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Hydronic Design Assistance

eblend
eblend Member Posts: 13
Hi guys, I'm new here but seems like a helpful place so I will see if anyone is able to assist. I am building a slab-on-grade house shortly and want to do hydronics throughout. This is going to be a DYI build for the whole house. My new house will have 3x bedrooms on the far side of the house which will be on a single zone, a large living room/dining room/kitchen area on another zone, a master suite on it's own zone, a garage on it's own zone, and a loft, also on it's own zone. I want to do a pump zoned setup and have been looking at lots of articles and youtube videos on the topic but kind of hitting a roadblock, as the more I read, the more I learn that this isn't so simple as I first thought. I want as an efficient system as possible, but things such as Delta T, Delta P, variable speed pumps, hydraulic separator ect seem to be the more modern items that play into the system design, but I don't entirely know how.

My plan is to get a Rinnai combi boiler to do my floors and domestic hot water. Majority of the lines would terminate in my utility room, but then I have a satellite manifold on the other side of the house, and another one in the loft. I don't really understand how to pipe those remote satellite manifolds and ensure that they get proper water flow ect being so far away, and which pumps would work best to make this all happen. I also read lots about short-cycling of the boiler and want to avoid that as well. Is anyone able to assist me in figuring this out? Seems like so much information, some old, some new, all mixed together, and it's making it difficult to decide what's the best approach.

Thank you in advance.

Comments

  • GroundUp
    GroundUp Member Posts: 1,907
    What part of the world are you in? There may be someone in here local to you that can assist.
  • eblend
    eblend Member Posts: 13
    GroundUp said:

    What part of the world are you in? There may be someone in here local to you that can assist.

    Sorry I should have mentioned. I'm in Calgary, Alberta, Canada
  • mattmia2
    mattmia2 Member Posts: 9,630
    The first step is to figure out the heat loss of the different areas, then figure out how much tubing at what flow and water temp you need to provide that heat, then work back to the equipment you need to provide that flow and heat. If you are using a combi it may mean that you need to make the appliance much larger to supply the heat you need for DHW vs what you need to heat the building.

    This is a good place to start:
    https://idronics.caleffi.com/magazine-archive

    Designing the tubing layout without using some design software is somewhat involved.
  • Paul Pollets
    Paul Pollets Member Posts: 3,656
    Uponor Canada offers design services with CAD design and thorough heat loss analysis. They should be able to help you.
    https://www.uponor.com/en-ca/customer-support
    Rich_49
  • eblend
    eblend Member Posts: 13
    edited January 2022
    Tha
    mattmia2 said:

    The first step is to figure out the heat loss of the different areas, then figure out how much tubing at what flow and water temp you need to provide that heat, then work back to the equipment you need to provide that flow and heat. If you are using a combi it may mean that you need to make the appliance much larger to supply the heat you need for DHW vs what you need to heat the building.

    This is a good place to start:
    https://idronics.caleffi.com/magazine-archive

    Designing the tubing layout without using some design software is somewhat involved.

    Thanks everyone for your input so far. Specific to what you said, I already have tubing design done by a professional as I needed it for my permit application, however, the equipment selection is up to me at the end of the day so I need to figure out a best system to run my setup. I have attached my looping plans and heating system summary, hopefully it provides enough information to design the rest. House will have 10' ceilings and 4" of concrete slab for main floor, and thin slab for the loft.

    Thank you everyone for your input.

    EDIT: I should mention that loops A-12,13,14 will be on their own manifold, which isn't how it was drawn. Also loop spacing is 12" apart.
  • eblend
    eblend Member Posts: 13
    Hi guys, going back to basics and looking over some of the designs, I think I came up with one that I would like for everyone to critique based on the previously attached PDFs.

    The picture I made in paint includes a Rinnai i120C Combi Boiler. This boiler has a circulation pump built in. Rinnai sells a special Primary-Secondary Heaking kit which is pictured in the picture I made. Boiler is condensing and can regulate temp, with outdoor reset.



    The picture is not really to scale but I am more looking at functionality side of things. I want to do zoning with pumps so that is what I have pictured.

