Cold baseboard


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Old 10-29-06, 10:00 AM
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Cold baseboard

Hi all, I am hoping you can help. I have a second floor baseboard that does not get hot. I don't think its an air problem, I am able to bleed all air out and get hot water in the baseboard, but once I close the bleeder, the baseboard gets cold again. Any suggestions?
Thanks
 
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Old 10-29-06, 03:49 PM
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Second floor

How much pressure is on the system? Should be around 15#.
Are you sure the zone valve or circulator, as the case may be, is working?
 
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Old 10-29-06, 07:20 PM
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its around 15 #, although the gauge is the most accurate - i even bumped it up a little until the relief valve started to drip. I only have 1 zone - its a 2 story cape. I am getting heat in 2 two other radiators on the 2nd floor and to the rest of the house, so I am assuming that the circ. is working. Its a Taco 007, installed on the return side of the boiler.

After much reading on the subject, I wonder if I am having some sort of balancing problem. From diagrams I have seen, it appears that my piping most closely resembles a 2 pipe (1 supply/1 return) - direct return system. This particular baseboard was installed by cutting out an existing 3 ft convector type radiator and adding this baseboard(around a 12 ft run of baseboard),plus about 15 of straight 3/4" copper to get to the baseboard.
 
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Old 10-30-06, 02:29 PM
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Balancing or air

Your problem could be either. Does the new basebord have a bleeder? If not, one needs to be installed on the return end.
 
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Old 10-30-06, 03:02 PM
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yes, the baseboard has a bleeder on the return side. I bleed until I get cold water than the water turns warm. I close the bleeder, and about 20 minutes later the baseboard gets cold again.
 
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Old 10-30-06, 04:53 PM
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Bleeding

Bleed until the water gets HOT
 
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Old 10-30-06, 06:12 PM
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ok - I bleed and I bleed - two 5 gallon buckets worth until the water is hot, and still same thing.
I have read that ideally the circ should be on the supply side, pumping away from the expansion tank. Do you think it is worth the effort moving my circ from the return side to the supply side?? Or adding a zone and a circ to the baseboard that is giving me trouble??
 
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Old 10-30-06, 06:18 PM
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2-story cape on one zone is a pretty tall order. What diagram suggests it's a 2-pipe? Sure it's not a series loop? In any event, my guess would be you've got too much pipe for the pump.

Suggest thinking about how you might zone the system. If you want to go that route, then yes pumping away from the expansion tank connection point on the supply side is the way to go. We can help with this stuff.
 
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Old 10-30-06, 06:27 PM
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Bled 'til hot

Sorry to put you thru that but I had to be as sure as I could be before I said you had a circuation problem. I think Xiphias is right in his judgement of too much pipe for the circulator.
 
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Old 10-31-06, 06:08 AM
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ok - tell me what kind of impact it would have on circulation if I switched the circ from the return side to the supply side. Is it worth the effort in moving it or would the effect me minimal.
 
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Old 10-31-06, 09:17 AM
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Before we start talking about moving stuff around, let's first see what kind of flow resistance (head) you've got through this system. You might fix this with just a pump swap instead of going through a whole repipe (assuming you are content with the performance of a 2-story, one zone system). Questions:

1) describe again what kind of piping layout you have?

3) can you post some pics of the near-boiler piping?

2) can you add up the number of straight feet of pipe, number of elbows, type of rads, etc.?
 
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Old 10-31-06, 03:50 PM
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Unfortunately, my digital camera is kaput but I will do my best to describe what I have.

1) describe again what kind of piping layout you have?
I have 2 1/4 inch black pipe running the perimiter of my basement. 1 is a supply and 1 is a return. At each radiator there is a 3/4 " pipe coming from the supply pipe to the radiator. The piping is returned to the return piping which returns to the boiler. It appears that the tees coming off the supply and return are standard tees, nothing on them suggest mono-flow. It is approximately a 3 ft run for both supply and return to each radiator on the first floor and about a 8'ft run both ways to each radiator on the second floor, with the exception of the newly added copper baseboard where I am having the problems with. This particular baseboard was cut from an old 3'ft radiator, now its a 64'ft run of pipe, compared to what it was originally a 20'ft run.
Looking at the Bell and Gosset diagrams, the layout appears to be a direct return system.

2) can you add up the number of straight feet of pipe, number of elbows, type of rads, etc.?
Doing some quick measurements I come up with a total of roughly 343' ft of piping including the various radiators/baseboard I have . I have 10 convector type radiators, each about 3' wide. 3 copper baseboards totaling 23', 1 cast iron footed radiator about 1' x 3'.
Also, I have a radiant heating loop in a 18x20 room, but I was smart on that one. It has its own zone and circulator.

I can't thank you enough for the assistance your are providing!!
Thanks!!!
 
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Old 10-31-06, 04:12 PM
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Main pipe size

What was the size of those two main pipes again, please? I'm not sure if there was a typo or I was reading it wrong. Are the pipes 2.25"?
 
