New here with a lot of crazy questions.

Snail

Hi,



I'm from New Zealand, where, steam has never been used for house heating, at least as far as I can tell from the web .  I stumbled upon this site looking for solutions for heating an old house I am about to move into and became an instant convert to the idea of steam!  I find it hard to see why anyone would go for anything else.  Of course, as a new and zealous, but mostly ignorant convert, I know nothing of the practicalities and possible limitations, even though I have since spent some time reading around the subject.  Clearly, there is no-one local around to ask, by some thousands of miles possibly.  So I'd be very grateful if anyone finds my dumb questions of enough interest to spend some time straightening me out.



My house, like many older New Zealand homes is poorly insulated and drafty.  These problems can only be reduced, not eliminated, unless I virtually rebuild the house.  Heating the air inside this house is just an indirect way of heating the air outside.  I am leaning toward radiant heating of just the the seating areas of lounge and dining, so I am just heating people not air.  Ceiling radiators seem ideal for this.  Has anyone ever seen this done for steam?  In theory, it seems to me that if I got large area, lightweight flat plate radiators made up and suspended them at a slight angle, they should work.  Any comments?



At first glance, hot water has the advantage that heat can be stored in a tank.  This would be a major advantage to me.  Natural gas is very expensive but, since I actually enjoy getting it, wood is free.  Natural gas firing can be modulated but wood is best burned flat out for clean burning, so in a suburban area it absolutely needs storage.  How about this for an idea?  I would have the boiler supplying directly to the base of the storage tank only.  There would be a vacuum steam generator in the top of the tank to supply the house.  25 inches of mercury vacuum, as is possible in the Vari Vac system, would allow me to extract heat down to 60C(140F).  26.5 inches would allow down to 50C(122F), which is still plenty hot enough for radiant panels.  That would make the usable heat storage per gallon about 2/3 as much as for a hot water system, which should be acceptable for my light loading.



Is there any experience of vacuum systems running in small-medium house environments.  The only one I have seen mentioned, the Vari Vac seems intended for apartment blocks.  Any chance of still getting components?



Finally, would there be any chance of getting something like this to work using the mini-tube system that Gerry Gill has revived?



To the Administrator:  I had to tell a white lie and pretend to be an Australian when I joined up.  NZ is not on the dropdown list.  Hope we are not all black-listed.  My other details are correct though.  However, the form doesn't like international prefixes, like +64 for NZ, so I had to omit that.

Charlie from wmass

As a steam guy I will say

you will be better off using water. Radiant panels with a good condensing boiler will work quite well. Steam is good for use is the infrastructure and support is there. I recommend sticking with what the local supply chain has for those days when you need a part now and can not wait for it to come in three days.

p.s. I was almost a Kiwi, my Da was torn between coming to the States or going to New Zealand. Since he is a Scot he went with the cheaper air fare ticket and he we are.

jonny88

Scots

very funny about the cheap air fare,if you cant make fun of yourself...............

Charlie from wmass

You can ask him Johnny

that is the reason he went state side.

jumper

how about some numbers?

Seems you've thought about this. How big a storage tank holding 26" HG vacuum? Hopefully your radiant panels drain so that you can use a one pipe system. Otherwise you might as well go hot water. Then there's the question of control. The colder it is outside the more vacuum you end up with. That means your vacuum system delivers less heat when you need more. Please keep us informed.

Snail

Why I'm still interested in steam

i Charlie,



My own Scots ancestry makes me sympathetic to yours.  Therefore I won't go into the crazy price of heating equipment and gas here, it would make you choke on your haggis.



I know that it will be a hassle sourcing parts from the USA or elsewhere.  But that's just normal for Kiwis.  A tiny economy in the middle of nowhere means that if you step out of an extremely narrow "maintream"  you will have hassles.  Even mainstream is ridiculously pricey.  We just make do, hopefullyw ith a bit of help from our friends.  Anyway, if the people on this sub-forum followed your advice and stuck to the mainstream, the forum would cease to exist!



I would be sticking with what I have at the moment, a modern woodstove, except that the new-old house has such a weird-shaped open plan living-dining-kitchen area that there is just no logical place to put it.  The only walls free of furniture have ranchsliders,  So nowhere to put conventional wall radiators.  I detest the stuffiness of forced air, and as I said heating air rather than people is not a good idea in this house, so kick-board heaters are also out.  They are not in use locally anyway.  That leaves floor or ceiling radiant.  There is zero local and not much national experience with anything radiant other than installation in new concrete floors or electric tape under carpet, which are also out of the picture one because I'm not demolishing and rebuilding and the other because of power cost.  So I'm on my own for any good option. (I suppose in a country which has 30 million sheep to 4 million people I could just throw on an extra jersey.  Now THAT'S mainstream here!)



