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question about heating water

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by kennyl70, Nov 7, 2012.

  1. kennyl70

    kennyl70 New Member

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    So i am one step closer to having the owb up and running. now what i am needing advice on is....... plate or sidearm for domestic water.... plate seems to be the way to go from what i hear but i also hear they plug easy with hard water..... and in Missouri where i am..... hard water is all we have. I really dont want a softner if i can get by without it. i have heard the sidearms r better for hard water, but do they keep up? what r my options guys.
    lets have it.
    thanks

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  2. Bob Rohr

    Bob Rohr Minister of Fire

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    Better performance from a plate style but the larger copper tube surface of the side arm tends to stay cleaner longer. Really the same amount of hardness will collect in either. The hotter you run the boiler water thru the HX the faster the sediment build up. If you can get by with 140- 150°, less sediment willl percipitate out of the domestic water.

    Plan on flushing either type out, maybe every year depending on how hard the water is, and how much water you run through it. Connect it with isolation ball valves and unions. Or use a valve like the Webstone that allows you to pump a acid cleaner thru it when needed.
  3. Bob Rohr

    Bob Rohr Minister of Fire

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    There are a bunch of flush kits on the market for cleaning out tankless water heaters and heat exchangers, and plenty of You Tube videos to show you how to use them.

    www.tanklessking.com/flow-aide-system-descaler-kit.html
  4. BravoWhiskey

    BravoWhiskey New Member

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    I'm still in the planning stage and it seems to me the best way is to run a separate 1/2" PEX loop out to the boiler (or storage) and use a tankless coil in the boiler (or storage). The Heatmor has an option for a DHW coil if I remember right. That way you don't need to run two pumps to have DHW in the summer or shoulder seasons and your DHW controls would be simpler.
  5. maple1

    maple1 Minister of Fire

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    Can a plate HX setup work adequately just using convection/gravity flow - as a sidearm can? Or are pumps a definite necessity with any plate HX?
  6. Bob Rohr

    Bob Rohr Minister of Fire

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    You need a pumped flow in a plate HX.

    The downside of the side arms was slow response due to lack of pumped flow, and the domestic hot water gets as hot as the boiler temperature! That could be a very dangerous scald potential with 180° hot water at the faucet. Those side arm HX must have a listed thermostatic mix valve at the outlet, in my opiniona
  7. maple1

    maple1 Minister of Fire

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    When I installed my sidearm, I also put in a mixer. Along with a zone valve on the sidearm supply to shut that off when things get to being hot on the domestic side. I didn't get the install right though, I need to do a bit of re-plumbing - and I don't have the zone valve wired/controlled yet either. The main thing concerning me going forward is what is the chance of something going bad with the sidearm that would get my domestic mixing with my heat supply - sidearms are a new thing for me (any type of heat exchanger, for that matter), and generally speaking not that common. Using as little electricity as possible & keeping things simple is also a priority - so I'm also doing something else that I haven't got quite all hooked up yet. I'll share that in my install thread once I get it up & conclude it won't be an outright failure. :confused:
  8. danjayh

    danjayh New Member

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    If you're running your boiler unpressurized, you really don't need to be too worried about having your boiler water get into your domestic (although I'd still use non-toxic additives). Your domestic water should be under somewhere between 40-80psi pressure, so if there were a leak, it would only go FROM your domestic water TO your boiler. While this could potentially cause an overflow, it's not as bad as worrying about having nasty boiler water get into DHW (at least to me).
  9. danjayh

    danjayh New Member

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    There's a seller on eBay who has sidearms that have multiple heat exchange tubes inside - I have the small one, an it easily outpaces my electric hot water heater in terms of recovery time. (the specific one I have is here: http://www.ebay.com/itm/160508275258 ). As a bonus, it also happens to be the cheapest sidearm on ebay. The same seller also has a 24" version that has a similar design, which would (presumably) have improved heat transfer rates. Add in the fact that my water heater tank now stays somewhere around 180 degrees (I have a thermostatic mixing valve), and we actually have a ton of hot water. Remember that if you let your hot water heater get up to 180, and use a mixing valve, your flow rate out of your water heater will be much lower. For example, if you were taking a 115 degree shower at 2 GPM with 55 degree tap water and your water heater tank at 175 degrees, you'd only be drawing 1 GPM from your hot water tank (the rest would be cold water used to bring down the temeprature). This effectively gives a 40 gallon tank the same storage capacity as an 80 gallon tank (assuming you mount your sidearm as low as possible on the tank). I actually mounted mine about 1/3 of the way up the tank for logistical reasons (which means that it is only able to quickly recover about 2/3 of the tank), and we still have way more hot water when we're using the sidearm than when we're using the electric heater.
  10. maple1

    maple1 Minister of Fire

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    My boiler is pressurized, but not that high. About 10psi cold & 15 hot. So yes that should help - I've got pressure guages all over the place to keep an eye on it.

