Can cast iron baseboard and cast iron radiatiors be

Steve Levine

I believe that the reason you would prefer two zones, in this case, is because of the two levels, not the difference between cast iron baseboard and cast iron radiators. Both have relatively high mass and both will be slow to heat up and slow to cool.

Because of the differences between copper tube baseboard and cast iron radiators, when used in the same zone, their performance is different from each other and will cause control problems.

The similarity of cast iron baseboard to cast iron rads avoids this problem.

Steve Levine Slant/Fin

Paul

mixing rads and baseboard

Can cast iron baseboard and cast iron radiators be used together in a forced hot water system? It is likely that the two types would be on different zones.

Floyd

No problem!!!!

My house has cast iron baseboard in the first floor and rads in the second floor, all on one loop. I just open and shut the valves on the rads to control the heat in the upstairs. Different zones would be great!!!! Wish mine were zoned, just never have taken the time to break them apart. Mine are all run with "mono-flo" or diverter tees.
Pay attention to getting everything piped properly and you can make the system work great!!!

Floyd

Unknown

copper and cast iron

If there is a conflict with mixing copper baseboard and cast iron radiators, why is it OK to use copper tubing to supply to the radiators. Wouldn't the same problem of mixing metals happen here?

Mark J Strawcutter

thermal response

The problem is not one of a galvanic reaction between dis-similar metals, but rather one of differing "thermal response" (not sure if that's the right term) - how fast they heat up and cool down. Perhaps "thermal inertia" would be a better description?

Previous owner replaced the cast iron rad in my kitchen with copper/aluminum fin tube baseboard. It heats up quickly but cools off just as fast. Meanwhile the large thermal mass of the CI rads in the rest of the house keep putting out heat for a long time after the call for heat is satisfied while the kitchen grows colder and colder.

Mark

Steve Levine

Mark is exactly correct. It is the timing of heating and cooling of the heat emmiter. The cast iron will be heating long after the copper element has cooled down. The operation of the thermostat is the problem. Which area do you put it in? What do you set it at? How do you set the anticipator on the thermostat?

Steve Levine Slant/Fin

Online Sheriff \"Murph\"

maybe slower

rise and cool, but by my chart it seems they have about the same output!!

Boilerpro

Continuous pumping solves \"mixng problem\"

If you continuously pump the cast iron and copper tube baseboard, the temperatures of the heat emiters should stay the same (assuming a reasonably well flow balance). Rewire the main loop pump for continuous flow and your kitchen will stay warm (if the baseboard capacity was balnaced with teh rest of the system). I have fixed and installed many baseboard and cast iron mixed systems with this simple solution.

Boilerpro

Paul

First, thanks for this great conversation.....

This is really helping not only to understand, but to begin to see why I receive conflicting info from different people; there is more than one way to skin the cat.

The idea of thermal mass [and the difference between copper as CI radiators] is clear.

I have bedroom closets along the perimeter of the house, intentionaly put there to help insulate the rooms from cold and noise from outside. One plumber is bothered by this: the closets will get ice cold. He wants to supplement the CI radiators in the rooms with a couple of feet of copper baseboard in each closet. Based on the concern stated, there should be no problem here as these rads will only be there to keep the closets from becoming a refrigerator. [apparently, this is a real sore spot with his wife in his home, and he is warning me].

Another plumber, who did not bring this up as a concern, suggested circulating water continuously, at a much lower temperature, and using valves to temper the rads heat output. He'd like to see the water temp at 80 degrees on a cool fall day.

Paul

First, thanks for this great conversation.....

This is really helping not only to understand, but also to begin to see why I receive conflicting info from different people; there is more than one way to skin the cat.

The idea of thermal mass [and the difference between copper and CI radiators] is clear. That said, I have bedroom closets along the perimeter of the house, intentionally put there to help insulate the rooms from cold and noise from outside. This bothers Plumber One: the closets will get ice cold. He wants to supplement the CI radiators in the rooms with a couple of feet of copper baseboard in each closet. Based on the concern stated, there should be no problem here as these rads will only be there to keep the closets from becoming a refrigerator. [apparently, this is a real sore spot with his wife in his home, and he is warning me].

Plumber Two did not bring up the cold-closet concern. He did suggest circulating water continuously though as Boilerpro said. He would like to see the water temperature low, and using valves to futher temper the rads heat output. He'd like to see the water temp at 80 degrees on a cool fall day.
Do these ideas retain heat?

Boilerpro

Ideas

Plumber one is probably right, those closets will be like refrigerators. Warm closets are nice, and I usually provide heat to them like they were another room. Sounds like plumber two is talking about outdoor reset, were the system water temp is adjusted to the variable heating needs, without cycling on and off. This is a very good idea with low mass baseboard, or with any zoned system, but with high mass systems and a properly sized boiler, the mass of the systems modulates the heat output quite nicely, so reset provides little benefit.

Boilerpro

Paul

Scratching my noggin

My house is old, and has lots of wood to drill to run lines. Most of the joists are 3” thick.
60% of the house is over a basement or crawlspace and the other 40% is on top of a slab, so running pipe through the floor joists will have to happen in large part.

Plumber One is kind of old school. He works with American manufacturers, likes copper, and black pipe for gas.

Plumber Two is the same age [a young master plumber] but is new school. Very heavy on Viessmann with the outdoor reset mentioned. He likes the idea of PEX tubing for the heat supply and return, and hot/cold lines, as well as flexible pipe for the natural gas supply lines.

I have not seen the price quote from either, which will certainly make a point to consider, but beyond price, what are folks feelings on old-tech vs. new-tech? Plumber One warned that for all of the savings in forgoing sweating copper and threading pipe, I am going to loose in the cost of manifolds and pricey material.

Mike T., Swampeast MO

Closets & valves

The "valves" plumber #2 is probably talking about are Thermostatic Radiator Valves (TRVs). These regulate the flow through individual radiators proportionally. That's why he said the rad would be 80 degrees (or even cooler) on a mild day. Using these valves constant circulation is inherent and outdoor reset (simply mechanical is generally fine) is a near requirement. Reset helps keep the valves working in their utterly silent and most effective range. Quality TRVs easily last decades with zero maintenance.

While standing iron (and to a bit lesser degree iron baseboard) are an inherently "even" heat, the TRVs make it uncannily even. You wind up with a system of near-radiant comfort while retaining the ability to quickly raise the temperature. You also gain the ability to independently regulate the temperature in each an every room. They're not terribly expensive and if budget allows you will NOT regret the decision to use them--either with your comfort or the energy bills.

As to your closets: Unless room-sized, closets are considered to be part of the room that they serve--included in the heat loss for the space. I have a large walk-in closet with 8' of W exposure in my home (it uses cast iron rads w/TRVs). While certainly somewhat cooler than the room, it is never an icebox during any weather. We hit zero every 3-4 years with a design low of 8.