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hot water improvement

in one of our buildings there is a 100 gal electric water heater, supplying a restaurant. even when new, the recovery is quite slow. i wonder if a wall hung gas-fired tankless water heater and pump could assist, by circulating the water in the tank through itself and heating the water quicker. maybe even so much quicker that we could disconnect the wiring, and simply use the tank portion.--nbc 

Comments

  • Slimpickins
    Slimpickins Member Posts: 327
    yes you can

    I don't want to publicly tell you how to do it on this forum because I don't want any negative feedback on safety and using controls for what they're not intended for. Although I'd recommend using a dedicated storage tank there is a way to SAFELY use the water heater for what you want to do. You can email me for details. 
  • kcopp
    kcopp Member Posts: 4,095
    just about all...

    the tankless water heater mfg. have lots of diagrams to show how to do this....
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,244
    quite popular actually

    It was often done for camps and state parks shower houses to use an A.O.Smith copper tube boiler designed for domestic water and a large storage tank with a bronze circulator to induce a good flow. We spent many  mid Summer days repiping and properly allowing for expansion in systems installed by the low bidders. Want to see windows blow out? Install a commercial copper tube heater and put a check valve on the inlet with no expansion tank and fire it from stone cold with an undersized circulator pump. Then in under a minute the steam comes and the relief valve does its job! Yep good times. No reason you could not pipe it up but I am wondering if maybe it would be better to just put them in series so you are feeding the tank from the tankless and if it does not keep up with demand the elements kick in to act as a booster. I am assuming the gas is cheaper than the electric per therm.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
    https://heatinghelp.com/find-a-contractor/detail/charles-garrity-plumbing-and-heating
  • Jack
    Jack Member Posts: 1,046
    I do it all the time

    for restaurants, apt bldgs, hotels etc. The best storage tank for this has 4 tappings. two low, two high. Aqua booster type is best. Feed the bottom tap. Pump to the tankless with the one above that. Return to the top of the tank, either T into the relief valve opening or into the hot water outlet. Bottom a-stat at 120, tankless at 140. You satisfy "down" to the astat.

    Do not put the tankless in series with the tank. Tankless are designed to guarantee output temp. As such they will reduce flow to guarantee temp. You can, in periods of high flow, watch your pressure drop with the series piping.

    While you may be able to re-use the E-tank, I think a new tank is in order for a new system, if possible. I usually spec at least two tankless. In part for recovery, In part for redundancy. It is commercial after all. Pipe bypasses so you can isolate the tank and keep making hot water. Two tankless with an 80 gallon tank piped correctly can carry a pretty good size restaurant.

    My normal disclaimer. I represent Rinnai in my local market! Oh, and Charlie is certainly correct about the expansion tank check valve. Go ahead ask me how I know;)
  • World Plumber
    World Plumber Member Posts: 389
    Domestic hot water.

    I have a site where the runs from the instantaneous water heater are long and in the cold weather they need to run the water a long long time to get it hot. I mean 2 sinks and 2 showers running for 3 to 5 minutes. Do you know of any options other than an gas fired tank and recirculation pump. I haven't been able to dream up a way to circulate the water from the instant water heaters. Any suggestions would be helpful. I go back over to the camp in October. This is one of the issues they want to address. It a Bible camp so money is in short supply.
  • Jack
    Jack Member Posts: 1,046
    The best solution

    IMHO, is the Metlund recirc pump. Go to www.gothotwater.com No time or temp controlled recirc will get Energy Star. Metlund's does. Larry Acher's, owner of Metlund, is an on-demand system. He uses I think 008/9 circs to move water at high velocities. The pump can be controlled either by push button/switch or motion sensor. It can be mounted under the master bath lav in a cross connect (except in MA), or if you have a dedicated recirc line, at the water heater. I wouldn't recommend the small buffer tank for recirc...ever.



    Let's assume it is first thing in the am. You have 60F in the hot and cold lines. Walk into the master bath and the motion sensor picks up your presence, makes the pump which pumps at HV and when the inlet sensor on the pump senses an 8F rise, which is adjustable, it turns off the pump. It never pumps hot into the cold line and at the 68f inlet it knows that 2 ft behind the 68 is 120. It will only recognize a call every 8 min. It only runs on the call.



