into a device called a Clear Wave electronic water conditioner. It will keep your hard water scale problems under control.



    At one point in time, we had a system that was called a drain DWON system, that used mechanical valves (SunSpool) that were supposed to drain the potable water out of the collectors if freezing conditions were sensed. We changed the name of the design to freeze down, because most, if not all of them failed at some point in time or another. Too many moving parts, and too much potential for total damage/calamity.



    I would have hoped that the industry would have learned a lesson from this, but I am aware of at least one internet peddlar of solar goods who thinks this type of system is the bees knees,.. Just because it is approved by the AHJ doesn't make it an ideal system.



    As it pertains to the motorized check valve, with the manual switch moved to the open position, you SHOULD have circulation. If not, you may have an air bound system, or a locked rotor on your pump. You may not be done yet... The pump will draw the same amperage with a locked rotor as it will with a free rotor, so don't let that fool you.



    There should be some means of eliminating air (high pressure/temperature automatic air vent at the top of the system.)



    You said you went from 1" to 1/2". How big is your solar array? How big is your storage tank?



    ME

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  • Karl_Northwind
    Karl_Northwind Member Posts: 139
    location

    this is most likely a case of inappropriate location. where are you located?

    I'm curious as to your phrasing, the equipment came with the house 10 years ago, does that mean you bought the house 10 years ago, with the equipment on it? and do you have any idea when it was installed? possibly a manufacture date on the water tank?



    There's no one right way to do solar thermal, but there are sure lots of wrong ways. 



    hopefully you can get descaling fluid thru the collector(s) I'm sure they're going to look worse than the transport piping.  this is going to be a fun one.  please post pics, I think we'd all like to see them.  it's always good to have "what not to do" photos.  unfortunately the usually come at someone's expense.  



    good luck, we'll help any way we can.



    karl
  • seekertom
    seekertom Member Posts: 20
    try to answer questions...

    First off, the house was built in 1990, but I have no idea when the solar system was installed. Any labels are no longer readable.  I bought the house about 10 yrs ago. The master bath is 80 ft away from the hwh, thus the recirc pump P1.



    Originally, I believed the pump on/off temp controller was not set correctly, or not working at all, since my elect bill was very high(>500.00/mo for 5000kwh/mo). I had traced the problem down to this: pump always on, cooling the hwh water as it looped thru the house, keeping the hwh running full-time. After I figured that out, I installed a timer on the pump and that helped a bit, but then had a problem of waiting for the hw.



    Sooo... I put a timer on the hwh, running it only 2 hrs in am when xyl got ready for work, and again 2 hrs around supper time, for dishes and baths, and matched the recirc timer to match. This worked fairly well, since the solar system was carrying the load well, back then. Mostly, the hwh was powered only 4 hrs/day for about 9 mos out of the year.



    This past winter, we had a freeze that was really unexpected, and I never thought about the solar, and so, it got trashed. Here in West Palm Beach, Fl, freeze is not a common word.



    So, now to today. My collector-in-progress is 15 pcs 1/2" copper, 10 ft long, spaced 2 3/4" apart, laid into the original collector box on the roof. It is angled about 45 deg  from horizontal, and faces south. The box is well insulated with rigid foam, and covered with appropriate type glass. The original collector fins were 24"x10' copper sheets sweated to the original 10 parallel pipes and painted black.



    This time I connected the house pipes to the collector using gator-bite flex pipes, to ease in flushing, repairs etc. There are both a manual pressure-release valve and a 50psi relief valve at the collector hot side, and the collector sensor is clamped to the last pipe inside the box on the hot side.



    My current project is to replace the collector fins. The original sheets are probably too wrinkled from removal, and new copper is soooo expensive. I may just go with aluminum fins if I can get my head around preventing galvanic action between the al and cu, and at the same time get good thermal transfer.



    Today I added a couple more valves so I can better flush the system and also isolate the mcv for testing. The motor is off the valve and I've disconnected the spring return on the actuator. Right now I do have good flow from pump P2, up thru the collector, and down past the mcv in the full-open position, back into the hwh. This part eases my mind a good bit. Without the fins the raw copper pipes don't raise the water temp by much, but that's to be expected at this point.



