heating with hot water on demand.

[Manalto]

It's definitely not overkill, though I would recommend picking up a copy of The Ideal Fitter, which contains information on how to appropriately size radiators for rooms. The only ones saying overkill are the ones who see forced air as the only heating option out there.

That ship has, unfortunately, sailed. I've got four nice radiators from a 1924 house ready to go. I've been in many houses that have radiators so I don't think the sizes of the ones I chose are terribly off. (The ones I've seen are mostly between Washington DC and Canada so, if anything, they may be overcompensating for the winters I'm likely to get.) Is it possible to tweak the efficiency of radiators by adjusting the temperature of the water that runs through them?

[1918ColonialRevival]

The best way to make sure a radiator is operating efficiently is to make sure the air is bled from it and the entire volume of the radiator gets filled with water. Otherwise, trapped air will get pushed to the top of the radiator and it will only partially heat. There's a bit of a science to balancing a radiator system. I always start with the radiator farthest away from the boiler and work my way closer.

[phil]

Is it possible to tweak the efficiency of radiators by adjusting the temperature of the water that runs through them?

nothing like answering a question with a question but good question..
Does the heat output get varied by the flow rate or by the temperature of the water fed to the radiator? or both? would you run the water at a hotter temp when there is more demand on the system?

[1918ColonialRevival]

Is it possible to tweak the efficiency of radiators by adjusting the temperature of the water that runs through them?

nothing like answering a question with a question but good question..
Does the heat output get varied by the flow rate or by the temperature of the water fed to the radiator? or both? would you run the water at a hotter temp when there is more demand on the system?

Not significantly. The water is sent through the system at around 12-14 psi by a circulator pump. You really don't want to have more than about 15 psi or so in a circulated hot water heating system. Also, most boilers only heat the water to about 150-160 deg F. Any hotter than that, the heat from the radiators would drive you out of the house. The water itself may cool slightly as it goes to upper levels, but remember heat rises. The amount of heat in the room lost would be minimal.

That said, you can experience some noticeable heat loss if there are significant areas of supply pipe that are not insulated. They knew this even a century ago and that's why you see pipes with insulation wrap on them, especially in older buildings.

My house, which has three levels and a basement, is fed 160 degree water at about 14 psi. That's more than enough to heat the house.

[Manalto]

The best way to make sure a radiator is operating efficiently is to make sure the air is bled from it and the entire volume of the radiator gets filled with water. Otherwise, trapped air will get pushed to the top of the radiator and it will only partially heat. There's a bit of a science to balancing a radiator system. I always start with the radiator farthest away from the boiler and work my way closer.

But... Is it advisable to tweak the system by adjusting the temperature of the water that runs through the radiators? That's my question.

[1918ColonialRevival]

But... II is it advisable to tweak the system by adjusting the temperature of the water that runs through the radiators? That's my question.

The only way you can really increase or lower the temperature of the water is to adjust your thermostat. Turn it up to 75, boiler runs longer and the water gets hot enough to heat the house to the point the thermostat shuts off. Turn it down to 60, boiler doesn't run as long and water doesn't get as hot and the thermostat will kick off quicker. It's as simple as that.

Some people turn the valves at the individual radiators themselves to increase or lower the temperature of a given room, but I don't recommend it. If a piece of a rubber washer breaks off and makes it down to the circulator pump, it can cause damage.

I've seen electronic temperature controls that can be added on to a boiler, but I've always been skeptical of them. You'd likely never recover your investment and who knows what other issues they can potentially introduce.

To keep a boiler operating at its peak, they all require maintenance at the beginning of the heating season. Oil burners require a new nozzle in the burner, electrodes cleaned, inspected, replaced if necessary, and gapped, new oil filter, and condensation drained from the oil tank. After that is done, the burner has to be primed, meaning the bleed valve on the oil pump has to be opened and the system turned on to bleed the air out of the fuel line. In addition to that, every couple of years you should open up the vent pipe, the burner, and the panels covering the heat exchanger and clean the soot out of them. Gas boilers are a little less complicated, but still require regular cleaning.