    I prefer the dedicated recirc line myself and depending upon the layout will jsut pump the mains, which is where the water vol is anyway. Every system has a personality and ymmv.



    Some homes definitely require recirc but your situation is extreme. There is no reason for the water heater to necessarily be installed in the boiler mechanical room with most tankless units. Water heaters were traditionally installed there because that is where the chimney is. As most tankless do not need the chimney there is no reason to necessarily place the new water heater where the old one was. As the gas and piping are there I suggest that the job be bid with the existing water heater position as position #1. Go for a walk and see if there is a position #2 that is actually better for the water heaters operation and the customers comfort. Tell them why position #2 is really position #1. Even if they choose not to go with 2 you have put the situation before them and have some ownership in the decision with the consumer.



    I have been in a lot of houses with this problem, but yours sounds like the worst I've heard of. How is this place piped and laid out? In some cases the house is so large that you should split the house and put one at either end of the house. I get into some houses and wonder what the original low cost bidder was doing with his piping lay-outs.
  • Jack
    Jack Member Posts: 1,046
    The best solution

    IMHO, is the Metlund recirc pump. Go to www.gothotwater.com No time or temp controlled recirc will get Energy Star. Metlund's does. Larry Acher's, owner of Metlund, is an on-demand system. He uses I think 008/9 circs to move water at high velocities. The pump can be controlled either by push button/switch or motion sensor. It can be mounted under the master bath lav in a cross connect (except in MA), or if you have a dedicated recirc line, at the water heater. I wouldn't recommend the small buffer tank for recirc...ever.



    Let's assume it is first thing in the am. You have 60F in the hot and cold lines. Walk into the master bath and the motion sensor picks up your presence, makes the pump which pumps at HV and when the inlet sensor on the pump senses an 8F rise, which is adjustable, it turns off the pump. It never pumps hot into the cold line and at the 68f inlet it knows that 2 ft behind the 68 is 120. It will only recognize a call every 8 min. It only runs on the call.



    I prefer the dedicated recirc line myself and depending upon the layout will jsut pump the mains, which is where the water vol is anyway. Every system has a personality and ymmv.



    Some homes definitely require recirc but your situation is extreme. There is no reason for the water heater to necessarily be installed in the boiler mechanical room with most tankless units. Water heaters were traditionally installed there because that is where the chimney is. As most tankless do not need the chimney there is no reason to necessarily place the new water heater where the old one was. As the gas and piping are there I suggest that the job be bid with the existing water heater position as position #1. Go for a walk and see if there is a position #2 that is actually better for the water heaters operation and the customers comfort. Tell them why position #2 is really position #1. Even if they choose not to go with 2 you have put the situation before them and have some ownership in the decision with the consumer.



    I have been in a lot of houses with this problem, but yours sounds like the worst I've heard of. How is this place piped and laid out? In some cases the house is so large that you should split the house and put one at either end of the house. I get into some houses and wonder what the original low cost bidder was doing with his piping lay-outs.
  • Jack
    Jack Member Posts: 1,046
    The best solution

    IMHO, is the Metlund recirc pump. Go to www.gothotwater.com No time or temp controlled recirc will get Energy Star. Metlund's does. Larry Acher's, owner of Metlund, is an on-demand system. He uses I think 008/9 circs to move water at high velocities. The pump can be controlled either by push button/switch or motion sensor. It can be mounted under the master bath lav in a cross connect (except in MA), or if you have a dedicated recirc line, at the water heater. I wouldn't recommend the small buffer tank for recirc...ever.



    Let's assume it is first thing in the am. You have 60F in the hot and cold lines. Walk into the master bath and the motion sensor picks up your presence, makes the pump which pumps at HV and when the inlet sensor on the pump senses an 8F rise, which is adjustable, it turns off the pump. It never pumps hot into the cold line and at the 68f inlet it knows that 2 ft behind the 68 is 120. It will only recognize a call every 8 min. It only runs on the call.