    I believe the purpose of the mcv is to prevent hwh water from flowing back into the collector at night, or when the solar system is otherwise shut down.



    Original hwh was 80 gals. I down-sized to 50 thinking less water to heat, less cost. 50 gals is plenty for me and the cats and dogs. Original collector had 1" manifolds at each end and 1/2" stringer pipes.



    Also, better filters, softeners etc have been added to the front end of the water system. Since adding them I have no buildup noticeable like I did before at the k and b fixtures, so hopefully I'm better protected than before.



    As for posting pics of my 'wrong-way', I don't get offended easily, so pics will be forth coming soon-as...



    Thanks for the support/help, and hope I've answered everyone's questions.



    t
  • Kevin_in_Denver_2
    Kevin_in_Denver_2 Member Posts: 588
    homemade panels can work great

    you can find excellent do it yourself collector details at builditsolar.com. I was never a fan of homemade collectors until I studied these designs.

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  • seekertom
    seekertom Member Posts: 20
    more problems...

    Today I added a couple valves and couple of hose bibs to the system to aid in finding out why my grundfos "P2" is hot, but water down is not.Pls see attached diagram. I wanted to create an isolated water loop which fed into and out from a bucket of water on the floor.



    I removed back screw plug from pump and the shaft spins, water dribbles out as normal so the pump motor is running.



    I closed valves V1 and V2, and cold supply valve. I opened hose bibs I and II. Hoses went into a bucket full of water. I started recirc pump P2, hoping to see it suck water out of the bucket and run resulting water back into bucket from the other end of solar system. Dint happen. Bucket is about 5 ft below P2.



    I tested flow thru system first like this: V1 open, bibb I shut, bibb II open, V2 shut. Water flows into bucket.



     Next test like this: V1 open, bibb I open, bibb II shut, V2 shut. Water flows into bucket.



    Any ideas why the pump doesn't flow water like this? Is it an input pressure issue? If so, how else can I find out why the motor is hot, but not due to hot water?



    thanks for your help.

    t
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    The difference between a circulator and a pump...

    What you have is called a circulator. It wasn't really meant to pump water vertically without having at least 5' of positive suction head at its inlet. In a closed loop situation, the water that is being raised, is being countered by the weight of the water coming down. If you really wanted to see if you could achieve true circulation in an open loop setting, you'd have to find an actual pump with the ability to physically lift water all the way to the top of the circuit, and establish a siphon on the downcomer.



    The screw you loosened is an access to the circulators armature. If it was spinning, while electrified, and with the cap off, then it is spinning. Doesn't mean it was moving fluid, just that it was spinning.



    On occasion, the impeller will break off of the carbon composite shaft, hence spinning with no water movement.



    You could verify it with the flame or fast closing ball valve tests.



    Could also be that the circulators impeller is loaded with solder balls, impeding water movement.



    ME

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  • seekertom
    seekertom Member Posts: 20
    next step...

    thanks for the insights, mark.

    i guess next step is back to idea of a sight glass. not shown in last diagram, i have two hose bibs, one above and one below the mcv. i could make up a clear hose section from bib to bib, close off the mcv, and i ought to see water mvmt.



    thanks again for the help.

    t
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    4 bolts and you will know...

    If you pull the 4 bolts that hold the armature to the body, you can power the pump up with the cartridge in it and see if it is spinning, or blocked, or whatever.



    ME

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  • seekertom
    seekertom Member Posts: 20
    more thanks!

    Mark, that probably just saved me a bit of head-scratchin'. Thanks.

    t
  • seekertom
    seekertom Member Posts: 20
    pump pics

    Mark, sure glad for your help. I pulled the pump motor from the pump assy and here are 5 pics of what I found... the impeller isn't attached to the shaft... is this ok? The shaft is able to move in and out a bit, is this ok?



    I suspect shaft spins out to contact the impeller to spin it, but there was a small 'rock' inside the pump housing. Probably the root cause of impeller not pushing water, huh? It appeared to be a bunch of mineral-stuff, rounded to a round shape about 1/4" diam. I don't see any damage to the parts, only the fact that plastic impeller isn't fastened to the shaft. I'll wait a bit before I reassemble it all, to hear your comments.



