Your thoughts on radiator heat?

[jharkin]

Dont assume that a radiator with two pipes is always hot water... there are also 2 pipe steam systems, where the condensate drains back down to the boiler via a second pipe, which has an oversized drum shaped device on it called a steam trap. These are the radiators you often see with one pipe at the top and the other at the bottom. And they should NOT have an air vent on them as seen on one pipe systems. The air gets forced out of the radiator thought the return pipe (hence the steam trap) and vents in the basement from a large main vent on the return lines.

Like so:


There are also system that have no vents at all (vacuum/vapor) though they are rare and typically converted to vented system when the vacuum valves and pumps failed. But working properly AFAIK they where far more efficient and quieter than other steam systems.


Back on track... Yes indeed 1psi is more than enough for ANY residential steam system.. the only thing the pressure has to do is be enough to force all the air out of the pipes and overcome pipe wall friction. The problem is that setting the pressure that low with accuracy is hard. The common Honeywell residential pressuretol is calibrated up to 15psi, but you want to target an operating range of 0.5 to 1.5! You have to experiment and basically crank it as low as it will go. Installing an add on 1-3psi low pressure gauge helps with this.

Even better, if you are willing to spend some money, is to install a vaporstat. This is calibrated in ounces and allows perfect fine tuning, typically a setting somewhere around 8-12 oz/in is enough.


Other things that help big time to make a steam system run right is to get the right size vents on all the radiators and the proper large vents on the mains in the basement. I did this when I first moved into my house and replaced the basement vents (improperly sized for radiators) with proper main vents the size of softballs - this made the heat come up in minutes rather than hours If you join a forum called heatinghelp.com there is a guy on there who goes by the handle "steamhead" who will give you recommendations if you provide him your system dimensions (# and size of radiators, length and diameter of mains, etc).

Oh and insulate the pipes. You can get paper faced rigid fiberglass insulation for the mains ( 1 inch thick for the 2-4in diameter typical main pipes) at any good plumbing supply house.

If you have steam, the best first steps is to buy Dan Holohan's "Lost art of steam heat" book. This explains everything and has handy tables for radiator balancing and vent sizing, etc.

[jharkin]

One other thought...

There was talk of converting steam radiators to hot water. Be VERY careful if you try this. Your typical steam radiator has been open to atmosphere for a century and the constant filling with steam and then air and then steam... plus the small amount of standing water at the bottom always draining out means that the inside are usually filled with rust scale and they rust though from the inside out starting at the bottom. I have one in my front hall with a pinhole leak on the bottom for this reason.

You take that radiator that's never seen over 2psi and suddenly hit it with 30psi water and there is a real risk one of the section seals will blow out. Test it carefully.

[jharkin]

what ken said makes sense. Its because the water has weight so to pump water up you have to overcome the weight of the water

One pound per square inch (lbs/in2 or psi) is approx- imately equal to 2.31 feet of water height (column of water) no matter how big around or square the column is. One foot of water height is approximately equal to 0.434 psi.

I found it interesting that to suck water up there is a maximum around 10 meters, after that the water cavitates. It will basicly boil if you have enough suction so there is a limit how far you can suck water. thats why if you have a deep well you put the pump down in the water and push the water instead of trying to suck it up.

steam is light compared to water so the head of the water doesn't need ot be overcome to create flow. I think what ken says is true, the steam doesn't have the same head as water. to lift water up in a tall building this weight factor becomes higher as the height of the building increases but steam doesn't' have the same factor due to it's weight so it can run at a lower pressure. I was surprised it's as low as he says but I guess that makes sense now.

Again, not exactly.

A well (or a sump pump) is an open system, so the head pressure is what you have to contend with the pump. A water heating system is closed loop, so the pump is both pushing water uphill in the supply lines, and pulling it downhill from the returns. Remember back in the old days before pumped systems there where gravity hot water systems, where the feed ippes where massive and the natural convection from the boiler heat was enough to keep water moving (the water on the hot side expanded and rose just like hot air does).

And for the steam system, head pressure is not a factor at all as true dry steam is actually LIGHTER than air.. Thisis why steam radiator vents go down low on the radiator - the steam floats to the top of the radiator and pushes the trapped air down).

[JacquieJet]

We have hot water radiators throughout the house. I have no complaints, other than the cost- if we have a cold snap and the rads are constantly "on", our gas bills can get high. That being said, that may have more to do with our lack of insulation in the home rather than the type of heat we have.
Our radiators aren't original to the house, but were installed around 10-20 years after it was built (it originally had a coal fired gravity fed furnace until around the 1930's.

A couple pluses to having radiators is that they are lovely to look at, and are great to dry off wet mittens/socks in the winter!

[1918ColonialRevival]

We have hot water radiators throughout the house. I have no complaints, other than the cost- if we have a cold snap and the rads are constantly "on", our gas bills can get high. That being said, that may have more to do with our lack of insulation in the home rather than the type of heat we have.
Our radiators aren't original to the house, but were installed around 10-20 years after it was built (it originally had a coal fired gravity fed furnace until around the 1930's.

A couple pluses to having radiators is that they are lovely to look at, and are great to dry off wet mittens/socks in the winter!

Once they heat up, the radiators should retain heat for some time. If your boiler is cycling a lot, I would check the thermostat and also check to make sure there's no air trapped in the system anywhere. If your thermostat is in a location where it's exposed to cooler temperatures, such as near an exterior door that sees a lot of opening, you may want to consider relocating it.

There was talk of converting steam radiators to hot water. Be VERY careful if you try this. Your typical steam radiator has been open to atmosphere for a century and the constant filling with steam and then air and then steam... plus the small amount of standing water at the bottom always draining out means that the inside are usually filled with rust scale and they rust though from the inside out starting at the bottom. I have one in my front hall with a pinhole leak on the bottom for this reason.

Although rare, I've seen that myself, though it's usually more attributable to a weak spot in the casting than rust or corrosion. In other words, a manufacturing defect that's taken decades to show itself. Radiators get surface rust on the interior, but it's usually not enough to compromise the structural integrity. Kind of like the surface rust that forms on automotive brake rotors. It's not pretty and there is some flaking, but it's not enough to fail the unit itself.

If you're seeing 30 psi on a residential hot water system, something's wrong. My system, which heats a three story house, runs around 14 psi. On the systems I've serviced in the past, the "normal" range for a circulated hot water system I've seen is about 12-15 psi, which still isn't a lot of pressure. Compare that to the public water service in most locales which is usually around 50-60 psi (in this area it's closer to 70 psi).

[mjt]

If you're seeing 30 psi on a residential hot water system, something's wrong. My system, which heats a three story house, runs around 14 psi. On the systems I've serviced in the past, the "normal" range for a circulated hot water system I've seen is about 12-15 psi, which still isn't a lot of pressure. Compare that to the public water service in most locales which is usually around 50-60 psi (in this area it's closer to 70 psi).

Agreed - mine is usually 12 psi on a hot water system heating two of our three stories.

[phil]

A water heating system is closed loop, so the pump is both pushing water uphill in the supply lines, and pulling it downhill from the returns.

good point kind of like a siphon effect. that makes perfect sense. thanks for correcting me. I stand corrected.