I've noticed a couple of houses that used to have a central warm air heating system, since replaced by a conventional gas boiler and radiators. But for some reason they've kept all the ducts, grilles, and in one case the boiler.
Any idea why?!
Probably did not want the cost of stripping it all out. Some houses were also designed for that kind of system - so a dedicated central heating "cupboard" which feed ducts to all the adjacent rooms.
My bungalow was like that. The oil-fired boiler was primitive - little better than a gravity-fed primus stove. Some neighbouring bungalows had electric ducted air heating, with ducts running under the floor to different rooms. As you say, probably not worth the cost and inconvenience of stripping it out.
Too much asbestos in the boiler?
That was part of my thinking. They wouldn't use asbestos in the ducting too?!
And as others have said, the cost and inconvenience of stripping out the ducts. although it all look very odd to my eye. Would reclaim some space I suppose, and a ready made conduit for cabling :-)
For info, I'm thinking of moving and have looked at some houses like this.
Costs too much to remove them
wouldn't bother
Good job that lunatic IMM isn't still around or we'd be suffering a torrent of bilge about warm air benefits.
Our duct outlets have simply been papered over. For the first couple of months here we couldn't work out the creaking in one bedroom when someone walked across the adjacent bedroom. Problem was sorted when we had new carpets and I got the carpet layer to raise a floor board. A couple of blows with a hammer and noise problem sorted.
I'd imagine it to be quite a large job, and a waste of effort, taking the ducting out but whether the heating would have been better than radiators is one I'd ask the experts here.
Could the ducts be repurposed for whole house ventilation with a heat exchanger to reclaim the heat?
Tim
Possibly, although you'd need a pair of ducts for each room (fresh air and stale air). Did warm air heating have any recirculation of room air, or did it just blast air into the room and assume it left via leaks?
Maybe you could subdivide them, or run a pair of inner pipes inside the duct.
Theo
Not necessarily. You could just have some vents in each room into the hall and the a single exit from the hall to the heat exchanger.
Can’t remember. My parents had a hot air system many many years ago. I’m guessing that there would have been vents above the doors of every room.
Tim
Of course the systems are balanced.
They have hot air rising on outer walls, and cold air collection on inner walls. You should have one vent type of each, in a room, so air does not go "rushing under the door".
Sadly, not all rooms are equipped that way.
They arrange the direction of floor joists, to allow routing of the heating pipes. The pipes are too big, to allow drilling through a floor joist and weakening it.
The cold air return, can be done by using two floor joists, and nailing some sheet metal to the joists to build a box. Because it's cold air, the details aren't too important.
Whereas the hot air is done with metal on all sides. As if it's a fire requirement or something.
The "spine" of the heating can be done with rectangular cross section pipe.
The runs off to the side of the spine can be done with circular pipe.
There are many variations.
And a lot of bad work.
Paul
Hot air blowers are far more efficient than radiators in terms of getting heat out of the ductwork and into the room, and dont take up so much space. But that depends on them having the power to begin with and fan assistance. Apart from heatpumps - which are probably not working in today's temperatures - there are no free lunches on heating.
You get out what you put in
The semi-detached house I bought in1984 had warm air CH (Johnson & Starley). There were vents in the wall near floor level in the lounge and dining area. Upstairs in the bedrooms the vents were in the ceiling, but the bathroom vent was at floor level as it was directly above the heating unit (which also supplied hot water - gravity fed - to the hot water tank in the bathroom's airing cupboard). The only input for the (cold) air was the heating unit in the kitchen.
I seem to be the only person here who loves warm-air heating and don't like radiators. I've often wondered about ripping out the hot-water system and replacing it with a warm-air system. Even though it wouldn't be too difficult to install warm air as it's a bungalow with suspended floors,i t would still be too much hassle. Also, if we started getting extended hot summers, the system could work in reverse with central air-conditioning.
I had a gas-powered warm air system in a small town house 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, from both air movement and fan vibrations. Cleaning filters, adjusting dampers and fan speeds never made much difference. I guess the duct and grille sizes were too small, and airflow was too high. 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
That's the problem when you have an install done.
The first inkling you have, that something wasn't gauged properly, is when bits of it fail prematurely.
For example, on a natural gas furnace with ventor (inducer), that thing is supposed to last 15 years. Mine lasted 9 years (covered under warranty). I still had to pay labour for the job.
You adjust the circulation airflow (which of four speeds to use), according to the delta_T across the heat exchanger. Too much or too little is bad, and can crack the exchanger (at some point). You take temperature measurements at the cold air return, at the hot air main pipe output, then consult the cover that screws onto the furnace, for the ratings decal with the details.
There are actually three temperatures of interest, cold air return, hot air output to room, and flame temperature. If you run the exchanger too cool, there is too much temperature difference between the flame and the other side of the exchanger. They make an assumption about the flame temperature, and just use two temp measurements when setting the airflow.
*******If you're running heat to the outside walls, and the "spine" is in the center of the house, there's a relatively long distance between sound sources. If a heating pipe was "shared" (run sequentially), maybe then it would be too noisy (hear conversations in the other room).
You can't really avoid the noise the circulation fan makes. It's a squirrel cage which is fairly well balanced. The ones I've played with, there didn't seem to be any opportunity to improve them. The motor for example, can have rubber mounts so the motor vibration does not directly couple into the chassis.
The pipes must remain bare metal. If a "duct cleaner" came to the house, they would tear any fabric inside a pipe to shreds.
Paul
I was thinking that... then again, I would happily swap some of the current posters for IMM - much of it may have been drivel, but at least it was vaguely on topic drivel!
I don't recall IMM, but I do recall Dr Drivel. I found his posts most amusing.
Perhaps there should have a moderated group?
One and the same, he nym shifted between Adam, IMM, Dr. Drivel, Dr Evil, and probably a few others.
We might not be at the peak of 8K posts per month, but even so, do you fancy it? Not many do, and to be fair this group has always had a fair amount of light hearted thread drift. The more persistent malicious posters are a newer thing, but easy enough to filter out.
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