Running out of hot water with a 60G tank

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by benze, Dec 8, 2013.

  1. benze

    benze New Member

    Messages:
    63
    Location:
    Montreal, Canada
    I've got a 60G bottom feed electric hot water tank that recently seems to be running out of hot water sooner that I would have liked. It has 2 gravity feedback loops on it that normally work fine. I checked the elements and they are both working properly, so I suspect it is more a question of water usage than anything else. The HW temp is set to be about 130-135F. The reality is that I don't have cold water coming out of the faucets; just warm. So I figure that although it is a 60G tank, I presume that under a constant use, I can't actually get 60G hot water out, but rather only 20-30G before the influx of cold water into the tank brings down the temperature too much.

    If my theory is correct, I figure the best I could do would be to raise the water temp before it goes into the tank, to reduce the temperature differential and the drop. So I'm wondering if I were to add a tankless system on the supply to warm to 70-80F, it should help reduce the thermal shock and provide me with more hot water. I live in Montreal, Canada, so the supply in winter is probably somewhere around 35-40F.

    Is this a logical solution? Or is this a bad concept - more of a bandaid solution but not fixing the problem itself? Is there a better way to approach the problem?

    Thanks!

    Eric
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,270
    Location:
    Cave Creek, Arizona
    IF your tank is set for 135 degrees and you only have warm water coming from the faucets, you DO have a problem but it is not because of the water heater size. We would have to do our own testing to find out WHY the water is not HOT. I would also want to know HOW you determined the elements are working "properly". But it is probably because the 'feedback loops" have gone bad.
  3. benze

    benze New Member

    Messages:
    63
    Location:
    Montreal, Canada
    Like I said, I do have hot water at the start. After a while (giving kids a bath, washing dishes, etc), it becomes warm. Too quickly for my taste, but it could well be that I've just drained too much hot water too quickly.

    I turned of the HW tank, detached the elements and tested their resistance. I do not remember the exact number, but they were not open circuit. Given I changed the lower one about 4 or 5months ago, and the resistance reading of the bottom and top elements were similar, i presume them to be properly functioning. Then, with the power back on and everything reconnected, I verified that I was getting 220V at the elements when the tank was heating and sure enough, both are being energized.

    How does a feedback loop "go bad"?

    Thanks,

    Eric
  4. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,833
    Location:
    NW Ontario, Canada
    The only proper way to diagnose an element is by measuring the current drawn.

    So what exactly are feedback loops? Are they a recirc to give you instant hot water? Aside from a bad element, thermostat or dip tube issue, change in usage is the most plausible explanation. One way to get more hot water is to raise the temperature and then use a tempering valve. They make special ones for recirc systems, but I don't know if that includes gravity types.
  5. DonL

    DonL Jack of all trades

    Messages:
    3,812
    Location:
    Houston, TX

    Not sure what model you have, But that does not sound correct for both elements to be heating at the same time.

    I am not sure what "energized" is for sure. Is your tank Grounded ?

    You may want to evaluate your testing methods.

    Be careful playing with Electricity.


    Good Luck.
  6. benze

    benze New Member

    Messages:
    63
    Location:
    Montreal, Canada
    Agreed... I was going the lazy way :) I don't have a clamp meter handy and didn't want to wire up my multimeter to it so figured this would be a safe cheat. Presuming know the resistance and the voltage, amperage simple math. I just don't remember the resistance value.

    Yes; they were added provide instant warm-to-hot water the faucet.

    What is a dip tube issue? Where is the dip tube located? In the tank?

    Well two things come to mind. 1) extra expense ofconstantly heating to a higher temp. 2) what will that accomplish? Just raising the internal temp and tempering at the faucet would imply that I want to minimize the impact of the cold source. In which case is it not a better idea to raise the temp of the source?
  7. benze

    benze New Member

    Messages:
    63
    Location:
    Montreal, Canada
    Can't say for they were both heating at the same time. I saw 220 on the bottom one and a few mins later 220 on the top one.

    Energized: 220V across terminals
    Yes, it is properly grounded
  8. Terry

    Terry Administrator Staff Member

    Messages:
    14,783
    Location:
    Bothell, Washington
    The top element goes on first, and when the top of the tank is heated, power is transferred to the lower element.
    They never come on at the same time. Recovery is about 25 gallons an hour. Once it's being used, you go through the first 60 gallons, then you have just a little bit of recovery with electric. A bath can be a lot of water. Hand washing dishes can drain a tank pretty quickly too. A dishwasher is much more efficient with water.



    The dip tube is normally below the input. A plastic tube that may or may not be intact. If you have little bits of plastic showing up in faucet aerators, then the dip tube is coming apart.

    Since you have a bottom feed tank, that is the "dip tube". Where it enters the tank.

    You can juice a bit more water out of the tank "safely" by adding a tempering valve and running the heater on high, blending down the output to a safe range for bathing.

    http://www.terrylove.com/forums/sho...atic-Mixing-Valves-(-water-heater-tempering-)
    Last edited: Dec 8, 2013
  9. DonL

    DonL Jack of all trades

    Messages:
    3,812
    Location:
    Houston, TX
    I am not sure a bottom feed tank would need a dip tube ?


