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Tarm mixing valve setting?

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by nporter, Jan 4, 2009.

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  1. nporter

    nporter Member

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    A question on my Solo30. On pg. 54 of my manual, in the Specification Data table, it refers to the Mixing Valve Opening Setting and states that it should be 140°F. So what is that referring to?

    I am befuddled to say the least!

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  2. Nofossil

    Nofossil Moderator Emeritus

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    I don't know what Tarm is referring to, but 140 is about the right temperature for input protection. You don't want really cold water coming into the boiler, and that passage might refer to the setting for a mixing valve that ensures that incoming water is hot enough to prevent condensation.
  3. nporter

    nporter Member

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    Thanks nofos,

    That sounds like what they might be talking about. I think that the Thermovar would do that mixing but don't know that it can be "set" to a certain temp thus my confusion.
  4. Nofossil

    Nofossil Moderator Emeritus

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    I think the Termovar has a thermostatic cartridge that's replaceable and available in different temperature settings. Their instructions might assume a different type of valve.
  5. flyingcow

    flyingcow Minister of Fire

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    My system should be up and running late next week(solo 30 innova w/800 gals of storage), but I'm using the termovar loading valve. Plus the diverting valve. Pretty much following tarms plans/and equipment, got valves from them,so I'm assuming settings will be by their specs(but I'll check). If I have problems down the line I can trouble shoot on my own. Not terribly clever with plumbing.
  6. sweetheat

    sweetheat Member

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    I was very befuddled too. for a non plumber or layman it seems they are not so clear on this. the mixing valve should be before the return termovar. directing hot water back into the return water. this will keep temps up to 140 for the return water going back into the boiler. Mine is almost closed, just a trickle is being sent back. sweetheat
  7. jebatty

    jebatty Minister of Fire

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    Do you mean that the mixing valve (balancing valve) should be on the boiler supply side to the Termovar to control boiler hot water flow into the Termovar?
  8. DaveBP

    DaveBP Minister of Fire

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    I'm confused. (What's new?).
    Is the "mixing valve" here the same as the "balancing valve" shown on all the Tarm piping diagrams. That IS between the Termovar thermostat and the boiler supply. They say to start with it half closed.

    http://www.woodboilers.com/userfiles/file/Solo Plus Plumbing.pdf
  9. jebatty

    jebatty Minister of Fire

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    I can't open the link reference.
  10. chuck172

    chuck172 Minister of Fire

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    The balancing valve that tarm refers to is just a ball valve that can be throttled.
    I believe the mixing valve is the termovar.
    The termovar mixes hot boiler supply water with the cooler return system water to protect the boiler. You balance this mix with a balance (ball) valve.
  11. sweetheat

    sweetheat Member

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    a yellow handled ball valve above the termovar, up is open, down is shut. depends on your install position and the way you look at the lever. this mixes hot boiler supply water into the termovar. the termovar returns 140 degree water back to the boiler. sweetheat
  12. hoth2oguy

    hoth2oguy New Member

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    Chuck172 and sweetheat you are correct. The balancing valve is simply a ball valve that we recommend is set half closed to introduce some head (resistance) prior to the Termovar so that water will be more 'inclined' to go out to the zones than to short circuit through the Termovar mixing valve. The Termovar mixing valve mixes 165*+ water from the boiler coming into port one of the Termovar valve with relatively cool return water coming into port two so that water leaving port three and returning to the wood boiler remains above 140*.

    nofossil, you are correct, the Termovar is available with several different cartridges that operate at different temperatures, but it cannot be 'set' or adjusted so I guess the wording in the manual is a bit odd. Will have a look at that tomorrow, thanks for pointing it out Than.
  13. nporter

    nporter Member

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    Thanks for all the "valve" education. I am still getting the balancing and mixing worked out and this thread clarified things for me.

    The explanation of the Termovar makes sense to me and I was curious if the 140° setting referred to in the manual was the particular Termovar cartridge because my has 72° stamped on the side plate.

    So does that 72° relate to 140° somehow or do I have the wrong Termovar in the system?
  14. DaveBP

    DaveBP Minister of Fire

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    72 is the temp in centigrade degrees: about 160F. I don't know why Tarm supplies mixing valves higher than some other recommendations I've seen (140F is a favorite minimum). I would think lower return temps would improve heat exchange within the boiler. 140F seems to be the concensus minimum.

    Would the optimum return temp thermostat differ for systems with pressurized or unpressurized storage?
  15. chuck172

    chuck172 Minister of Fire

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    The way I understand Chris, the 160* element is located in port 1. Port 1 can be throttled (constricted) by the balancing valve feeding it. This sets up the restriction to force cooler boiler return water enter into port 2.
    Then the mix occurs to push 140*+ water through port 3 into the boiler return.
    A 140* element would mix with the cooler boiler return temp resulting in less than the 140* desired return boiler return temperature.
  16. jebatty

    jebatty Minister of Fire

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    Chuck -- thanks for such a clear statement on the operation of the Termovar. Yesterday when I was charging storage, and return from storage was 140F and rising, I fully closed the balancing valve for the remainder of the charge. I will partially open it again when the boiler is next fired, as bottom of tank or system return will be less than 140 on re-firing.