    Pics attached...



    t
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    edited April 2011
    She's dead Jim....

    I'm a PLUMBER, not a DOCTOR. I can't bring her back.... (Star Trek) ;-)



    You need a new pump/circulator. Guess its time to educate you and others as to how to select a pump.



    Need to knows:



    Net collector aperture area.



    Developed pipe length from tank, to collectors, and back. (including pipe size in I.D.)



    Number of elbows in the circuit.



    Other"devices" in the circuit. (motorized check valves, ball valves etc.)



    Once you have all that data, we can determine the optimum circulator for your application, and you can order it from wherever you want.



    Buummer dude...



    ME

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  • Kevin_in_Denver_2
    Kevin_in_Denver_2 Member Posts: 588
    rose colored pump

    It looks like a cast iron pump. The failure mode is a broken shaft when used in an open system

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  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    Well.....

    If it weren't for the exposed bronze casting where the impeller has been wearing on the volute, I;d agree with you :-)



    ME

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  • seekertom
    seekertom Member Posts: 20
    more info on pump/system

    This is what I have:

    collector pipes are 45" x 118" arranged 15 pipes spaced 2.75 " apart (oc), 117 " long

    collector: 158 lf

    total pipes from tank up to coll: 19 ft

    total pipes from collector down to tank: 16 ft

    total elbos: 40

    1 check valve up

    1 motorized check valve down

    2 in-line valves up

    2 in-line valves down



    all pipes are 1/2 in copper

    pump is Grundfos UP15-18b5, 120vac, brass pump housing, sweat 1/2 " fittings, 'rose-colored' motor



    Anything I missed?

    thanks,

    t
  • seekertom
    seekertom Member Posts: 20
    don't shoot!

    How is the impeller fastened to the motor shaft?



    I know you guys are going to throw shoes at me for even asking this, but... if the impeller is supposed to be fastened to the motor shaft, can't the impeller be stuck back on the shaft with something like jbweld?



    sorry, had to ask. Money is dear these days and jb is cheaper than a new pump, right?



    t



    ps



    motor inside (probably) defunct mcv is branded :

    640  120v  50/60 hz  5w  6/5 rpm  35294L-106-6  9:19  synchron



    what's available as replacement? don't care if used, as long as it works. Mine won't spin the gears, but the valve opens/closes manually ok.



    thanks too,

    t
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    Lack of bucksitis understood...

    Honestly, I've never tried to figure out how it is attached because when its broken, I replace them. Could be a press fit. Could be a mechanical connection.



    I suppose at this juncture, it (JB Weld or other epoxy) couldn't hurt. Just make certain all surfaces are good and clean before applying, and avoid excess glue dropping behind the impeller. Also make certain that the impeller is as flat and straight as possible or you will be able to hear your circulator from a block away.



    Will get back to you on pump sizing, but I think that you will probably end up replacing like with like. The 1542 is one of their smaller pumps.



    ME

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  • seekertom
    seekertom Member Posts: 20
    more info on pump/system-2

    After reading up some on the web I see a need to know ft of head. I measure 10 ft from tank water level up to bottom of collector, and adding in 25% moe, I get 12.5 ft of head needed. The grundfos I have will do up to 14 ft, and a flow rate of 0 to 15 gph.



    After reading a bit i found new respect for what goes into designing a solar system.



    I will first try to repair what I have, if nothing else, just to get it running enough to flush out any other problems lurking in the wings. I'd be real happy to find a simple field repair fixes what I first thought was a flow problem



    many thanks,



    t
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    Not there yet...

    Need to know the square footage of your solar array. How many square feet of glass? And how many collectors?



    ME

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  • seekertom
    seekertom Member Posts: 20
    sizes

    Glass is 4'x10', 400 sq ft, single panel.



    thanks, mark
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    edited April 2011
    OK then....

    40 square feet at .02 GPM per square foot equals .8 GPM.



