Aquastat wiring question

Reply

  #41  
Old 01-26-12, 08:53 AM
Member
Thread Starter
Join Date: Mar 2003
Location: Delaware Co, NY
Posts: 174
Received 0 Votes on 0 Posts
I made some measurements with a hand held IR thermometer, of which I'm sure you're aware of their shortcomings. I put blue tape everywhere I took measurements, making sure there was good contact, and still the numbers were widely scattered and I don't really trust them. When I finally get this HX thing resolved I'll install a temp monitoring system. In any event, there seems to be a ~10 degree loss between the wood boiler and the house. If it's not too cold and there is less than 6 in of snow, the snow will melt on the ground above the pipe. It's losing some heat.

A standard insulated pex pipe is available for this application. Mine is 11 years old and what is available now is supposedly better than mine.

See here: ThermoPEX® - Insulated Piping

7.5 sounds better.
 
Sponsored Links
  #42  
Old 01-26-12, 12:09 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
And would swapping the 014 at the boiler for the 36 in the basement do the job?
I think it would be a step in the right direction.

Since the loop from the HX to the boiler is so short, there is very little head there... the majority of the head in that loop is probably in the HX itself.

By the way, the 0013 Taco is quite close to the PL36 curve.

Some numbers:

At 5 GPM, 500 feet of 1" PEX is about 20 feet of head.

At 10 GPM, it's about 68 feet of head.

A very steep curve. The way to estimate the flow with a particular pump is to plot a SYSTEM curve on the PUMP CURVE chart.

Remember that the system curve always starts at zero head with zero flow. Placing the above numbers on the Taco curve chart, you would look for the point that the pump curve intersects your system curve. That's the predicted flow rate with that particular pump.

The problem with a steep system curve is that you don't really gain much by going up in pump size. For example, even the standard 007 pump would give about 3 GPM through that circuit. So from the 7 to the 14 all you pick up is maybe 2 GPM...

I wonder if adding a second 0014 pumping back to the woody is a possible choice?

Pumps in Parallel or Serial Connection
 
  #43  
Old 01-26-12, 12:38 PM
Member
Join Date: Feb 2011
Location: US
Posts: 552
Received 0 Votes on 0 Posts
Is the outside loop filled with anti-freeze?

If so that changes all the numbers, many for the worse.

If there is 5.5 gpm flow now and it's dropping 10 degrees
that's a loss of of over 26,000 btu's.
Ouch!
But probably something you can live with? Maybe?
Of course there are more losses on the return pipe also.Guesing another 18,000 btu's?
44,000 to melt a little snow. ugh.
I can pretty well heat my house with 44,000 btu's hr at 5-10 below .

Peter
 
  #44  
Old 01-26-12, 04:48 PM
Member
Join Date: Jun 2005
Location: ontario canada
Posts: 381
Received 0 Votes on 0 Posts
im gonna jump in here as a real novice but an outdoor wood burning owner i think the first thin to consider is it sounds like the outdoor stove has more water than the indoor boiler (?) if this is correct than the next think i would do is make sure the heat exchanger you are using is equal (in btu per hour) as your indoor boiler is rated at (and hopefylly less or equal to your out door stove)

next is your delivery rate (GPM) the gurus here will be able to tell you haw many that should be by the rating of your indoor boiler (i think)

now as for your pumpon that outdoor system i have a question of my own to the group my pipes are 1 inch pex and travel 250 feet one way i use a taco 0011 and have never had a problem with water delivery But my pump is in the basment and is lower that the outdoor furnace. would the slight pressure from the outdoor furnace negate the first 250 of pipe?
 
  #45  
Old 01-26-12, 05:26 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
would the slight pressure from the outdoor furnace negate the first 250 of pipe?
No, because it has to go back up again... the two altitude changes cancel each other out. In general, it's not the altitude difference that causes the pressure change, it's the FRICTION from the fluid flowing in the pipe. The more water you try to pump, the more 'head' is created due to that friction.