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Old 10-31-06, 04:23 PM
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oops... typo -the pipes are 1 1/4" (one and one quarter inch).
Thanks!
 
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Old 11-01-06, 06:38 AM
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Got a link to the B&G diagrams? I'm not familiar with this kind of piping layout (yet).
 
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Old 11-01-06, 09:19 AM
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oops -it wasn't B&G - the diagram is here:
http://www.pages.drexel.edu/~mvj22/AED1/A5/hydronic.htm

Scroll down to two pipe direct return...
Thanks
 
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Old 11-01-06, 01:51 PM
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Interesting. My guess is that the new baseboard and piping has sufficently more resistance than the old piping and convector to not want to flow, or at least flow very sluggishly. In which case, given your piping scheme, this may be a tough nut to crack and somewhat out of my realm.

Thoughts I'll throw out for the group to kick around, keeping in mind I'm out of my realm here:

1) balance the system somehow (i.e., valves on one or more of the other rad supply pipes) to force more flow through the problem loop. Being careful not to degrade the rads valved that way. Looks like the early rad(s) in the loop would be the candidate(s). At some point, you may introduce sufficient flow restriction that you start really reducing the flow and overworking the circulator. That would not be a good thing.

2) repipe to a reverse return set up and hopefully eliminate the need to balance.

3) put this new loop on it's own zone.

4) undo the added baseboard and put things back the way they were.

If you consider 2 or 3, then it might be worthwhile to redo the near-boiler piping (unless you already did it for the radiant) to have a proper set of headers for supply and return, and move the circs over to the supply side, with the pressure reducing/feed valve and expansion tank connections just upstream from the circs.
 
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Old 11-01-06, 04:47 PM
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I agree that is a lot of piping for that pump, maybe it is near shut-off (a pump term meaning minimal flow) but I'm more inclined at this point to agree that it is most likely a balancing issue.

I would not consider any major repiping to a "reverse return" system although going to a "pumping away" configuration may help. After you bleed the air from your problem baseboard does it collect more air? If yes, then a pumping away configuration is definitely called for.

I don't know how much trouble it would be to install balancing valves on the individual radiator supply or return lines (not both) but if not too difficult that would be my plan of attack. You don't need to restrict the flow a great deal, just enough to make the water flow through the new baseboard.
 
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Old 11-01-06, 07:15 PM
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i do have manual valves at each radiator. by turn some of them off, would that accomplish the same thing as balancing valves?
 
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Old 11-01-06, 07:31 PM
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Radiator valves

Throttling back on the radiator valves should have the same effect.
 
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Old 11-03-06, 07:01 AM
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I have a Taco 007 circulator - giving the amount of pipe I have - do you think that this circ is sufficient? I can never make sense out of those charts that tell how much a circ can handle. What if I just replace my circ with a bigger one for the whole house and kept it one one zone. (can you tell I am trying to avoid, if I can, the repiping necessary to add a zone)
 
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Old 11-03-06, 09:43 AM
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If you want to experiment, get a Grundfos 15-58 superbrute. Has three speeds built in. I think the speed 2 is roughly a 007. Speed 3 is somewhat more oomph.

If you want to size the pump to the load and avoid buying pumps until you find the right one, then let's have an inventory of the footage of straight pipe of each diameter, number of tees and elbows (plus or minus a few) and see if we can figure up a resistance curve. Not exactly as straightforward a calculation as a series loop, but I think it can be done without too much pain and suffering.

Note also bigger pump = more noise, more energy used. It would be good to have the required specs then shop for a good pump.
 
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Old 11-04-06, 09:16 AM
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ok - heres the breakdown of footage of pipe I have:

164' of 1 1/4" black pipe
22 1 1/4" Tees
8 1 1/4" 90 degree elbows

179' of 3/4" copper and black pipe
22 3/4" 45 degree elbows
30 3/4" 90 degree elbows

thanks xiphias for taking the time... it was a cold morning here in NJ!
 
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Old 11-04-06, 11:56 AM
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somewhat educated guesses

For the 1.25" piping, I get a total equivalent length (TEL) of 272 ft. For the 3/4" piping, I get a TEL of 266.75 ft.

I get the following heads (ft) for these flow rates in the 1.25", which are what you want for effective flow and air elimination.

gpm head
8 3.1
9 3.8
10 4.6
12 6.4
14 8.3
16 10.5

and these for the 3/4", which again are what you want for effective flow and air elimination.

gpm head
3.5 6.6
4 8.3
4.5 10.2
5 12.3
6 16.9

I don't have tables for iron piping, so I used copper. Iron probably is slightly more resistant to flow than copper. So these values above are probably minimum.

My guide says you want between 8-16 gpm in the 1.25" piping, and 3.5-6 gpm in the 3/4".

Where my knowledge breaks down is how to determine the total resistance. It's probably more difficult than a simple sum of the two. I was hoping that an old table I have for monoflow tee systems would be helpful, but it isn't really.