    Please critique my setup, and if you have some suggestions to my questions below please answer those as well:

    1. What types of pumps should I use for this setup? I am guessing ECM, do I need to worry about Delta T/P and all that other stuff? Looking for recommendations.
    2. What size should my expansion tank be? I don't really understand how to decode the heating system summary I have attached in the previous post.
    3. Is this boiler good enough for my setup? Will it provide enough GPM and all that to make this system work?
    4. I want to do a hydronic feeder system, do I have it pictures correctly on where it feeds?
    5. Am I missing any filling/purge valves or other components? Seems like filling ports are included in the Primary-Secondary Heating Kit already, not sure if I need more?
    6. Should remote manifolds be closer to the boiler or does it not matter?
    7. Anything else I might be missing?
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,517
    1. delta p if you are controlling flow through the loops if not ECM

    2. yes

    3. you need to calculate approx fluid volume in the system. Your documents say 50 gallons for the tubing u need to add for boiler volume, and pipe volume both supply and return between the boiler and the manifolds

    4. Your total heat load is 111,123 btu/hr your boiler input is 120,000 you will have to look up the boiler htg. capacity

    5. Manifold location doesn't matter as far a operation goes. You just need to know approx for piping head loss and system volume
    6. I would say you have enough valves unless you want to isolate the expansion tank and the dirt separator. More valve a re better especially when dealing with glycol

    7. The tubing is usually flushed /filled at the manifolds other than that ok

    8. You need 1 1/4" mains to feed the manifolds supply & return. 3/4 pex will feed all the manifolds except for a-5-11 which needs 1"


    You size the pumps by head and flow rate. Some of this is on your documents, some you have to calculate. Will the pumps run 24/7 based on oa?


    Others that know more about radiant can sling some arrows at me . Will see how well I fare
  • ScottSecor
    ScottSecor Member Posts: 855
    Just some random thought to consider. Please keep in mind that I am not at all familiar with 'standard practice' in your neck of the woods. I visited Alberta (Banff) with my family on vacation a few years ago and found the winters sure can be brutal up there.

    I suspect hydronic heating systems in Calgary would be more likely use antifreeze than here in NJ. However, if at all possible, we avoid antifreeze in hydronic systems. Leaks seem to appear out of nowhere, pumps have to work harder to get the same flow when compared to just 'plain' water, all hydronic systems (radiant, hwbb, etc.) need to be run at hotter to produce the same number of BTUs and finally antifreeze can wreak havoc on systems components if not maintained properly. If practical, (and you supply of electricity is very reliable in your area) I would suggest a few permanent very small electric heaters with independent thermostats, perhaps one in the mechanical room, one in each bathroom and one in the kitchen. The electric heater would serve as a backup only, they are very reliable and could save a huge headache if ever needed.

    Again, just sharing ideas. In 2004, my parents made the decision to retire in northern Vermont, about eight miles from the Canadian border. They owned the property for years that included small A frame cabin. They planned on building their new home with the primary goal of indoor comfort, regardless of the time of year. Being on the side of a mountain with numerous days below -20F meant they needed a robust heating system. They ended up with radiant heat for the entire basement, two car garage and first floor. Second floor, besides the radiant bathroom was heated with hot water baseboard. In addition, they added hwbb to a few rooms on the first floor for those days when the outdoor temperature stayed below 0F. In simple terms, even with SIPS walls and roof (eight or ten inch thick) they still needed the hwbb as the radiant could not do the job alone. My parents finally moved in the the house in 2006 and traveled often after they retired. They never worried about the heating system as my father (in the heating business since 1976) assumed with all of that heated mass (concrete, tile, cement, etc.) it would take about a week for the house to get cold enough for the pipes to freeze.

    Until Dad passed in 2016, they never had an issue with a frozen pipe or lack of heat, with the exception of a five or six day period when they had a freak storm hit and were without a power. They used a portable generator to keep the heat going and the well water flowing (oh, and the coffee pot in the morning), Dad cooked every meal on the grill. After Dad passed, Mom was alone and worried about the heat (and indirect dhw tank) often. Mom would ask friends to check on the house whenever she left town, especially during the heating season. Since electric power failures were relatively common in this remote area, Mom looked into adding a permanent generator or solar for electricity. With no natural gas available, lots of shade on roof and almost no contractors locally to install or service the equipment Mom decided to do skip the backup system. Mom sold the house and now lives in NJ
  • eblend
    eblend Member Posts: 13

