I am finishing my basement and bringing in hot water heat from a boiler in my garage (a floor above and located on a slab adjacent to the basement). I am using four fan convectors - two in kickspace; two in the wall in a one pipe system. Because of the way I have to bring the main line into the basement and return it to the garage, and the locations of the convectors, I am concerned about the layout.

I need to drop the main down from the boiler about 8 - 10 feet, tee off it low for two convectors, then bring it up a few feet and tee off it for the other two convectors, and then return it to the boiler.

The branches for the second two convectors will be teed off in the downward direction because the convectors are below the main at those points. I understand that I should use two monoflow tees (one on the supply and one on the return) for each of those branches because the convectors are below the main.

The first two convectors will be close to the same height (one slightly above and one slightly below) as the main at the points where they are connected to the main because of the framing around and under the stairs and the way I have to pipe the main.

My questions are these:

1. Can I connect the branches for the first two convectors such that the supply monoflow tee for one and the return monoflow tee for the other are connected to a vertical section of the main, while the other two tees are facing downward? In other words, does the main part of the tee always have to be lying horizontally?

2. When you are using two monoflows in each branch, which way should the supply and return face on each branch?

3. With four convectors in the system, should I use a balancing valve (s) and where should they be located?

4. Will my layout work; will there be air or turbulence problems? How to I avoid that. I do not have a lot of choices on the layout of the main line.

 

If I understand your installation correctly, you intend to supply multiple convectors off one set of monoflo tees. If this is correct, it problaly will not work. Here's some information on monoflo tees which may help.
http://www.bellgossett.com/Press/BG-monoflo.asp

 

Thanks for responding. Actually, I have eight monoflow tees for four convectors. My first question is whether i can install any of them in a vertical run of the main without any difficulties.

 

I would recommend against installing Monoflo's in a vertical run.

I have a few questions about your project.

1. Is this going to be a separate loop (one-pipe) from the rest of the heating load or is it going to be combined with the existing main?

2. Is this area going to be one zone with its own thermostat?

3. Are you planning on using zone valving or a separate circulator for this project?

 

1. Can I connect the branches for the first two convectors such that the supply monoflow tee for one and the return monoflow tee for the other are connected to a vertical section of the main, while the other two tees are facing downward? In other words, does the main part of the tee always have to be lying horizontally?

2. When you are using two monoflows in each branch, which way should the supply and return face on each branch?

3. With four convectors in the system, should I use a balancing valve (s) and where should they be located?

4. Will my layout work; will there be air or turbulence problems? How to I avoid that. I do not have a lot of choices on the layout of the main line.[/QUOTE]

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1. Yes, you could.
2. Opposite each other - it's clear in any literature.
3. It can't hurt - typically before the convector.
4. Hard to follow what you're saying. A sketch would help.

Just remember, every high spot needs a way to clear air...

Could you be more clear about the path of the main loop? I'd try and keep the main loop on one level if possible.

 

Who,

Thanks for your response to my questions. I could send you a sketch of the proposed layout of the main but I think I need your email address. I don't know how to make a sketch here. There would be one dip in the main, off of which the first two convectors would be branched. I suppose I could try to keep the main completely at one height, but that would mean that the branches for the convectors would be longer and include more turns/resistance. I was trying to avoid that.

I have another question regarding the tees. I purchased the scoop type instead of the venturi type. Is there a big difference? I imagine that the scoop type creates more turbulence but what do I know. Can I use the scoop type in a vertical leg of main as well?

Furd,

This is going to be a separate loop from the other two in the house. I plan on using a zone valve with one thermostat for the whole basement space. My house presently has two zones, one ciruclator, two thermostats. I may need a new boiler. Mine may be undersized. It is 15 years old anyway. May be time for a new one.

 

Rocky, I'm not familiar with the scoop tees, only the venturi tees. You need to remember that they work on velocity. Kind of like a plane's wing... you get enough speed, the plane lifts. Same deal with diverter tees. You get enough velocity/flow on the main run and you'll get flow through the branch. Not enough velocity/flow and the heated water won't be diverted through the branch, the heat will stay in the main or at least miss a branch or more.

You would be surprised what you can do in the way of branch lengths. I'd really focus on a clean path for the main. The one exception would be if you wanted to get the piping low so that you only had to use one special teee per emitter by piping from unerneath. Of course the advantage to dropping all of your branches is that you won't need to bleed them. The downside is having to use 2 special tees on each and the remote risk that if the branch is closed and then reopened when the water in the branch is much cooler, that it isn't so heavy that the flow through branch is skipped... andyway, that's rare.

You probably should use a separate circ for this... or at least be ready to put one in if the ZV option doesn't work. What size pipe are you using for the main and branches and how many GPMs do you think you can get from opening a ZV to that zone?

(The flow calcs for diverter systems are something I've never really been able to figure out how to do accurately.)

I'll PM an email addie...

 

(Rocky sent me a diagram)

Rocky, the diagram has the circuit you are talking about but doesn't show where the it connects to the rest of your heating system. If it is up at the top near where you show the circ, then you should be fine and not need much in the way of a bleeder/autovent.

I would put a bleeder/autovent right above where it does the big drop. I would also add a drain at the lowest part running across.

For the 7.5' height section, I would tray and keep some type of very gradual upwards slope through that whole section leading back up to the circ.

The circ would be better better on a vertical section, less chance of being airbound.

As for bleeder/autovent choices, what kind of expansion tank do you have - a traditional style tank or a diaphram tank?

 

Who,

Thanks again. The circulator on my existing hot water system is located in the return to the boiler. So, I guess my diagram is a little inaccurate. The boiler is above the basement ceiling in height. The discharge side of the boiler is probably about 10 to 11 feet above the lowest part of my basement main. I intend to connect the basement main to the boiler manifold with a zone valve as a third zone. I have two zones now, the main floor and the upstairs. I intend on making the basement number three. But I assume that I will need a bigger boiler and a bigger circulating pump based on the btu/hr and flow needed for all of my baseboards and the new fan convectors for the basement. There is no expansion tank with my system.

Thanks again,

Rocky

 

It might be a lot easier to tap into one of the mains for the two existing baseboard circuits, since they both run through the basement ceiling before they go upstairs, but I want the basement on a separate thermostat and zone. I assumed running a third zone is the way to go. Am I overcomplicating things?

 

Rocky... I think the best step would be to start doing some heatloss calculations. Slant-Fin's heatloss explorer software is quite good and quite free as well.

You really should get an idea of how much heat you need there. Is it currently insulated? If not, that'll really reduce the heat needed.

Putting 4 forced convectors may be overkill...

 

I did the heat loss calculations and I came up with 29,500 btu/hr. The convectors I have will on their normal setting put out about 27,500 btu/hr. On boost, they will put out more. I thought I was in the ballpark. The space will be insulated.

 

So 29K just for the addition? How many square feet? That sound show...

 

The space is 700 square fee and there are several partition walls. That's why I have four convectors.

 

Whoops... meant to say that sounds high.

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Even at 25,000 MBH, that's over 35 BTU per square foot for a basement area.

If you were at near design temps, I'd suggest you start adding 1500 watt heaters (approx. 5000 MBH equiv.) one at a time down there until its comfortable. Unless you have no insulation, bad infiltration and your basements above ground with the slab imbedded in wet clay, I can't see you needing 5 or 6 of these. I would think 2, maybe 3 at the most.

What's the heatloss for the rest of the house?
What's the outer basement wall structure/insulation?
What's your geographical situation?
What the lowest temperature in the basement when is it unheated?

 

I live in upstate New York. Half of my basement is above ground due to the grade outside. There is a door to the outside at ground level. The basement, as it is now, can reach very close to outside temperatures, which in the dead of winter can be below zero. I am improving the insulation above the concrete block walls and concrete floor. Two by four construction against the concrete walls. No insulation on the floor. Right now, there is no insulation except in the ceiling to the upstairs. I want to keep that insulation, because if the basement is not in use, which it will not always be, I'd like to keep the temperature down, by keeping it on a separate Zone and not sharing the upstairs heat with the basement. Everything I have read suggests 50 btus per hour per square foot for my neck of the woods. My present boiler puts out about 82,000 btus per hour to heat 1.950 square feet. That's more than 50 Btuh per square foot. It fires up constantly in the winter. Do you think I am way off with 27,500 btuh for my 700 square foot basement?

 

Yeah....

Rocky, my basement's roughly the same size, half below grade, in the Toronto area. I have a combined length of 14' of fintube heating it with at most 140°F water. I really can't see your needs being much above 10,000 BTUs. Even 15K would sound on the high side.

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Don't put your 2x4s directly against the concrete. They'll bridge heat out, especially as they absorb more and more moisture from the concrete.

Use good 1" R5 styrofoam firectly against the concrete. Then you can do your framing against the stryfoam or leave a small gap. You'll be surprised at how much of a change a continuous R5 will make (be sure to tape the joints and try and use the tongue and groove boards). Huge difference! I'd love to see a test of continuous R5 vs a stud wall with R12-14 fibreglass.

You can go thicker with the styrofoam, but it is always a matter of declining returns when using insulation. At 2" you'd be doubling the cost, with maybe a 20% improvement... batts are a cheaper way to maximize heat retension.

Do the framing and add the batts right before you drywall (no vapour barrier needed). My preference for batts is rock wool over fibreglass. You may have a hard time finding it. Roxul is a brand sold around here that has a nice product.

Most of my basement was done by spacing 2x4s 2" from the concrete wall and using unfaced R22 2x6" rock wool batts with the vapour barrier facing inside. In hindsight, I'd have rather done 1" XPS, then 2x4s with unfaced R14 rock wool batts and no vapour barrier - the XPS does that. The utility room is being done that way.

I also have a 600 sf crawlspace. This past winter, I put up 1" R5 XPS and covered it with fibreboard to do it quickly. What a difference from bare walls! I was thinking that I should use 2" but afterwards I was glad I didn't spend all the extra money. That are is below grade.

If you do a good job insulating and sealing the joist band area and the basement walls, I can't see you needing much heat. Unless you have the room to build up the floor, I wouldn't worry about the lack of floor insulation. It's a heat sink so your heat losses going downwards won't be too hard on you, but it won't ever make the floor feel completely warm either. My basement floor is uninsulated.