Soooooo, I'm going to make a somewhat-educated guess. I would suggest a Grundfos 15-58 Superbrute on speed 2. If you plot each piping diameter independently, you get good flow rates with that pump for each. If you do the likely incorrect simple sum of the TELs and apply the flow rates for the 3/4" piping, you get a head of 13.3 ft at a flow rate of 3.5 gpm. That value plots right on the superbrute curve at speed 2. Speed 2 is a bit more oomph than a Taco 007.

So find one of these pumps and let 'er rip. If that doesn't work, then try speed 3, which is more like the high-head Taco 008 and high-velocity 0010.

If the system used to work ok with a 007 before you added the new piping/baseboard, then speed 2 should give you a bit more than the 007 and perhaps enough to get things flowing right. Failing that, crank it up to speed 3.

Disclaimers:

Not a pro. Little real-world experience. A fair amount of common sense and math ability. And, as one of my favorite captains used to say when we wanted to get dicey at sea "go ahead and do it, I ain't got a dime in her."

Seriously, if this really is a flow problem, and it sounds that way to me, this is a logical thing to try.
 
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Old 11-06-06, 07:23 AM
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thanks for your efforts. Comparing the specs of both the Taco 007 and the Grundflos 15-58, I noticed that the flow rate of the Grundflos is rated 0 - 17 gpm, whereas the flow rate of the Taco is 0 - 20gpm. However, the Head of the Grundflo is 0 - 19ft compared to the Taco at 0 - 11ft. What is Flow Rate and what is Head? I guess I expected that the Flow Rate numbers on the Grundflos would be higher than the Taco. I am just trying to make sense of the numbers.
 
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Old 11-06-06, 07:48 AM
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Flow rate is how much water the pump moves (gallons per minute). Head is the resistance to flow (measured in feet, long story why, has to do with units of measure).

Start on the right of the chart. When head (resistance) is low, flow rate is high (~17-20 gpm). As head increases, the flow rate decreases. It is totally possible to have a piping system with sufficient resistance (high head) that flow drops to near zero.

Over-simplified example: you can easily blow air through a straw in a tall glass of water and displace all the water so air bubbles come out the end. Head (resistance) is low and you supply sufficient flow at that low head to move air through the straw. Try doing that with a 100 foot garden hose. You are the same pump, but now there's so much resistance you can't achieve any flow.

The 007 is a lower-head circulator (11 ft) than the superbrute. At lower resistance, it can (on paper) move water faster. But if you have a lot of resistance, then at head >11 ft, it's not going to move any water. This is called "shut-off head."

You most likely, I think, have sufficient piping resistance that the 007 isn't moving the water fast enough to deliver the heat supplied by the boiler all the way around the house. So you need a higher-head pump. Keeping in mind that I'm partial to Taco stuff (I have three 007s on my system...), the Grundfos in this instance is one-stop shopping. With the selectable speeds (and thereby 3 curves to choose from), you basically have three or four Taco pumps in one. Install it, find the speed that works, and you're done. For "different" styles of system distribution piping like yours, I think this approach makes sense, particularly for DIY applications. If you had a very simple series loop system, then it would be a simple matter to size the pump exactly, in which case I'd probably suggest a Taco or maybe B&G that met the specs.

More info on flow and circ sizing is at

http://www.taco-hvac.com/uploads/FileLibrary/SelectingCirculators.pdf
 
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Old 11-06-06, 08:34 AM
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thanks for the info - i wasn't really sure what Head meant. Thanks for the clarification. I am shopping for the pump and I will report how I make out.
Thanks!
 
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Old 11-12-06, 06:25 PM
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just an update - I got the Grundfos and swapped it out for my Taco and still no heat to the baseboard. My next step is to put this baseboard on its own zone with its own circ (using the Taco that I just took off) mounted on the supply side of the run. My question now is will I have any issues with one circulator being on the return (the Grundfos) and one circulator being on the supply (the Taco)??
 
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Old 11-13-06, 06:41 AM
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Hmmm. Interesting. You put it on speed 2?

Yes, you will probably have problems if you have the circs positioned like that. Pumping in series, basically. If you can't post a picture, can you make a diagram of your piping layout?

You also have a radiant zone? How's that piped?
 
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Old 11-24-06, 04:00 PM
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I have had this problem

Have you checked to make sure nothing is clogging that radiator. I struggled for a while with a problem radiator until I found that a washer for the balancing valve had partially disintegrated and clogged the radiator just enough to restrict flow. Also make sure that the return piping does not make any whaky turns or has no long horizontal run. I bet your problem is something simple and does not requrie redisign.

ONE MORE THING: Make sure there are no abandoned monoflow tees in the main pipe loop. Some times single loop systems get converted and the old monoflow tees just get capped insted of removed. This can cause all kind of flow problems
 
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Old 11-25-06, 12:59 PM
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thanks for everybody's 2 cents. just to close this out, I resolved the problem by closing off everything except the problem baseboard and lo and behold heat arrived at the baseboard. I than began turning the rest of the house back on 1 radiator at a time. I am still not sure if it was an air problem or not, but so far so good. It would be nice to have the upstairs on its own zone, but that project is for another day. Thanks again!
 
 

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