    Not much flow REQUIRED, but the pump is going to use what the pumps going to use regardless. So next, we calculate a pressure drop for the circuit as a whole, then generate a system pressure drop against the circulators performance curve and see how many GPM we will be moving, and I can just about guarantee it will be more than the 8/10 of GPM required as the minimum.



    Gotta switch PC's to do this because I use software that doesn't work on a Macintosh format...



    Back in a few :-)



    ME

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  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    The envelope please........

    Unfortunately, Siggies soft ware doesn't include the curves for a 1518 pump. The smallest is 1542, and it will move 2.3 GPM in your situation.



    Sorry for the false start. I thought his software had EVERYONES pump curves in it.



    The alternative isn't working either. Can't seem to find a performance curve for the 1518...



    IF you end up having to replace that circulator, go with the 1542 SF, which is a stainless steel pump and is compatible with potable water. Has pretty much the same flange to flange dimensions as the 1518. And I'd can the motorized check (zone) valve in favor of a good old spring check valve. Just make certain that you can drain the collector in case old man WInter decide to take another vacation in your part of the hood.



    Did the glue work? I know it says on the package that it won't work with certain plastics...



    ME

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  • seekertom
    seekertom Member Posts: 20
    I have the envelope, but no stamp...

    Hi, Mark.

    First, thanks. 2nd, decided against glue job for now. Maybe you can see it in my pics, but to me it looks like the rotor was eaten up by the rock. The curving spines from the center to the outer edge are two different heights, making me think the outer parts were ground down to about half the height, midway between center and outer edge.



    Also, maybe in the pics you can see that there is a 'wedding ring' slid over the shaft. The end of the shaft is star-shaped, and has a hole in it to supply water to the internal bearings (I'm guessing here). The ring easily slips up and down over this part. I'm guessing that the plastic impeller used to be attached to this ring; impeller hole way to big for the star-shaped shaft for it to have been attached there. BUT, the ring doesn't have a nice seat with the impeller. What I would have liked is to find the two parts fit together nicely, just needing some glue to keep in place. However, there is no position the two parts snap together as if they used to be that way, so I don't see glue as a viable fix. Gotta have mechanical strength in the raw joint first.



    Next thought is this: the repair-first was based on an old price I'd seen for the pump which started with the number three and had two more numbers after it. However, current 'sale-prices' have put the first number at one, the second at three and the third number, who cares. This means more affordable.



    What is the diff between the motor you suggested and the up15-18b5 original that would make me select it instead of same for same?



    Thanks again for your help.

    t
  • seekertom
    seekertom Member Posts: 20
    don't laff...

    When I first read your post, i failed to connect your 1518 and 1542 numbers, duh! ok, the 1518 is my up15-18b5, so I guess we are talking the same pump. Pls disregard my dumbpitity on my previous post.

    Interestingly, my house-loop circ pump is actually a up15-42sf. End plates suggest dom as 98 and 99 for each pump.



    In an earlier discussion, it was suggested to replace mcv with a spring valve. Will the spring valve still automatically shut off the flow when the circ pump stops? The mcv does. I still need to find a replacement clock motor for it.



    t
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    edited April 2011
    Try this...

    Take the 1542 out, and replace the 1518 with it. you don't HAVE to have circulation return. Only thing its going to cost you is time and water and a little bit of energy.



    If they are 2 bolt flanged pumps, should swap out fairly cleanly. Might have to rotate the rotor stator assembly, but I thin you've already figured out how to do that (4 bolts will get you there).



    As for differences, they both are 1/25th HP motors, so shouldn't be a LOT of difference in the cost of operation. I've never tried to do it, but you might get lucky and be able to switch the rotor/can assemblies out between the two pumps. If not, you might have to find some brass or bronze flanges to mate up to the 1542.



    THe check valve will eliminate the need for the MCV.



    Also, try going to ebay. Sometimes there are people there peddling pumps that don't always show up on a google search.



    Let us know when you are harvesting free BTU's once again.



    ME

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  • Kevin_in_Denver_2
    Kevin_in_Denver_2 Member Posts: 588
    edited April 2011
    Method to the MCV madness

    I found this link that explains the reasoning behind the MCV, and it has a great schematic of your exact system: http://shop.solardirect.com/product_info.php?products_id=669

    The rationale is that the MCV is more reliable than a mechanical check valve. I'm quite skeptical of that claim. The electricity it uses is negligible, though, roughly only $0.25/yr.



    Coincidentally, I've been doing some research on "cold climate direct systems", and I have another theory about using an MCV in a system like this.



    One of the simplest, least costly, and most efficient system designs for Florida would be a direct system like this with recirculation freeze protection. (To learn how to configure it, you should be able to download the installation manual for the controller).



    In a recirculation freeze protected (RFP) system, one of the failure modes occurs when there is a power failure during a freeze event. Since a freeze event often CAUSES power failures, it's a real problem.



    The Erie MCV is available in a normally open configuration. Stay with me on this. I know Tom determined his MCV is normally closed, but if a normally open zone valve is used, that means it would open up during a power failure. Then thermosyphoning would occur and the collectors would be protected from freezing passively. (I know of some Japanese guys that wish their system had failed safe when the power went out) The end switch on the Erie is used to avoid adding a relay to the control system.



    That's a pretty easy way to sharply decrease the likelihood of freeze damage to the collectors. 3/4" pipe works much better than 1/2" pipe, and the collector loop must be well insulated.



    As we have learned above, a collector pump failure will also cause freeze damage. The normally open MCV will help against this problem if you add a freeze switch to it. If the outdoor temperature drops to, say, 42F, then power is cut to the MCV which opens, and the system stays happy.



    Note in the schematic above, a Dole "freeze valve" is also recommended as another defense against freezing. The Dole valve is probably inappropriate for cold climates because it would waste too much water during the winter months.



    Grundfos brags about this pump only using 65 watts, fair enough, that's only about $2.50/yr. I'm currently testing a pump that only uses 17 watts and has enough flow for most one and two collector systems. Although it's half the price of the Grundfos, its life expectancy in the real world is unknown. http://www.freefuelforever.com/Scripts/pump_solar_water.php



    Also, I should have mentioned that the builditsolar.com site shows a good way to attach the aluminum fins to your homemade "harp". http://www.builditsolar.com/Experimental/CopperAlumCollector/CopperAlumCol.htm

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  • Kevin_in_Denver_2
    Kevin_in_Denver_2 Member Posts: 588
    edited April 2011
    Method to the MCV madness

    dp

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  • seekertom
    seekertom Member Posts: 20
    different pumps?

    In the grundfos line, they have two materials, bronze and cast iron. Is the bronze considerably better, worth the extra 50.00?

    Also, could I benefit from using their 3-speed pump?



    My house loop is -42, flange, solar is -18 sweat fittings.



    Also, just wondering, why all the admin edits?



    t
  • Kevin_in_Denver_2
    Kevin_in_Denver_2 Member Posts: 588
    Cast Iron for closed systems only

    Bronze is needed for open systems like yours. A closed system doesn't have fresh water introduced daily, so the oxygen gets used up quickly and the rusting stops.



    The pump I mentioned above is all plastic, so scale should be less of a problem even compared to bronze. It's rated to 230F.

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  • Karl_Northwind
    Karl_Northwind Member Posts: 139
    build it solar

    I will second the suggestion.

    it's a great resource for the home build experimenter.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    Admin edits...

    It says admin, but it is actually done by the original poster. SO after I post, if I see something mispelled, or unclear, and I go back in and change it, it shows as an Admin Edit, but Dan' doesn't usually change anyones posts. He can delete them if need be but doesn't usually mess with peoples posts. They're mine, really :-) Trust me:-)



    And as Kevin so eloquently stated, if you don't use stainless or bronze, you will have rusty water coming out of your DHW taps. Not a good scenario, when washing whites.



    SF on the -42 indicates stainlsss, flanged.



    ME

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  • Karl_Northwind
    Karl_Northwind Member Posts: 139
    edited April 2011
    admin edits

    when the original poster goes back and changes something about their post, it shows up as an admin edit.  no big brother here censoring.  

    Karl



    yup, edits like when someone else posted the same thing seconds before and they post at the same time.
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