Modifying current baseboard heat layout

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Old 06-10-13, 04:42 PM
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Modifying current baseboard heat layout

Hello everyone,

First time poster, here. Lots of great info here, but I have a few questions regarding hydronic baseboard heat. I currently have baseboard heat in my home piped in 2 zones. This was a conversion from radiators about 28 years ago by the previous owner. He was a DIY'er. I am amidst gutting the house and have to remove all the baseboards, and when I replace, I want to use pex for the supply and return lines, and any intermediate runs between elements. I know about the oxygen barrier pex I need. My few questions are these...

Currently between rooms, there are up to 4 feet of bare copper run against walls without an enclosure, connecting a few separate rooms. I obviously want to hide these in the floor, and come back up to meet the element as to avoid an unnecessary run of visible piping with no cover, instead of just putting a dummy enclosure over it. This is on the second floor, and I plan on running through the floor joists, but I will have to cross the joists eventually. Can I run the pex perpendicular to the joist via drilling a hole through them?

Secondly, on most the element lengths, there are several 4' sections connected together. I there any harm in making those say, one 8' length, instead of 2 fours?

And lastly, when running new baseboards, are there any special considerations, aside from the oxygen pex, like any valves or purge vents that need to be installed or are required? I have a feeling the existing work was Mickey moused, so I want to make sure it's redone correctly.

Thanks again guys! I appreciate any help you can lend!
 
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Old 06-10-13, 07:07 PM
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Some general info to think about:

I'm not sure it's a good idea to assume that the previous owner knew what he was doing when he sized the heat emitters to the rooms. You might consider doing a "heat loss" calculation of your entire home, that'll give you a good starting point for your project.

And because the house is being gutted, that gives you a lot more options with regard to piping. Depending on the size of the house, # of rooms and some other factors, you might even consider "home run" piping to each heat emitter (or room). Among other potential benefits, that would allow you to use smaller diameter tubing which is easier to run through joists and walls.
 
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Old 06-10-13, 08:44 PM
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Thanks. By home run, you mean pex piping correct? If so that was my plan. I've been playing with the slant fin heat loss app, but I'm having some trouble understanding some of the parameters, and I can't seem to get a heat loss #.
 
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Old 06-11-13, 05:18 AM
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By 'home run', he means each radiator or baseboard having it's own supply and return back to the boiler to a 'manifold' mounted there. I don't know that's necessary though, as it might end up more costly and more controls.

Tell us what problems you are having with the program, there are several here who have used it and may be able to help.
 
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Old 06-11-13, 05:25 AM
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instead of just putting a dummy enclosure over it.
Certainly the easiest way... and sometimes the 'wall to wall' enclosures actually have a better appearance... but:

Can I run the pex perpendicular to the joist via drilling a hole through them?
Yes, you can, following the 'rules' about drilling joists in regard to the placement and size of the holes, etc.

Make sure the holes aren't tight on the pex as it will expand and contract to some degree as it heats and cools. You need to leave room for this movement.

I would probably opt for PEX-AL-PEX myself...
 
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Old 06-11-13, 06:38 AM
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How long have you been in the house?
I noticed right away the first winter in my place, which rooms/areas needed more radiant heat then others (based on the current setup).
Given the insulation isn't top notch yet in my place, it did give me a very good idea how the heat/air moved within the house and where I was lacking or over heated.
 
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Old 06-11-13, 10:47 AM
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Thanks for the info gents.

The problem I was having with the program was that I didn't understand what some of the measurements were, but I have the user guide now, and it cleared up most of my confusion.

I live in a 2 story 1200 sq/ft house, so I don't think a home run type setup would be anything but costly. I'd like to keep it 2 zones, for each of the floors.

I agree that the enclosures are easy, but I am tearing out all the existing baseboard, so I can install a new subfloor etc, plus the old ones got beat up during demo. That being said, I now have the ability to not have long runs of copper or pex to interconnect 2 elements. I can now go under the floor and keep the enclosures looking separate.

I don't think that prior owner did any type of heat loss before they installed. Just by looking at the basic numbers I have inputted in the app, it appears that the house is currently overheated by a lot. For instance, my 9x9 dining room currently has 14' of baseboard on 2 walls, and the heatloss recommends 4.5'. To me that seems too little, but I'm just basing that on what we currently have.

Based on those numbers on a 9' wall, would it be beneficial to put an 8' element in, or should I put a 5', and have the rest be an enclosure, to keep the baseboard looking nice, instead of having 5' on a 9' wall.

Hope that's not too confusing.

Thanks again!
 
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Old 06-11-13, 04:23 PM
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When yer done with the heat loss, let us know what the numbers are as a 'sanity check'.

it appears that the house is currently overheated by a lot.
Let's call it 'over-radiated' instead.

This is not necessarily a bad thing! Having more radiator than you need means that you can heat the home with cooler water, say 160 instead of 180. This will save you some money.

Using your dining room as an example, if there are 2 walls exposed to outdoors, and both walls have windows, it's best practice to install the baseboard under the windows. This will help fight cold drafts pouring off the windows and across the floor. If this means splitting the requirement for the room in two, so be it.

The idea though is to over radiate PROPORTIONALLY in every room so that no rooms are cooler or hotter than the others.

You can experiment with the numbers in the program. Once you are satisfied that you pretty much have it to where you believe it's all correct, drop the boiler temp from 180 (you are using 180, yes? not 200?) down to 160 and watch the length of baseboard needed in each room change.

What did you set as your "Outdoor Design Temperature". You should use a number that's valid for your area.

Let us know your 'numbers' and we'll go from there...
 
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Old 06-11-13, 05:20 PM
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Thank. I'm currently waiting my plumber to install a new condensing tankless boiler for heat and HW, so I'm unsure of the temperature it will be. I'm converting to natural gas from oil. Where can you change the boiler temp in the program? Unfortunately my boiler isn't listed because its a rinnai, not a slant fin.
 
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Old 06-11-13, 06:35 PM
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Short answer for now, short on time...

If you are installing a condensing boiler that is WAY ALL THE MORE REASON to OVER RADIATE!

You want to be able to heat with the coolest water possible in order to take advantage of the condensing feature of the boiler.

I'll get back withya later on the program.
 
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Old 06-12-13, 10:36 PM
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Ok thanks. Im getting the Rinnai E110CN, 96% efficiency. Just for some FYI, below are my a few examples of rooms in my house, with current (well, just ripped out) baseboard, and what the heat loss recommended.

First Floor (HLW)

Dining Room 7.5x12x9
Recent baseboard 20'
Recommended 6'

Living Room 7.5x13x13
Recent baseboard 24'
Recommended 12'

This is just a few examples, and I dont know the science and magic that goes into the heat loss aside from some hidden equations, but it seems that the program cuts in half what I had for baseboard. Thats cool with me, but if I have a 12' wall, Id rather put a 12' element in it, than a 6' one centered looking silly, or with dummy enclosures.

Thanks again NJ
 
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Old 06-13-13, 05:06 AM
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Holy wow you had a lot of radiant heat in those rooms.
I wish I was remotely close to what you have/had. I'm currently working on my living room/dining room (pretty much open all the way through) which is ~15ftx45ft and I've only got 2 baseboard rads totaling ~12ft (at approximately 450-550btu per ft).
 
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Old 06-13-13, 06:57 PM
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As trooper stated if you are using a condensing unit you want more radiation not less. The more radiation the lower the water temperature the higher the efficiency. The higher the water temperature the lower the efficiency. Twice as much radiation is better then the correct amount. This same rule applies to cast iron equment also. Putting in the exact correct amount of radiation do not expect the advertised efficiency if you need to run higher temps.
 
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Old 06-14-13, 06:22 AM
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The down side with more then required baseboards is the wall space consumed by them.
In rooms where this could be an issue, look into high output baseboards.
 
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Old 06-18-13, 05:31 PM
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Ok thanks guys, so in my particular situation, the heat loss should be used as a bare minimum, and the more I have, the lower the temp?
 
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Old 06-18-13, 07:19 PM
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In your particular situation, yes...

With a CONDENSING boiler, you will only achieve the rated efficiency when the boiler is ACTUALLY condensing, which it will only do if it's running at water temperatures no higher than say 135F.

Once a condensing boiler starts operating ABOVE the temp (appx 135F) at which the flue gases condense, the efficiency drops back to that of a STANDARD efficiency boiler.

The spring and fall are what we call the 'shoulder seasons'. During this time the home won't require hot hot water in any case, and your boiler will probably be operating in the condensing region.

When the weather gets COLD and the home requires HOTTER water to maintain the temperature, if the boiler needs to get hot enough that it stops condensing, you lose that extra efficiency.

The point then is to install enough (if possible given wall space) radiation so that the home can still be heated with cooler water.

In your Heat Loss Explorer program, go into JOBS / EDIT

You should get a drop down box which says "Edit Job Information"

Make sure that your "Indoor Temp" and your "Outdoor Temp" are appropriate for your area.

I don't think you ever answered this question:

What did you set as your "Outdoor Design Temperature"? You should use a number that's valid for your area.
It is CRUCIAL that you have this number correct! The program will not calculate correctly with the wrong data entered here. This number can be found from tables on the web... or if you tell us your general vicinity we can look it up for you.

Make sure that your original calculation was done with the "System Design Water Temperature" set to 180F.

Change that to 140F and click "OK".

The program will recalculate the amount of baseboard needed in order to heat the home with 140F water. If you have enough room to install that amount, then do so. If you do NOT have enough room to install that amount, then PROPORTIONALLY reduce the amount in ALL rooms. You can keep bumping the System Design Water Temp up until you find an amount of baseboard that will fit your wall space in all rooms. Yes, there may be a 'compromise', but the idea with a condensing boiler is to be able to run the temp as low as possible for the greatest portion of the heating season.
 
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Old 06-24-13, 08:54 AM
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Thanks NJT. I have the design outdoor temp set to 9 degrees, per slant fins temp chart. I set the indoor temp to 65, as I understand its the minimum temp to be maintained. I tend to keep it low when im not home. I can't find where to set the boiler temperature in the app.
 
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Old 06-24-13, 04:02 PM
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In your Heat Loss Explorer program, go into JOBS / EDIT

You should get a drop down box which says "Edit Job Information"

...

Make sure that your original calculation was done with the "System Design Water Temperature" set to 180F.
Should be at the bottom right of the JOBS/EDIT box...

My suggestion to lower it to 140F is based on the fact that you are installing a condensing boiler. Lowering the temp to 140 will recalc the number of feet of baseboard.

set the indoor temp to 65, as I understand its the minimum temp to be maintained.
I usually use 70F ... but 65 is OK as long as that is the warmest you intend to heat the home on the coldest days of the year.

You can 'fiddle' with any of the numbers to see what changes. Go ahead and change it to 70 and recalculate and compare the numbers.

One thing to keep in mind is that the heat loss is only going to be at the 'design value' when the outdoor temp is also at 'design'. All other times there will be excess BTU available from the boiler, and excess radiation.
 
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Old 06-25-13, 08:52 AM
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Thanks. I upped the interior temp, as I misunderstood what that temp was. I thought it was the minimum temp to be maintained, it's now 68. I can't find the boiler temp part of the app, but that's not a big deal. Just to clarify, I'm using the iPad heat loss app, so this may not have that option if you're referring to the desktop program.

Thanks again!
 
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