All boilers and thermostats are a little different. You'll probably have some trial and error in getting the settings right for your particular setup. But once it's there, it's the most comfortable heat you'll ever experience.

[Manalto]

My grandparents' house and my apartment in New York both had cast iron radiators, so I know what you mean. When so many people (not here) responded to my idea with negative or disparaging comments, I knew I was probably on the right track.

I thought this was interesting:
https://www.energydepot.com/RPUcom/library/HVAC018.asp

[1918ColonialRevival]

I believe one reason the idea has been met with some resistance is it's beginning to become a lost art. Cast iron radiators gave way to hot water baseboard units by the WWII era and hot water baseboard heat started to fall out of favor by the mid 1980s or so, likely due to the expense of installing them versus forced air systems. There's probably not too many plumbers or HVAC technicians around who have installed a circulated hot water heating system, so it's out of their comfort zone. The only exception is probably in larger cities in the North and Northeast that have thousands of buildings fitted for radiator heat. If you look around, there are still people in places like NYC, Philadelphia, Cleveland, etc., who do radiator heat systems, but they may be a little tough to find in Alabama.

The newest place I ever lived in that had hot water baseboard heat had a small cornerstone dated 1983. I'd say just about everyone in the trade then has either retired or is strictly in an owner/manager role now. In other words, they aren't the guys running the pipes anymore.

[phil]

maybe they are used more in apartment buildings. the norm is forced air in houses but in apartments they cant' share air circulation but they can share water circulation. Perhaps speaking with a power engineer could help. Usually any big building or place that uses ammonia like skating rinks has to keep them on staff. Maybe they dont work on the same type of system but they might have more training than some of the "heating experts" who do mostly home gas and electric heating. The ticket has level 1, 2 and 3, and different types of systems require different levels of the ticket. In the us there could be some variation, like a trade level might be called a "master" in the US.. instrumentation techs, plumbing piping and steamfitting are all sort of related trades.

[phil]

I added an electonic thermostat to my gas heat. with the old mercury thermostats they just either connect the two wires or disconnect them so if that's what it is then it's pretty simple. mine had an additional wire just to power it but it also holds it's settings with a battery backup.

it has a program with heating time period so I have it set so it isn't keeping the house too warm if I'm at work, and it comes on for a morning warm up so its running when I shower. I think it's paid for itself many times over. i have it set to dip a little at night, warm up around dinnertime. with forced air the recovery is faster though I'm not sure if you'd save so much with hot water. maybe a bit. anytime the house can be cooler of course there is less heat loss.

ill give mine a thumbs up though it wasnt' so complex and it cost under a hundred bucks and has lasted at least 10 years with no issues. I can pull the thing off the wall and sit and go through the settings and stick it back. I haven't had a set time period for battery replacement but it doesn't' seem to draw them down so I think its mostly using the battery to back up the memory of the program. if people want it higher or lower there is just an up or down button and that adjust the heat and then it goes back tot he scheduled program once it gets into its next time zone setting so I found after I programmed it I really didn't need to do anything technical. If im home and off on a workday I simply bump it up if I want and I tell anyone in the house to adjust it using the two up and down buttons as they see fit and it doesn't change the scheduled programming once it goes to the next time zone.

I'm not sure if a thermostat for hot water heat would be more complex, maybe it is if it is varying the tank temp or heating cycle time of the tank. and not simply turning on and off like a gas furnace, or electric. all the electronic timer really does is connect or disconnect the two wires.
Im not normally one to be sold on these electronic devices. I hate when devices dont need the electronics and add them anyway because often that's the weakest part of the design.

some have internet connectivity and so on so you can change stuff remotely from your cell phone. there was a recent program on the news where they were showing how some were installing these high tech systems with cameras, locks and temperature controls and people were hacking in and messing with them and watching through the security cameras because they hadn't set passwords properly. The issue with one particular model is that if people set them up right out of the box they were not prompted to set up the password protection and there were these websites where you could browse through all the cameras and spy on the residents through their own security cams if they failed to change the default password.