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Electric hot water source for radiant floors and domestic hot water

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I do not have a gas line. For new radiant in floor heat we need a source of hot water and also need hot water for domestic hot water. Three systems have been proposed:
1. Combomax 70-20Kw to serve all.
2. Thermolec 20 kW boiler with heat excnager with 2 tanks, one domestic one radiant
3. Viessman 100 11 Kw boiler plus Lochinvar 30G tank for radiant; 2 50G electric tanks 4.5 Kw each.

Constraint is total Kw available - need to keep it under 20. Heat load calculated, 11 Kw is too small, but I have AC on heat pumps which are also capable of providing hot air and can make up the deficit on the few colder days with that.

Prefer to keep it simple and easy to program. Was advised to have outdoor reset for hydronic.
Any suggestions?
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Comments

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,167
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    I do not have a gas line. For new radiant in floor heat we need a source of hot water and also need hot water for domestic hot water. Three systems have been proposed:
    1. Combomax 70-20Kw to serve all.
    2. Thermolec 20 kW boiler with heat excnager with 2 tanks, one domestic one radiant
    3. Viessman 100 11 Kw boiler plus Lochinvar 30G tank for radiant; 2 50G electric tanks 4.5 Kw each.

    Constraint is total Kw available - need to keep it under 20. Heat load calculated, 11 Kw is too small, but I have AC on heat pumps which are also capable of providing hot air and can make up the deficit on the few colder days with that.

    Prefer to keep it simple and easy to program. Was advised to have outdoor reset for hydronic.
    Any suggestions?

    You are aware that the colder it gets outside the less heat there is in that outdoor air? A heat pump takes the heat from the outside air and compresses it to make hotter air inside. the colder it is outside the harder the heat pump works to make heat. So there may be a flaw in your logic. Is Propane or Butane liquid petroleum gas available in your area. That will make things much easier. But it all depends on the cost of getting LP Gas delivered compared to the cost of electricity.

    (I hope you don't tell me that the 20 kW constraint is based on the diesel generator you have on site)

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • orange_cat
    orange_cat Member Posts: 27
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    I have utility-provided electricity, but I have a 200 Amp service and the back of the envelope calculations show we have approximately 20 Kw to dedicate to to both.

    I am aware of heat pump limits, but it is a cold-weather model (Mitsubishi Zuba), so that is accounted for.

    I really just need to pick the electric boiler/water heaters.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,167
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    OK... there is a growing interest in Heat pump water heaters. I'm not sure about the capacity on that end of the equation, but look up Heat Pump Water Heater using the search tool at the top of the page. (or in the drop down menu on a mobile device).

    The amount of energy you have available should not be the driving factor in calculating the size of the heater you need. The load calculation of the space being heated should be the first consideration. You don't build a building that is going to be an automobile assembly plant by saying, We only have this many bricks so make all that stuff for building cars fit inside this space. At least... I don't think Henry Ford looked at it that way

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    Larry Weingarten
  • orange_cat
    orange_cat Member Posts: 27
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    I am sorry - I do have the load calculation.
    I do have reasons for excluding heat pumps.

    I am truly trying to choose between the three options.
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,917
    edited October 2023
    Options
    Option 1 or option 2 with just the DHW tank. You’ll be happy with either. Option 3 would be fine if the boiler was bigger and you 1 had larger DHW tank and no buffer tank. These options are all really close to one another, so don’t get too bogged down. 
    orange_cat
  • GroundUp
    GroundUp Member Posts: 1,957
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    Option 4: Electro 12kw boiler for the radiant and standalone 40-50G electric water heater (4.5kw) for domestic. Easy peasy, and far more reliable than any of your other options.
    WMno57GGrossorange_catRich_49
  • orange_cat
    orange_cat Member Posts: 27
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    I called Electro because I could not find a local distributor, but they never called me back with the name of a dealer and they would not sell direct. It is a bit odd. I would try them again.
  • pecmsg
    pecmsg Member Posts: 4,965
    edited October 2023
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    I can respect not dealing directly with the end consumer. 