    Does it really matter how high up the DHW tank the sidearm is mounted? Is lower really better?

    As I mentioned I've still got some tweaking to do with mine. But it's mounted high - I wanted to get it up above the top of my storage tanks so the hot water from those would have a more natural path up to the exchanger. That put it almost at the top of my DHW tank (80 gallons) - maybe about 6" below the top. It circulates by convection all night when everyone is in bed, and when I go down in the morning it's still circulating, by feel of the hands on the pipe measuring anyway - with the DHW entering it from the bottom of the DHW tank pretty warm by this time. I'm not visualizing how a low mounted sidearm will make more hot water.

    EDIT: That's the same sidearm I have.
  11. kennyl70

    kennyl70 New Member

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    SOooooooooooooooooooooooo... water softner then i guess. dang it i really dont want one. wife hates um. i really dont wanna clean the dang thing out every year.
  12. Fred61

    Fred61 Minister of Fire

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    I had lime and scale build-up and was gumming up all the components in my water system. I didn't want a water softener either. I don't like the feel of the water, the flushing of the unit, salt or anything else about softeners. I did some research and finally found exactly what I needed. It's a scavenger as opposed to a softener.It's called a NUVO H2O. It hooks into you incoming water line and has a disposible cartridge that contains citric acid.The Cartridge is changed about every 6 months depending on useage. It has no way if indicating the amount of time left but I did a post mortemo on the first cartridge after 6 months of use and it had only been depleted by 2/3rds so I could have used it for another 3 months.
    It's not cheap but it does everything I want it to do without affecting the feel of the water and keeps the salt out of my body.

    http://www.nuvoh2o.com/
  13. rkusek

    rkusek Minister of Fire

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    I would think with the sidearm mounted lower would have improved thermosiphon action on the DHW side of the HX. If your storage tanks were lower than the bottom of your DHW you would have an ideal situation. It sounds as though 6" below the top of your DHW is enough to do the job however. I will need a pump on the boiler side of mine but I hope having the sidearm at the bottom of the DHW tank will work. Sounds like it should.
  14. maple1

    maple1 Minister of Fire

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    Actually - I was just in the basement checking the fire, so double checked that. The top of my water heater (which I put up on a stand to get as high as possible) is at about the middle of the body of the sidearm - not above at all. I put the water heater as high as I could, and couldn't do much about the height (or lack of) of my storage tanks - so only had so much elevation change to work with. There is a rise out the top of the sidearm, then a short run, then a drop into the top of the heater though - maybe that's helping me. I also wasn't going for fast recovery since I've got a big tank. Most of our use comes with a couple of showers first thing in the morning, then more showers & other things in the evening. So it basically has all night then all day to recover. I have some temp probes to hook up so I can get to monitoring this stuff better - still on the to-do list.
  15. Bob Rohr

    Bob Rohr Minister of Fire

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    A good compromise for a softener is to put it just on the supply to the water heater. That way all the cold, outside faucets, drinking water, icemaker, etc are un-softened. As long as you don't drink hot water, you are not dealing with the "taste" of water softened by a salt based, ion exchange device.

    The long time "rule of thumb" is the average home uses between 15- 20 gallons of hot water per person, per day. I believe with flow restricted faucets, dishwashers and washing machines using less water that might be a high number. For solar sizing I now use 20 gallons for the first person, 15 for additional members of the family. So a lot less load on the softener to do just the hot.

    DHW is a hard number to get exact, it really varies from family to family. The only way to get an exact number is to put a water meter on the supply to the water heater for a few months or so.
  16. danjayh

    danjayh New Member

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    It does matter. Because the thermosiphon effect is dependent on the difference in density between cold and hot water, you will only get a good siphon action until the water in the tank is heated to the bottom of the sidearm, after that it will go much slower (due to the reduced density of the water that's even with the sidearm in the tank).
  17. BoilerMan

    BoilerMan Minister of Fire

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    I agree with danjayh, but if your system works with no pumps Maple, i'd say you are in the best position one could be in. You may only be useing the top 1/3 of your tank volume, but if it's enough to satisfy all your DHW needs, then that's all you can ask for right!

