In message <rn69oa$bg3$ snipped-for-privacy@dont-email.me, Vir Campestris snipped-for-privacy@invalid.invalid writes
We used to live in an early 60s place that had it. To describe it as heating was getting close to misleading advertising, more like a slight warm draught. Even if it had worked anything like, it was very difficult to control compared to a radiator with a thermostatic valve, basically vent open/vent closed. It got replaced with a conventional gas fired CH system.
Adrian
Noisy? I would imagine if we go down the reversible heat pump route, then some kind of air moving system is going to be needed again? Brian
Without air conditioning ducts, how would all those adventure programs have got their stories though. Brian
Out of fashion where? I understand that in Sweden they are the norm - air ducts to take take warmed fresh air to each room and air ducts to take exhaust from rooms. Air in and out are controlled with heat exchanges and heat is recovered from the warm house exhaust air.
The obvious way to do it when you have a larger temperature variation than we experience. Such heating systems are fairly common in the US of A, too.
I'll tell you why. To be blunt - because it didn't f***ing work ;-)
The house that my parents bought (new build) in 1972 had a huge floor-to-ceiling gas boiler for ducted-air central heating. It needed its foam air-filters cleaning out of dust every week. It made a very loud noise and so was relegated to the downstairs cloakroom, away from any room that we used. That room was lovely and warm - so a lot of heat was being "wasted" instead of heating the rest of the house. The house was always cold, because what came out of the floor ducts was a feeble breath of air that was barely tepid. The only room that was warm was the lounge, because that had a gas fire in it. Ducted air also made the house dusty - it kept dust in circulation which would otherwise sink into the carpet and remain "hidden" until the room was hoovered. Being facetious now, it was also a "great" way to spread nasty smells around the house: one time there was a horrible sweaty-foot smell in some of the bedrooms, which we eventually traced to the duct in my sister's room where she'd shoved an unwanted cheese sandwich as a prank ;-) My parents were on the point of having the ducted-air system replaced with a conventional radiator system, because we all hated it so much, but then dad got a new job so we moved and passed the problem onto the new owner.
I'm sure ducted-air technology (insulation of ducts, efficiency of boiler) has improved a *lot* in 50 years, but can it *really* heat a house up as quickly and to such a high temperature as hot-water radiators (fed from a boiler that is powered by whatever fuel is currently not condemned)?
When we were house-hunting the other year, we looked at one house where the owner was proud of the energy-efficient heating system. But through the whole house we were conscious of a continuous moaning noise which I presume was the noise of the air fan being propagated along the ducts. I stood in front of a duct - yes, the air was almost stone cold, just like it had been in my parents' house.
Men do too. We want to be comfortably warm and not to be left shivering if the sun goes in.
My parents' house with ducted air had a little gas "boiler" in the airing cupboard which just heated the water for the cylinder. I imagine one that could have heated the water on demand rather than for heating a cylinder would have been a lot bigger.
That's a very good point. I hadn't thought of that...
IMLE noise & dust. Then there's fire.
NT
In places that still have oil heating, the tank goes outdoors now. The house I was born in, the tank is still inside, and it's been highly reliable compared to the track record of outdoor tanks. But if you want to save space on a 200 gallon tank, you can do it.
The places using oil heating, would not be using it if natural gas was available. The price of oil is astronomical. And electric heating is similarly stratospheric pricing, so a non-starter as an option. Electric heating was tried here (because, well, we got a bunch of nuclear reactors and what are you doing to do?), and a few people at work were always bitching about theirs. The elements used to fail in the electric furnace. You won't find many electric furnaces today (Bill Gates maybe?).
The biggest liability with oil heat, is leaking oil and cleanup cost.
And before we got oil, some of the houses were still using coal. I was lucky as a kid, I was down at my friends house when a coal truck came up and delivered a load of coal. And we watched while my friends dad shoveled coal through a basement window, into the basement :-) Some of the members of the family, use to have arguments about which person was supposed to be cleaning out clinkers. Well, all that changed when the oil came along. The coal room was re-finished and became my friends bedroom. And we were careful to *never* mention he was sleeping in the coal room. It's not like he had a choice in the matter (big family).
*******As for the routing of ductwork, my house has a 10"x20" rectangular cross section pipe running along the spine of the house (in the basement). There is also a steel I-beam that runs the length of the house and it's near that pipe. Whereas other houses used sistered wooden beams nailed to one another for the spin, this house series they used a steel beam instead.
Smaller round pipes (6" diameter) feed from the 10"x20" galvanized sheet metal pipe, and the round pipes run between floor joists. This reduced the impact of the heating distribution in the majority of the room area. The basement has the penalty of headroom dropping to 6'3" below the rectangular pipe. Whereas the rest of the basement has a ton of headroom.
In two story houses, the round pipes may be replaced with a rectangular cross section pipe running vertically up the walls. Which makes for a long run of pipe, and makes it hard to balance the system. Each run of pipes has a "vane" inside the pipe, and a lever on the outside which you can rotate. You adjust the lever to get the degree of heat you need in the room (with the second floor ones being at a disadvantage because of the flow resistance). In the dead of winter, the people on the second floor are freezing to death :-) That's why they get extra blankets up there. In late fall and spring, everything is fine.
The hot air vents go on the outside walls. The cold air return are on the inside walls. The cold air returns get little attention, so it's hard to say whether the flow rates are really all that balanced between the two sides. If you don't get that part done correctly, the furnace starts sucking air through any available crack, from basement air. Which isn't always the best thing.
The only draft in the house, comes from wall sockets. And todays R2000 techniques (sealant and proper boxes for outlets) helps control that kind of leakage. In the old days, the build quality wasn't all that good on that sort of detail.
The combustion furnace has a range of delta_T it can handle. You can damage the heat exchanger if the conditions are not properly met. The speed of the motor (four speed motors being typical) helps set the delta_T. The door of thr furnace states how much temperature difference is allowed between the "heat" central pipe and the cold air return pipe (aka "ambient"). The speed requirements for heat and AC are different. In some cases, the same speed used for both, in other cases, one season runs the motor faster than the other season. If you get this wrong, you can crack the heat exchanger. (You would think moar air for heat distribution would always be good, but that's not the case.) Part of checking an air circulating furnace, is making sure some wacko hasn't buggered the delta_T. (Two furnace techs can get into a fight about which wacko did it :-) That's why they work in pairs.)
Paul
One thing I've noticed, is the home heating people aren't very good at design.
The ductwork on houses is seldom all that good. A long narrow pipe is expected to deliver the same air as a short larger pipe. All sorts of non-intuitive stuff going on.
If you had a saleman come into your house today, he'd sell you a 60,000 BTU furnace, because he'd tell you that the "longer run time gives more efficient heating" and would save you a tiny bit of money. But at the expense that if you put your toes over the register, you can't really "feel" the heat.
I've had both a 60,000 BTU furnace (current one) and an 80,000 BTU furnace, and the 80,000 one really did "warm toes".
You can't go too high though, because the ductwork is designed with a certain size of furnace in mind. If you connected a 120,000 BTU furnace, the delta_T between the hot air output and the cold air return would be too high, and the heat exchanger would melt. The furnace has a four speed motor, to allow some adjustment to flow rates (most of the time it runs on high or just-below-high). Each pipe arm has at least one damper on it, a vane with a rotating lever to set the airflow in the pipe. But this is not designed to make large corrections, only small ones. For example, if you had two identical runs of pipe, the dampers could make fine adjustments so the airflow was made equal. But you can't balance 10sqin of pipe with 40sqin of pipe, just using dampers. If you damp down the 40sqin pipe to 10sqin, now there's too much overall resistance to airflow and the furnace overheats.
After a while, you'll realize that every analogy in the air circulation system, has an equivalent one to a water based system. Many knobs. Maths. And occasionally, a result.
To show you how stupid people can be, on a hot air system, the hot vents go on the outside walls, the cold air return is on internal walls. Yet, one house I was in, they reversed that, and put the wrong pipes on the respective walls. Naturally, the results are far from ideal. Miserable even. Any time the exterior walls get cold (due to the weather conditions outside), those walls will suck the life out of you. If you're sitting in a chair, you move away from the wall :-) Because cold air will be streaming down the wall at you.
Paul
They are not. All the houses I visited had UFH, many pure electric. Sweden has nuclear and hydro power. Go figure.
Oh yes. And much quicker too. As any large supermarket demonstrates.
But that means a high peak power and it is always a bit noisy. Simply put wet radiators are adequate, cheap and quiet for reasonably high water temps. At lower temps UFH allows a greater 'radiator' surface area and is more even in its heating, but is an impossible retrofit in most cases.
But it is pretty cheap on new builds. The cost of laying plastic pipe in screed or between joists is no worse than running copper.
I had a gas-powered one in a small town house nearly 50 years ago. Warm-up was fast, lack of radiators made room layout easier.
Every room was heated, including kitchen and bathroom, but these two had no direct return duct.
The system was noisy, both air movement and fan vibrations; cleaning filters, adjusting dampers and fan speeds never made much difference. In three years we got through two transformers and a fan motor.
In a family house, noise transmission along the ducts could have been a problem, conversations could be heard around the house.
Water heating was by a large instantaneous gas heater, which gave no trouble.
Chris
I think women prefer heating to be invisible and want magic underfloor heating that warms the room but isn't too hot underfoot.
We also like being able to put our socks and pants on the radiator in the morning :-)
Owain
No need. leave the on the heated floor and they will be warmed all through
Mine didn't.
In a new build you can (and indeed have to) insulate such that you don't need a lot of heat in the first place, which removes the need for a giant furnace and duct system. Although central air has its advantages - can use heat pumps to heat and cool. I wonder if we'll start seeing that coming back for cooling purposes.
Theo
Some parts of the USA are hot enough, the AC is duplicated or triplicated. In the event that the AC dies in one "zone", the people in the house "evacuate" to the side of the house with the working air conditioning. It's a bit like living on Mars.
HVAC people work long hours in summer. Up for 8AM in the morning (or as early as consumers would allow), heading home at 10PM. That means five days a week of 14 hours. That's because they're banging in new installs, and they try to schedule two installs a day, and they get pissed if the morning install takes too long and that makes the afternoon install go forever. In heating season, there's still work, but not 14 hours worth. They can fit just the heat in winter (if there is a heat exchanger failure and it's leaking CO), and wait until summer to finish the install and put in the AC components. It's hard to do a refrigerant fill when it's cold outdoors.
Only the R2000 homes here have air-to-air heat exchangers. The windows don't open. To get fresh air, an air handler brings in fresh cool air, and as the stale house air leaves the house, the heat from it is transferred into the inlet air. These can be relatively large boxes in the basement, so you don't end up with a lot of storage area in the basement, and there is a lot of HVAC equipment down there. All done for bragging rights. The one good part of the R2000 program, is some of the techniques were inherited in ordinary home construction (acoustic sealant and plastic sheeting around electrical boxes in walls for example, no cold air leakage). Not too many people would necessarily buy into the double-glazed-windows-that-don't-open.
Paul
If you have a well insulated house in the UK, just how often would you need air-con?
The US is a bit like the UK. Why insulate a house (making it cost a lot more) when energy is cheap enough to cool it? Rather like their excessively large engined cars.
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