Bleeding hot water radiators - Conflicting instructions

Could not get an answer to this on alt . hvac of all places:

There are many well-intentioned articles on how to bleed your basic hot wat= er radiator heating network.=20

Most recommend bleeding when system is *relatively* cool(is off or hasn't f= ired in a while).=20

Where they differ most is the starting point. =A0Some suggest moving from r= adiators closest to boiler(1st floor) to the farthest(IE 2nd flr). =A0This = site -

formatting link
=A0su= ggests the opposite! =A0=20

Does it matter?=20

Also, I was told that after a good bleed job none of my radiators should ri= ng like bells when knocked on with my fist. =A0Some of mine do, even though= they are evenly heated side-side and top-bottom. =A0Does that indicate tra= pped air bubbles?=20

And how do I remedy those?

Reply to
thekmanrocks
Loading thread data ...

On Sat, 19 Jan 2013 21:16:43 -0800 (PST), snipped-for-privacy@gmail.com wrote:

radiator heating network.

in a while).

radiators closest to boiler(1st floor) to the farthest(IE 2nd flr).  This site

-

formatting link
 suggests the opposite!  

like bells when knocked on with my fist.  Some of mine do, even though they are evenly heated side-side and top-bottom.  Does that indicate trapped air bubbles?

I've had a couple 2 story houses with hot water radiators, and bled them numerous times. No zone control valves. All radiators are connected in a loop to the supply and return headers. What I would call a "basic" systems. One was natural circulation, the other had a circ pump. I've bled cold and hot. Best to do the bleed with the circ pump running, or hot enough to move the water with natural circulation. Trapped air doesn't care about heat, but water circulation aids in moving air to the highest point. When I've done uncirculated fills I always had to redo the bleeding later in the heating season. You want to at least fill and bleed the first level of radiators before you start the boiler to ensure return flow to the water jacket and pump. It goes like this on a fresh fill. Make sure the system is getting feed water. Open the highest rad vent. Use your judgement on watching it for water. I trusted an upstairs tenant to watch it for me once, and the result was stained walls. You don't have open to open the highest vent, but I found I got faster fills with it open. Up to you. Just don't leave it unattended. Test a radiator on the lowest level until it's full. Then do the rest on that level until all are full. Move to the second level and do the same. Then do a final recheck of all radiators, low to high. Sometimes a slug of air eludes you while you move from radiator to radiator. For bleeding a filled and running system, just start low, and move high. Never heard of the "tone" thing. Sound like voodoo. Cast iron isn't very consistent in producing tones. Not the best thermal conductor either, so it's always been easy for me to feel the difference in heat when there's water or air behind it. So if it's as hot at the top as the rest, there's no trapped air. If in doubt, just crack the bleeder to see. I have, and never got air when the top was hot.

Reply to
Vic Smith

Thanks for the steps Vic.

I do have one radiator - the second floor bathroom's - that blows out one t= o two seconds of air before bleeding water, two days after a process simila= r to yours. I'll bleed em again in three weeks, same 1.5sec hiss of air fo= llowed by water. Other radiators up & down piss nothing but water.

Always has for as long as I've occupied the house, before and after a circu= lator was added as part of a boiler replacement 11 yrs ago.

Reply to
thekmanrocks

Those guys are "professionals" and don't want to be bothered by the great unwashed. Biggest bunch of a-holes around

radiator heating network.

in a while).

radiators closest to boiler(1st floor) to the farthest(IE 2nd flr).  This site -

formatting link
 suggests the opposite!  

I'd do it both ways. And then I'd go back in a week and do it again. Air can get trapped in places you'd not expect. Check for evenness of heating when done.

like bells when knocked on with my fist.  Some of mine do, even though they are evenly heated side-side and top-bottom.  Does that indicate trapped air bubbles?

Never heard of that, but it may work.

Reply to
Ed Pawlowski

ater radiator heating network.

fired in a while).

radiators closest to boiler(1st floor) to the farthest(IE 2nd flr). =A0Thi= s site -

formatting link
the opposite!

ring like bells when knocked on with my fist. =A0Some of mine do, even thou= gh they are evenly heated side-side and top-bottom. =A0Does that indicate t= rapped air bubbles?

All a load of bollocks. You can bleed them in any order. Hot or cold. Whether or not they ring like bells is neither here nor there. You may have to repeat the exercise twice if air gets moved around during the operation

If you have to do this more than once a year, you may have a corrosion/ galvanic action problem. Your system needs to be dosed up with a chemical to prevent this. Very important. Especially with the newer systems that may have aluminium/stainless steel components.

Reply to
harry

water radiator heating network.

t fired in a while).

m radiators closest to boiler(1st floor) to the farthest(IE 2nd flr). =A0Th= is site -

formatting link
the opposite!

If he does it one way and then immediately does it the other way, he'll know if it matters or not. If no more air comes out the second time, then he knows doing it the first time got all the air out. Next time he bleeds he can start in the other direction and repeat the process. If he gets no additional air both times, then it doesn't matter. And if he does, he'll know which way works better.