    To the OP, what is your hardness number? I installed WS on 15 grains with dramatic results, the customer was soooooo happy that their dishes were clean, and the shower walls were no longer spotted up. Old Bock oil fired WH there, I'll bet lots of scale in that, although the anode rod was good. Family of two, they say they only use a 40# bag of salt in two months. The WS has a flow meter so it only regenerates when needed. Piped to do the whole house, accept the cold side of the kitchen sink, and outside hose bibs.
    TS
  18. maple1

    maple1 Minister of Fire

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    I didn't know whether to start another thread or put this here - but it's kind of on topic so here it is. Hopefully others get some use of it.

    Here's some doodles:

    [​IMG]

    As I mentioned, I have some re-plumbing to do. Current setup is 'A'. Main problem with that is when someone turns a hot tap on, all the water goes through the sidearm & bypasses the electric tank - the sidearm goes cool pretty quick. I thought the way the T's were oriented would limit that, but not so. I'm also not sure how good the sidearm is actually working when there is no tap on - I think it is, but not sure. I just hooked a couple of temp probes up & turned the tank down some so will have a better idea in a couple days. I put the sidearm up high to help with flow through the A side (from storage), but didn't give much thought to what that would do to the B side. The 10" rise then 14" drop might be messing me up.

    'B' is what I was planning to change it to. Drop the sidearm 8" to make the A side inlet the same height as storage output header, and use the T&P port for hot DHW entry from the sidearm. There would still be an up & down in that of 3-4 inches, but hoping the water would still circulate. And hopefully the bypassing of tank would be stopped. But I'm not sure how much the tank would charge up with the sidearm still that high, after reading this thread. I might be able to get the electric tank up in the air a couple more inches, but that would be it.

    'C' is what I'm now thinking I should maybe get closer to. Drop the sidearm even more to get the DWH outlet to have an uphill shot to the DHW inlet at the T&P port. But, will that mess up the A side flow from storage too much? Will it still circulate like that with the sidearm dropped below (maybe a foot? more?) the outlet from my storage? And, should I use the drain port on the electric tank for the sidearm DHW bottom cold feed? I don't really want to if I can help it. I'd have to drain all my tank for starters, but I also don't want to mess around with the factory installed doodads any more than I have to (the drain valve is plastic) - that's why I just T'd off the inlet to start with.

    TIA for the input/advice - I never even heard of a sidearm until a year ago.
  19. BoilerMan

    BoilerMan Minister of Fire

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    Maple, you are not off grid or anything are you? I don't recall that you had any special power requirements. The best location for the sidearm in as low as possible in relation to the hot water tank. The rise out of the sidearm is what drives the convection into the water tank. You may have to install a circulator on the storage side for this to happen, but you can control that circulator with an aquastat on the water tank (top one of the existing ones used for the top electric element). This said the circulator would not be on long and could be very low wattage, like 40W.

    TS
  20. maple1

    maple1 Minister of Fire

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    No, not off grid at all. But I am trying to plan everything I change or do here with a big consideration for what happens in a power outage - because it happens quite often here in the NS boonies, and I'm not always here to drag a genny out (plus it's a PITA). Then that has a secondary effect on the power bill - which is always good.

    I think I could utilize my existing main circ pump (3 speed 15-58) to help circulate the A side in the non-heating season (despite my attraction to simple natural flows :)) , that actually was crossing my mind a bit when sitting there staring at things for a while last night. So I am leaning to 'C' - and if it doesn't work out the best convection wise on the A side I think I can run a few wires & use my circ pump.

    Can an electric tank stat be used to control the pump & still have it turn the elements off & on? Or would adapting that to run the pump disable that element? I'm a bit electrically challenged. But, I do have an extra tank stat kicking around - thinking I should be able to strap that on somewhere & wire my zone valve in the A side loop through it, then tie the end switch in the zone valve to the existing pump circuit?

    EDIT: Any input on using the drain port for sidearm feed? It would likely make the whole setup work better, but not crazy about taking a wrench to the factory one & also draining my whole 80 gallons of hot water.

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