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# Trying to Install Baseboard with Pipe With Pipe Reverse Return

Member Posts: 32

I am trying to run a high-efficiency hydronic system on my second floor. My plan is to maintain the water temperature at 150°F. According to the fine tube 3/4" baseboard chart, the heat output is 360 BTU/hr at 1 GPM and 380 BTU/hr at 4 GPM. The total BTU requirement for the second floor, rounded to the nearest high value, is 40,000 BTU/hr. Therefore, I calculated that I would need 114 feet of baseboard line.

One of the rooms is 140 square feet, and I have installed 18 feet of baseboard there. The house has a rectangular layout, so I am planning to divide the second floor into two zones: the front part (which is colder) and the back part (which is warmer).

Initially, I wanted to install a manifold for each zone. However, this has proven to be difficult because the baseboard pipe is 3/4", and it is challenging to achieve 4 GPM in a 1/2" pipe. As an alternative, I am considering running a two-pipe reverse return system for each zone. However, I am unsure about how to balance the system and whether each emitter needs a balancing valve due to the pressure drop at the emitter.

I do not want to use a series loop because with a water temperature of 150°F, the delta T for each emitter would likely be 20°F, which would not be sufficient. Any advice or suggestions on this setup would be greatly appreciated.

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• Member Posts: 351

"Initially, I wanted to install a manifold for each zone. However, this has proven to be difficult because the baseboard pipe is 3/4", and it is challenging to achieve 4 GPM in a 1/2" pipe."

To achieve 40,000 BTU/hr with a 20F temperature drop you have to have 4GPM. It's just math. I'm not sure where your 1/2" pipe is, but if it's the supply for the second floor, you need a bigger pipe.

Where are you getting the 40,000 BTU/hr? Did you do a room-by-room heat loss calculation? Just off the cuff that sounds high, but I don't know what your house looks like.

• Member Posts: 32

I calculated the BTU requirements for the entire apartment using the square feet of each room with SupplyHouse calculator. This helped me determine the number of baseboard feet needed and the specific BTU requirements for each room. It was like 37000btus/hr but I round it to the whole number because I want to run this at the lowest temp possible. I had not calculate the head loss but I have long baseboards, anything I just increase the temp.

What I'm getting stress it the piping work. I just want to have two zones. Each with two pipe reverse return piping because series loop would not work with my long baseboards. Let's says I set the boiler to 140f, once it hits the first baseboard which is 18", the water would drop like to 120f which would not be enough for the next baseboard. Therefore, I trying to have a parallel system of two pipe reverse return where each baseboard have roughly the same temperature. I read that is complicate to balance this system. Can you do a piping work example for two rooms with two-pipe reverse return

• Member Posts: 23,746

As a matter of fact, reverse return is the easiest of all the methods to balance — since if done right the flow resistance to each emitter is the same, and so all emitters will get the same flow — or very nearly — and thus the same amount of heat.

Better yet, use decent valves on the inlet to each emitter, and once you get the system up and running tweak the valves as needed to get a bit more heat where you need it and a bit less where you don't.

On your heat loss, however… basing it solely on square feet of space, though very common and very easy, can equally easily give really poor results.

Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 351

Is this the calculator you used:

https://www.supplyhouse.com/sh/control/BaseBoardCalculator

It has two questions:

Which of the following best describes your climate?

Very Cold

Cold

Moderate

Warm

What is the square footage of the room/s you are heating?

That's going to be worse than useless.

Do you have a history of heating bills? That's probably the best way to estimate your actual heating load.

• Member Posts: 32
edited August 1

This is the apartment diagram. This program tell me 40000btu/hr needed. I choose many other square feet calculators and they gave me roughly less than 40000btu/hr. Also I am doing long baseboard:

ROOM 2 = 6ft line/2000;
ROOM 3 = 18ft line/2000
ROOM 4 = 12ft line/2000;ROOM 5 = 18ft line/2000;
ROOM 6 = 18ft line/2000;
ROOM 9 = 6ft line/2000 or 6ft line/80;
ROOM 11 = 18ft line/2000 or 12ft line/80;
ROOM 12 = 18ft line/2000 or 12ft line/80;

Goal: Run @ either 140f or 150f

(the thicker brown lines are the exterior walls, the thinner brown lines are the interior walls, the yellow lines are windows). The house does not have insulation, and still have the lath platers walls. It is currently heat by steam boiler.

I really don't know how to calculate head loss, and don't know how important it is. Can you explain that more

As you can see, I have long baseboards. Almost double of what they recommended. in Case I just increase the temp to 180f. Tomorrow I bring the same diagram with the piping draw, so you can suggest me any changes. Thanks for your reply men, hope to hear back from you tomorrow.

• Member Posts: 32

@DCContrarian, take a look a the pdf I post above. It includes the sqrt foots of the apartment. details on the of the apartment condition. Also, it is the second floor. (Room 2) point to North size in my compass.

• Member Posts: 23,746

OK. First question.

Why in blazes are you considering switching from steam to hot water? I could never recommend that.

Now if we are talking adding hot water heat in just some new construction, that's OK as while it is not as satisfactory or simple as steam, it's a lot easier for the run of the mill contractor to install.

To avoid having real headaches in balancing the system, it's really important to have the radiation in each space reasonably proportioned to the heat requirement of the space. That heat requirement is determined almost entirely by the length of the exterior wall and the percentage of windows. That said, the numbers on your drawing are at least not outrageous, although I note that there are a couple of rooms which seem to be missing.

Whatever, if you don't have access to historic comfort information with the steam heat, I suggest that you proportion the baseboard length in each space to the heat load.

Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 32

I am trying to convert my existing steam system to a hot water system. The current steam system has several issues: the steel pipes are too large and obstruct my basement, they are rusted due to basement moisture, and there are multiple leaks in both the pipes and the radiator shut-off valves. Additionally, the system is not balanced, and the steam from the second floor also heats the attic unintentionally.

The unnamed rooms you see are the front and back stairways. The other two small rooms are closets. My plan is to switch to a hot water combi boiler with PEX tubing. This new system would be more compact, cleaner, and would eliminate the large, rusted pipes currently obstructing my basement.

To balance the new system, I plan to install balancing valves on the return of each heat emitter and set them to a 4 GPM limit, which is not cost-effective. As shown in the space heating layout, you can see the amount of baseboard I have allocated for each room.

I am considering creating two zones: the front part of the house, which is colder due to the many windows, and the back part, which is warmer with fewer windows.

Do you think the amount of baseboard I am planning to install is adequate, or should I add more to ensure proper heating? base on the space for each room

• Member Posts: 23,746

Your house, your choice. I would invest in keeping the steam… it would not be at all difficult to repair the leaks and balance it properly, probably very few (and inexpensive) or no parts required…

Now switching the whole house to hot water is potentially problematic. You will need all new piping — don't even think about using the old pipes and risers; they will leak. Then the radiators also will, very likely, leak (you have about a 50/50 chance on that). Then unless the existing radiators are wildly oversize, you will need bigger ones anyway, as a hot water system puts out — at best — only two thirds as much heat from a radiator as a steam system does with the same radiator.

The old radiation, if you keep it, absolutely must be on its own zone or zones with its own thermostat or thermostats. Do no try to mix fin tube with cast iron under one control — they behave very differently.

And then… I'd be very cautious about using a combi boiler. They are wonderful space savers, true. But unless you happen to be very fortunate (and rather unusual) they are either oversize for the heating load, leading to short cycling and other headaches, or undersize for the domestic hot water load, leading to a reduction in domestic tranquility.

Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 32

I have couple of hvca technician come and advise that steam is old system and require more mantainance than other. Also, the pipes are rust and obstruct the basement, that is why I want to remove the system.

I trying to use pex and baseboards not radiators. The job would be more expensive than keep the existing one but it would be less problematic in the long run.

I would test the system, if I see any short cycling, I would install a storage tank.

Do you think the amount of baseboard I am planning to install is adequate, or should I add more to ensure proper heating? base on the space for each room

• Member Posts: 23,746

I haven't done a Manual J on your property, so I am certainly in no position to comment on the amount or distribution of radiation — nor the size of boiler you need to power it.

To be blunt: the HVAC technicians you mention don't favour steam for a very simple reason: they don't understand it and aren't willing to learn. The job will be more expensive — probably at least twice as much, if not more — and would not be any less problematic in the long run. Nor, unless you put in a LOT of baseboard, will it save any money or energy in the short run.

Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 32

@Jamie Hall I still have steam install. I would try to see how much max btu capacity it has. Do you think it can give me clues of how much load need it ?

• Member Posts: 23,746

Yes. Two considerations. Are you comfortable? Are some rooms too warm and others too cool? Which ones? If the existing system can get all the rooms warm enough (don't worry about some being too warm at this point) then it is quite safe to assume that all the radiators are at least big enough for the spaces they are in — when used with steam (if some rooms are too warm, then those radiators are bigger than they need to be). That gives you a very practical measure of the heat loss. The next trick is to determine the effective size of the radiators (which is called "EDR:), and if you posted pictures of one or two typical ones we can help with that. And that, in turn, can be used to find the BTUh output when used with steam and thus the heat loss in BTUh.

