hydronic circulating pump and TRVs

Crunch

cool line

Or maybe you were referring to the cool line that used to be hot a decade or so ago.

 

Wish we had a valve to check!  If there is one, it's behind sheetrock somewhere, and I have no idea where.

 

I think you and some others mentioned the possibility of a contractor doing something.  Not likely, but possible.  The apartment at the bottom of that line has had a lot of work done over the years, and who knows what might have been altered.

  

I think we'll wait until the system is running and then take our IR gun and see if we can isolate where the problem seems to be coming from.  We get heat on that line on all floors at all radiators, just not enough of it.

 

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Crunch

pex

Rob,

 

Haven't been able to find a definite answer.  One group indicates that it can't be used for potable water in NYC but can be used in heating applications that don't go over 180 degrees.  Another group says it can't be used at all because rats can chew through it. 

 

I'll keep digging.

 

Crunch

Crunch

Pex is okay

Rob,

 

Definitively found the NYC code.  They have a whole section on hydronic piping.  Pex is allowed for non-potable use so long as it meets ASTM F876/877, which I assume most Pex would.  ASTM F876/877 is where the 180 degree requirement comes from.  We might occassionally get up above this when it is really cold and the boiler is firing at 200 degrees, but it might be below 180 by the time it gets to the radiators.

 

Mark, thoughts on this?  MIght it be a better bypass pipe?

 

Crunch

Mark Eatherton

Pumps and stuff...

To the best of my knowledge, B&G doesn't make a check flange for that series of pump. If you can't see a check, then its probably not checked, which means if only one pump is running, the OFF cycle pump has to be isolated with a valve, otherwise the OFF cycle pump will act as a bypass and will "turbine" running backwards.



Pumps operated in parallel double (approximately) the flow rate. Pressure generated remains (approx) the same. Pumps in series doubles the pressure differential. Flow remains the same (approx).



If it use to work before, something has changed (sound familiar?) and needs to be changed back. Due to the bypass requirements of your baseboard, the TRV's will not address any hydraulic imbalances. It will keep the rooms from over heating, but not under heating. The additional increase in pressure drop may or may not be an issue, and you won't know until you try it. If at any point in time you need to drain the system, THEN would be an ideal time to add a good accurate pressure gage on the pump so you can read its differential. At that point, you'd be able to at least establish a semblance of a "system performance curve" for that given weather condition, and would be in a better position to determine how much more pump you need. Pumps whine under a lot of different conditions. No one has asked this yet, and we've not seen enough pictures of your system to say whether its right or not, but the pumps MUST pump away from the expansion tanks connection to the system piping.



When the flow rate doubles, the static pressure doesn't decrease. The pressure DIFFERENTIAL increases due to the additional friction drop associated with increased flow of water. You'll still have good pressure at the top of the system, assuming your pumps are pumping away from the expansion tank.



Dead center alignment is to avoid affecting the convective currents going upward through the finned tube section of the convector. That's what strips the heat from the fins and adds it to the air passing through the convector. Doing so (blocking air flow patterns) could significantly affect the output of the baseboard, which may or may not be an issue..



ME

Crunch

Pumps

Mark,

 

Thanks.  Been busy and haven't been back here recently. 

Will be going away this weekend for a few weeks.

 

We don't know what changed on that cool line.  It was apparently about a decade ago.  Unless we can pinpoint it with an IR gun, we'll have to rip up a lot of sheetrock and make a mess of people's apartments otherwise.  We have no valves, balancing or otherwise, anywhere on the system.  Zip, nada, none, unless they're buried under sheetrock.

 

Not looking for the TRVs to address any hydraulic imbalances.  Right now, we're chasing hotspots, and these couple of hot apartments are next on the list, after we got the ODR working correctly last winter.  Two pressure gauges, right?  on either side of the pump?

 

For what it is worth, Oventrop said much the same thing about the pump, but added that they're usually oversized.  It won't be real accurate, but I should try to sketch out the known feet of pipe that we do have.

 

Pumps are pumping away from the expansion tank.  I do have some pictures, but don't remember how good they are as to the pumps.  If they are, I'll post them.

 

Aha!  Now I see why you say dead center.  Got it, thanks!

 

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Crunch

Pics

Mark,

 

Here are two not so good pics of the pumps.  Pic #1 shows the pump on the floor, which ran the first half of the winter but was shut off for the 2nd half.  Both isolation valves are off.  You can just glimpse the bottom of the B&G expansion tank at the right of the picture.

 

You can just barely see the 2nd pump at the top of the next pic, way in the background, above the expansion tank.  This pump is the new one we installed this winter.  You should be able to pick out the two isolation valves.

 

Don't know if you can make out the piping adequately, but the hot water feeds into the pumps from the pipe partically buried in the wall in the background, to the left of the bottom flange of the old B&G air separator.  It splits at a Tee and goes to either of the pumps.  Comes around again and joins up at another Tee in the foreground sort of just behind and obscured by that vent pipe that hangs off the backflow preventer.  When it comes off this tee it disappears into the ceiling.  Don't know where it goes after it disappears behind the ceiling sheetrock.

 

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Crunch

order fouled up

The pic in the previous post is actually pic #2.  Attached here is what is described as pic #1.

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Crunch

Eureka from a newbie, I think

Was reading a pub last night from B&G "Zoning Made Easy" that briefly mentioned the installation of bypass piping and a trv on a series loop of radiators, much the same as Danfoss mentions at http://na.heating.danfoss.com/PCMPDF/Se ... GWA122.pdf. The thing that always perplexed me about the Danfoss layout was that they recommended that the bypass pipe be 1 size smaller than the finned pipe, typically meaning the finned tube is 3/4 inch and the bypass is 1/2 inch.



B&G explains this a bit. The higher resistance encountered by trying to go down the 1/2 inch tube means that the water will naturally flow down the finned tube and through the TRV provided the TRV is open and is not of higher resistance than the 1/2 inch tube. As the TRV closes, the water will be forced down the 1/2 inch tube to bypass that radiator. Very clever and completely eliminates the need for any type of 3 way valve.



What B&G goes on to say, and Danfoss doesn't, is that the flow down the 1/2 inch tube will be less than half of what it would be if it were going down a 3/4 inch tube and the water bypassing and going to some of the other radiators in the loop via that bypass tube will now be too cool to do any good. Other radiators down the line might be big duds.



Elsewhere in the pub, they mention that 1/2 inch pipe is good for about 25 feet of total radiation and 3/4 inch pipe is good for 67 feet. We'd have about 45 feet on each loop, so 1/2 inch bypass pipe won't work for us.



Have I got this basically correct, or am I missing something? We haven't done anything yet, and I'm inclined to stick with 3/4 inch pipe and 3 way valves, except perhaps the last radiator on the loop.



Crunch