  • GroundUp
    GroundUp Member Posts: 1,957
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    pecmsg said:

    I can respect not dealing directly with the end consumer. 


    Supply house d com Carrie’s them. 
    No they don't
  • GroundUp
    GroundUp Member Posts: 1,957
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    I called Electro because I could not find a local distributor, but they never called me back with the name of a dealer and they would not sell direct. It is a bit odd. I would try them again.

    Where are you located? I'm sure you already saw it, but there is a dealer locator on their website. Otherwise eComfort has them online, or if you're in dire straights, I am a dealer and high volume installer for them in Central MN (about 40 miles from the factory) and could ship you one.
    GGrossAlan (California Radiant) Forbesorange_cat
  • pecmsg
    pecmsg Member Posts: 4,965
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    GroundUp said:
    I can respect not dealing directly with the end consumer. 

    Supply house d com Carrie’s them. 
    No they don't
    Few if any manufacturers will deal directly with the end consumer. 
  • hot_rod
    hot_rod Member Posts: 22,480
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    pecmsg said:


    GroundUp said:

    pecmsg said:

    I can respect not dealing directly with the end consumer. 


    Supply house d com Carrie’s them. 
    No they don't

    Few if any manufacturers will deal directly with the end consumer. 

    Deal with? Or sell to? :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    EdTheHeaterMan
  • pecmsg
    pecmsg Member Posts: 4,965
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    hot_rod said:
    GroundUp said:
    I can respect not dealing directly with the end consumer. 

    Supply house d com Carrie’s them. 
    No they don't
    Few if any manufacturers will deal directly with the end consumer. 
    Deal with? Or sell to? :)
    Deal with and sell to. 
  • GroundUp
    GroundUp Member Posts: 1,957
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    pecmsg said:


    GroundUp said:

    pecmsg said:

    I can respect not dealing directly with the end consumer. 


    Supply house d com Carrie’s them. 
    No they don't

    Few if any manufacturers will deal directly with the end consumer. 

    I am aware. But my response was to your comment stating that supplyhouse carries Electro boilers. They do not.
  • pecmsg
    pecmsg Member Posts: 4,965
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    GroundUp said:

    pecmsg said:


    GroundUp said:

    pecmsg said:

    I can respect not dealing directly with the end consumer. 


    Supply house d com Carrie’s them. 
    No they don't

    Few if any manufacturers will deal directly with the end consumer. 
    I am aware. But my response was to your comment stating that supplyhouse carries Electro boilers. They do not.

    I did a search, and they came up. Should have copied and pasted!

    Did another search and Your correct they do NOT carry it!
  • orange_cat
    orange_cat Member Posts: 27
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    I am in Ontario, Canada. There is one distributor listed with multiple locations. I called 3 locations and they all said they did not think they distributed those units; that they will do and check and call back, none did.
    I then called Electro and asked them to give me a name of a distributor that recently placed an order and did not hear from them either.

    At this point I am concluding they do not sell to Canada.
    GroundUp
  • GroundUp
    GroundUp Member Posts: 1,957
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    I am in Ontario, Canada. There is one distributor listed with multiple locations. I called 3 locations and they all said they did not think they distributed those units; that they will do and check and call back, none did.
    I then called Electro and asked them to give me a name of a distributor that recently placed an order and did not hear from them either.

    At this point I am concluding they do not sell to Canada.

    Ah, I suppose that could be a hindrance. I guess Thermolec is Canadian and has both 10 and 15kw options, but personally I do not care much for Thermolec products. A lot of leakers and control failures around my parts. Perhaps the Combomax isn't such a bad option after all, or possibly a Thermo 2000 12kw boiler and separate water heater- depending on pricing
    orange_cat
  • hot_rod
    hot_rod Member Posts: 22,480
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    Thermo 2000 has great electric boilers
    A  Canadian company 
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    orange_cat
  • orange_cat
    orange_cat Member Posts: 27
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    thank you. The combomax 70 is by Thermo2000.

