Poor Heat Flow in HWBB zones


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Old 02-05-07, 06:50 AM
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Poor Heat Flow in HWBB zones

Hi there.

I have a house with a 2-zone HWBB heat system. Each zone has a run of maybe 100 feet each, covering about 600 sq ft.

Recently I've begun to notice a distinct drop-off in heat from one end of my home to the other. On the end closer to the beginning of the run, the temp is higher than the end close to the end of the run. The difference is about 10 degrees.

I can set the thermostats to super-high to force the zones to call for heat, but the boiler doesn't seem to kick-on. In fact, when I look at the boiler temp while these zones are open the temp hardly changes.

So it seems like the flow in each zone is below-par. I have to believe that the boiler temp would drop if the zones were flowing freely, and thus it would turn on.

Can someone help me diagnose the problem? How can I test to find out what's hindering my zone flow?

Thanks in advance for your help!
 
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Old 02-05-07, 12:17 PM
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Make sure the boiler is HOT!! I made this mistake on my 1st house. It needs to be 190 F ? 200 F ??? Maybe Grady can comment. But if it's been dialed down to 150 or so, it won't heat the house. You need the DELTA T to make it work!

Other than that, bleed your registers. They won't work if they're air-bound.

Stick
 
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Old 02-05-07, 12:46 PM
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I don't know if my boiler has ever been that hot. It's always been at 160 or so. I think this may be because my boiler also provides my house with on-demand hot water (no water heater in my house), but I'm not sure.

I'd love to be able to determine if my problem is the circ pump or a massive case of being air-bound. If people will mention some tests I can do, that'd be really helpful.
 
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Old 02-05-07, 01:37 PM
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Is it colder out than normal? What I'm hearing is that you have two loops of HWBB and the water temps at the end of the loops are much lower than at the start.

If you don't mind a pretty simplistic analogy your boiler is a heat factory and has highways that it uses to supply its customers with heat on a first come first served basis. The water carries the BTUs and the HWBB unloads them.

If it's colder out, HWBB #1 will be grabbing that much more heat as the water comes by thereby leaving that much more for the others. That's a function of it being a loop.

That said, if your circ is older and the impellors on the pump not quite what they used to be, then the water will b moving around the loop that much slower. In doing so, it gives the first HWBBs that much more time to extract more heat, leaving less for the next in line.

If it's the pump, replace it. If it's just the cold, then perhaps you could temporarily wrap some of the basebaord near the front of the loop with tin foil so that the water finds it harder to let off as many BTUs as it flows through.
 
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Old 02-05-07, 02:03 PM
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Hi Who. Thanks for the reply.

I understand what you're saying about the first radiators in the loop using up all the heat and thus the last radiator ends up at room temperature. I'm sure this is in fact happening.

What confuses me is that my thermostat is calling for heat, and if the water is at 60 degrees by the time it returns to the boiler, why wouldn't the boiler's temperature decrease (and thus cause the boiler to turn-on)? That's the
stickler.

I need to examine the possibility that I'm actually getting NO circulation at all, and that the heat of the air in the pipes is what's keeping my house warm (again, these are really short runs, so that is possible).

I wish there was a way to know whether my circ pump was running or if it was broken. Anyone have a tip for me?

Thanks again to all!
 
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Old 02-05-07, 07:11 PM
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If you are putting 160* water into the loop, and it's coming back at 60*, I am thinking like you that your circs aren't circ'ing at all.

Do you have and know how to use a multi-meter ?

The heat you are getting in the house is from "thermo-siphon" or "gravity" flow. Hot water being less dense (lighter) than cold water will flow upward, and the cold water in the pipes will flow downward, so you will get some circulation and some heat.

What kind of boiler? fuel ? (gas,oil) ... is there only one circulator with zone valves, or do you have more than one circ ?
 
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Old 02-06-07, 04:14 AM
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NJ:

That confirms my fears I guess. I've been suspecting the pump or an air block for some time now. Let's hear it for gravity!

I have an oil burner with 2 zones. I "inherited" everything from the prior owner of the house, but the boiler looks to be 5 years old at the most. The house is about 30 years old though.

Here are two pics of the boiler:

http://www.dpsw.net/temp/picture3.jpg
http://www.dpsw.net/temp/picture2.jpg

I know how to use a multimeter and have access to one. Tell me what
to measure and where.

Thanks very very much for your help!
 
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Old 02-06-07, 12:53 PM
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If you listen closely to pipes the pipes away from the circ you should normally hear flow.

Air is usually the problem. You should learn how to bleed/purge your system.
 
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Old 02-06-07, 01:29 PM
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Thanks again, Who.

I'm ready to learn how to purge my system. Do you have any information for me on how to do this? The pics I listed in my last post should give you all the specifics on my boiler.
 
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Old 02-07-07, 01:05 PM
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dpsw, I have bleeders so I'm the wrong person to ask. The hose bibs above your zone valves look to me like they'd be where you'd purge.
 
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Old 02-07-07, 02:41 PM
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WARNING 120VAC present! Excercise due caution!

Turn off power to boiler.

Remove the cover from that gray box on the front of the boiler (that's your aquastat), there should be two terminals in there marked C1 and C2 . That's where your circulator power is coming from.

Set the meter to measure AC VOLTS (use proper scale to measure 120VAC).
Connect meter to C1 and C2.

Restore power to boiler, and force heat call by turning up thermostat.

You should see 120VAC on the meter.

If you don't, you _could_ have a bad control.

If you DO, the problem is either the wiring to the circ, or the circ itself.

OR... maybe the circ IS running but not circulating due to air block.
 
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Old 02-10-07, 04:52 PM
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Trooper, et al.:

Thanks to everyone for helping me out. It turns out the problem was a
dead circulator pump relay switch on my controller. Once NJ suggested
that I could have a controller problem, I just gave-in and brought in a
pro. I'm glad I did, too, because the heat is SO GOOD now!

Thanks again, everyone!
 
 

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