    I prefer the dedicated recirc line myself and depending upon the layout will jsut pump the mains, which is where the water vol is anyway. Every system has a personality and ymmv.



    Some homes definitely require recirc but your situation is extreme. There is no reason for the water heater to necessarily be installed in the boiler mechanical room with most tankless units. Water heaters were traditionally installed there because that is where the chimney is. As most tankless do not need the chimney there is no reason to necessarily place the new water heater where the old one was. As the gas and piping are there I suggest that the job be bid with the existing water heater position as position #1. Go for a walk and see if there is a position #2 that is actually better for the water heaters operation and the customers comfort. Tell them why position #2 is really position #1. Even if they choose not to go with 2 you have put the situation before them and have some ownership in the decision with the consumer.



    I have been in a lot of houses with this problem, but yours sounds like the worst I've heard of. How is this place piped and laid out? In some cases the house is so large that you should split the house and put one at either end of the house. I get into some houses and wonder what the original low cost bidder was doing with his piping lay-outs.
  • Jack
    Jack Member Posts: 1,046
    The best solution

    IMHO, is the Metlund recirc pump. Go to www.gothotwater.com No time or temp controlled recirc will get Energy Star. Metlund's does. Larry Acher's, owner of Metlund, is an on-demand system. He uses I think 008/9 circs to move water at high velocities. The pump can be controlled either by push button/switch or motion sensor. It can be mounted under the master bath lav in a cross connect (except in MA), or if you have a dedicated recirc line, at the water heater. I wouldn't recommend the small buffer tank for recirc...ever.



    Let's assume it is first thing in the am. You have 60F in the hot and cold lines. Walk into the master bath and the motion sensor picks up your presence, makes the pump which pumps at HV and when the inlet sensor on the pump senses an 8F rise, which is adjustable, it turns off the pump. It never pumps hot into the cold line and at the 68f inlet it knows that 2 ft behind the 68 is 120. It will only recognize a call every 8 min. It only runs on the call.



    I prefer the dedicated recirc line myself and depending upon the layout will jsut pump the mains, which is where the water vol is anyway. Every system has a personality and ymmv.



    Some homes definitely require recirc but your situation is extreme. There is no reason for the water heater to necessarily be installed in the boiler mechanical room with most tankless units. Water heaters were traditionally installed there because that is where the chimney is. As most tankless do not need the chimney there is no reason to necessarily place the new water heater where the old one was. As the gas and piping are there I suggest that the job be bid with the existing water heater position as position #1. Go for a walk and see if there is a position #2 that is actually better for the water heaters operation and the customers comfort. Tell them why position #2 is really position #1. Even if they choose not to go with 2 you have put the situation before them and have some ownership in the decision with the consumer.



    I have been in a lot of houses with this problem, but yours sounds like the worst I've heard of. How is this place piped and laid out? In some cases the house is so large that you should split the house and put one at either end of the house. I get into some houses and wonder what the original low cost bidder was doing with his piping lay-outs.
  • Jack
    Jack Member Posts: 1,046
    The best solution

    IMHO, is the Metlund recirc pump. Go to www.gothotwater.com No time or temp controlled recirc will get Energy Star. Metlund's does. Larry Acher's, owner of Metlund, is an on-demand system. He uses I think 008/9 circs to move water at high velocities. The pump can be controlled either by push button/switch or motion sensor. It can be mounted under the master bath lav in a cross connect (except in MA), or if you have a dedicated recirc line, at the water heater. I wouldn't recommend the small buffer tank for recirc...ever.



    Let's assume it is first thing in the am. You have 60F in the hot and cold lines. Walk into the master bath and the motion sensor picks up your presence, makes the pump which pumps at HV and when the inlet sensor on the pump senses an 8F rise, which is adjustable, it turns off the pump. It never pumps hot into the cold line and at the 68f inlet it knows that 2 ft behind the 68 is 120. It will only recognize a call every 8 min. It only runs on the call.



    I prefer the dedicated recirc line myself and depending upon the layout will jsut pump the mains, which is where the water vol is anyway. Every system has a personality and ymmv.