    But when I look at Thermo2000, I see that in addition to Combomax 70-20Kw proposed by the HVAC installer,
    https://e4m6s3b8.rocketcdn.me/wp-content/uploads/produits/ComboMaxUltra/combomaxULTRA-Specifications-EN.pdf

    Then there is also Combomax-109- 20Kw - the differences seems to be the size of the tank and the "commercial" rating on this one. Is there any reason to not go for this one? (I am simply looking at the water tanks, and 109 gallons sounds better - we have a family of five and kids all have similar school hours and long showers).
    https://e4m6s3b8.rocketcdn.me/wp-content/uploads/produits/ComboMax109/combomax109-Specifications-EN.pdf
    Hot_water_fan
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,917
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    The larger tank is the way to go for high DHW demands. Either integrated or separate, I’d go with the ~100 gallon options for DHW. Let us know what you decide! 
    orange_cat
  • orange_cat
    orange_cat Member Posts: 27
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    Is there a problem that the 109 gallon is marked "commercial"? I see the same Amperage and Kwh so it looks like it would work for residential too - but could there be a problem?
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,917
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    Nope just marketing 
    orange_cat
  • orange_cat
    orange_cat Member Posts: 27
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    So Combomax is not what I need as the storage reservoir is for the hydronic, the domestic supply functions as an on-demand pretty much and that would not work (the flow/recovery rate).

    So the alternative is to use Thermo2000 boiler 20Kw like these
    https://www.thermo2000.com/wp-content/uploads/produits/bthULTRA-4elements/bthULTRA-flyer-EN.pdf

    pair it up with a Taco boiler zone control like Taco SR 504 https://www.tacocomfort.com/documents/FileLibrary/SR-SubmittalDataSheet_101-052_120820.pdf

    and add an indirect hot water tank and rely on Taco to prioritize domestic hot water (it seems to come with a Priority switch).

    I wonder if it is worth adding a small storage tank for hydronic heat at all?

    And I still have not located the indirect tank and generally would welcome any and all input.
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,917
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    So Combomax is not what I need as the storage reservoir is for the hydronic, the domestic supply functions as an on-demand pretty much and that would not work (the flow/recovery rate).


    Not quite: the combo max IS an indirect, just a different kind - a reverse indirect. The combo max stores energy in non-potable water then uses a heat exchange to transfer the heat to potable water. Another boiler might store energy in an indirect full of potable water, heated by a heat exchanger filled with non-potable water. It's the same thing, you just don't have a circulator in the combomax set up and it's all one piece of equipment. The domestic is "on-demand" but it does have storage (just not potable water storage). So the Combomax would still work for you.

    I wonder if it is worth adding a small storage tank for hydronic heat at all?


    No, I wouldn't. Electric boilers have staged heating and you'll have some good buffering with the floor.

    I think you're at a point when you can reach out to an installer and get this project moving. A boiler + external indirect vs. a boiler with integrated storage are basically the same product in a different shape.

    Here's what each option has:
    1. 20kw of electric heating elements
    2. A tank to store hot water
    3. A heat exchanger to transfer heat between potable and non-potable water.

    Here's what's different:
    1. One tank has the elements in it, the other has a circulator to pump the heat from the elements into it. This is a pretty minor distinction.
    orange_cat
  • orange_cat
    orange_cat Member Posts: 27
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    I spoke with Thermo2000 and they advised against Combomax for high domestic hot water needs due to GPM flow rate and said 50/70/109 is not domestic storage, but the infloor heat storage, so for domestic that really would not deliver enough water for a concurrent use.

    The HVAC installer was the one who suggested Combomax, which is why I am not all that confident. In their defense, most people here have gas, so electric boiler plus hydronic makes me a weird outlier locally that nobody really has much experience with.
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,917
    edited October 2023
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    I spoke with Thermo2000 and they advised against Combomax for high domestic hot water needs due to GPM flow rate and said 50/70/109 is not domestic storage, but the infloor heat storage, so for domestic that really would not deliver enough water for a concurrent use.