    1. delta p if you are controlling flow through the loops if not ECM

    2. yes

    3. you need to calculate approx fluid volume in the system. Your documents say 50 gallons for the tubing u need to add for boiler volume, and pipe volume both supply and return between the boiler and the manifolds

    4. Your total heat load is 111,123 btu/hr your boiler input is 120,000 you will have to look up the boiler htg. capacity

    5. Manifold location doesn't matter as far a operation goes. You just need to know approx for piping head loss and system volume
    6. I would say you have enough valves unless you want to isolate the expansion tank and the dirt separator. More valve a re better especially when dealing with glycol

    7. The tubing is usually flushed /filled at the manifolds other than that ok

    8. You need 1 1/4" mains to feed the manifolds supply & return. 3/4 pex will feed all the manifolds except for a-5-11 which needs 1"


    You size the pumps by head and flow rate. Some of this is on your documents, some you have to calculate. Will the pumps run 24/7 based on oa?


    Others that know more about radiant can sling some arrows at me . Will see how well I fare

    Hi EBEBRATT-Ed, thank you so much for taking the time to answer some of my questions. I will try to summarize your answers into new bullet points and maybe you could confirm that I understood it all correctly:

    1. Pump I am looking at the Taco 0018E-2F4 pump. It has various modes, I think this one should work in this application correct? It might be overkill in my situation but would allow me to tune speeds indefinitely, and bluetooth for monitoring which is nice. Advertises these features for the various operating modes. I believe for pump zoned I would run it in a tuned fixed speed mode:
    Operating modes in 0018eTM Mobile App activation:
    - Fixed Speed - infinitely adjustable MIN/MAX settings
    - Constant Pressure - variable speed - 9 constant pressure differential settings
    - Proportional Pressure - variable speed - 9 variable pressure differential settings
    - activeADAPTTM - Designed for constant circulation systems. Automatically adjusts
    to system conditions

    2. Expansion Tank Not sure what you said yes to for item number 2. Watts has a nifty calculator where you can enter System volume (I used 60 GAL, 50 gal for tubing and 10 gal for everything else should be enough), mixture (30% glycol), relief valve pressure of boiler (30 psi), initial and max temp (104-180F), which spat out an expansion factor of 0.0241 and an acceptance volume of 1.4460Gal. Looking at their chart it appears that a 4.5 Gal Tank would suffice as it has acceptance volume of 2.5Gal. Seems right?

    3. Boiler If I understand correctly, I think my boiler choice is good. I have 111000 BTU, and the boiler is rated for 120000 BTU for the Heating application, and 199,000 for Domestics Hot Water. Seems right?

    4. Hydronic Feeder Seems like it's in the right spot as pictured for feeding the system.

    5.Manifolds Good to know that location doesn't matter. I found manifolds in all the necessary sizes as pictured in my drawing.

    6. Valves Thank you for the tip. I have added valves to isolate the air separator, and dirt separator. I will add another to the tank as well.

    7. Pipe Size Thank you for the pipe size. I had a hard time figuring out the inlet size on the boiler but it is 1 1/4" so I will make the main feed supply and return 1 1/4". I will go down to 3/4" copper to the pumps, and then 3/4" copper down to a Pex-A 3/4" to the manifolds. For the large 7 zone manifold I will go down to 1" copper to and post pump, before converting to 1" Pex-A.

    I don't know exactly what you mean about OA and running 24/7? I want each zone controller by a thermostat, so I don't think the pumps will be on 24/7
  • eblend
    eblend Member Posts: 13

    Just some random thought to consider. Please keep in mind that I am not at all familiar with 'standard practice' in your neck of the woods. I visited Alberta (Banff) with my family on vacation a few years ago and found the winters sure can be brutal up there.

    I suspect hydronic heating systems in Calgary would be more likely use antifreeze than here in NJ. However, if at all possible, we avoid antifreeze in hydronic systems. Leaks seem to appear out of nowhere, pumps have to work harder to get the same flow when compared to just 'plain' water, all hydronic systems (radiant, hwbb, etc.) need to be run at hotter to produce the same number of BTUs and finally antifreeze can wreak havoc on systems components if not maintained properly. If practical, (and you supply of electricity is very reliable in your area) I would suggest a few permanent very small electric heaters with independent thermostats, perhaps one in the mechanical room, one in each bathroom and one in the kitchen. The electric heater would serve as a backup only, they are very reliable and could save a huge headache if ever needed.

