calculation for circulators


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Old 02-22-12, 12:27 PM
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adding baseboards and adding zone

I have a one zone 2-pipe hot water heating only system. All baseboards are BaseRay cast iron from Burnham. The main line is 1 pipes and the branches are pipes. I planned adding zones 2 yrs ago when I converted from oil to gas. So the Burnham alpine 105 gas boiler is big enough for planned additions.

Our 1950s house is a one floor Ranch style house with a full basement which has the same size and layout as the first floor. The size of the first floor is 1600sft. The basement is underground and only has less than 1 above the ground.
There is a living room, family room, two bedrooms, a bath and kitchen on the first floor. The family room is an addition and is heated with electric heaters now.

Now I am planning to do two things:

1. Remove the electric heaters and add cast iron baseboards in the family room to use hot water heating;
2. Split the bedrooms out from the existing zone to create a separate zone and add a basement bedroom into the new zone.

A further plan is add the third zone to heat the basement after it is finished few months later.

Here is the layout of the existing system: ExistingHeating | Flickr - Photo Sharing!
And here is the my new plan or design: Heating2Zones | Flickr - Photo Sharing!

I have done the heat loss with HeatLoss Explorer 2 and the results are the followings:
Zone 1:
(FamilyRoom) 15060 + (LivingRoom) 14030 = 29090 BTU/HR

Zone 2:
(Bedroom1) 5409 + (bedroom2) 5409 + (bedroom3) 2657 = 13475 BTU/HR

So I have figured out the family room needs about 30 ft CI baseboards. I have bought enough WeilMcLain CI baseboards for family room and basement.

I am trying to figure out the circulator size but have two questions to ask first:

1. The existing CI baseboard (BaseRay) has openings but the branch line is size. I think that is why the existing baseboards are much longer than required length based on my heat loss number. The new WeilMcLain CI baseboards are the same as BaseRay with openings. Should I use branch line or use branch line? If I use 3/4, I am worrying about two different branch pipe sizes in one zone may cause uneven heating. I am fine to add little more baseboards to use branch line. What you will do for this?

2. Do you think my above heat loss numbers make sense from your experience?

I will ask my circulator calculation questions later.

Thanks,
 
  #2  
Old 02-22-12, 03:32 PM
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I'm gonna comment in bits and pieces as I study your drawings...

I see that it was set up as a 2 pipe, (more or less) direct return system.

Note 2 on one of the drawings says that 2 years ago a plumber connected the ends of the two runs.

WHY? That makes no sense to me.

What happened after that? Didn't you lose heat in the rooms out at the end? I'm certain that the flow decreased, probably in ALL the heating loops because of this. Water moves from high to low pressure. By connecting the ends of that loop, the Delta P (difference in pressure) has been reduced on ALL the loops. It would be most noticeable at the end, closer to the 'short circuit'.
 
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Old 02-22-12, 03:42 PM
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The new plan has some advantages in that you've managed to use a 'reverse return' scheme for the new and modified piping. Reverse return helps to balance the flow through each of the radiators because the piping is more or less an 'equal length' to and from each radiator. The first one on is the last one off.
 
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Old 02-22-12, 03:47 PM
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Let me ask a question or two about the existing boiler setup.

The drawing appears to have a pump on the supply, and a pump on the return, with a bypass between them. Is that correct?

[edit: drooplug pointed out (thanks Droo!) that your boiler is a mod/con which I missed in my quick read of your first post. This might explain the multiple pumps... I'm guessing the what looked like a bypass in the drawing is a pair of closely spaced tees? ]
 

Last edited by NJT; 02-22-12 at 04:21 PM.
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Old 02-22-12, 03:53 PM
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You have a mod/con boiler. That tells us that the water temperature used in your home is probably less than 180F. Make sure you take this into account when figuring the amount of baseboard you will be installing.
 
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Old 02-22-12, 03:54 PM
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A few rules of thumb...

Designing for a 20 delta t, and 2-4 FPS of flow velocity,

1/2" pipe can move appx 15K BTUH

3/4" pipe can move appx 40K BTUH

1" pipe can move appx 80K BTUH

If the connected loads are 15K or less, then 1/2" pipe is fine.

Your 'main lines' need to be able to carry the required BTU for all the individual connected loads. You are probably OK with 1" ... I believe that's what you said is already there?
 