I would not necessarily trust the rated heat output of the existing boiler, however. It's likely not too small — but it is very likely, particularly if it is a replacement of the original, to be too big. Very likely much too big. Steam boilers need to match the installed radiation — not the heat loss of the structure — and that is one of those things which seems to be very hard for people to grasp…

Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 32
edited August 1

This is the second floor and attic boiler and radiator. In the attic there only two radiators. Clients says it is too warm when it is own. I think it short cycle. I also think it is oversize for the attic and second floor. But as you can see the output is 135,000btu/hr

• Member Posts: 32

@Jamie Hall as you see the output btu for the second floor is 113,000btu/hr and that specific radiator is Room 6 on the diagram

• Member Posts: 32

@Jamie Hall On the other hand the first floor, which practically same as the second floor has an 75,000 btu/hr, we never use thermostac on this, we just turn on and off when need. Let me tell you that this thing burn any room if you leave this for couple of hour, it warms too quite.

• Member Posts: 668

So you are the contractor, not the homeowner?

• Member Posts: 32

Do you think that 40000btu/hr would be too little and 114' of baseboard would not be enough as you see the numbers above ?

I was thinking to buy a 60,000 btu/hr boiler and add an expansion tank in case of short cycling.

• Member Posts: 32

@dko im the home owner

• Member Posts: 23,746

You are making the mistake of equating the rated output of the boiler with what the radiation can deliver. Without an end view of the second radiator there — the one with 7 sections — my best estimate of the output of that radiator is around 7,000 BTUh on steam. The bigger one might be as much as twice that.

It is the power output of the radiators which you are interested in — the power from the boiler, provided only that it is at least enough to power the radiation — is irrelevant.

And your comment on the system overheating the first floor if you just leave it on just confirms that even the radiation you have is more than adequate to heat the structure.

Seriously, you need to go bac to the basics. Figure out — preferably with a Manual J type calculation — how much heat each room needs. Figure out from the radiators — not the boiler — how much heat each room is getting. Then go from there. Since I get the impression that you intend to tear out the steam — regardless of how well it works — start from scratch. Don't plan to use the old radiators at all (even if they don't leak, they won't play well with baseboards) and install the correct amount of baseboard for each room, then add up the total load and install a boiler sized for that.

Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 181

An engineering response to a homeowner who is not at all cognizant of what a "Manual J" is and the capability of determining the BTU output of the radiation is not helpful in any way.

• Member Posts: 32

I am trying to convert my existing steam system to a hot water system. The current steam system has several issues: the steel pipes are too large and obstruct my basement, they are rusted due to basement moisture, and there are multiple leaks in both the pipes and the radiator shut-off valves. Additionally, the system is not balanced, and the steam from the second floor also heats the attic unintentionally.

The unnamed rooms you see are the front and back stairways. The other two small rooms are closets. My plan is to switch to a hot water combi boiler with PEX tubing. This new system would be more compact, cleaner, and would eliminate the large, rusted pipes currently obstructing my basement.

To balance the new system, I plan to install balancing valves on the return of each heat emitter and set them to a 4 GPM limit, which is not cost-effective. As shown in the space heating layout, you can see the amount of baseboard I have allocated for each room.

I am considering creating two zones: the front part of the house, which is colder due to the many windows, and the back part, which is warmer with fewer windows.

Do you think the amount of baseboard I am planning to install is adequate, or should I add more to ensure proper heating? base on the space for each room

• Member Posts: 668

Jamie, he wants you to do all the legwork and give him an exact calculated answer. What part of that don't you understand? /s

I still have my suspicions this is a contractor, "Clients says it is too warm when it is own." That among other little hints.

If i'm wrong, sorry.

• Member Posts: 32

@Jamie Hall Thanks for your response.

Now I understand you all. I will manual determine around how much btu/hr each radiator outputs, to know the whole apartment load. Then I would exchange those btus per room into baseboard length.

I will also contract an hvac technician for the "manual j" and compare it to my results.

I will reply back with the result. Hope to hear back from you @Jamie Hall

• Member Posts: 32

I quite don't understand your comment. Can you formulate better for me ?

• Member Posts: 32

I am the homeowner of the house, which has multiple floors. I live on the first floor, and the second floor is rented out. Since I don't live on the second floor, I rely on my tenants' feedback, and they claim it gets too warm quickly. I appreciate @Jamie Hall for explaining the importance of Manual J in determining the heating load needed to size my baseboard accordingly.

Even if I were a contractor, I am here seeking tips and help to better understand the situation. I am not seeking for a complete workout, that is impossible.

• Member Posts: 32

I am also using chatgpt for my texts, I am not an English speaker. But here are some other counter hints

"I am trying to convert my existing steam system to a hot water system."

"we never use thermostac on this,"

"I still have steam install."

But in case I was a contractor, that does not deserve your comment. This is a site to help not judged

• Member Posts: 23,746

Permit me to say, @joseluisheating , that you are really doing a fine job of getting your questions and thoughts across — and thank you for making the effort to translate. I'm kinda weak on other languages (French, well maybe. Spanish, not much, and I'm the worse for that).

Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 32

@Jamie Hall Thanks.

I actually speak Spanish but this terms are hard to translate. Tomorrow I will try to bring updates. Thanks so much for your generosity.

• Member Posts: 15,885

For a small 40,000 btu load you really don't need reverse return but if that is the way you want to go that is fine. Just install a balancing valve on each loop and measure the temp on the return end. Close the valve on the loop that has the warmer return until both loops have the same return temperature.

To calculate the pump you need a pump that will move 4 gpm. To calculate the head draw out the system if going reverse return measure both loops from the tee where the loops split on the supply to the tee where the loops split on the return include the baseboard in the loop length.

Take the longest loop and estimate the flow. The flow will be the BTUs of the baseboard on that loop/10000btu. That equals the gpm for that loop. Figure the other loop the same way.

Size the head by taking the gpm for that longest loop and the pipe size for that loop. You can download the B&G system sizer for that or post it here and I can do it for you.

Then measure the length of the common piping (supply and return) and figure the flow through that pipe (it should be at least 3/4") at 4 gpm

Once you get the head calc for the longest loop and the head for the common supply and return piping add them together and multiply them by 1.5 to allow for fittings. That is your total head.

• Member Posts: 668
edited August 2

edit: nevermind, i'm not really being helpful in any case. I'll move along.

• Member, Moderator, Administrator Posts: 10

Thank you all for sorting this out. It's a good reminder that we need to take a moment before making assumptions about other forum members and situations.

@joseluisheating, thank you for sharing this with us. You are right that we built this website to help others.

Forum Moderator

• Member Posts: 1,254
edited August 2

@joseluisheating - recommend you take another look at the BTU requirements as your estimate seems very high. I'm heating a 3000SFT house with around 40K BTU at design day temp of 11F. House was renovated with good insulation and air seal but has something like 60 window.

You may be in colder area but I'd guess your estimate is off by 40%.

Keep us posted.

• Member Posts: 23,746

I think, @PC7060 , that you are right — but there is a good reason for it. As I read through the comments, it seems clear that he was basing his heating load estimate on what the installed boilers were rated for — not on the radiation or the actual heat load.

This is a VERY common error which even professionals do from time to time, but I think that we have this corrected now.

Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 32

My goal is to have an efficient system. My goal is to run the water at 140-150f with long baseboards. However, knowing that series loop can drastically reduce the water temp 20f per baseboard, would not be my best option. Therefore, I choose reverse return because out of all that is the one that maintain an even water temp supply and keep the system balance.

I have couple of questions for you:

I want to install two zones. Frontal and back part of the house with a single pump. Can each zone has reverse return layout ?

The boiler would be on the basement but the baseboards would be on the second floor. Should I run the main through the first-floor ceiling or should I run the main across the basement ceiling with parallel pipe to the baseboard. If yes, how to deal with less resistance path ? Should I install tees with restriction ?

Also, Each baseboard loop is 3/4" pex pipe and planning to run 4gpm per baseboard. What size should be the main to satisfy each baseboard loop per zone ? (For the frontal part, there would be 5 long baseboards)

• Member Posts: 32

Good morning guys,

I contacted several HVAC technicians to conduct a Manual J or perform a heat load and loss calculation for my apartment. Unfortunately, they all declined to provide this service. I am not sure how to perform a heat load and loss calculation myself, and I also don't know how to estimate the BTU output of each radiator.

Based on information from Jamie Hall, it seems that one of my radiators has an output of 7,000 BTUs and another has an output of 14,000 BTUs. If that's accurate, my apartment might require more than 40,000 BTUs in total.

Here are my main concerns:

1. How can I determine the BTU output of each radiator?
2. How can I calculate the heat load and loss for my apartment?

For context:

• My house does not have insulation on the second floor.
• The walls are lath and plaster.
• There are many windows in the front part of the house.

Any assistance or guidance on these issues would be greatly appreciated.

• Member Posts: 32

It is important to know the manual j or headload and loss of my apartment because I would size the baseboards, pipes, and boiler in accord to that load and loss. Avoiding having a oversize or undersize system. I understand @Jamie Hall completely now. However, estimating radiators output are very complicate.

• Member Posts: 32

Another question, when you refer a 'loop' you referring as the zone loop or you referring at each loop per baseboard ?

Context:

I am trying to have two zones. Frontal with 5 baseboards. Back with 3 baseboards.

• Member Posts: 23,746

We usually use the term "zone" to mean a radiator or group of radiators controlled by one thermostat and valve or pump — so in your case, the front (with five baseboards) would indeed be one zone, and the back (with three) the other.

Now how things are piped within a zone is another matter. In terms of getting things to balance and control well, either reverse return or home run piping, with a manifold, will work.

Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 32