Your 011 is a bit more pump than the 014. Probably flowing in the neighborhood of 6-7 GPM...

But let's try not to lose focus on Gary's thread.

The BTU rating of the indoor boiler isn't really relevant, as long as enough heat can be transferred from the outdoor boiler in order to heat the home.

1" pipe/tubing is generally considered to be able to move 80K BTUH.

Gary, from what I see on the specs, your 20 plate unit should be plenty big enough.

In order to determine if the HX is functioning as it should, we really would need to know the 'Delta T' (DT = temperature difference) between the in/out on the boiler side, and the in/out on the wood side.

If you've got 180 water in from the wood, and 170 out, then you aren't taking out a heckuva lotta heat... ditto on the boiler side.

Have we asked yet about whether or not the pumps on the wood side are BRONZE or not? Corrosion inhibitors will help slow the destruction of a cast iron pump, but those should really be bronze $$$.
 
  #46  
Old 01-26-12, 05:32 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
A little bit more about the first paragraph in my first post:

When a CLOSED and pressurized system is being pumped, the 'height' or altitude change has NOTHING at all to do with the pump performance. This is for the reason I mentioned, that the UP is canceled out by the DOWN. It's just like a Ferris Wheel of water. You only need to put enough energy into the water from the pump in order to overcome the friction in the piping.

In an OPEN system, such as a potable well, or other water distribution system, the altitude changes have a LOT to do with the pump performance. In ADDITION to the friction in the pipes, the pump must also overcome the change in height.

Even though the wood boiler side IS technically an OPEN system, the fact that the supply and return terminate at almost exactly the same altitude, it can be considered as a closed system for reasons of pump selection.
 
  #47  
Old 01-26-12, 05:58 PM
Member
Join Date: Jun 2005
Location: ontario canada
Posts: 381
Received 0 Votes on 0 Posts
im gonna make another assumption here, i read that the 20 plate exchanger is not losing much heat, ther eis not a large heat loss between the in and out sides of the exchanger (i think i read that) also it seems that the 0014 is a smaller pump that what i have..i have a 50 foot 1/2 inch copper heat exchanger hooked to my domestic water and am able to draw the temp on the return line down around 20 degrees i i think we can determine that if i am pumping water faster than gary and drawing the temps down farther, then his exchanger is dirty and not allowing the transfer it is capable of?

if his pump is not pumping enough water and his exchanger was (is) the proper size then he should be drawing the water temp down much more?

sorry i am not being helpful with answers but maybe more questions will help with the thinking process
 
  #48  
Old 01-26-12, 06:20 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
sorry i am not being helpful with answers
No problem Billie... yeah, the juices need to flow ...

then his exchanger is dirty and not allowing the transfer it is capable of?
That seems to be the general thought...

if his pump is not pumping enough water and his exchanger was (is) the proper size then he should be drawing the water temp down much more?
Yep... the slower the flow, the more the difference across the HX should be. With a general idea of the flow on each side, and the temp difference, we should be able to calculate the BTU being transferred. As an example, if one knew they were flowing 5 GPM and the DT from input to output was 20° we would know that 50K BTUH were being taken out and moved across.
 
  #49  
Old 01-28-12, 02:36 PM
Member
Thread Starter
Join Date: Mar 2003
Location: Delaware Co, NY
Posts: 174
Received 0 Votes on 0 Posts
I have one more question, not having been a personal friend of Bernoulli's, I was wondering where the numbers with regard to GPM, head loss, etc., come from starting with a PL-36? That is, where and how are you guys coming up with these numbers?
 
  #50  
Old 01-28-12, 03:24 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
I just had a beer with him! Kirchoff was there too and we got him to spring for a round as well!

If you google " PL-36 PUMP CURVE " you should get a bunch of hits... wade through them and you will find a 'chart' that shows the curve. Here is a link to the pl-36 pump 'submittal' document:

http://completewatersystems.com/wp-c...011/04/155.pdf
 

Last edited by NJT; 01-30-12 at 04:56 PM.
  #51  
Old 01-28-12, 03:33 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
Calculating the 'SYSTEM CURVE' is a bit more involved... how are you at math?