    Again, just sharing ideas. In 2004, my parents made the decision to retire in northern Vermont, about eight miles from the Canadian border. They owned the property for years that included small A frame cabin. They planned on building their new home with the primary goal of indoor comfort, regardless of the time of year. Being on the side of a mountain with numerous days below -20F meant they needed a robust heating system. They ended up with radiant heat for the entire basement, two car garage and first floor. Second floor, besides the radiant bathroom was heated with hot water baseboard. In addition, they added hwbb to a few rooms on the first floor for those days when the outdoor temperature stayed below 0F. In simple terms, even with SIPS walls and roof (eight or ten inch thick) they still needed the hwbb as the radiant could not do the job alone. My parents finally moved in the the house in 2006 and traveled often after they retired. They never worried about the heating system as my father (in the heating business since 1976) assumed with all of that heated mass (concrete, tile, cement, etc.) it would take about a week for the house to get cold enough for the pipes to freeze.

    Until Dad passed in 2016, they never had an issue with a frozen pipe or lack of heat, with the exception of a five or six day period when they had a freak storm hit and were without a power. They used a portable generator to keep the heat going and the well water flowing (oh, and the coffee pot in the morning), Dad cooked every meal on the grill. After Dad passed, Mom was alone and worried about the heat (and indirect dhw tank) often. Mom would ask friends to check on the house whenever she left town, especially during the heating season. Since electric power failures were relatively common in this remote area, Mom looked into adding a permanent generator or solar for electricity. With no natural gas available, lots of shade on roof and almost no contractors locally to install or service the equipment Mom decided to do skip the backup system. Mom sold the house and now lives in NJ

    Thank you for sharing. Yah, I heard some nasty things about glycol. I guess if I design a system to run on 30% glycol mix I could always decide to run water. I don't know the power situation out in the county as it's a brand new house and no idea. We get very cold up here sometimes so I am worried about running just water for that chance that we will lose power for an extended period of time and don't have standby available. I might wire in a plug for a portable generator, I think it makes sense to have regardless, even if I plan on a full blown generator later. Small expense for some protection.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,517
    edited January 2022
    1. Those pumps are way overkill. Look at the manifold summary in your documentation, that tells you the flow and head for each manifold. Thats how you size the pumps. The ones you pick will not go that low. If you run 1 1/4 like we talked about above back to the boiler both supply & return you need to allow for pump head for that pipe and fittings. the resistance with glycol included at the flow you have is 5.77feet of head/100 feet of pipe or 5.77/100=.0577/foot of pipe

    so figure how much pipe you will need x,057/foot get that total and multiply x 1.5 to allow for fittings.

    example :

    so if you had 100 feet of pipe it would be 100x .057=5.7 x 1.5=8.55 feet of head so add that number to the head requirement of each pump in addition to the head loss for the tubing as shown. The flow comes from the manifolds flow


    3. With the expansion tank if you tell them 30# relief valve you may end up with an expansion tank where you will have 25 psi on the system when hot. They include the pressure rise in the tank. Better to use 25 psi for the relief valve (in the Watts calculation) and end up with 20 psi hot

    3. boiler is ok

    4. feeder location is ok
  • eblend
    eblend Member Posts: 13

    1. Those pumps are way overkill. Look at the manifold summary in your documentation, that tells you the flow and head for each manifold. Thats how you size the pumps. The ones you pick will not go that low. If you run 1 1/4 like we talked about above back to the boiler both supply & return you need to allow for pump head for that pipe and fittings. the resistance with glycol included at the flow you have is 5.77feet of head/100 feet of pipe or 5.77/100=.0577/foot of pipe

    so figure how much pipe you will need x,057/foot get that total and multiply x 1.5 to allow for fittings.

    example :

    so if you had 100 feet of pipe it would be 100x .057=5.7 x 1.5=8.55 feet of head so add that number to the head requirement of each pump in addition to the head loss for the tubing as shown. The flow comes from the manifolds flow


    3. With the expansion tank if you tell them 30# relief valve you may end up with an expansion tank where you will have 25 psi on the system when hot. They include the pressure rise in the tank. Better to use 25 psi for the relief valve (in the Watts calculation) and end up with 20 psi hot

    3. boiler is ok

    4. feeder location is ok

    Hi EBEBRATT-Ed again, thank you so much for all of your info and assistance. I actually chose that pump as an option because I have been slowly leaning away from pump zoning, and instead towards zoning with zone valves. I made a new drawing today, can you critique this one as well? I think if I do the zoning with valves, then the Taco 0018E-2F4 might work as the sole circulator in the whole system? I would set it to the constant pressure mode, which is Delta-P from my understanding. Would that work? I presume everything else more or less remains the same. I have tried researching head and I kind of understand it, but not fully. I don't want to say more to confuse this situation. I see that total head loss is listed as 8.2 on my heating summary (if I understand correctly, it's the biggest number from all manifolds in a parallel circuit) and total flow listed as 12.33GPM. The 0018e lists Flow range from 0-16GPM and Head range from 0-18'.....am I right to assume it's properly sized for this zone valve zoned system? Do I add the 8.2 to the 8.55 you calculated (probably overkill), which gives me just under 17'...thus less then 18' supported by the pump...or am I completely out to lunch?

    I'm don't entirely understand your point #3. The 30PSI is the pressure relieve specified on the boiler, so that's what I put, perhaps that's not the right number to use? The boiler lists central heating pressure as this (Minimum: 13 PSI (90 kPa) Maximum: 45 PSI (310 kPa) Recommended: 17-26 PSI (117-180 kPa)), the feeder says this (digital pressure switch adjustable from 0 kPa (0 psig) to 310 kPa (45 psig) cut-out pressure; factory cut-out pressure set to 115 kPa (18psig)). So many pressures involved not sure what I need to enter into the Watts calculator. Moving some numbers around I still end up with a Tank acceptance over 1 Gal, so I think the tank with 2.5 Gal acceptance is still the one I would need, a 4.5 Gal tank. Is this not the case?

    Sorry for so many questions! I am getting very close to my final design I think and you have been a tremendous help!

    Here is my picture of the valve zoned system. If I am not mistaken it's pretty close to correct:




  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,517
    @eblend as far as pressure goes you fill to 12 psi. The boiler relief is 30. I have found in the past some manufacturers will calculate the pressure rise with the expansion tank from 12-25 psi. In my opinion that is too close to 30 psi and the relief valve may drip. Especially where some calculations are not as exact as they might be,

    I would use a relief valve setting of 25. It just leave a little margin for error and the extra cost is peanuts.

    Those pumps may be ok. You also have to consider the resistance of the zone valves now.

    You need to sit down and visualize the manifold locations and make a sketch of the pipe runs and include an accessories valves, strainers zone valves etc and download the B & G system sizer and calculate the head
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,840
    That heat loss seems high - do you intend to heat the garage to the same temperature as the rest of the house? There's 32,000 btu/h of Infiltration/Ventilation losses too, which makes sense if that's because the garage is heated up to 70 degrees and the doors are sieves.
  • eblend
    eblend Member Posts: 13
    edited January 2022

    @eblend as far as pressure goes you fill to 12 psi. The boiler relief is 30. I have found in the past some manufacturers will calculate the pressure rise with the expansion tank from 12-25 psi. In my opinion that is too close to 30 psi and the relief valve may drip. Especially where some calculations are not as exact as they might be,

    I would use a relief valve setting of 25. It just leave a little margin for error and the extra cost is peanuts.

    Those pumps may be ok. You also have to consider the resistance of the zone valves now.

    You need to sit down and visualize the manifold locations and make a sketch of the pipe runs and include an accessories valves, strainers zone valves etc and download the B & G system sizer and calculate the head

    Hey EBEBRATT-Ed, sorry so confused on this pressure stuff. Where would I set this relieve valve setting? You mentioned extra cost being peanuts, I'm just not sure what this cost is for...do I have to buy some additional component?

    I found the B&G app you specified and will play around with it and see what I can figure out. All manifolds in my system will be basically right below the stuff I pictured, except for B1-B5, which will be just above in the loft, and A1-A4, which will be on the other side of the house, probably about 70 feet away one way. The head for that distance I believe is already included in the calculation more or less, as that zone shows the highest head loss, despite being one of the smaller zones. Will study this System Syzer app and see what I can figure out.

    That heat loss seems high - do you intend to heat the garage to the same temperature as the rest of the house? There's 32,000 btu/h of Infiltration/Ventilation losses too, which makes sense if that's because the garage is heated up to 70 degrees and the doors are sieves.

    Hi Hot_water_fan, no the garage will be kept relatively cool, about 15c (59f) or lower vs the house which will be at 21c (70f). The garage doors have 2" thick R10.4 insulation in them, and even have insulated glass (not sure of R value). The garage window is dual-pane with R3.846 or so. Whole garage will be spray foamed as well as the rest of the house, not sure on final R value in those walls, but it should be fairly warm. The pad will be insulated as well. None of this is yet finalized so I think very general values were used for calculations, the house should be built much more tight then the heating summary leads to believe. There is a note on top that says "Design based on information provided by the customer and generalizedR-values are used for heat loss summary. For a 100% accurate calculations
    exact building specifications must be given (eg. R-values of walls, floors,ceilings, windows, doors etc)"

    So with that said, I think the heat loss will be much less in reality. With that being said, would anything really change if the house is built better then the heating summary assumes? If the system is built to match the heating summary, it would just work less hard and less often if the house was better built then assume right? Sorry still learning all of these things. I enjoy these things so learning them as I go, so thanks everyone for your assistance so far.
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,840
    edited January 2022
    So with that said, I think the heat loss will be much less in reality.
    Me too! Just making sure you don’t get spooked into sizing up the boiler. What you’ll find is not that the system will run less, instead it’ll be able to use lower water temperatures and a lower modulation level, both of which will be more efficient and more comfortable. It's quite possible the system will run non-stop for weeks on end. 
  • eblend
    eblend Member Posts: 13

    So with that said, I think the heat loss will be much less in reality.
    Me too! Just making sure you don’t get spooked into sizing up the boiler. What you’ll find is not that the system will run less, instead it’ll be able to use lower water temperatures and a lower modulation level, both of which will be more efficient and more comfortable. 
    Awesome, thanks for the info. Forgot to mention that for the rest of the house, I got Triple pane, two Low-E coatings, Argon windows with R-value of 7.521, so it will be more insulated then the garage portion.

    Thanks for the info. I picked out the boiler myself out of the blue, liked the Japanese brand (my wife is Japanese, so we have lots of Japanese stuff), it's fairly well known and available in Canada, and glad to see that it should be enough for this system. When I initially looked at the heating summary and saw 111000BTU and this boiler being 120000BTU I thought that it was going to be the right size, and it appears as thought it will work just fine. It does modulate down to 15000 BTU so it will run at a lower range the tighter and more insulated the house is, but should have enough power for the brutal winters we sometimes have, with assistance of forced air system as well if it can't keep up. In December we had two straight weeks of ~30C(-22F), dipping down to -35C(-31F) and sometimes even lower, so it get's cold for short spans in the winter....before a Chinook wind comes and temp swings to +15c (59F) the following day for a bit....and then right back down. I can predict the weather by the huge headaches I get every time this happens...it's a somewhat unique geological phenomenon that happens only in Calgary and the surrounding area.
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,840
    before a Chinook wind comes and temp swings to +15c (59F) the following day for a bit....and then right back down.


    Now, this will be a shortfall of radiant slabs - they're bad at changing temperatures and will lead to swings. If that's important, look at lower mass radiant (could be floors, radiators, baseboard, etc.) or just be aware.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,517
    @eblend

    It's this simple. They (the expansion tank sizing program) wants to know the relief valve setting and the fill pressure setting (12psi fill) and the (30 psi relief) so they can take the difference of (30-12) 18psi into the expansion tank calculation. So they will pick a tank that will allow the system pressure to rise from 12 to about 25 when the water gets hot.