    Some homes definitely require recirc but your situation is extreme. There is no reason for the water heater to necessarily be installed in the boiler mechanical room with most tankless units. Water heaters were traditionally installed there because that is where the chimney is. As most tankless do not need the chimney there is no reason to necessarily place the new water heater where the old one was. As the gas and piping are there I suggest that the job be bid with the existing water heater position as position #1. Go for a walk and see if there is a position #2 that is actually better for the water heaters operation and the customers comfort. Tell them why position #2 is really position #1. Even if they choose not to go with 2 you have put the situation before them and have some ownership in the decision with the consumer.



    I have been in a lot of houses with this problem, but yours sounds like the worst I've heard of. How is this place piped and laid out? In some cases the house is so large that you should split the house and put one at either end of the house. I get into some houses and wonder what the original low cost bidder was doing with his piping lay-outs.
  • Jack
    Jack Member Posts: 1,046
    The best solution

    IMHO, is the Metlund recirc pump. Go to www.gothotwater.com No time or temp controlled recirc will get Energy Star. Metlund's does. Larry Acher's, owner of Metlund, is an on-demand system. He uses I think 008/9 circs to move water at high velocities. The pump can be controlled either by push button/switch or motion sensor. It can be mounted under the master bath lav in a cross connect (except in MA), or if you have a dedicated recirc line, at the water heater. I wouldn't recommend the small buffer tank for recirc...ever.



    Let's assume it is first thing in the am. You have 60F in the hot and cold lines. Walk into the master bath and the motion sensor picks up your presence, makes the pump which pumps at HV and when the inlet sensor on the pump senses an 8F rise, which is adjustable, it turns off the pump. It never pumps hot into the cold line and at the 68f inlet it knows that 2 ft behind the 68 is 120. It will only recognize a call every 8 min. It only runs on the call.



    I prefer the dedicated recirc line myself and depending upon the layout will jsut pump the mains, which is where the water vol is anyway. Every system has a personality and ymmv.



    Some homes definitely require recirc but your situation is extreme. There is no reason for the water heater to necessarily be installed in the boiler mechanical room with most tankless units. Water heaters were traditionally installed there because that is where the chimney is. As most tankless do not need the chimney there is no reason to necessarily place the new water heater where the old one was. As the gas and piping are there I suggest that the job be bid with the existing water heater position as position #1. Go for a walk and see if there is a position #2 that is actually better for the water heaters operation and the customers comfort. Tell them why position #2 is really position #1. Even if they choose not to go with 2 you have put the situation before them and have some ownership in the decision with the consumer.



    I have been in a lot of houses with this problem, but yours sounds like the worst I've heard of. How is this place piped and laid out? In some cases the house is so large that you should split the house and put one at either end of the house. I get into some houses and wonder what the original low cost bidder was doing with his piping lay-outs.
  • Jack
    Jack Member Posts: 1,046
    The best solution

    IMHO, is the Metlund recirc pump. Go to www.gothotwater.com No time or temp controlled recirc will get Energy Star. Metlund's does. Larry Acher's, owner of Metlund, is an on-demand system. He uses I think 008/9 circs to move water at high velocities. The pump can be controlled either by push button/switch or motion sensor. It can be mounted under the master bath lav in a cross connect (except in MA), or if you have a dedicated recirc line, at the water heater. I wouldn't recommend the small buffer tank for recirc...ever.



    Let's assume it is first thing in the am. You have 60F in the hot and cold lines. Walk into the master bath and the motion sensor picks up your presence, makes the pump which pumps at HV and when the inlet sensor on the pump senses an 8F rise, which is adjustable, it turns off the pump. It never pumps hot into the cold line and at the 68f inlet it knows that 2 ft behind the 68 is 120. It will only recognize a call every 8 min. It only runs on the call.



    I prefer the dedicated recirc line myself and depending upon the layout will jsut pump the mains, which is where the water vol is anyway. Every system has a personality and ymmv.



