Some Radiators Hot on Top, Cold on Bottom

Ken_40

More accurately, a velocity issue.

If the water lazily arrives at the supply connection, it will have a stronger desire to simply allow the hot supply water to "float" to the top of the rad, rather than push all the cool water along and out the return hole, heating ALL the water rapidly and completely inside the rad.

There are two ways to overcome this (assuming nothing else is "wrong"). First, make sure the valve on cooler rads are wide open. Second, make sure the valves on the hottest rads are slightly closed/restrictive.

The presumption that hot rads will get cold by closing the supply valve just a tad is false. If we divert SOME (not all) the water from the hottest rads, we merely divert it to those with too little.

Once you properly balance the rad valves to balance the entire heating system (and each room as desired) you are done - forever! Or until one of the kids decides to "adjust" it to their liking (;-o)

Some of the assumptions I make are: The circulater is correct for the entire system; that zones (if present) are properly sized and that there is no air in any of the rads. If bleeding is a system normalcy, the circulator may be backwards. Dan's seminal book called, "Pumping Away" would be a problem solver if in fact "contaminating system air" is a cuasitive factor.

Let us know how you make out, please

Sam_16

Radiators hot on top cold on bottom

I have a hot water system with about 20 radiators on three floors. Several of the radiators are hot on the top and cold on the bottom--and full of water. Some of the radiators are hot all the way through--and the third floor units are mostly cool. What might be going on?

Sam_16

> More accurately, a velocity issue.

>

> If the

> water lazily arrives at the supply connection, it

> will have a stronger desire to simply allow the

> hot supply water to "float" to the top of the

> rad, rather than push all the cool water along

> and out the return hole, heating ALL the water

> rapidly and completely inside the rad.

>

> There

> are two ways to overcome this (assuming nothing

> else is "wrong"). First, make sure the valve on

> cooler rads are wide open. Second, make sure the

> valves on the hottest rads are slightly

> closed/restrictive.

>

> The presumption that hot

> rads will get cold by closing the supply valve

> just a tad is false. If we divert SOME (not all)

> the water from the hottest rads, we merely divert

> it to those with too little.

>

> Once you properly

> balance the rad valves to balance the entire

> heating system (and each room as desired) you are

> done - forever! Or until one of the kids decides

> to "adjust" it to their liking (;-o)

>

> Some of

> the assumptions I make are: The circulater is

> correct for the entire system; that zones (if

> present) are properly sized and that there is no

> air in any of the rads. If bleeding is a system

> normalcy, the circulator may be backwards. Dan's

> seminal book called, "Pumping Away" would be a

> problem solver if in fact "contaminating system

> air" is a cuasitive factor.

>

> Let us know how

> you make out, please



Thanks for the ideas.

The circulator on my system is a Taco 007-F3 cartridge circulator that is mounted just above the drain valve on the return line--which is just before the return goes back into the boiler. Looks something like this:
R
TacoR
R

But the writing on the Taco is sideways with the left side on the top.

The boiler says it is a 1983 Burnham P-208-WI with an IBR rating of 165,200 BTU.

I have some occassional air in the 3rd floor radiators--which is sometimes followed by water coming out, and sometimes after the air is gone there is no water.

But the hot on top cold on bottom radiators never bleed anything but water.

Sam_16

Thanks for the ideas.

The circulator on my system is a Taco 007-F3 cartridge circulator that is mounted just above the drain valve on the return line--which is just before the return goes back into the boiler. The flow indicator on the Taco is pointing down into the boiler.

The boiler says it is a 1983 Burnham P-208-WI with an IBR rating of 165,200 BTU.

I have some occassional air in the 3rd floor radiators--which is sometimes followed by water coming out, and sometimes after the air is gone there is no water. The 3rd floor radiators don't get too hot, which has never been an issue because we don't spend too much time up there.

But the hot on top cold on bottom radiators never bleed anything but water.

Any more thoughts would be appreciated.

Ken_40

If you are going to try to fix it

yourself, you must buy Dan;s book: "Pumping Away." He wrote it with your system in mind!

If you aren't going to fix it yourself, use the "Find a Professional" search at the extreme top left of this webpage, and ask the repsonder, "Do you fully comprehend the words, "Pumping Away"? If the responder is unsure or has no clue, move on. You're wasting your time (and his).

