Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Indirect or Combo Boiler with Recirc DHT?

TerryR
TerryR Member Posts: 28
We have a Trainco Heatmaker supplying heat and DHW. It's 17 years old and showing it's age. Parts are expensive and I'm considering replacing it.



It heats about 3200 sq ft by underfloor radiant heating with 8 zones in the mountains of western NC. The built-in DHW tank is too small, so that the shower gets cold before the boiler can get fired up. So we installed a holding tank long ago. There is a DHW recirculating system, which we love. It has a timer and an aquastat, but in 17 years I've never found the circulator shut off by the aquastat, so I wonder whether it works. Some of the lines thomosyphon so there is some circulation all the time.



I've looked at tankless combo condensing boilers and "standard" condensing boilers with an indirect tank. I'm concerned about using a tankless unit with the recirc system, both because is seems to largely defeat the advantage of going tankless and because it seems to shorten the life of the boiler. I have found the HTP Versa-Flame which seems to somewhat address this issue by using a 55 gal tank as a heat sink, reducing the cycling of the boiler.



Still, I'm leaning toward an indirect system as being more compatible with a recirc system. 



An I on the wrong track? Any suggestions?



Terry
«1

Comments

  • Snowmelt
    Snowmelt Member Posts: 1,414
    Go with

    Go with a standard condensing boiler and an indirect with the recirc keep it simple, taco has the new smart pump that remembers when you use domestic water and will work well.



    They also make a pump called on command made for tankless and electrical savings.
  • heatpro02920
    heatpro02920 Member Posts: 991
    edited March 2014
    First step

    Heat loss and DHW load calculations...



    Pretty simple, figure out how much heat you need on your design day and how much hot water you need at once....



    So for conversations sake say you need 97K BTU's of heat and 5gpm {70 degree rise, oversize it a little on the DHW side} of hot water...



    You look into buying just that size boiler and weigh your options for the water heater....



    I would put together a price for high efficiency and a price for conventional cast iron for heat and then a price for an indirect water heater and a tankless water heater....



    So it would look like this...



    a williamson gwa140 with a smart 40 ga indirect



    and on the other side of the spectrum a Triangle tube Solo 110 with a smart 40...



    Or either of the two with a properly sized rinnai tankless, I prefer going tankless since, I have had great luck with them, they last a long time, use very little energy, allow you to shut down your boiler for half the year, ect ect ect.. and the price vs an indirect is not much....



    another option is a combi, a triangle tube excellence would be most likely your best option, there are a few others....



    as far as the recirc goes, I like the grundfos http://www.pexsupply.com/Grundfos-97525908-UP10-16B5-ATLC-1-2-Sweat-115V-Pump-w-Timer-and-Aquastat?gclid=CLPewZjZvb0CFa_m7AodKwYAyw it has a timer and aquastat, they also sell one with check valve flanges, and I have had great luck with them, plus they dont use much power at all...



    But like I said, first things first, get your heat loss and dhw load figured out and then look into your options...



    You can make a ci conventinoal boiler very efficient, piped pri/sec with delta t circs and an ODR control will get you within the range of a mod con {minus teh combusiotn efficiency which could be around 8-12%.. So do you spend $50-100% more on the install to save 8-12% per year for a unit that will cost more to maintain and most likely not last as long with parts support and service being more difficult????
  • TerryR
    TerryR Member Posts: 28
    edited March 2014
    Indirect or Combo Boiler with Recirc DHW?

    Thanks, Snowmelt.



    That's the direction I'm leaning.



    About the smart pump -- we're home all day and liable to use the water at any time. It would not be happy if it decided we were not going to use it when we decided to.



    The on-demand units are the ones you tell to recirc with a button or something? I don't think we are interested in waiting till it gets the water to the point of use.



    Terry
  • SWEI
    SWEI Member Posts: 7,356
    Waiting for water

    is not that long.  If you install an occupancy sensor for the bathroom light, you can wire the recirc pump to that and put a Taco 563-2 aquastat in series (which will stop the pump once the water arrives.)
  • TerryR
    TerryR Member Posts: 28
    edited March 2014
    First Steps

    Thanks Heatpro,



    I'm working with a contractor, and I'm going to leave the sizing to him. But he's open to various technologies and I'm trying to figure out which direction to push that.



    I gather you are suggesting that a condensing boiler may not be the best way to go, so I should look at conventional?



    You say you have used Rinnai tankless with good success. You've had no problems with using a recirc system with them?



    Terry
  • TerryR
    TerryR Member Posts: 28
    edited March 2014
    Occupancy Sensor?

    Thanks, SWEI,



    I don't see an occupancy sensor on the light being acceptable. We don't turn on the lights when we use the bathroom at night, nor most of the time during the day either, for that matter.



    We're talking 4 bath rooms and the kitchen, so you would need sensors in each and aquastat in each, with a relay system to make it all work. No?



    We're in the house all day, so I'd think occupancy sensors would be triggered all day long - isn't a simple timer and aquastat more practical?Terry
  • Snowmelt
    Snowmelt Member Posts: 1,414
    Navien

    The navien has the recirc built right into it also 2 inch venting with a negative gas valve. If you go tankless that's what I would go with.
  • Snowmelt
    Snowmelt Member Posts: 1,414
    No light in bathroom

    I just read your post about bathroom and don't turn the light on, if I did that I would miss the bowl. My girl would be pissed
  • TerryR
    TerryR Member Posts: 28
    No light in bathroom

    It's hard to miss if you are sitting on the seat. Seems to me a small price to pay for not having the glare of the lights in the middle of the night, but I suppose that's a personal preference. :)







    Terry
  • Tim Potter
    Tim Potter Member Posts: 273
    Do Your own heatloss !

    you said: " I'm working with a contractor, and I'm going to leave the sizing to him. "



    The contractor will be scared to death to suggest anything close to the correct size boiler, he will fall into the I dont care how much more it costs to run mode, because he won't be paying your gas bills.....



    Do your own heatloss, Its not that hard.



    There are HUNDREDS of posts on this forum of:

    " My contractor oversized my boiler, now it short cycles, breaks down & costs me a fortune to run "



    I have never seen a post about one that was not big enough.



    Hope this helps:



    Tim
    Winter Park, CO & Arvada, CO
  • SWEI
    SWEI Member Posts: 7,356
    Occupancy sensors

    are just one way to skin the cat.  You can add a single pole switch downstream of the occupancy sensor if needed.  Four baths and a kitchen is a different animal.  Home run 3/8" manifold systems are one answer, and you can mix those with recirc as long as you follow the rules (no recirc through the manifold, at least with the Manabloc.)



    24 x 7 recirc works if you really minimize the flow with something like a B&G ecocirc e3 Vario.  If you install a "standard" recirc pump (003B or similar, or even worse, one of those 006B's they have on the shelf at the local supply house) you will consume much more of both electricity and gas.
  • TerryR
    TerryR Member Posts: 28
    edited April 2014
    Do Your own heatloss !

    Tim,



    You said "Do your own heatloss, Its not that hard." Can you suggest where to find information on how to do that?



    On the other hand, the 130k BTU unit has been in service 17 years with little sign of being over-sized that I am aware of.



    Terry
  • TerryR
    TerryR Member Posts: 28
    edited April 2014
    Occupancy sensors

    Thanks, SWEI,



    The system is piped with 1/2" copper for the returns, and most of that is buried in the walls or upper floors, so isn't going to get changed. There are three return legs, one from the kitchen one floor above and 30' offset, another from the master bath two floors directly above (that's the one that auto-siphons) and one from the guest baths one and two floors above and maybe 40' to the side. They all join with simple tees, which are in accessible space. Is there something better than can be done as a manifold?



    As I said initially, the current system has a timer, which is set to run about 18 hours a day. There is an aquastat  at the pump, which so far as I can tell never shuts the pump off. The current pump is a B&G 9U/LW - I gather I can do much better?



    Terry
  • SWEI
    SWEI Member Posts: 7,356
    edited April 2014
    Recirc pumps

    The 9U curve runs from about 9 feet to 12 GPM.  It consumes about 40 Watts.



    The ecocirc e3-4 curve runs from about 5.5 feet to 5 GPM.  It consumes 2-10W at full speed -- even less if you buy the Vario version and turn it down.



    The overwhelming majority of DHW recirc systems (both commercial and residential) we encounter are overpumped.  This makes some sense with a demand system, since the pump is only powered for a short time and you need the water to get there fast.  For continuous recirc or timed systems, it wastes a lot of both heat and electrical energy.



    If the existing piping is copper, and especially if it increases to 3/4" as it nears the pump, you might consider reducing the size of accessible portions with PEX, perhaps even 3/8" from the individual branches.  I'd also look at balancing valves for the branches.  Don't forget lots of insulation.
  • Tim Potter
    Tim Potter Member Posts: 273
    Heat loss program

    Hi Terry,



    Here is a program:



    http://www.slantfin.com/index.php/professionals/heatloss



    Your boiler sized at 130K is about 40 btus per square ft. even when you take into effect efficiency & altitude de-ratings, ill bet its still way oversized & your heat loss is way less than that.



    My example, 2000 square ft house with lots of glass at 9000' in Winter Park, CO.

    150,000 boiler @ 80% efficiency = 120,000 @ 9000' (2% per 1000') . = 98400 btus to the house. If you clock the gas input it matches it come up 99K so its close. When its cold in grand county (-30* is NOT uncommon) it only runs about 32% of the time. I came up with a heat loss of slightly more than 50,000 btus when I ran the numbers.



    If I were to replace my CI boiler tomorrow, i would have installed the WHN055 55,000 btu Locinvar Knight. It modulates down to 11,000 btus

    I have a 80 gal indirect so we still would have plenty of hot water with that setup.

    Thats how much oversized mine was.

    I am looking forward to hearing more about your install.



    Tim
    Winter Park, CO & Arvada, CO
  • heatpro02920
    heatpro02920 Member Posts: 991
    The ru's have a recirc program built in

    I personally design it a little different, I install a Bosch ES8 and a grundfos circ after the tankless, so the tankless runs through it, and the electric water heater takes care of the recircs heatloss... It works much better than cycling a tankless just for a recirc loop...



    I have drawings and pictures of them jobs, you pm me and I will forward them along...



    After you find your heatloss you make a decision on which way you want to go and let us know what you decide we can give you an idea of how to recommend your contractor to do the install... I have tons of drawings of systems I have done, Im sure I can find one to fit your system... Not all contractors are familiar with certain practices... but most can figure it out with a drawing...
  • TerryR
    TerryR Member Posts: 28
    edited April 2014
    Heat Loss

    Thanks a lot Tim,



    I downloaded and use the SlantFin app, and get a heat loss of 97k BTU, not counting DHW. One thing I don't see a way to account for is the high winds we often get in the winter. We commonly have 50 to 60 MPH winds at 10 to 15 degrees, for a day or two, and occasionally temps to zero or a little below. We got to -7 a couple of times this year. I used an outside temp of 5 but have no idea whether that's appropriate.



    Terry
  • Tim Potter
    Tim Potter Member Posts: 273
    Wind factor

    Terry, congrats on the heat loss, nice 1st step.

    97K sounds more like it, but its still 30 btus per square ft, seems like a lot, others may chime in on it.



    There is a built in fudge factor to the heat loss, to account for things like wind i believe.



    I remember a story a while back from Mark Eatherton, on a job he personally did the heat loss, designed & installed the system, he was at the house on a 'design day', the boiler was modulating at 50%. you could probably ping him for verification & more info.



    If any of the local contractors are versed in the Locinvar or Triangle Tube boiler, you could pair it up with a goodsize indirect & will make a killer combo. You could even add a 30gal Boiler Buddy buffer tank to the heating side, would even eliminate the short cycling of the smaller zones in shoulder season.Go for the mod-con with constant circulation, you won't be unhappy with the results, I am very happy with my constant circulation systems



    Tim
    Winter Park, CO & Arvada, CO
  • TerryR
    TerryR Member Posts: 28
    Heat Load Calcs?

    I found a different heat load calculator - online at loadcalc.net, which is telling me that my heat load is 170k BTU/hr. Obviously there is a wide variation, and this one is wide of the mark since 130k BTU has been totally sufficient for 17 years.. How does one find something reliable?
  • TerryR
    TerryR Member Posts: 28
    edited April 2014
    Thanks

    Thanks, heatpro.





    Will do.

    Terry
  • TerryR
    TerryR Member Posts: 28
    edited April 2014
    Thanks

    Thanks, Tim,



    I'm not feeling very confident about the results - lots of factors required where I have no idea of the correct values. I selected from their suggestions, but some of them didn't fit my situation all that well. I noticed showing windows on two sides vs one for the infiltration factor changes the results by 20k or so. Since the house is almost totally open, I'd think for infiltration purposes all rooms are effectively exposed on 2 or even 3 sides, since nothing blocks airflow from room to room.



    Terry
  • Tim Potter
    Tim Potter Member Posts: 273
    Not confident about results....

    I could see where you would be concerned, 20k is a lot of btu's to be off.



    Here is a table to figure out your design day temp.

    As far as i know, you don't use the "coldest its been this winter" temp, but some percentile, which is why for example, Asheville is listed at 16*



    http://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/Outdoor_Design_Conditions_508.pdf



    LOTS of people on this site use the slant-fin program, I'm sure its accurate, otherwise I think there would be discussion on the topic.



    I used slant-fin to figure out my heat load, and as born out of the actual runtime of the boiler at -32* its at least 30% oversized



    Its been said on the site many times, picking the contractor is way more important than picking the boiler.



    with your heatloss in hand, you can judge the contractors knowledge.

    you reported you were working with a contractor, what does he say the heatloss is???

    Has he done one? if not, you could ask him to do one & see what he comes up with.



    keep the info coming,



    Tim
    Winter Park, CO & Arvada, CO
  • TerryR
    TerryR Member Posts: 28
    edited April 2014
    Design Temps

    Hi, Tim,



    I've seen that table - there's a link to in in the Slant/Fin app. Trouble is there is no place on it that has weather even remotely close to ours. Ashville is less than two-thirds as high as we are and gets much less cold weather than we do. That's why I made up my own number.



    It's not just the 20k BTUs that bothered me - I posted that I'd found an online heat load tool that said I had a load of something like 170K. Clearly that was wrong.



    I've not gotten serious about replacement with my contractor yet. We've had a couple of conversations about which technology to use, but he's still working on what we can do to keep the current unit in operation. I need to get him more serious about a replacement I think.



    Terry
  • 4Johnpipe
    4Johnpipe Member Posts: 480
    Boiler

    Terry...I use the HTP product almost exclusively for radiant it is like peanut butter and jelly. It contains its own mass or buffer tank if you will. Also it is a water heater. I would suggest asking your contractor to see the heat loss...A heat loss is a must and most programs are deigned for 20 or 30 MPH winds from all directions...don't ask me how but that is factored into most heat loss software. I use Design Suite from Uponor...



    Picture is a Versa Hydro Solar
    LANGAN'S PLUMBING & HEATING LLC
    Considerate People, Considerate Service, Consider It Done!
    732-751-1560
    email: langansph@yahoo.com
    www.langansplumbing.com
  • TerryR
    TerryR Member Posts: 28
    edited April 2014
    HTP Products

    Thanks,



    As I mentioned in my first post I'd looked that and though it sounded like a good solution. Thanks for the confirmation. If I'm reading their material correctly, their smallest unit is 130k BTU, which I know from experience is adequate, though my attempts to do a heat load suggest that may be larger than needed. With modulating boilers how much of an issue is that?



    Terry
  • 4Johnpipe
    4Johnpipe Member Posts: 480
    HTP

    Terry...The Versa Flame functions as a boiler first and the heat exchanger is what gives you domestic hot water like a tankless. The Versa Hydro in the picture I attached is a water heater first and the heat exchanger gives you space heating. The 199K BTU model offers 135K BTU's of space heating. Here is the awesome part. The burner modulates at a 5 to 1 turn down so that is 39,800 BTU's...now for awesome the circulator has a flow that modulates down 10 to 1 so that is 3,980 BTU's. It is a perfect match for radiant. The unit in the picture is a 7,560.00 square foot house with a 108,000 BTU heat loss on design day. We designed to 0 degrees...This boiler can handle a little oversizing well. If you see the square footage for this example you can see why a heat loss is sooo important.
    LANGAN'S PLUMBING & HEATING LLC
    Considerate People, Considerate Service, Consider It Done!
    732-751-1560
    email: langansph@yahoo.com
    www.langansplumbing.com
  • TerryR
    TerryR Member Posts: 28
    edited April 2014
    Heat Load for DHW?

    I've gotten some help with heat load for heating, but am having trouble trying to figure out what the load is for DHW. On the one hand I find comments that water heating typically amounts to something like 20% of energy usage. 



     But the only hard numbers I've found are gal per min for sinks, gal per shower, gal per dishwasher load, etc.  How to convert these into gal per hour average usage is a mystery - if I could do that I can easily enough convert to BTU per hour. My efforts so far have run much lower than 20% of the heating load, let alone the total energy load of the house.



    There are two people in the house nearly all the time, we run the dishwasher every other day, and the cloths washer maybe twice a week. How do I get from there to a heat load? And should I consider that an unusually low usage for a three bedroom house, and allow some more so future owners won't run short?



    Terry
  • Tim Potter
    Tim Potter Member Posts: 273
    DHW Math

    Terry,

    I searched the forum & came up with this post from July 2012;



    "Boiler sizing for DHW"



    Its very helpful in sizing the Indirect



    for example:



    2.5 gpm shower (low flo) x 50* dT (55* incoming 105* shower) x 8.33 (water lbs/gal) = 1041 btus/min x 60min = 62000 btu boiler ( for continuous shower )



    substitute any changes in numbers to the formula

    eg: our city water in winter park comes out of the ground at about 40* in the winter so the dt for me would be 65*



    now any water stored in the indirect will lower the needed btus in that first hour, or be able to run a 2nd shower, washer, or dishwasher at the same time.



    we have an 80gal indirect, with 100,000 net input boiler and we are unable to run that out even with 3 showers, dishwasher & washer going, when we are out skiing, all hell breaks loose after a big day on the mountain....



    takeaway from that post: size the boiler to the HEATING load, & size the Indirect for the domestic load. its a lot cheaper to upsize the indirect (one time pmt) than pay every day in lowered efficiency to upsize the boiler.





    carry on:



    Tim
    Winter Park, CO & Arvada, CO
  • TerryR
    TerryR Member Posts: 28
    edited April 2014
    DHW math

    Thanks, Tim,



    Looks to me like there are really two questions here. One is sizing for first hour, especially with an indirect heater if I go that way.



    But the issue I was currently looking at was heat load on the boiler for DHW, which seems to me is more about average load than first hour. For that, based on some figures I found, I got:



    showers - 10 min per day @ 1.5 gpm = 15 gal

    hand washing dishes - 15 per day @ 1.5 gpm = 23 gal

    dishwasher - 6 gal every other day = 3 gal per day

    hand washing - 5 min per day @ 1 gpm = 5 gal

    clothes washing - 7 gal twice a week = 2 gal per day

    total 48 gal per day = 2 gal per hr = 16 lb per hr @ 90 degree temp rise = 1425 BTU per hour.



    Even if I'm off by a factor of three or four, it really doesn't count in boiler sizing. 

    What am I missing?

    Terry
  • Tim Potter
    Tim Potter Member Posts: 273
    You are not missing anything,

    The general comment I have found here is DON'T add DHW to your heat load.

    The heat loss has gobs of fudge factor in it, so if you were to add the two, you would be even more oversized (oversized = bad)



    your indirect size in gallons will determine first hour max flow rate, but rarely do you use max rate for even close to an hour.





    Tim
    Winter Park, CO & Arvada, CO
  • TerryR
    TerryR Member Posts: 28
    edited April 2014
    Recirc pumps

    Thanks, SWEI,



    That's helpful. It looks like I could do a lot better by reducing the recirc flow. I see that there is a version of the e3-4 with a built in aquastat. You have any experience with that?

    The existing piping is 1/2" copper all the way to the pump. I'm wary of reducing the size because the only leg that's much exposed is the longest one, so don't I court balance issues if I introduce more drag in that one?



    The entire supply and return lines are insulated, such as it is, with the black foam stuff. I would probably do well to increase the insulation on the part that's exposed, since it's in nominally unheated space (heated only by all the loss in the exposed part of the radiant piping).



    Terry
  • TerryR
    TerryR Member Posts: 28
    HTP

    Thanks for the additional info. I was confused by their description of the two models by HTP. I gather from your explanation the Versa Flame has a 55 gal tank of heating water, and uses that to buffer the tankless DHW system. The Versa Hydro does the reverse - holds 55 gal or more of domestic water, and uses that to buffer the space heating. Their description of the Flame as for installations that prioritize space heating made me think since space heating is by far the biggest load I should look at that model. I hear you suggesting the Hydro is a better choice.

    Terry 
  • icesailor
    icesailor Member Posts: 7,265
    edited April 2014
    FWIW (Enlightened)

    FWIW, You can buy a GFCI for the bathroom plug (all bathrooms are supposed to have a GFCI) that comes with a light sensitive LED night light.