    Some homes definitely require recirc but your situation is extreme. There is no reason for the water heater to necessarily be installed in the boiler mechanical room with most tankless units. Water heaters were traditionally installed there because that is where the chimney is. As most tankless do not need the chimney there is no reason to necessarily place the new water heater where the old one was. As the gas and piping are there I suggest that the job be bid with the existing water heater position as position #1. Go for a walk and see if there is a position #2 that is actually better for the water heaters operation and the customers comfort. Tell them why position #2 is really position #1. Even if they choose not to go with 2 you have put the situation before them and have some ownership in the decision with the consumer.



    I have been in a lot of houses with this problem, but yours sounds like the worst I've heard of. How is this place piped and laid out? In some cases the house is so large that you should split the house and put one at either end of the house. I get into some houses and wonder what the original low cost bidder was doing with his piping lay-outs.
  • Jack
    Jack Member Posts: 1,046
    The best solution

    IMHO, is the Metlund recirc pump. Go to www.gothotwater.com No time or temp controlled recirc will get Energy Star. Metlund's does. Larry Acher's, owner of Metlund, is an on-demand system. He uses I think 008/9 circs to move water at high velocities. The pump can be controlled either by push button/switch or motion sensor. It can be mounted under the master bath lav in a cross connect (except in MA), or if you have a dedicated recirc line, at the water heater. I wouldn't recommend the small buffer tank for recirc...ever.



    Let's assume it is first thing in the am. You have 60F in the hot and cold lines. Walk into the master bath and the motion sensor picks up your presence, makes the pump which pumps at HV and when the inlet sensor on the pump senses an 8F rise, which is adjustable, it turns off the pump. It never pumps hot into the cold line and at the 68f inlet it knows that 2 ft behind the 68 is 120. It will only recognize a call every 8 min. It only runs on the call.



    I prefer the dedicated recirc line myself and depending upon the layout will jsut pump the mains, which is where the water vol is anyway. Every system has a personality and ymmv.



    Some homes definitely require recirc but your situation is extreme. There is no reason for the water heater to necessarily be installed in the boiler mechanical room with most tankless units. Water heaters were traditionally installed there because that is where the chimney is. As most tankless do not need the chimney there is no reason to necessarily place the new water heater where the old one was. As the gas and piping are there I suggest that the job be bid with the existing water heater position as position #1. Go for a walk and see if there is a position #2 that is actually better for the water heaters operation and the customers comfort. Tell them why position #2 is really position #1. Even if they choose not to go with 2 you have put the situation before them and have some ownership in the decision with the consumer.



    I have been in a lot of houses with this problem, but yours sounds like the worst I've heard of. How is this place piped and laid out? In some cases the house is so large that you should split the house and put one at either end of the house. I get into some houses and wonder what the original low cost bidder was doing with his piping lay-outs.
  • Jack
    Jack Member Posts: 1,046
    The best solution

    IMHO, is the Metlund recirc pump. Go to www.gothotwater.com No time or temp controlled recirc will get Energy Star. Metlund's does. Larry Acher's, owner of Metlund, is an on-demand system. He uses I think 008/9 circs to move water at high velocities. The pump can be controlled either by push button/switch or motion sensor. It can be mounted under the master bath lav in a cross connect (except in MA), or if you have a dedicated recirc line, at the water heater. I wouldn't recommend the small buffer tank for recirc...ever.



    Let's assume it is first thing in the am. You have 60F in the hot and cold lines. Walk into the master bath and the motion sensor picks up your presence, makes the pump which pumps at HV and when the inlet sensor on the pump senses an 8F rise, which is adjustable, it turns off the pump. It never pumps hot into the cold line and at the 68f inlet it knows that 2 ft behind the 68 is 120. It will only recognize a call every 8 min. It only runs on the call.



    I prefer the dedicated recirc line myself and depending upon the layout will jsut pump the mains, which is where the water vol is anyway. Every system has a personality and ymmv.



    Some homes definitely require recirc but your situation is extreme. There is no reason for the water heater to necessarily be installed in the boiler mechanical room with most tankless units. Water heaters were traditionally installed there because that is where the chimney is. As most tankless do not need the chimney there is no reason to necessarily place the new water heater where the old one was. As the gas and piping are there I suggest that the job be bid with the existing water heater position as position #1. Go for a walk and see if there is a position #2 that is actually better for the water heaters operation and the customers comfort. Tell them why position #2 is really position #1. Even if they choose not to go with 2 you have put the situation before them and have some ownership in the decision with the consumer.