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Old 02-22-12, 04:15 PM
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How many BTUs of electric heat now exist in the family room, and is it 'adequate' to heat the space?

Is the baseboard going in an equal amount of BTU?

I think that is why the existing baseboards are much longer than required length based on my heat loss number.
Probably not. 'Back in the day' it was pretty much common practice to line the entire outside wall with heat emitters, and hope for the best. I doubt anyone did a heat loss calc on your home in 1950.

But this brings up a point that must be considered, especially in view of the fact that you have a mod/con boiler.

MORE heat emitter than you need is a VERY GOOD thing when running a mod/con. It allows the use of lower water temps to heat the home, saving money and allowing the boiler to spend more time in the condensing range.

Hopefully, they are all the same PROPORTION larger than needed.

And, if so, you should also increase the amount of emitter in the family room by the SAME PROPORTION, because if you don't, you will need two different temperature water to give the correct output in the two areas of the home.
 
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Old 02-22-12, 04:18 PM
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Here's a 'trick' you can play on HE2...

Lower the water temperature in the system until the heat output of the radiators matches the required heat output on your 'design day'. This should be the hottest water you will ever need out to your system.

Recalculate the amount of baseboard needed by the family room at this new temperature.
 

Last edited by NJT; 02-22-12 at 05:00 PM.
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Old 02-22-12, 06:58 PM
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Thank you sir

you are the real expert! i will play HE2 to find the best water temperature.
 
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Old 02-23-12, 10:26 AM
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calculation for circulators

Continues on yesterday's adding baseboards and adding zone.I have the following calculations for the circulators. Please have a look to see if it make sense or not:

Zone 1:
(FamilyRoom) 15060 +( LivingRoom) 14030 = 29090 BTU/HR

Flow rate: 2.9gpm

main line:
1 pipe length: 137ft
1 ball valves: 2*1.8=3.6ft
1 90 elbows: 11*2.62=28.82ft
1 gate valves: 1*0.7=0.7ft
1 flow check: 1*83.7=83.7ft
1 tees: 10*5.25=50.25ft
1 total: 304.07ft

H1 = k*c*L*f^1.75 = 0.000845*0.933*304.07*23.002 = 5.51

longest branch:
pipe length: 56ft
ball valves: 2*.6=1.2ft
90 elbows: 6*1.55=9.3ft
total: 66.5ft

H2 = k*c*L*f^1.75=0.0159*0.933*66.5*6.839=6.75

H1 + H2 = 12.26
Use Taco 008 circulator
?


Zone 2:

(Bedroom 1) 5409 + (bedroom2) 5409 + (bedroom3) 2657 = 13475 BTU/HR

Flow rate: 1.3 gpm

main line:
1 pipe length: 26ft
1 ball valves: 2*1.8=3.6ft
1 90 elbows: 4*2.62=10.48 ft
1 gate valves: 1*0.7=0.7ft
1 flow check: 1*83.7=83.7ft
1 tees: 6*5.25=31.5ft
1 total: 156ft

H1 = k*c*L*f^1.75 = 0.000845*0.933*156*23.002 = 2.83

longest branch:
pipe length: 42ft
ball valves: 2*.6=1.2ft
90 elbows: 6*1.55=9.3ft
total: 52.5ft

H2 = k*c*L*f^1.75=0.0159*0.933*52.5*6.839=5.33

H1 + H2 = 8.16
Use Taco 005 circulator? But I have one Taco 007 circulator already. Can I use the 007
?
 
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Old 02-23-12, 02:35 PM
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I'm going to add this post onto the end of your other post since it's all dealing with the same system and I asked some questions there which weren't answered...
 
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Old 02-23-12, 03:20 PM
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There's a few problems with your calculations...

First, I'd like to know:

Where did the ' k ' and ' c ' factors that you used come from ?

Since the individual loops are not all in series, the values won't all add. There is some calculation that needs to be done to figure them in parallel... IF you want to get that close to the actual number.

Using the 'longest loop' won't actually work here because of all the parallel connections.

If going to this trouble, it is far better to make a 'table', plugging in different values for ' f ' and then plot a system curve on a pump chart.

Remember too that your 2.9 GPM and your 1.3 GPM are basically a MINIMUM flow required for a 20 delta, and the amount of radiation on the loop. You CAN have more, and in most cases, you probably SHOULD have more.

I'm willing to bet that the 007 would work just fine for both loops. You may instead consider, depending on your budget, a more expensive pump which would 'adapt' itself to your system, and also use less power. See Grundfos Alpha:

Small Variable Speed Circulator Pump: ALPHA | Grundfos

Here is a 'non-specific' chart that shows a better way to select a circulator:

This shows an arbitrary 'system curve' plotted on a pump curve chart for a Grundfos 15-58 3 speed.

 
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Old 02-23-12, 03:39 PM
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In these calculations, I wonder how you ciphered them?

H1 = k*c*L*f^1.75 = 0.000845*0.933*156*23.002 = 2.83
H2 = k*c*L*f^1.75=0.0159*0.933*52.5*6.839=5.33
If these are both for the same flow of 1.3 GPM, how does f^1.75 come out to 23.002 one time, and 6.839 the second time?

My calculator tells me that 1.3^[SUP]1.75[/SUP] = 1.58
 

Last edited by NJT; 02-23-12 at 03:58 PM.
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Old 02-23-12, 03:58 PM
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answers to your questions about the first post

The 1" main line are there already.

Yes, there is a boiler loop (you call "bypass"?) which is recommended by Burnham manual.

I don't know the BTU the electrical heater will provide. It is about 10ft long. We never use it since we moved in. We use the wood stove in that room temporarily. The number, 15060, I got is from the HE2.
 
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Old 02-23-12, 04:03 PM
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OK, if you've never used it then we can't know if it was enough or not!

I'm sure the wood stove heats it just fine though!

The 'boiler loop' ... that loop feeds into a pair of closely spaced tees on the main line then? If so, it is what is called a ' primary/secondary ' arrangement, which is fine... as long as it's been done properly. I wouldn't mind seeing a picture of the boiler installation if you can...
 
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Old 02-23-12, 04:10 PM
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answers to your questions about the calculations

All the calcualtions are based on this doc from Taco: Selecting Circulator

H1 is for main line which is 1" pipe.
H2 is for longest branch line which is 1/2" pipe.

So I think the zone head loss will be H1 + H2.

There is a minimum and maximum flow rate table at the beginning of that doc. So I didn't use the flow rate I got to do f^1.75. I use the last table, table 5, in that doc to get a number directly instead.
 
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Old 02-23-12, 04:15 PM
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zone 1

the zone 1 has 137ft 1" pipe and 56ft 1/2" pipe, plus tees, elbows and valves. It is much bigger than zone 2.
 
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Old 02-23-12, 04:17 PM
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diy007 - I admire your desire to calculate the hydraulics for your system. But, particularly for residential hot-water systems, such calcs are very seldom performed (and, I suspect, a significant percentage of those that do are us weirdos on this forum).

I'm not a mechanical or chemical engineer (although some of my friends are). Sometime in their education, they will be required to do the type of calculation that you are confronting. It will be a major assignment of a hydraulics course, and probably half of the students will botch it. But, nowadays, they will use a computer program.

Most sizing of residential hot-water heating systems is (or used to be) done by plumbers - who were taught by their uncle or father: for this size boiler, use 1.25" mains, 3/4" or 1/2" supplies to radiators, etc. Such an old-timer prepared the riser drawings, which I have, for my early '50s system, and it works great. I could have ten newly-minted mechanical engineers redesign my system from scratch, and I'd bet a few would be botched.

If you're serious about getting into hydraulics calcs, here are two valuable references: "Cameron Hydraulic Data," various editions since 1926; and "Flow of Fluids Through Valves, Fittings, and Pipe," Technical Paper 410, Crane Co.
 
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Old 02-23-12, 04:31 PM
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Exactly... I'm one of those weirdos... but I enjoy complicated mental exercise even though there's really no point to it. Except for the fact that when one knows the 'whys' it's that much easier to make confident intuitive educated 'guesses'.

That's why I would tell you to use the 007 for both loops.

The main reason is PRICE and AVAILABILITY. You can probably get a 007 almost anywhere, and the price is right. There certainly are other pumps that would work, but they are going to cost way more, and if a pump goes down you don't want to have to hunt around for a replacement.

The Head calculations for 2 pipe system with radiators in parallel all along the loop are WAY more complicated than you have worked out... the stuff at the Taco site you were looking at is all geared toward a SERIES loop of baseboard. Won't work for your arrangement.

Another text I would highly recommend is "Modern Hydronics" by John Siegenthaler. Everything you ever need or want to know about hydronic heating is in that book. Make sure you get the LATEST EDITION.
 
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Old 02-23-12, 04:37 PM
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If you want to get an idea of just how complicated the parallel calculations are, take a look at this article:

Determining Flow Rates in Parallel Piping Systems Constructed of Smooth Tubing - Archives - PMEngineer
 
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Old 02-23-12, 04:57 PM
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photos

I uploaded two photos for the existing installation: HeatingSystem - a set on Flickr
 
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Old 02-23-12, 05:07 PM
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the zone 1 has 137ft 1" pipe and 56ft 1/2" pipe, plus tees, elbows and valves. It is much bigger than zone 2.
OK, but that doesn't help solve your situation.
 
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Old 02-23-12, 05:11 PM
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I uploaded two photos for the existing installation: HeatingSystem - a set on Flickr
Those two photos don't help much. What, exactly, is your question?
 
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Old 02-23-12, 05:12 PM
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why I am here?

I am not trust ALL calculations from mine. I am here is to get YOUR estimate. You have given to me and I trust your experience. I got what I want now. Expert's experience is much better than novice/stranger's calculation.
 
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Old 02-23-12, 05:17 PM
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photos and issue

They will help to know why there is another strange circulator.

I am here try to get help from you guys to determine which circulators I should buy for my zones.
 
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Old 02-23-12, 06:06 PM
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I asked for the pic of the boiler because I wanted to see if it was a proper primary/secondary and it looks from what I can see that it is.

Gosh, that is a HUGE water heater! How come?

I think I'm going to stick with my 007 recommendation.

But NOT the IFC model. Since I see that you included flow check valves in your list of parts, you don't need the IFC in the pump. Although, if you DO use the pump with the IFC (Internal Flow Check), then you don't need the other ones.

The thing about using the 007, it's cheap enough that if by some very slim chance it does not pump enough (VERY slim chance) then you can change to a more expensive pump easily. But I'm fairly confident that you won't need more than the 007.
 
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Old 02-23-12, 07:34 PM
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water heater

It is 80 gallon, I think. It is Solar water heater with electrical assistance. My inherited old (1980s) solar panel was freezed and then leak last year. Then I cut them off. I will put them back after I find time fix them.
 
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Old 02-23-12, 07:41 PM
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flow check

because we have two zones now, there must be a flow check in each zone. Is this right?

the existing zone doesn't have any flow check device yet. So I will replace the existing 007 circulator with a IFC 007.

in the new zone, I can put a separate flow check valve and then put that 007 in.

Above arrangment is good?
 
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Old 02-23-12, 07:46 PM
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there must be a flow check in each zone. Is this right?
Yes, correct.

Above arrangment is good?
It will work.
 
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Old 02-23-12, 08:12 PM
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flow check valve

how often the flow check valve may fail? should I use thread flow check valve with thread circulator flange for easy replacement or no need to worry too much about the future?
 
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Old 02-24-12, 01:43 PM
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Where is the 30" of CPVC pipe on the vent of the Alpine? It was supplied and must be used.
 
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Old 02-24-12, 02:43 PM
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Does that mean the plumber didn't follow the requirments?
 
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Old 02-24-12, 02:47 PM
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baseboards are under the main line

I have the third zone which is the basement zone. All the baseboards will be under the main line about 7 ft in this zone. Does this mean the circulator for this zone need to be stronger? because it needs to push all the water up 7 ft.
 
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Old 02-24-12, 03:15 PM
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Does that mean the plumber didn't follow the requirments?
If he didn't use the REQUIRED BY MANUFACTURER components which were supplied by the manufacturer with the boiler, then YES, that is what it means.

Does this mean the circulator for this zone need to be stronger? because it needs to push all the water up 7 ft.
NO. In a CLOSED system, the height of the building, has absolutely NOTHING to do with the pump capacity. It is a BALANCED system, just like a FERRIS WHEEL. All the pump has to do is move the water past itself and overcome the friction in the pipes.

Remember that the pump is both PUSHING AND PULLING at the same time, and GRAVITY is helping.
 
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Old 02-24-12, 03:16 PM
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no need to worry too much about the future?
Failure of a flow check valve is rare.
 
 

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