    I don't like that much pressure rise. It's to close to the relief valve setting IMHO

    So I use a relief valve setting of 25 which may cause the tank to be slightly larger so your pressure rise will be more like 12-20 psi

    You will have less problems that way and if some of your design calculations are a little off you won't over pressure. The difference in cost between the tanks is peanuts
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,517
    @eblend

    As far as flow and head calculations go you need to understand that they did not calculate any head loss for the manifolds themselves or any piping between the manifolds and the boiler or any pex or copper between the main supply and return to and from the manifolds and zone valves. You have to calculate this and add it to the head loss of your tubing that they provided. Andy you only need the head to the circuit with the most resistance
  • eblend
    eblend Member Posts: 13
    edited February 2022

    @eblend

    It's this simple. They (the expansion tank sizing program) wants to know the relief valve setting and the fill pressure setting (12psi fill) and the (30 psi relief) so they can take the difference of (30-12) 18psi into the expansion tank calculation. So they will pick a tank that will allow the system pressure to rise from 12 to about 25 when the water gets hot.

    I don't like that much pressure rise. It's to close to the relief valve setting IMHO

    So I use a relief valve setting of 25 which may cause the tank to be slightly larger so your pressure rise will be more like 12-20 psi

    You will have less problems that way and if some of your design calculations are a little off you won't over pressure. The difference in cost between the tanks is peanuts

    Hey EBEBRATT-Ed, so I went back to the Watts calculator and think I maybe wasn't fully doing it right.

    I entered these variables here: https://tools.watts.com/ETNP/
    System Volume: 60 Gallons (mostly a guess, 50 in radiant tubing, guessing about 10 everywhere else at most)
    Fluid Type: Ethalyne
    Glycol Percentage 30%
    Supply Pressure The boiler lists recommended central heating pressures at 17-26 PSI...so should I use a number in this range? For fun I put 18 here
    Air Pre-Charge Left this at 12
    Relief Valve I put 25 here as you recommended
    Initial Temp Boiler says 104 is lowest temp, so I put 105
    Max Temp Boiler says 185, so I put 185

    It spits out two values, and looking more into it, looks like I need to care about both of them:
    It spits out Calculated Acceptance Volume of 1.5720 Gallons, and a Calculated vT of 15.9155 Gallons. With that being said....does it mean I need a tank at least 16 gallons in size for my system? Playing with the supply pressure really has a big impact on the vT size.



  • eblend
    eblend Member Posts: 13
    Confused about this Expansion Tank. Downloaded another program and it shows that I only need 5.1gal tank, so a 6 gal should do..very different numbers from the Watts calculator. I'm leaning towards this 6gal tank, as most systems I see on the internet don't have a massive tank.


  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,517
    Your running radiant. Your temp will never be 185 max. Probably more like 130? Your supply pressure should match the expansion tank precharge.....always in any system and that is usually 12-15 psi unless you have a system more than 2 floors high
  • eblend
    eblend Member Posts: 13

    Your running radiant. Your temp will never be 185 max. Probably more like 130? Your supply pressure should match the expansion tank precharge.....always in any system and that is usually 12-15 psi unless you have a system more than 2 floors high

    Ah okay, that makes sense. The second tool I used didn't allow me to change from the 10 PSI for some reason, so it skewed some calculations as well. So I played with the numbers a bit and and looks like if I set my supply at 12 and air precharge at 12, relief valve at 25, and max temp at 140 (to be safe), then i need 2.46 gallon expansion tank..so would be a EXT-30 with 4.5 GAL. If I change the Pre-charge and Supply pressure to 15 and leave rest same it's 3.45, so still within the 4.5GAL tank. If I up the pre-charge to 17 and supply pressure to 17, it jumps to 4.7 GAL so would need a bigger tank.

    My question, and I swear it's the last one on the expansion tank topic, is that my boiler min pressure is 13 PSI, and shows recommended range from 17-26, and you say 12 PSI...isn't 12 PSI going to be under the min range of the boiler? My main concern now is just selecting the right tank, if I should get the 4.5 which will work with the PSI ranges you specified, or if I should go for the 6 gal, the price is negligible.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,517
    never saw a hw boiler that recommends 17-26 but i suppose anything is possible
  • eblend
    eblend Member Posts: 13

    never saw a hw boiler that recommends 17-26 but i suppose anything is possible

    Yah, this is what it list and is confusing me