    I have been in a lot of houses with this problem, but yours sounds like the worst I've heard of. How is this place piped and laid out? In some cases the house is so large that you should split the house and put one at either end of the house. I get into some houses and wonder what the original low cost bidder was doing with his piping lay-outs.
  • Jack
    Jack Member Posts: 1,046
    The best solution

    IMHO, is the Metlund recirc pump. Go to www.gothotwater.com No time or temp controlled recirc will get Energy Star. Metlund's does. Larry Acher's, owner of Metlund, is an on-demand system. He uses I think 008/9 circs to move water at high velocities. The pump can be controlled either by push button/switch or motion sensor. It can be mounted under the master bath lav in a cross connect (except in MA), or if you have a dedicated recirc line, at the water heater. I wouldn't recommend the small buffer tank for recirc...ever.



    Let's assume it is first thing in the am. You have 60F in the hot and cold lines. Walk into the master bath and the motion sensor picks up your presence, makes the pump which pumps at HV and when the inlet sensor on the pump senses an 8F rise, which is adjustable, it turns off the pump. It never pumps hot into the cold line and at the 68f inlet it knows that 2 ft behind the 68 is 120. It will only recognize a call every 8 min. It only runs on the call.



    I prefer the dedicated recirc line myself and depending upon the layout will jsut pump the mains, which is where the water vol is anyway. Every system has a personality and ymmv.



    Some homes definitely require recirc but your situation is extreme. There is no reason for the water heater to necessarily be installed in the boiler mechanical room with most tankless units. Water heaters were traditionally installed there because that is where the chimney is. As most tankless do not need the chimney there is no reason to necessarily place the new water heater where the old one was. As the gas and piping are there I suggest that the job be bid with the existing water heater position as position #1. Go for a walk and see if there is a position #2 that is actually better for the water heaters operation and the customers comfort. Tell them why position #2 is really position #1. Even if they choose not to go with 2 you have put the situation before them and have some ownership in the decision with the consumer.



    I have been in a lot of houses with this problem, but yours sounds like the worst I've heard of. How is this place piped and laid out? In some cases the house is so large that you should split the house and put one at either end of the house. I get into some houses and wonder what the original low cost bidder was doing with his piping lay-outs.
  • Jack
    Jack Member Posts: 1,046
    Holy Smokes

    I stutter now and again...but that is ridiculous!
  • kcopp
    kcopp Member Posts: 4,095
    wow...

    how much coffee did you have! lol!
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,839
    A BTU is a BTU is a BTU....

    Regardless of the source (electric, solar, NG, LP, oil).



    NBC, here in Colorado, the state health department dictates the size of the water heater (storage as well as btuH capacity) for ALLL food service applications. Had they been involved, you would not be here asking this question.



    The load needs to be determined prior to sizing the additional capacity. Even at that, it will be based on worse case scenario, which we all know, rarely occurs, so short cycling is inevitable.



    With all of the new modulating/condensing tankless water heaters available these days, you'd be CRAZY to not go with that option IMHO.



    The only bad thing if you will, about pumping a boiler through existing tank tappings is that you may be forcing 5 lbs of sugar into a 1 pound hole. In other words, if you are running 10 GPM though a fitting/pipe that is only rated for 4 GPM, you can expect some consequences at one point in time or another.



    Instead of piping the tankless in parallel to the tank, you could pipe it in series with the tank, but then you will experience l-o-n-g-e-r- recoveries after having sat for periods of time without use.



    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,572
    tankless * tank HW

    i was certainly thinking of some sort of series arrangement using a pump, wherin the tankless heater keeps the tank temp at the normal HW temperature. this commercial, electric hot water heater uses a lot of our electrical capacity, and making this change would free up that amperage for some other uses, if we cut off the heating elements completely.

    as i see it, the tankless can then be mounted 30 ft. away on an outside wall, for venting purposes; and would take up very little space.

    thank you all for your many suggestions!--nbc

    i am getting so much better at mental math thanks to the new security check!!
This discussion has been closed.