half rads are cold


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Old 05-15-06, 06:09 PM
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half rads are cold

I just bought a 100 year old house. It has a hot water radiator system. one of the pipes that comes out of the furnace is hot. it splits to feed four rads. 3 out of the four are cold. 2 are on first and 2 are on second. The one that is hot is on the second. I have opened the bleeder on the 3 that aren't heating and water comes out. Why is no heat coming out?
What do I need to do to get heat to these?
 
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Old 05-16-06, 01:07 PM
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Cold Rads

Sometimes it takes considerable bleeding to get the air out. Also check any inline valves to make sure they are open. Water can back feed thru the return & make you think the air is out when it really is not. The same thing can happen if a valve on the supply is closed. Try bleeding the air with the circulator off first. If that doesn't work try with the circulator on. It's strange but some systems bleed better with the circ on & others with it off.
 
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Old 05-22-06, 06:32 AM
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Thanks for getting back to me Grady. I finally got a chance to try what you suggested and was able to get heat to my bedroom, but I also had to increase psi as it was down to 9. I raised it to 14 and I checked it the next day and it was at 12. So from all that I read it sounds like a leak. But since I don't see water coming from any radiator, how do you determine where it is coming from?

Thanks again.
 
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Old 05-22-06, 12:48 PM
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Depending on when you check the pressure (when it's hot, cold, running, not), and how the system is pumped (e.g., pumping away from the expansion tank vs. not), and where your circulator and expansion tank are in relation to the gauge, you might see 3-5 psig pressure changes just in the normal operation of the system.

So maybe not a leak, just normal pressure wanderings (and keep in mind these gauges are not terribly sophisticated measuring devices). "Normal" pressure for a 2-story house is 12 psig.

For the moment, I'd go with the assumption that there is no leak and that the rads that aren't warming are air-bound. In which case you need to keep bleeding. And it sounds like you have a monoflow-tee (aka diverter tee) type system. Those can be tough to purge.

That said, the way your system is pumped can also make bleeding easy or difficult. If further bleeding and checking the system per Grady's suggestions don't improve the situation, then I'd look at how the system is set up. We can get into that at the appropriate time.
 
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Old 05-24-06, 05:45 AM
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Thanks xiphias. It was a little chilly here in CT last night so I got a chance to turn on the heat and see if our bedroom got heated and it worked. The pressure was still at 12psi however, it took the longest to heat up. It is though the farthest from the furnace. The system is not a loop. Let's see if I can explain this accuratly and hopefully you will know what I mean. The line out of the furnace T's off and then T's off again to feed four radiators total. There is another line out that does the same but feeds three rads.
I would think that if it was a loop then the farthest would be the last to heat up. But with the T'ing off wouldn't that not be a big factor?
Also the shutoff on my rad is broken off. Since it is upstairs can the system be drained down enough to replace it. I assume I would need to shutoff a valve so water is continuosly running through it, but which? The main line in from the street?

Sorry for being so ignorant. I am very handy, and like to take care of as much as I can, but I am new to this stuff and am not strong in the plumbing area.
Thanks again for all the help.
 
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Old 05-24-06, 07:23 AM
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Sort of sounds like a gravity system, or maybe a mono-flow (diverter) tee system, but this is definitely not my strong suit. Grady can likely tell you from what you described.

How are the returns piped? What are the diameters of the major pipes?

Is there a circulator pump on this system?

Check out the diagrams at this site for gravity and diverter-tee systems. See if one looks like yours.

http://www.heatinghelp.com/heating_qa.cfm

There's also some tips about care, feeding, draining, and venting of these kinds of systems.

Let's figure out what kind of system you've got and then see about fixing the heat distribution problem and the broken shut-off valve.
 
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Old 05-24-06, 10:50 AM
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I am pretty sure it is the gravity system because during inspection we went to the attic and there was the old expansion tank sitting there. But it has been upgraded since then and there are two tanks in the basement and I think the circulator pump is installed on the return line, not home at the moment to verify. The pipes are like 2-3" dia. Again not home to verify.
The returns are just like the output lines, t'd off. If memory serves me right I believe there is one return line.
 
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Old 05-24-06, 02:40 PM
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Cold Rads

mzup:

This sounds like a converted HW gravity system; this could be a really tough nut to crack, especially if you're new to the house & unfamiliar with the heating system's quirks.

If you could draw a basic diagram of the boiler & its piping system with all the Tee-offs & how the risers are connected to the rads & post it via Paintbucket, or others, it would be a great help.

It might be worthwhile to talk to the previous owner, or current/past service tech who has worked on the system to get an idea how long it's been like this; it may be well worth the $50 service call (if you have no current service contract) to get a tech in there who is familiar with HW systems; you can consult the Yellow Pages under "Heating Eqquipment & call several parts houses & talk to the couuntermen & ask them to refer someone who has a lot of hydronic experience.

Sometimes when a HW system is converted from gravity to forced HW, the circulator pump installed has inadequate head to push the high volume of water thru the piping; the piping that was installed may be just allowing the hot water to short-circuit & not pass thru the rads.

There should be BALANCING VALVES installed in the mains near the boiler, as well as a purge valve near the circulator pump to purge the air out of the system.

Cold rads can be caused by either AIR PROBLEMS or FLOW PROBLEMS, & it often takes getting an experienced crackerjack hydronics tech in there to size up & sort out the problem & come up with a solution; a good tech can install balancing valves, a purge valve & re-arrange any piping necessary in a very short time & get you back in business.

Meanwhile, if you have access from the cellar/boiler room to the different pipes that make up the mains, & the supply/return risers, feel with your hand to see which ones are hot & which are cold, to try & figure out which way the water is flowing inside the pipes.

As Grady & Xiphias have noted, go to the Heating Help site & check the diagrams on the "diverter tee pipe water heating", and the "Loop hot water pipe heating"; also read the text by Dan Holohan on how water flows thru pipes & takes the path of least resistance under different conditions.

http://www.heatinghelp.com/heating_qa.cfm
 
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Old 05-25-06, 10:18 AM
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Here's a website with pics of system.

http://65.84.181.66/mzup/furnace/

Main issue now is just the shutoffs at the radiators and balancing the heat.

I was thinking of calling someone in in June but would like to know a little bit more so that they don't rip me off when I sound like I don't know what's going on.
 
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Old 05-25-06, 12:03 PM
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Neat stuff. It does appear to be a gravity conversion. These are interesting systems and as Jack Horner says, can be a tough nut to crack. There are people in the Northeast who specialize (i.e., they have an expertise built from years of study and working with these systems) in gravity and gravity conversions. The best resource to find someone good would be to use heatinghelp.com's Find A Professional service. IMHO, it would be worth the cost of a service call from a top-shelf heating specialist to look over your system, help you understand it, address the current problem, and talk about its future.

I hear you about the potential for dealing with poor pros. I have a totally plain vanilla series-loop baseboard heating system, and the number of "professionals" who failed to identify and correct a relatively simple problem I had last winter was astounding. Much money and time wasted, lots of stress, etc. Point being that you have a system that is anything but vanilla, and you should really get a good pro to look at it.

If you plan on staying in the house for a while, it might also be quite cost-effective to replace the boiler. (e.g., return on investment <6-10 yr). Of course if you just bought the place, you might be cash-poor right now.... Just something to think about.

Would be helpful to also have a pic of the back of the boiler where the pumps and supply/return lines are.
 
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Old 05-25-06, 06:32 PM
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Added pic of back. Only plan on being here 2-3 years if all goes right. While down stairs I noticed a wet spot under a pipe. It is from the radiator on first floor in living room. I had tried to turn that off before and didn't notice it leaking. It is a slow leak and is not lowering pressure but looks like another shutoff that needs changing. It would probably be wise to replace all, wouldn't you think?
I do plan on calling someone so I wait and see what happens then.
 
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Old 05-26-06, 06:33 AM
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The gray one appears to be your heating circ. The green Taco looks like it serves the water heater.

Depending on the amount of dripping the leak may or may not be causing a pressure drop. 1566 shows your autofill valve (blue tag). If the red gate valve below it is open, then the autofill should be adding make-up water to compensate for the leak. Long-term, that's not good for your system. Constantly adding new oxygen-rich water leads to corrosion. If the red gate valve is closed, then over time you'd see a slow pressure drop. If you don't have a low-water cutoff (I don't see one), then this could potentially allow your system to empty. At which point bad things happen....

Could also be your gauge is bad. You could check the system pressure using a tire gauge on the expansion tanks. Should be a shrader-type valve (like a car tire) on the bottom. Gauge and tank should read close to the same.

Agree. Get a good service guy over there to evaluate, suggest what to replace, etc.
 
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Old 05-26-06, 09:46 AM
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What I did earlier to increase pressure was to lift the lever on that auto fill valve. So that says the red valve is open. Was that the right thing to do?
Since then though the pressure hasn't dropped. And I was able to stop the leak by tightening the shutoff.

Thanks for all your help. After I get someone in here I will probably be back asking more questions.
 
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Old 05-26-06, 10:52 AM
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Yes. Good luck.
 
 

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