Poor heat from radiators


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Old 10-04-10, 03:39 PM
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Poor heat from radiators

Hey Guys,

I just went through and bled out all the radiators, checked the pressure in the boiler, and fired up the heat as per my previous thread on LOW FURNACE PSI. I get warmth to all my radiators, but they just don't do a good job at heating up the house.

Here are the basics.

1940s Cape
Weil Mclain gas fired boiler about 8-10 years old.
Upgraded plumbing in the basement to copper, 3/4" which then connect to the old 1/2" branch lines, one-pipe system with monoflow T's on the branch inlet only, regular T's at the branch return...
3 zone (basement, 1st and 2nd)
Old in-wall 1940s radiators with fins (I think these are the problem)
Aquastat is at ~190.
Poor insulation in the house (blown in cellulose in some??? of the exterior walls and in the attic crawl space)

The house was updated a few years back and some of the rads were exchanged for finned baseboard. They put out decent heat.

The problem is that the rooms with the older rads just struggle to get up to temp...

I know this is vague, but is there a way to increase the heat output of the system?

Thanks Guys,

Bryan
 
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Old 10-04-10, 04:31 PM
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Fin-tube baseboards heat up fast - but not so for big, old radiators. But the radiators keep emitting long later.

You may need to set up your controls for a longer runtime in some zones. You can tweak the heat-anticipator settings on the thermostat controlling the zones needing a longer runtime.
 

Last edited by Mike Speed 30; 10-04-10 at 06:50 PM.
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Old 10-04-10, 06:53 PM
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Problem is I only have the finned baseboard in 2 locations... The show me that I have hot water getting to the rads, but the old rads just don't pump out much heat.

The are not the bog solid rads, but rather smaller finned rads inside the wall with a cover flush with the wall surface. The inside of the rad compartment is metal... Just seems heat transfer sucks from the old rads...

Thoughts?
 
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Old 10-04-10, 07:03 PM
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Photos of your system might help us understand what might be going on.

Older cast-iron baseboards with internal fins are seldom a problem. Your aquastat is set at 190 deg? What does the boiler themostat say?
 
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Old 10-04-10, 07:10 PM
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Convector cabinets

Bryan, I'm willing to bet those old convectors are all clogged up with dust between the fins. Take the front cover off and put a flashlight under, and look down... how much light do you see?

When we moved into this crib, which had previously been inhabited by more cats than humans, I was absolutely astounded at the amount of heat they put out after they were cleaned.

It ain't easy, and it's VERY messy... vacuum cleaner don't work for beans... you can't find a brush that gets between the fins... here comes the messy part... COMPRESSED AIR... what I found worked best was running the air nozzle in short bursts, with the shop vac running underneath. You will be vacuuming like crazy when yer done, dust everywhere... you might be able to get creative with plastic sheeting and keep most of the dust inside the plastic sheet... I have been tempted to try something like spraying windex between the fins to wet the dust down and catching it with old towels and such... experiment... wear old clothes!

Monoflo systems can be troublesome to bleed, so make sure all the air is out of them. With all fresh water in the system, you will probably have to do this several times in the next couple months.
 
 

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