    I'm sorry, but that's just wrong on their end. From their own published flyer, the 20kw ComboMax ULTRA 70 has a first hour rating of 186 gallons. That's enough for your household. The storage is for both, it literally has a copper heat exchanger running through it for the DHW. The tank is kept at a high temperature, so the 70 gallons can storage a good bit of energy (in non-potable water) and then transfer it through the heat exchanger when called upon. I'm not sure why they don't know their own product. It's actually a pretty smart design! It's similar to how some gas boilers work.

    https://e4m6s3b8.rocketcdn.me/wp-content/uploads/produits/ComboMaxUltra/combomaxULTRA-flyer-EN.pdf
    orange_catSuperTech
  • orange_cat
    orange_cat Member Posts: 27
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    Those were the numbers I saw. But he says GPM would not suffice - so who am I to argue.
    This is all so confusing.
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,917
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    It can do 9 GPM for the first 10 minutes, that's a lot of flow. Regardless, you have two nearly identical options here and either will work about the same.
    orange_cat
  • Alan (California Radiant) Forbes
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    Option 3 is looking better and better. 

    I assume you have low temperature radiant heating?


    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    orange_cat
  • CPHNed
    CPHNed Member Posts: 14
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    https://alliedboilers.com/

    canadian company i believe
    orange_cat
  • orange_cat
    orange_cat Member Posts: 27
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    Yes, it is low temp - ecowarm (warmboard type) - pex embedded in plywood under wood floors.

    To me option 3 is not as good on recovery rate (at 9kw) while option 2 with priority (taco) allows full 20 kw - so better recovery rate.
    What do you think?
  • orange_cat
    orange_cat Member Posts: 27
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    Thermolec is Canadian too, but Thermo200 seems to have better reveiews (here at least - including past discussions?)
  • Alan (California Radiant) Forbes
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    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,917
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    It’s just so cheap to add the full 20kw capacity, I see no reason to undersize and then install two additional tanks when 1 can do it all with more capacity (if you actually need that DHW recovery, which is an open question). 

    Hybrid water heaters would be great if the space allows - you can get 120V ones that max out at 1kw, so fitting 1 with an electric boiler is easy, even if you include an indirect anyway. 
  • orange_cat
    orange_cat Member Posts: 27
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    Combomax delivery beyond 10 minutes is an issue - according to Thermo2000. Since they are trying to sell ne a cheaper unit instead of a Combomax and actually sending me to buy an indirect tank elsewhere as they do not offer them - to me was persuasive.

    Hybrid water heaters recovery rate is no improvement over two plain 4.5 Kwh electric heaters - setting aside the hybrid part for the moment.
    It just seems to make sense to borrow against domestic should I need more heating in the winter, and to borrow against in floor should I have a brief demand for domestic by using a shared 20Kw capacity?

    But I might be missing something?
  • hot_rod
    hot_rod Member Posts: 22,480
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    A 20 KW boiler would recover a standard indirect quickly, 68,000 BTU/hr!
    Just put DHW on priority.
    You have almost 5 times what a typical electric water heater element is.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    orange_cat
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,917
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    Combomax delivery beyond 10 minutes is an issue - according to Thermo2000. 
    20kw is 20kw. The recovery is the exact same whether the tank is integrated or separate. I also think the recovery rate isn’t a concern here- you’d have a almost 200 gallons first hour rating. That’s plenty!
  • GroundUp
    GroundUp Member Posts: 1,957
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    There is almost zero chance that you need anywhere near 20kw for domestic water, when you have some storage. This does not need to be so complex. What Thermo 2000 told you was either misinterpreted, or the person you talked to doesn't understand their product.
    Alan (California Radiant) Forbes
  • Alan (California Radiant) Forbes
    Options
    I understand that you are trying to satisfy your DHW needs, but even if you come up short, you have options. Your biggest DHW load will be mornings or evenings, so low flow shower heads, shower scheduling (some shower in the morning, some in the evening), short showers. 

    I installed a solenoid valve on the hot water line to the shower when my kids were young. Attached a timer which would turn on once water flow was detected. After 10 minutes, the timer would energize the solenoid. 
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    ratio
  • orange_cat
    orange_cat Member Posts: 27
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    I have low flow shower heads.
    But I have had enough of scheduling showers and baths. This is not the hill I am prepared to die on.

    Instead, I want enough hot water.