[Alketi]

Looking for some advice on a DIY solution to heavy sludge buildup in 6 home radiators (recessed in the wall, circa 1950).

The radiators are hot at the top, and luke-warm to cold moving toward the bottom. It's taking a long time to heat the house.

The standard solution seems to be remove the radiator and flush it with a hose. However, considering the age of the radiators and their weight and the fact it's the winter -- I don't want to go that route yet.

- I'm wondering if draining and refilling the system multiple times will break loose some of the sludge?

- Or if there's another DIY approach that can be tried?

Some pictures of my new boiler and piping. There's a drain valve on the right side. And, a new Fernox magnet trap (installed in October) that doesn't seem to be picking up any sludge -- so either it's not working, or the sludge is not actively moving through the system.

 

[WhatRnsdownhill]

how do you know its sludge in the radiators? did you take on apart to physically see sludge?

 

[Alketi]

how do you know its sludge in the radiators? did you take on apart to physically see sludge?

The radiators are hot at the very top and cold in the middle and bottom, which is a telltale sign of sludge buildup. They're also about 70 years old and are fed with iron pipes. So, yes, I'm making a (mostly warranted) assumption.

Are you suggesting a different diagnosis?

 

[WhatRnsdownhill]

did the radiators ever heat in full with the old boiler?

 

[WhatRnsdownhill]

I have removed big radiators like that and none ever had much sludge in them to block off heat, not that it couldnt happen, but im thinking something else is the issue here..sludge is not metal, so your magnetic trap is not going to do anything..

 

[Alketi]

did the radiators ever heat in full with the old boiler?

Tough to answer. The radiators were so hot on the top with the old oil-fired boiler that I never checked their temperature toward their lower extremities.

So, either the water temperature was so much hotter that I didn't notice the cold spots, or this is a new problem.

The boiler is currently set for 160-170 degrees, I believe -- have to check when I get home. The old boiler might have run at 180. So, at most it'd be a 10-20 degree difference.

I started suspecting a problem when I noticed my thermostat was predicting ~50 minutes to raise the house 1 degree F.

This is my first winter with the new gas boiler.

 

[WhatRnsdownhill]

ok here is a possible problem..the new boiler has no water storage, it heats the water that comes into it and sends it back out, the thermal mass of water in your system and that type of unit werent designed to work together...you might have to get a storage tank to make that system work..its hard to explain...but in a simple way put, that boiler cant make enough hot water to heat those big radiators..

 

[WhatRnsdownhill]

also, is that a combo unit, where you get both hot domestic water and heat from?

 

[Alketi]

Yes, I suppose that's also possible, if the new boiler can't keep up with heating that volume of water -- though I would have expected that the radiators would be more evenly luke-warm rather than hot on the top and literally room temperature at the bottom. No?

Yes -- it also heats hot water, which is held in a storage tank to the right of it. That's what the lower circulator pump drives. The vertical circulator is driving the radiators upstairs.

If I wanted to drain the system, to see if any particulates come out, should I isolate the boiler from the water flush by shutting the two valves underneath it?

 

[WhatRnsdownhill]

when that unit calls to heat domestic water, it shuts down heating the house...as far as the radiators, one would think they would be luke warm, but hydronic heat does some weird stuff, scientific if you want to get deep into it, but I dont think sludge is your problem, and if it is its rock solid in those radiators and not going tobe flushed out, you would have to disconnect the radiators and try flushing with a hose or pressure washer, but again I dont think thats your problem, and not being there to give a one on one look and feel around on the piping..its hard to give a definitive answer.. when you get home, turn the thermostate up to 80 for testing purposes...go around and feel if the water going into the radiators , how hot it is and then leaving the radiators and see how much of a temp drop there is..

 

[Bondo]

The boiler is currently set for 160-170 degrees, I believe -- have to check when I get home. The old boiler might have run at 180. So, at most it'd be a 10-20 degree difference.

Ayuh,.... When it comes to hydronic heatin', That a World of difference,....

Cast iron rads, 'n baseboard rads, need HOT water,.... 180°, or higher,....

In-floor radiant, runs 'bout 150° water,....

I too, doubt it's sludge, as of all the ole cast iron rads I've busted up, 'n scraped, never had a lick of sludge in 'em,....
The only way to clear it would be pull the inlet, 'n outlet fittin's, 'n run a rod through the base passages,...

Turn the aqua-stat up to 180° - 185°, 'n see if ya get an improvement,....

 

[beenthere]

ok here is a possible problem..the new boiler has no water storage, it heats the water that comes into it and sends it back out, the thermal mass of water in your system and that type of unit werent designed to work together...you might have to get a storage tank to make that system work..its hard to explain...but in a simple way put, that boiler cant make enough hot water to heat those big radiators..

I have small tankless boilers like that installed with rads. They heat the rads and house fine.


OP: When the boiler was installed, did they check to see if the rads were getting enough water flow.

 

[Alketi]

Well, after some more investigation I'm happy to report that you were both right. I don't believe sludge is a problem.

My radiators are partially recessed into the wall, and as such have metal vanity covers. Thus, the top of the metal cover is hot, and the middle to bottom is cold. However, upon removing the cover I see that the radiator is basically warm all over.

So ... the top part of the metal cover is being heated by warm rising air, and the lower parts are not catching much convective heat I'm presuming. Happy to report that physics still works.

Thank you for being persistent with your questioning!

My new gas furnace was running about 172 F. I turned it up one click, and will keep an eye on it.

Another form of improvement was that I finally looked closer at how the radiators were balanced, since I have one room that gets excessively hot (close to the furnace, so shortest pipe run I'm assuming) and others that are cool or colder. I turned the flow down in the hot room and turned it up elsewhere and it seems to have made an appreciable difference in the overall comfort level.

Thank you all again.

 

[WhatRnsdownhill]

thats how those convectors are, they pull in cool room air from the bottom and it goes out the top, the heat causes the are to move,they are not called radiators, usually radiators refer to any of the free standing cast iron ones...

 

[Alketi]

The radiator itself is cast iron and free standing.

Just for my own knowledge, would you call this a radiator with a convector cover?

 

[WhatRnsdownhill]

thats a radiator someone made a custom in wall installation...and is trying to make a convector out of it...you would get more heat if ditching that metal cover..

 

[beenthere]

That was done on some upper end homes around here. Gave the home a much nicer inside appearance. Does restrict the heat some what.

Radiators with convection covers as you said.

 

[WhatRnsdownhill]

if you want a radiator thats made to be sunk in the walls, look up sunrad radiators, here is a link to a picture..they are cast iron radiators designed to be sunk into a 2 x 4 wall with only 3/4 inch stick out..http://search.aol.com/aol/imageDeta...C0715E9&oreq=35e601b6f2894abb9f0eaebdc804ec25

 

[beenthere]

His rads have been there and working like that for 60 years. Why spend money on others needlessly.

 

[WhatRnsdownhill]

sunrads at a fraction of the size give off much more heat while making the system more efficient..the op can make his mind up what he wants todo...more options avail to him..