    What is the model number ?
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,817
    Location:
    New England
    If you recirc lines don't have a checkvalve, or the checkvalve is no longer working, when drawing water from the tank, water will flow through the path of least resistance, which may very well include from the (colder) bottom of the tank AND from the hotter top of the tank, resulting in a much cooler mix than what it could be.
  11. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,833
    Location:
    NW Ontario, Canada
    Jim makes a good point about the the loops possibly reversing, but that should result in diluted water from the get-go. Another possibility is a crossover situation but that too, would manifest from the get-go.

    Another possibility is a leak where hot water is being lost. Some folk may go for months before noticing the higher electric and water bills.
  12. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,817
    Location:
    New England
    If the WH hadn't been used for awhile, you'd have hot water at both the top and the bottom, so you might not notice a mix. Shortly, though, as you draw in cold to replace what's there, it would cool off fairly quickly if there were no functioning checkvalve(s).
  13. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,833
    Location:
    NW Ontario, Canada
    I think you are basing your theory on the cold supply entering the bottom of the tank in a different place than the return side of the loops. Without a definitive from the OP, it is conjecture.
  14. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,817
    Location:
    New England
    If I remember, he said his cold inlet was low, rather than being on top like it is on many tanks with a dip tube.
  15. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,833
    Location:
    NW Ontario, Canada
    How many bottom ports would there be on a HWT? I am going on the assumption that the same one is used for the cold feed as well as the loop returns. So, if the loop was reversing, the cold would split in two directions, some of which would feed the HWT and the rest backfeed through the loop return. I would not expect blending in the bottom of the HWT.
  16. benze

    benze New Member

    Messages:
    63
    Location:
    Montreal, Canada
    Thanks for all the feedback. My WH is a Giant Cascade 60 (Model #172B-3F7M) from 2008. It is a bottom feed tank, with 2 ports - one for the inlet and one for the drain. My gravity recirc loop goes from the HW line under the sink (at the end of the line) to the drain port on the tank. I've actually got 2 loops plumbed the same way. The recirc loop does have a slightly-off horizontal check valve in it and three cutoff valves (one to each recirc loop, and one just before the drain return). I'm attaching a pic of the tank install to clarify the layout (forgive the clutter around it - I was just trying to get the pic quickly). I know others have used a check valve with a small hole drilled in the flap, but I remember reading that positioning it just off horizontal, such that the flap was slightly ajar, would allow the recirc loop to work, but close if water tried to flow up that side.

    You might notice that I have temporarily shut off the recirc loops (shut the main valve just above the drain on the left hand side) to see if they are part of the issue. But I have had this tank in place like this for the past 2 years, and never have had it this bad before. I've been using the water on and off a lot today so tomorrow morning I'm hoping to get a good indication of what the steady-state temperature is, but as far as I can tell, the water temp coming at the faucet is about 120F. Considering that I have both temperature settings at about 135F, I'm a little surprised that I'm losing 15deg to the ambient surroundings between the tank and the faucet.

    Once I am able to pinpoint the exact steady-state temp tomorrow, I'll re-enable the recirc loops and see if/how they are affecting it. Short of removing/replacing the check valve, is there an easy way to test if it is functioning properly?

    I'm considering the concept of bumping my WH temp to 150 (as suggested previously) and putting in a tempering valve. I'm not thrilled at the extra heating costs, but I suspect that it should give me an extra 15-20% capacity out of the tank. From what I understand, I figure I should still be able to use it with a gravity recirc loop - right? The water leaving the valve would still be 120-130ish so I would not expect the valve being there affecting the recirc loop. Is that a correct understanding / assumption?

    Thanks,

    Eric

    P1030995-2.jpg
    Last edited: Dec 8, 2013
  17. DonL

    DonL Jack of all trades

    Messages:
    3,812
    Location:
    Houston, TX
    That model had 2 different elements available.

    3000 watt and 4500 watt. Did you install the 4500 watt ?

    A IR thermometer would help in verifying the thermostats are working at the correct temperature.


    Good Luck.
  18. benze

    benze New Member

    Messages:
    63
    Location:
    Montreal, Canada
    Yes - I installed the larger element on the bottom.

    Where would I aim the thermometer? The thermostats themselves don't particularly heat up to the touch. I'd love to be able to verify the exact water temp of the tank, but the only way I can imagine doing that would be to use the pressure-release valve to extract water, but opening that valve will spew out water at too high pressure to catch it safely without too much mess. Is there a better way?

    Thanks!

    Eric
  19. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,817
    Location:
    New England
    Do you still have a drain valve? While opening it could lead to a leak, if you wanted to, you could draw a bit of water off there after it had been sitting for awhile so the temp was pretty consistent, and just stick a thermometer in the vessel. If there is a hot water tap somewhere close (maybe the washing machine?), disconnect it there and run it into a cup after clearing the line to get the hottest possible water.

    An IR thermometer on copper needs to either be one with an adjustable emissivity setting, or you need to either paint the pipe with flat black or wrap it in something like hockey tape (or tape you'd use to wrap a baseball bat handle). Otherwise, the emissivity can vary between about 0.07-0.87, a huge range, and not likely to give you useful info, except for relative differences. http://www.scigiene.com/pdfs/428_InfraredThermometerEmissivitytablesrev.pdf
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