I would think going from closest to the boiler, moving up floors, would be the preferred way. But it may not make much difference either. The question is if the air tends to remain trapped in the radiator, as opposed to easily moving from one to the next.

ring like bells when knocked on with my fist. =A0Some of mine do, even tho= ugh they are evenly heated side-side and top-bottom. =A0Does that indicate = trapped air bubbles?

Reply to
trader4

t water radiator heating network.

n't fired in a while).

rom radiators closest to boiler(1st floor) to the farthest(IE 2nd flr). =A0= This site -

formatting link
the opposite!

ld ring like bells when knocked on with my fist. =A0Some of mine do, even t= hough they are evenly heated side-side and top-bottom. =A0Does that indicat= e trapped air bubbles?

______________

Really appreciate it, guys!

Still, the issue is the hisser in the bathroom on 2nd floor. It's a narrow= , taller unit behind the old claw tub. The whole system is bled to the poi= nt where I haven't hissed air out of any radiators except that one. =20

Is it possible that bathroom unit is at a particular "hot spot" where syste= m air likes to congregate? It never hisses more than 2 seconds before wate= r shoots out, so maybe I'm just over thinking.

Reply to
thekmanrocks

hot water radiator heating network.

asn't fired in a while).

from radiators closest to boiler(1st floor) to the farthest(IE 2nd flr). = =A0This site -

formatting link
the opposite!

ould ring like bells when knocked on with my fist. =A0Some of mine do, even= though they are evenly heated side-side and top-bottom. =A0Does that indic= ate trapped air bubbles?

ow, taller unit behind the old claw tub. The whole system is bled to the p= oint where I haven't hissed air out of any radiators except that one. =20

tem air likes to congregate? It never hisses more than 2 seconds before wa= ter shoots out, so maybe I'm just over thinking. ________________

"Haven't hiss air out of any radiators except that one - IN TWO YEARS"(corr= ection)

Reply to
thekmanrocks

Is there a tank in the radiator that fills with air, before the air fills t= he radiator itself? Because unless that's actually full of air (no water le= ft in it) then there's probably no air in the radiator itself and it's not = that big an issue as it's designed to keep air out of the radiator. So you = wouldn't need to bleed that often. Just enough to keep that from completely= filling with air (empty of water).

I'd bleed when cold because any minor benefit (if any) of bleeding hot is m= ore than counterbalanced by the annoyance/danger of burning yourself.

As far as the order? If you're bleeding when cold there's nothing circulati= ng so it probably makes no difference.

Modern systems have a small valve in the basement that releases any trapped= air so there's no need to bleed them (my house doesn't have a bleed valve = in the baseboard radiators)- don't know if it's possible to install that in= an older system (or whether it'd be worth the expense).

Reply to
missingchild

the radiator itself? Because unless that's actually full of air (no water = left in it) then there's probably no air in the radiator itself and it's no= t that big an issue as it's designed to keep air out of the radiator. So yo= u wouldn't need to bleed that often. Just enough to keep that from complete= ly filling with air (empty of water).

more than counterbalanced by the annoyance/danger of burning yourself.

ting so it probably makes no difference.

ed air so there's no need to bleed them (my house doesn't have a bleed valv= e in the baseboard radiators)- don't know if it's possible to install that = in an older system (or whether it'd be worth the expense). _______________________

Nope. Plain boring York units from the late '20s:

formatting link
No speci= al tanks or other features. Bleeds with classic
formatting link
key.

As far as a global bleeder valve in the basement, wouldn't know where that = is. Home had new Burnham V8 installed 11 years ago along with circ.

The bathroom rad does get hot, for sure, so I think a 1 and a half second h= iss from one radiator after monthly bleeding a houseful is no big deal.

Yes, I do bleed cold(or lukewarm!) and I start in the kitchen(closest run f= rom boiler), work my way around the 1st floor, then upstairs.

Reply to
thekmanrocks

Bleeder valve would be a small can with a small nipple sticking up, if you = google it you'll find all sorts of pictures. In my house there was air in t= he system because somebody screwed the nipple back down so it wouldn't let = air out. Took about four or five plumbers before one guy said "Here's your = problem" after a bunch of earlier ones kept telling me to empty and refill = the system, that there was no way to bleed it.

Reply to
missingchild

u google it you'll find all sorts of pictures. In my house there was air in= the system because somebody screwed the nipple back down so it wouldn't le= t air out. Took about four or five plumbers before one guy said "Here's you= r problem" after a bunch of earlier ones kept telling me to empty and refil= l the system, that there was no way to bleed it.

__________________

Help!!!

formatting link
!

Reply to
thekmanrocks

to two seconds of air before bleeding water, two days after a process simi= lar to yours. =A0I'll bleed em again in three weeks, same 1.5sec hiss of ai= r followed by water. =A0Other radiators up & down piss nothing but water.

culator was added as part of a boiler replacement 11 yrs ago.

It's not actually air. It is hydrogen gas left over from the corrosion going on in your system.

formatting link

Reply to
harry

The air scoop might be it- leave it alone (unsnug) and watch it, and if no more water shoots out, that may solve your problem (it solved mine, although my baseboard radiators don't have bleeder valves).

Reply to
missingchild

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.