This article is stated as being for 'parallel' systems, but the principles work just fine for single loops also:

Determining Flow Rates in Parallel Piping Systems Constructed of Smooth Tubing - Archives - PMEngineer

To summarize it a bit, the first thing you need to do is determine the 'total equivalent length' of the circuit by adding all the various fittings and things together. In your case, the tubing, the HX, any elbows and such...

Then calculate the 'hydraulic resistance' (the ' R ' term in the equation)

a = .05212 for WATER (different for anti-freeze!)

c = number from the chart

and L = the 'total equivalent length'

Then, solve for H at the flow rates you wish to plot.

Plot the points on the pump curve chart and the point they intersect the pump curve will be the 'operating point' of the pump.
 
  #52  
Old 01-28-12, 03:43 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
I believe that Peter is using the 'Hydronic Design Suite' which is a program that comes with John Siegenthaler's excellent book, "Modern Hydronics". I use a calculator.

Here's an example of what your chart would look like. This is of course for a different pump and system:



The three pump curves are for the three speeds on this pump, L M H.
I forget how many feet of 3/4" copper this system curve was for [I think 50'], but one can see that on Low it will flow about 4 GPM (perfect for 3/4), Med about 5-1/2, High a bit over 6.
 

Last edited by NJT; 01-30-12 at 04:54 PM.
  #53  
Old 01-29-12, 06:29 AM
Member
Thread Starter
Join Date: Mar 2003
Location: Delaware Co, NY
Posts: 174
Received 0 Votes on 0 Posts
Thanks, I'm wading through this now.

.. how are you at math?
Calc l, Calc ll, Calc lll, Differential Equations, and Analytical Geometry.

I have an MS in engineering, but it's been 40 years since those physics classes and I got off that career path in the late 80's.
 

Last edited by Gratefulgary; 01-29-12 at 08:55 AM.
  #54  
Old 01-29-12, 09:02 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
I'd say you can handle the math!

H=1.22(1.75lnf)
Maybe I'm a bit slow this morning, but I don't understand this?

Yes, 1.22 is the R term for 500' of PEX.

Multiply that times the 'f'low raised to the 1.75 power.

H=1.22(f)[SUP]^1.75[/SUP]

I was gonna paste some values from a spreadsheet, but for some reason the 'table' functions of the editor aren't working so it's impossible to read... here's the Head at 0-15 GPM

0.00
1.22
4.11
8.35
13.82
20.42
28.10
36.80
46.49
57.13
68.70
81.17
94.52
108.73
123.79
139.68
 
  #55  
Old 01-29-12, 10:00 AM
Member
Thread Starter
Join Date: Mar 2003
Location: Delaware Co, NY
Posts: 174
Received 0 Votes on 0 Posts
ln f is taking the natural log of the flow, then multiply by the exponent, 1.75, take the inverse natural log of that result and multiply by 1.22.

No worries.

It would appear that I may get ~7 GPM with that 36. When my guy from Syr. Therm. gives me a recommendation we'll know what flow is required. He's aware of how far away the boiler is, etc.
 
  #56  
Old 01-30-12, 04:51 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
ln f is taking the natural log of the flow, then multiply by the exponent, 1.75, take the inverse natural log of that result and multiply by 1.22.
Not to belabor a point... I just wanna make sure I'VE got this straight...

I know that:

LN(f[SUP]1.75[/SUP]) = 1.75(LN(f))

I can't see how that's the same as R(f)[SUP]1.75[/SUP]

Not sure how the natural log slipped into the equation?

But I've given most of my synapses to Jim, Jack, and Sam... so maybe I'm missing something?

I'm certain that the 36 is too much pump for the boiler side... I hope your guy agrees. I'm quite sure you could run a 007 on the boiler side and still have too much flow... but check the head specs on the HX before you do anything, because that will be key.