    Just for the fun of it, would it make any sense to have a zone valve along with the balancing valve on the line to port 1, and an aquastat or thermostat which would close the zone valve when the line to port 2 was 140F+? This would force all boiler output into the system. Is there any benefit to the boiler or operational efficiency to continue to feed boiler output directly back to the boiler to let the boiler return rise to 160F, for example?
  17. chuck172

    chuck172 Minister of Fire

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    Jim, if you do that you can just rip out the termovar. Just use the aquastat and zone valve as the mixing valve. You'll probably have less restriction.
    Thank Chris Hoskin from Tarm for the explanation of the termovar.
  18. hoth2oguy

    hoth2oguy New Member

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    you've got it Chuck. The 72*C (160F) designation is the temperature at which the valve starts to open port two and close port one allowing return water through the valve. This results in the desired 140 return to the boiler. Because port one never closes completely we recommend the balancing valve to get us closer to the ideal situation that jebeaty describes. When using our Termovar loading unit (thermostatic valve with integrated circ pump and thermometers), however, port one does eventually close completely, so no balancing valve is needed. Pretty slick unit actually.
  19. chuck172

    chuck172 Minister of Fire

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    Chris, you really cleared up the workings of the termovar. I had no idea that the termovar loading unit automatically closed port one.
    As I told you on the phone, your continued input to this site is really appreciated.
  20. Jackpine Savage

    Jackpine Savage Member

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    Chris, is there more information available on your Termovar loading unit? I'm just starting my Solo 40 install (I've had it sitting in my garage for over a year), so I haven't seen any recent sales literature.

    On a somewhat related note, I've been trying to decide where to place my circulating pump. I have John Siegenthaler's book that recommends placing it after the expansion tank on the supply side. But I've 'heard' that the Termovar may not work correctly in that configuration.
  21. jebatty

    jebatty Minister of Fire

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    I first noticed the effect of this yesterday, when my system return water to port 2 was at 150, port 3 to boiler was at 172. It was at this point that I closed the balancing valve completely.
  22. DaveBP

    DaveBP Minister of Fire

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    Click the 'products' tag.

    http://www.acaso.se/english/index.html

    I have been eyeing the loading unit for my pressurized storage install. Expensive but elegant.

    Chris, if the loading unit WITH the backflow preventer is installed with a closely couple pressurized storage tank can it actually thermosiphon enough in a power failure to take the boiler load without an 'emergency load through automag' setup as in your diagrams? I bought a Solo 40 from you but haven't installed it yet and so have time to fiddle my system design before this summer's actual installation.
  23. flyingcow

    flyingcow Minister of Fire

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    I'm sure Chris Hoskin can provide you with a link, but I'm not real good with these computers. Go to Tarms website, click on scantec solo boiler, click on plumbing schematics. There are 10 pages of various setups with the termovars with and without storage. I've got more info on the termovars, but don't know how to post it here. Got to get my 10yr old to do it.
  24. hoth2oguy

    hoth2oguy New Member

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    http://www.acaso.se/english/produktblad/TERMOVAR Ladd-paket EN 0502.pdf

    is the link directly to the loading unit .pdf.

    Jackpine, while "pumping away" is a good practice in general, you need to pull through a mixing valve as I understand it. That is why we show our C3 pump between the Termovar valve and the return on the woodboiler. We know this setup works well, but there is some discussion around the office about if this is true or not. Would appreciate any thoughts anyone has.

    DaveBP, I am not sure about two things: first, I am not sure if the loading unit we stock ships with the back flow preventer or not, second, I am not confident about how well a thermosiphon would work through a tank. As you know we recommend baseboard element equal to 10% of the rated output of the boiler be mounted high up on the boiler room wall for a power-outage dump zone. We know this works, but I am not sure if the thermosiphon through a pressurized tank will flow enough and/or radiate enough heat away - especially if the tank temp is already high. Does the vertical distance of a thermosiphon improve it's effectiveness? In other words, if a couple of baseboard elements are mounted ten feet above the boiler will it dump heat more quickly because of increased flow than the same setup mounted five feet above the boiler? Or is flow through both setups identical? Not sure if it works like that. Thoughts?
  25. DaveBP

    DaveBP Minister of Fire

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    Now I see what's going on here. The automatic URL linking and underlining feature on this forum stops if there is a space in the URL so that it doesn't pick up any characters after the space and so you get the 404 error. You have to copy and paste the whole thing into your browser's address bar to get it all.

    Chris, your link directly to the loading unit did the same thing one of my posts recently did. The URL works, you just have to manually punch all of it in.

    At the bottom of the second page where it shows the cutaways of the unit with and without the back-flow preventer it says "In case of power or pump
    failure the backflow preventer will open automatically for self-circulation". Of course, the amount of that flow and whether it is enough will depend on a handful of factors.I don't think there is a simple answer. It depends on too many variables. I just wondered if your mad scientists out back there had done any tests.

    When I was there to pick up my Solo 40 I asked a bunch of questions and got a great tour of operations in the test facilities in back. Travis (?) told me that the loading units with the back-flow preventer were not stocked at that time but might be in the future as they were intended for use with pressurized storage. Your pressurized storage units were not out at that point but being tested.

    I have some physics background but no hydronic heating experience. Thermosiphons run on the difference of density between water in one tank and another. The colder denser water will want to settle to its lowest point because it's heavier than the stuff above it. I don't believe the height difference changes anything as long as the water can settle DOWN into the boiler and push the warmer water UP back to the storage. There are people on this forum who might have experimented with this.
    perhaps on sidearm DHW setups. I don't think one should be loading a lot of wood into the boiler if the storage tank is close to full, so there might not be a lot of BTU's to absorb for a long time.

    I appreciate your posting here. It helps a lot to narrow down some of the speculation that we indulge in here to have somebody " on the inside" to answer so many questions and point to other sources of information.
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