    If the light is an issue, you will barely notice it. And, it is my long held belief from long experience, that for those late night bathroom trips, NEVER open both eyes, only one. The left eye stimulates the right side of the brain and the right eye stimulated the left side of the brain. Therefore, if you only open one eye, you only stimulate one side of the brain. If I follow that rule, I go right back to my usual noisy slumber. If I open both eyes, I'm awake until morning.

    Unlike the old State of Maine story I heard about the old fisherman.

    Seems he was quite renowned as one who could always catch fish. Once, someone asked him the secret of his successful fishing.

    Well, when I wake up in the morning, and my wife is sleeping on her left side, I fish off the left side of the boat. If I wake up and she's sleeping on her right side, I fish off  of the right side of the boat. After a pause, the inquisitor asked: What happens if she's sleeping on her back? To which the old Captain relied, "Then I don't go fishin'".

    Keep one eye open in the dark. Don't trip on anything.



    http://www.amazon.com/Pass-Seymour-1595NTLTRWCC4-Receptacle-Nightlight/dp/B001H1GQRC
  • Snowmelt
    Snowmelt Member Posts: 1,414
    Another

    Another way to put it.



    Look at a taco zone or pump contro board they have the indirect as a priority because when the indirect calls all the zones go off except the domestic water so it will keep up with your domestic use.



    What they want you to do is do a heat loss for the house and your domestic, in a house with multiple showers and a jacuzzi they will have a bigger heat /btu demand.



    That is when you have to get a bigger boiler or might want to go tankless and measure your gpm. At that time it may be feasible to install a tankless water heater or two.
  • heatpro02920
    heatpro02920 Member Posts: 991
    When I size a boiler with dhw

    I size the boiler for the dwellings heatloss on a design day {with modulating burners I try to match the smallest load for the turn down}, for the dhw sizing, measure your needs in gpm and then size the dhw tank for a little more than that amount with the boilers priority output.. I use smart tanks and they tend to be spec'd for large amounts of input btu's....
  • SWEI
    SWEI Member Posts: 7,356
    edited April 2014
    Consider your monthly use

    If you have something like a soaker tub that gets used once a week, it may make sense to install an electric tankless as a dedicated booster just for that load.
  • TerryR
    TerryR Member Posts: 28
    edited April 2014
    Nightlight

    Icesailer,



    That's pretty cute. Actually, I got a plug-in LED nightlight several years ago that works very well and uses so little energy that leaving it on all the time seems to not be an issue. Only problem is it's so bright we had to hide it behind a towel on the towel bar.



    Terry
  • TerryR
    TerryR Member Posts: 28
    edited April 2014
    Tankless with Recirc?

    I'm now confused. The question I started with is are tankless heaters and constant recirc a good match? Everything I've read says no. Now people are suggesting I add a tankless heater to a system using recirc?



    BTW, we removed the big tub in our bathroom remodel several years ago, and good riddance so far as we are concerned.



    Terry
  • SWEI
    SWEI Member Posts: 7,356
    Recirc complicates things quite a bit

    with the vast majority of tankless water heaters.  That's why Heatpro adds the baby electric tank -- to keep the tankless from short-cycling as the recirc line cools.



    What I was suggesting is a variation on the European model, where you install an electric tankless near each point of use.  Our fuel costs are radically different here, especially with current NG prices.  On a per BTU basis, electric resistance costs 6X what NG does here, but I still recommend it for specific applications.  If the electric heat source only runs a few hours per month (filling a big tub) or even a few hours per year (backing up a solar DHW system) the reduced installation cost, maintenance, space requirements, and simplicity can easily trump that of a larger gas-fired heater.  Properly sizing the primary system will save on first costs, fuel, maintenance, and space requirements.  If a building has a remote bathroom or small kitchen in a guest house, an electric tankless can heat the water until hot water from the main heat source makes it down the line.  It only runs for a minute or so each time the faucet is opened, and drops out of the circuit as soon as it is not needed.
  • TerryR
    TerryR Member Posts: 28
    edited April 2014
    Recirc and Tankless

    Thanks, SWEI,



    OK, that confirms what I was understanding. The way to make tankless work with recirc is to add a tank. That rather seems to defeat the concept of tankless, seems to me.



    I understand the concept of a tankless at point of use, and can see the application in situations like you are describing. But we don't have low frequency high demand loads, and don't have access to point of use locations for the most part. I think I'll stick with recirc, trying to reduce the recirc volume as has been suggested.



    Terry