I'd be surprised if you got 7 GPM with the 36 on the wood side. My money is still on 5 .
 
  #57  
Old 01-30-12, 05:06 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
Ya know, the more I think about this, the more convinced I am that the root of the problem is that monster pump on the boiler side...

I don't recall if we've asked this?

How is the exchanger piped?

In COUNTER flow? it should be...

I can't attest to the quality of these, but how bad could they really be? You can get a whole box of these for the price of ONE from ITT...

250,000 BTU/hr: 20-Plate Heat Exchanger, 1 MNPT ports, 4-1/4 x 12

I've been reading about cleaning these things... you need a 5% solution of phosphoric or oxalic acid (I bet Coca-Cola would work!) and a pump... BACK flush for some period of time to dissolve scale... then flush with baking soda solution to neutralize the acid, then with clear water.

I'm reading also that a WYE filter is a good idea... probably especially on the wood side...
 

Last edited by NJT; 01-30-12 at 06:08 PM.
  #58  
Old 02-01-12, 04:06 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
I got some information on your heat exchanger:

BP412-20
2.5gpm, 0.14psi
5.0gpm, 0.45psi
10.0gpm, 1.63psi
15.0gpm, 3.48psi
20.0gpm, 5.94psi

Multiply the PSI * 2.31 to convert to HDft.

It's really not as restrictive as I thought it might be.

If you don't count the short lengths of tubing, and the head of the boiler, just the HX, a lowly 007 would pump about 13 GPM through this exchanger and save a ton of electricity too! This pump runs continuously, right?
 
  #59  
Old 02-01-12, 04:15 PM
Member
Thread Starter
Join Date: Mar 2003
Location: Delaware Co, NY
Posts: 174
Received 0 Votes on 0 Posts
The natural log part is to resolve the fractional exponent, and then multiply by R to determine H.

The exchanger piping can be seen here: Heat Sys w/ Labels | Flickr - Photo Sharing! with labels indicating flow direction.

I've been giving a filter system some thought, but not anything in particular at this point.

My oil burner people will flush HX's with a product they use and have success with.

Haven't heard back from my guy yet. I'll post his recommendation.
 
  #60  
Old 02-02-12, 04:21 AM
Member
Thread Starter
Join Date: Mar 2003
Location: Delaware Co, NY
Posts: 174
Received 0 Votes on 0 Posts
It does run continuously. And that is a great idea.

You have been a great help, thank you for your patience.
 
  #61  
Old 04-05-12, 07:29 AM
Member
Thread Starter
Join Date: Mar 2003
Location: Delaware Co, NY
Posts: 174
Received 0 Votes on 0 Posts
I just wanted to touch base with an update. During that warm spell recently, I swapped those pumps. Took the PL-36 from the basement and swapped for the 014 at the boiler and....Holy Sh*t Batman. The oil burner has not fired since, and that includes some low teens nights.

So I conclude, as you guys had surmised, that the 014 was totally under capacity for that length run, and probably the PL-36 inside was too much for the circulation through the water boiler and HX. By upping the wood fired boiler pump and decreasing the flow in the water boiler/HX, I now have better performance than when I had both pumps PL-36's.

I think, therefore, that under the circumstances I will wait another year before I replace the HX. And devise a temperature monitoring system to see what's what. I will also take a close look at replacing those thermostat/circulator controllers. In the end I need the oil burner to fire up only when the water goes below some threshold if the WFB cools down or cannot keep up. Currently, the only thermostat wired to the aquastat is in the master bedroom, which is above the basement, where the heating plant is and therefore rarely calls for heat.
 
  #62  
Old 04-05-12, 03:11 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
I've been looking at this thermometer for some time now... looks like a neat device and the price ain't gonna break the bank either:

Digital Temperature Gauge, Digital Temperature Gauges for Radiant Heat Systems, Digit-Stat DS-60P for Hydronic Heating Systems

You might even be able to drop the 014 down to an 007...
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: