Cast iron vs flat panel rads

Users who are viewing this thread

Nanker Phelge

New Member
Messages
16
Reaction score
0
Points
1
Location
Ontario
I am leaning toward going with new cast iron rads over newer flat panel style. I really dig the antique look of the cast iron, and although i have been googling high and lo, I can't much of a price difference. I am looking for used rads which would make cast iron all the more an attractive option, but with no luck sofar I am prepared to buy new.

So esthetically and price-wise it's the cast iron rads hands down. Is there any practicle downside I might be overlooking going with cast iron over flat panel rads?
 

Dana

In the trades
Messages
7,889
Reaction score
509
Points
113
Location
01609
Nope, no downside at all except for a (very) short lag time getting up to temp from a deep setback. Cast iron is just as comfortable, and the thermal mass helps suppress short cycling.

I guess the other practical downside is that to run the boiler at condensing temps in low performance houses may take some mighty big & hefty rads. That's not too much of a problem if your girlfriend is an Olympic weightlifter though. :)
 

WorthFlorida

Clinical Trail on a Cancer Drug Started 1/31/24. ☹
Messages
5,727
Solutions
1
Reaction score
982
Points
113
Location
Orlando, Florida
With used cast iron you have no idea how old they are and what might be the condition of the iron inside the rad. There are outfits that restore old cast iron radiators but they can get pricy. Even though they usually will last forever, old cost iron can have a crack or leak. They take a lot of cleaning and repainting. Very old units were from the days of steam heat so some might need to be converted for hot water. All doable but the price starts to climb. So go with the new iron.
 

Nanker Phelge

New Member
Messages
16
Reaction score
0
Points
1
Location
Ontario
Ok, so we are just about there (I hope). Our house has a main and lower level that requires heating. I was originally and I am still planning to treat both spaces as separate zones. I am thinking at this point to use (new) cast iron rads on the main floor, where 95% of our time is spent, both living and sleeping, and cheaper copper tube and fin base boards on the lower level. So far so good I hope.

I wonder though whether on the main level I can get away with installing three cast iron rads in the main living space (combined dining, living rooms and kitchen with adjacent sunroom) and install copper tube and fin baseboards in each of the two bedrooms. This would again be driven as a cost saving effort. We love the aesthetic appearance as well as heat possibilities cast iron rads offer, but our reality is that installing cast iron throughout the house is cost prohibitive at this point. Therefore we thought cast iron in the living space in which we spend the bulk of our waking time, and cheaper copper tube baseboards everywhere else seems like a decent compromise.

The problem it seems, however, is that the copper tube baseboards heat up at a much faster rate than the cast iron rads, likely bringing a room up to temperature before the cast irons can ever heat up properly to be effective. But if the bedroom doors are kept closed then perhaps this conflict might be averted or at least minimized? If so, then I wonder if perhaps the living space with cast iron rads on the main level should be considered and treated (fed) as a separate zone from the bedrooms?
 

WorthFlorida

Clinical Trail on a Cancer Drug Started 1/31/24. ☹
Messages
5,727
Solutions
1
Reaction score
982
Points
113
Location
Orlando, Florida
... I wonder if perhaps the living space with cast iron rads on the main level should be considered and treated (fed) as a separate zone from the bedrooms?

When you state separate zones, do you or can you install a separate circulation pump for these "zones"? If you can then it be OK since you can get your comfort by tweaking the thermostats. A big BUT is how are your floors separated. are there doors between the floors or just one big open stair case. Remember the first thing you learned in 3rd grade science glass, heat rises. As you are trying to heat the first floor, all that nice warm air rises and the cold air from above drops.

Here one reason cast iron radiators are more comfortable over baseboard heating. Baseboards give off far less infrared since most of the heat is absorbed by the air.

Radiant heaters From http://radiatorsuk.com/g/33364/heating-guide.html

Radiant heaters work by heating infrared rays, which are then radiated out and absorbed by surrounding objects like, for example, floors, furniture or people. The increased temperature of these objects then heats the air surrounding them - and as floors absorb the heat, you'll find these kinds of heaters create warmer floor-level temperatures than many others.
 

Nanker Phelge

New Member
Messages
16
Reaction score
0
Points
1
Location
Ontario
When you state separate zones, do you or can you install a separate circulation pump for these "zones"?
Now that we are just about ready to purchase a boiler and heat emitters, I am starting to consider the nuts and bolts of how it will go together. I imagine at this point that the boiler out and return will feed into hot and cold manifolds supplying the 2 or 3 zones, each with its own pump.

I am sold on the system design detailed on page 28 of Grundfos Hydronic (PDF) Handbook found at this url: smartgreenbuild.com/blog/download/414/

As you are trying to heat the first floor, all that nice warm air rises and the cold air from above drops.
Our main floor is in fact the upper level. So our biggest concern in that department then, is heat loss through the roof.

A big BUT is how are your floors separated. are there doors between the floors or just one big open stair case.
We don't currently have doors separating the floors connected via the staircase. Probably unnecessarily, we did put a heavy double curtain on the upstairs doorway to the stairs leading downstairs. Although heat rises, we thought it couldn't hurt since we keep the downstairs area ~10 degrees colder in winter just because there are no living activities occurring downstairs at present beyond laundry activities.
 
Last edited:

WorthFlorida

Clinical Trail on a Cancer Drug Started 1/31/24. ☹
Messages
5,727
Solutions
1
Reaction score
982
Points
113
Location
Orlando, Florida
The more I read it sounds like you are going to install the new boiler and rads? It's tricky to install and not as easy as you might think. Incorrect install will void any warranty plus it can be dangerous. Please tell me your having all the work done by a licensed heating contractor.
 

Nanker Phelge

New Member
Messages
16
Reaction score
0
Points
1
Location
Ontario
The more I read it sounds like you are going to install the new boiler and rads? It's tricky to install and not as easy as you might think.
I am planning to perform as much of the equipment install as I feel appropriate. I will buy the boiler, manifolds, air separator, expansion tank, backflow preventor, circulators, hose bib/boiler drains and install them adjacent to the wall on which my NGas manifold is mounted. I will buy the PEX and run them from the manifold circulators to where the rads will be mounted.

I have a licensed NGas tech lined up to do the gas hook up to the boiler, and a plumber lined up to perform all copper connections required between components.

I can appreciate the complexities involved and that is the reason I have and continue to spend a great deal of time working out all the details unique to our house. I have extensive experience installing and testing equipment for a profession, in addition to spending several years as a quality auditor that has made me quite anal that equipment be installed properly, albeit not in the plumbing field. So I do feel mechanically confident to perform the equipment installation detailed above with little trouble.

Incorrect install will void any warranty
I have read online about enough instances in which people have had equipment, generally the newer mod con boilers, incorrectly installed by a "licensed" HVAC tech. So although I readily admit such occurrences are surely not common, the fact they do occur suggests that work performed by "licensed" HVAC tech does not necessarily guarantee a proper installation.

I hope that by having a licensed gas tech perform the gas hook up and tests, and a plumber perform the copper work in and around the boiler that the warranty requirements will be satisfied. If not, I have come to terms with the fact my boiler may well not be covered by warranty. But I have never based any buying decision on the guarantee of a warranty, since I know getting warranty work done often times is akin to pulling teeth. So if I do in fact void the boiler warranty in the process of doing what I feel will be my own meticulous work, then "c'est la vie."
 

Dana

In the trades
Messages
7,889
Reaction score
509
Points
113
Location
01609
In most systems today you'd be better off with one ECM drive "smart pump" operating in constant-pressure mode with zone valves on the radiation than separate low-efficiency dumb-pumps per zone. Whether or not it can be plumbed as the ONLY pump rather than a primary/secondary configuration requires a bit of design work. If you don't have sufficient radiation on each zone to emit the minimum-fire output of the boiler at condensing temps ( or sufficient thermal mass in that radiation t deliver at least 3 minute minimum burn times) you'll need to add some thermal mass in the system. A common way to do that is to use a thermally massive tank as the hydraulic separator rather than closely spaced tees.

With a thermally massive hydraulic separator you can micro-zone the hell out of it without short cycling the boiler if you do the basic math, using only two pumps:

PME_0907_Feat2Fig10Lg.jpg


The most common error in DIY (and pro) mod-con system designs is to oversize the boiler for the radiation. Thermal mass helps, but it's still important to not oversize the boiler. The minimum fire output, and the ratio of heat emitter to minimum fire output are necessary to max out both the comfort & efficiency. If you can do it all with more radiation rather than mass it's better.
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks