I'm probably not going to tell you what you want to hear, but I am going to let you know what you should know: "The technician told me he had checked to see if there was enough water in the boiler, and there was." Now, do you know where the water guage is, the pressure guage and the temperature guage? That is how you tell what is happening in the boiler. You can have burners on and very little water in the system which can lead to problems, serious ones. Every homeowner should know something about their units. To be ignorant is not bliss. Anytime you let air or water or both out of a bleed valve, the pressure in the system drops and you will eventually need to add some water from the inlet valve. This should be marked and off during normal operation. Also, you have an expansion tank? Probably. It needs to be checked also. They get full and then the heated water has no place to expand. You should only need to bleed from a radiator upstairs, not the baseboards although they pronbably have a bleed valve screw also. At the end of the run. Do you know how to know if a radiator top is full of air? By feeling with your hand. Cool top sections may mean air is trapped there and heat doesn't transfer as well thru the air pocket. Do you know if the valves on each radiator are open? Not the bleed valve but the inlet near the bottom of each radiator. They may be 1/4 turn valves, not like on a garden hose valve on the house. You might call the tech back and this time have him show you where things are and what you should be aware of. Did you have a thermocouple changed? (CDM/DMC), is what? What is the psi and temp reading on the guage when the boiler is operating? Should be a guage on the top or side of the boiler. " "Maybe the radiators always did have to fill up each time they kicked in, but I never heard water trickling in before." Think of the radiator system in your car. There is x amount of water and antifreeze in the system. It is always there waiting to extract the heat from the engine block and dissipate it thru the radiator coils. Once the car starts, a pump circulates the water. It is always there, but sitting still when the system is off. A fan is added next to the radiator to speed up the process of dissiapating heat. Also, a heater coil (mini radiator) is installed in the passenger compartment with a fan to use some of that heat in the wintertime to warm the occupants. If too little water is in the system, it overheats, boils, and the excess pressure opens a safety valve on the radiator cap allowing the overheated water/antifreeze to escape. Remember the old pics of the stranded motorists? Your boiler also has a safety valve, and opens at about 30psi. You probably should have about 12-14 psi in the system whether or not the boiler is on or not. You may have a circulating pump on that system also and should know something about it also. As for the trickling noise, I would call the company back and report that there is something different with the system after the tech visited and that he did not fully explain things to you. Try to get a free visit buy you may have to pay something for their time. Remember to ask about the expansion tank. Do you have yearly service?

For those still looking for radiators, check out ebay or craigslist for used radiators that you can get cheap. Make sure you know ur'e system (Forced Hot Water or Steam) as some radiators are built for one system or the other. Also make sure you know if it's One Pipe or Two Pipe system if it's steam - (it will definitely be two if it's Forced Hot Water), and that the replacement will put out the same BTU's the old one did. There is a science to it - count the number of tubes (bars running from front to back (near wall) of radiator - these are usually more for hot water radiators), and number of bars left to right as well as height of rad. The bigger the rad. the more heat it will give you. If u're in the Northeast, there's a guy in Somerville, MA (near Boston) that sells tons of them and you can look and choose u're style. He'll help you as well and you can exchange the old one and get a big discount on the new one. I know there are probably lots of other rad. places in the Northeast as well since so many homes still use em. I love these old systems. All the systems I've been around, I find these old radiators put out the most comfortable heat and create a neat old atmosphere that is irreplaceable today. Some other sites you can check out for brand new remakes or refurbished ones: This is the guy in Somerville: www.antiqueplumbingandradiators.com/ Burnham makes a lot of good repros too: www.usboiler.net/residential-hydronic-heating-products.html

My understanding is that boiler, pump and radiator reps often do a lot or all of the engineering calculations for boiler and radiator installations. I must be missing something because I don't understand this at all" Runtals use 1/4 of the water of Myson, so this justifies their higher price - you get it back in energy savings. A btu is a btu. The boiler makes it, the structure looses it. How it gets to the room from the boiler has little effect on efficiency provided the return water is the same temperature. Even if you have to put 2 or three times the electricity into pumping with an inappropriate piping/pump and maybe radiator system, it won't make that much of an impact. I can't say much about CI rad design with respect to internal water volume. Water carries the heat so flow has to be sufficient and transfer from water to metal and metal to room has to come out right. It really boils down to the rated heat output of the rad at a given temperature and the rate needs to maintain that given temperature. Cast iron baseboard need not be any more of a dust collector than the higher mounted Runtal rads and has the advantage of putting the heat low where you need it most and heat transfer will be maximized. Are you sure about that 40k calculation? Right now I am looking at heat loss calcs for a home about that size. It is 50 years old and, although the insulation and air sealing is excellent for a home of that vintage, it is only good overall. The calculation comes in at below 50k at a design temp of of 0F. My fuel use calculations, however, come up below 30k. I put more faith in the latter since there is guesswork involved in the energy rater's estimate.. The walls have insulation blown in, The ceiling is filled to over the joists and there are double pane windows. Exterior doors are good.

It is possible to replace your radiators. Take a look at Runtal Radiators for ideas. You can use cast iron radiators if you have an old house and want to keep that look. There are places which specialize in refurbishing and selling old cast iron radiators.