Bottom line; you're system is sucking the water through the pipes. Instead, it must "push" the water through. If the circ. suck the water, it also sucks in air. Guess where the air that "leaks in" goes?

Top floor radiation - every time.

Let us know how you make out, please.

Mike T., Swampeast MO

Is the boiler cycling on and off frequently while the thermostat calls for heat?

If so, your circulator may well be defective.

Sam_16

Mike T--Boiler does cycle on and off alot. I am in St. Louis. I have never found anyone around here that is any good with problems. Do you know anyone good?

Ken--I will order the book. In the mean time, are you saying that among other things, the circulator should be on the supply side?

Mike T., Swampeast MO

Does then sound as if the pump has failed--some rads are getting hot and others only hot at the top and others stone cold because all you're getting is uneven gravity circulation.

Try Gaines HVAC Inc., 5120 Northrup (off S. Kingshighway) 314/772-5550

Ken_40

Yes.

Without going into the history of why people put the circulator on the return, the newer, higher head, wet-rotor type you have on your system, especially with a three-story house, is verboten. You MUST put the circ. on the supply.

Without reading the "Pumping Away" book, suffice it to say the vacuum the present location of the circ. causes is what's actually causing air vents, bleeders and components generally designed to se only pressure; are now allowing air to be drawn into your system - instead of the desired "being expelled" action you need.

By re-locating the circulator to "pump away" from the fitting that ties the expansion tank to the boiler and piping array that exists, you force the circulator to "push" the water through the system rather than what's happening now; i.e., "suck" the water around - which also sucks air into the system, and all the attendent "problems" that factor induces.

Among the problems a backwards circulator will induce: The water will be in a slight vacuum, allowing the water to boil at well below the sea level temp of 212F. With a 3-story house, the problem is exacerbated beyong any hope of that NOT happening, by virtue of the need to have at least 16 p.s.i. on the boiler gage, simply to get water to the top floor with zero p.s.i. at that height (and be able to bleed and get all air - and some water (merely to "prove" all air has been bled from the top floor radiation - by witnessing the water squirting out after the all the air having been expelled).

Without knowing exactly how high each floor and the basement ceiling is, I suspect you will need to run your system minimally (when the entire heating system and boiler are at ambient temp.) at 18 p.s.i. to operate properly.

Get that book. The diagrams, fundamental basics and simple designs and solutions shown needs to be completely understood by you, or whoever you select to make it right.

After you re-position the circulator to the correct relationship to the expansion tank, you will never bleed the system again. You won't have to. After making the re-location, you will have to bleed the system once, and never again!

Promise.

sam_18

no luck so far, need ideas on re-piping

Following up, I ordered and read Pumping Away and also similar info from Bell & Gossett's web site. I have called three companies about putting a bigger circulator on the supply. The short version of the responses:

1) I have been doing this 30 years and I put the circulators on the return. You need new radiator valves.(Telephone Call)

2) Agreed it was a velocity problem. Said I should turn down hot radiators. Not interested in putting circulator on supply. Said it be worth it. Might be noisy. Said replumbing would cost thousands. (On Site inspection)

3) My regular plumber said he could do the plumbing, but wasn't qualified to design. Gave me a mechanical contractor to call who said he had never done one that way, but would investigate and get back to me. Hasn't done so yet, but it has only been a couple days (Telephone).

Anyway, here are some pictures of what I have. I do not know what the green thing is and neither did the man who came out. The green thing is on its own branch off a pipe that runs from the supply to the air/water tank.

Suggestions???

And do I need an air separator?

Thanks,

Sam

Steamhead (in transit)

That green thing

is a damper regulator for an old coal-fired boiler. This one was made by the "D&T Engineering Co.". You have an old "D&T Tank-in-Basement" system from the 1920s- this was one of the first to locate the expansion tank in the basement instead of an upstairs closet or attic.

A beam balance was attached to the pivot at the bottom, and was connected to the dampers by chains. Look up at the ceiling joists and you may find some old pulleys that routed the chains to the dampers.

Yes, I'd install an air separator in a Pumping Away configuration. Every hot-water system should have one.

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