I've looked at hydronic under the timber floor.  To get reasonable efficiency, you need spreader plates and underfloor insulation.  Spreader plates are not available, so I'd have to make them.  Underfloor insulation would conflict with my intention to seal, insulate and condition the crawl-space.  I've also looked at the option of hot water piping above the existing ceiling.  The upper surface of the plaster is unbelievably rough, so good contact is not going to be possible, meaning very hot water is going to be needed.



Suspended radiators definitely seem to be the most promising option, potentially at least.  Hot water ones would be very heavy.  Not attractive in view of the number of quite grunty earthquakes we have been having.  So I'm REALLY REALLY keen to find out if I can use steam for that.  The big IF seems to be whether or not the amount of slope practically available, say 1 to 10 or 12, is enough to allow the condensate to drain fast enough and also to prevent too much air-steam mixing.  If it can, it does really seem to me that a modern micro-tube, suspended ceiling system could be a good option, not just for me but for any existing house. 



A second IF that is pretty important to me now and it likely to become more so to others in the future is how to make steam work with wood.  Pellet burners are not an option here but they do seem to be able to be modulated a bit.  Straight wood needs storage though.  To have storage I would have to be able to come up with some sort of vacuum boiler system.  That appears to mean a forced water heat exchanger, as well as the vacuum pump.  Also, pipes that won't collapse at nearly 1 atmosphere of vacuum.

Charlie from wmass

I am not saying steam is dead

I am saying it may not even be available to you due to efficiency regulations based on max fluid temperatures instead of total system energy use. I was not suggesting hanging radiators off your ceiling. In the radiant section there are several threads about radiant tubing embedded in the ceiling. I will find a link to the a post for you.

You can check my posts I am defiantly pro steam. as well as definitely pro steam. 

I just think a plane ticket to install your system would be cost prohibitive for the project.

Charlie from wmass

here is a start

http://www.heatinghelp.com/forum-thread/146556/Radiant-Ceilings

Snail

Significace of vacuum

Hi Jumper,



Our posts crossed.  I may have mislead you, the vaccum is not applied to the storage tank, which would be 500 US gallons plus unpressurised and insulated to the teeth.  The only reason I was thinking of putting the vacuum steam generator inside the tank was so it could share the insulation.  Logically it could be anywhere.  Basically, the idea was that hot water from the tank top would be circulated to heat a steam generator, which in this case is a water/boiling-water heat exchanger.  The steam generator won't work of course unless the steam side is under vacuum, so the heat receiving part of the exchanger and all the radiators and associated piping are also under vacuum as well, as in the VariVac system.  That means that the steam in the radiators condenses at lower temperatures, but that is fine, provided that they are designed accordingly.  The trick may be to be to find a suitable heat exchanger design that combines enough water/water contact with enough evaporation surface.



I don't understand your comment about the vacuum being a function of the weather.  It would be monitored and controlled by sensors and the vacuum pump.



As you note, one critical factor is how flat the radiating surfaces can be laid before the condensate build-up gets too thick and acts as an insulator.  Also, we rely on the density difference between air and steam to keep them reasonably separate at start-up, air to th e bottom, steam on top.  How flat is too flat for this to work?  Has anyone ever looked at this?

SWEI

Kiwiland

We've had a few posts from other Kiwis here, and I have thus far not found much in terms of NZ distribution for major players.



A quick search turned up these folks, who appear to sell Viessmann http://www.reddwarf.co.nz No experience or direct knowledge of them, but Viessmann is pretty good about educating their distribution chain.

Charlie from wmass

So sounds like you really want the steam

If you have flat ceilings you need to make sure the heat emitters you use can drain. The use of standard design radiators will leave a lot of water in them after a couple heating cycles. The use of flared copper like Gerry used has the advantage of being able to withstand vacuum well. I seldom see ceiling mounted radiators that do not have draining issues as they were not made even state side to lay flat. The heat exchanger to make steam from water also needs to give room for the water to separate. a drying chamber would help on the outlet of the heat exchanger well insulated 6" pipe would work. You can use it as a manifold for your steam tubes. The wall thickness allows enough metal where you could drill and tap into the pipe for sizes 1/2" BPS or smaller. From what you described I would say read up on the fire tube system and use it for a model. 

What are you planning to use for heat emitters? 

Charlie from wmass

Also as for the storage tanks

If you use pressurized tanks you can heat the water to above boiling and your circulators and related piping do not need to be for open system use. In other words spend more on the tanks and spend less on the other parts. The tanks will last far longer then the circulators will.

Snail

Radiator design

Hi Charlie,



You and your Dad, both of you have problems with air ticket prices.  Sorry to say, much as I'd love to see you down here, there are still no cheap tickets to be had. So whatever I do it will have to be happy with your advice only.  I know that even with a good local plumber it'll be up to me to obtain the right advice to get it designed right.  If the scheme gets a tick for feasibility here, I will be looking for someone to do the detail design.  Are there any engineering outfits in the US who would take on such a small job at reasonable cost?  There are plenty of steam engineers here, we are the worlds biggest dried milk powder exporters, but they won't know much about house heating.



Your comment about standard radiators not working like that indicates that it has been tried.  If they were actually mounted dead flat against the ceiling, I'm not surprised, or seriously worried at this stage, since mine will be tilted.  On the other hand, if they WERE tilted it IS a worry.  



I have always expected to have to fabricate my radiators.  The basic idea was just two sheets of 304 stainless, about 10mm(3/8inch) apart.  They would be about 2m wide from inlet to outlet header (About, I have forgotten the standard sheet sizes just now).



The top (back) one would be ridged for stiffness and dimpled or studded to keep the sheets apart.  25mm diameter headers would be formed in the sheets.  The top would be insulated.  A sump would be connected to the bottom header and a combination float/temperature bleed valve connected there.  The control feed valve would go to the top header.  (One thing we certainly can do in this town is fabricate stainless steel.  This is Dairy country.)



I figure that I can get about a 10 or 12 horizontal to 1 vertical slope on a 2m wide radiator, before occluding the top of the windows.  I think that it would look OK at that slope but not any steeper as well.  At that slope, I would expect no more than a thin film to be present in the radiator after shutdown.  My main worry is during operation, the water film thickness has to be considerably thicker than for a normal, vertical radiator.  The runoff speed has to be lower but you still have to move the same amount of water, so the flow cross-section must be thicker to compensate.  The water will act as a heat insulator.  Is that going to be significant or not?  It looks as if I may have to suck it and see if no-one has done the experiment before.  Or they may have already done so and the curse of the under-reported negative result has struck again I suppose.



I'm not sure what you are referring to regarding the heat exchanger, the in-boiler one or the vacuum side one downstream of the storage tank?  I'm not too worried about the boiler one at present, with combustion temperatures to play with it shouldn't be too hard to suck a good proportion of the heat into the steam.  I've read some of Dan Holohan's stuff on this site, so I saw the bit about the header.  I assume that this acts as a demister?   I'm more unsure about a practical vacuum evaporator.  Would a standard plate exchange, pump circulated on the hot water side and bubble-assisted vertical convection on the house (vacuum) side work?  Feeding into a header of course.



To get a 40C(72) usable temperature range, to make the storage effective enough, above 100C(212F) would require 40psi.  That is certain to get me into the range of regular costly inspections and will require a very much more sophisticated boiler.  We need a pressure reducing valve and a high pressure injector pump, which adds to the cost.  Given all that, if you do go that way, would it not be better to go to higher pressures, say 100-150psi and really add some efficiency to your storage?  Either way, I don't think that pressurization will be viable with my relatively limited heating demands.  And once again, I suspect that pricing and options will not cater for domestic use.  Chicken and egg really.  No demand because no viable supply, so no supply because of no demand. It looks like a really good option for those with real serious demands though.



thanks for taking the time with me.





Hi SWEI,



Thanks for posting the link.  Unfortunately it appears to be dead now.

SWEI

Red Dwarf

Looks like the front page is down this morning for some reason.  http://www.reddwarf.co.nz/contact/ still works here.



Edit: Their site is fine -- the link in my first post is not formatting correctly.  There's a trailing space and slash that I can't seem to get rid of.

jumper

heat transfer

Each time you transfer heat it costs you. So if stored hot water is boiling other water it costs you in multiple ways. Much easier to let stored hot water flash into steam.



Yes you can control vacuum but how do you intend to do it? One option is to control rate of water going into flash tank. What you call a steam generator. 500 gallons at 210° may supply you with about 200,000 btu. That's four hours at 50,000 btu per hour. Enough to take chill off in the morning. If you can pressurize storage tank to 230° it'll be a big improvement.

Snail

Flash boiler option

Hi Jumper,



I did think about using a flash boiler but I gave up on the idea. The following is my reasoning. It's all completely theoretical, so I may have screwed up. See what you think.



It's very easy to set up the injection, just pipe from the top of the storage tank through a control valve and into the flash boiler, possibly through a spray nozzle. The water will flash, taking all the energy needed to reduce the temperature of the water/steam from the storage tank temperature to the lower working temperature in the radiator system. So far so easy. However, only a few percent of the weight of the water turns into steam. Of course, this few percent carries all the useful energy so it is good to use. The other 98% or so is now just water at radiator temperature and cannot be used to put heat into the house. It is still warm however, so needs to go back to storage, also it's filling the flash boiler and has to be ejected. Now comes the problem. The flow of ejected water is 98% of that which you would be using to transfer the same amount of heat in a hot water system. Actually it's more, because you can probably arrange the hot water feed return to be colder thus using the storage more completely. Unlike the hot water pump, which typically needs to deliver the flow against a couple of pounds back-pressure, you are fighting against a vacuum head of possibly 25 feet or so! Because the inlet of the pump is in vacuum, I imagine that cavitation would also be quite a problem.

jumper

good point

You'll need a special lowNPSH pump to pump from flash tank to storage. You need it also to pump condensate back to storage. And you need two storage tanks. One to store radiator temperature water to feed boiler; the other for the hotter water from boiler. It's true that a heat exchanger can make your pumping easier but you'll still need two tanks or heating capacity gets reduced as you heat your home.



Solar heating requires storage. People have built systems using multiple tanks. For example six 100 gallon tanks for 500 gallons. The idea is that there's always a tank for used water. It gets messy. Easier to caulk and weather strip.



Also a big advantage of steam heating is that you don't need pumps, so keep thinking.

Snail

May have to give up on storage.

Thinking about all your comments, storage doesn't seem to be a goer.  As you point out Jumper, it is destroying the main advantage of steam, its brilliant and elegant simplicity.  That's a blow because I was hoping to use it with wood. 



There is one last chance.  If I have a steam generator wood boiler that supplies the radiators directly it could also heat the storage by steam when the radiators'  control valves don't want it all.  The storage heat cannot be used in the radiators but can heat the domestic hot water.  This would be a really simple system.  the only controls would be the valves on the radiators and the pressure head of the water in the tank, i.e. a poppet valve would allow steam into the bottom of the tank once the steam head was enough to overcome the water pressure.  This does mean that the steam pressure could get up to 2psi though, which has implications for the radiators.



The system would hardly fit the modern demand for click of switch operation, to put it mildly.  However, we intend to be carried out of this house, so if it's OK by me then it's OK.



Whether this even makes sense depends of whether the average hot water use is sufficient to keep up with the excess heat supply.  However, I think I see a way to provide a degree of turn-down for the boiler and still get clean burning, so it could work.  I need to look at my old bills to check our pattern of water use and do some calculations.



Can anyone tell me how much power it is practical to put though the micro-tubing?

jumper

much more practical

Yes it's much easier to store energy for domestic hot water. Especially with an after heater so that you don't run out. Years ago Veissmann provided me with a wood fired hot water boiler and a storage tank with a stainless steel coil in it. I located the tank well above the boiler to eliminate the circulator. Against Veissmann's recommendations. With practice the operator could estimate how much wood to feed to prevent safety valve from opening. I think she had to feed wood two or three times each evening to produce enough how water for morning showers. Probably that issue could be eliminated with a circulator or locating tank even higher.



Getting back to your original idea with steam heat. In some ways it's not original. In some industrial applications steam is produced with an unfired boiler. The fired boiler heats a non volatile liquid like molten salt. That hot salt boils water. Evidently pressure without fire is less dangerous.



You should begin with some numbers. Heating requirements. Annual cost. The people I worked with in Canada used expensive electricity but their home was insulated.

Snail

Some Numbers

Cost estimates are difficult.  We only ever use wood for space heat, which is free for the cutting and stacking.  Water heating accounts for about half our electricity use , so about 3 or 4,000 KW hours per year.  Electricity is very expensive -  30 cents American per kWh.  We will be moving to natural gas, which is cheaper but still very expensive.  So getting the system to preheat the domestic water heat will be worth it.



 Looking at sizing.  I estimate that I will be needing approximately 20kW total capacity, 70,000BTU/hr.  This based on the fact that we get by fine with a 16kW stove at present, not on detailed heat calculations, which I may need to do later but this should be good enough for initial scoping.  The stove is also a bit less efficient than it is rated to be, as it is an insert into an old external chimney, I strongly suspect without insulation around the back.  The biggest radiator would be around 8kW.    All this may seem ridiculously small but remember, it's for spot heating in a mild climate, not whole-house heating.  (Note, I'm not quoting square feet of radiator area, because the output of the ceiling radiators will be a lot less per square foot than a wall radiator.)  That's around 70 pounds of steam per hour, I think.



What further details should I sort out to allow a consultant to prepare an indicative design?,  (I know I'll need plans of house layout and boiler and heating locations.)



Are there any good websites of valve manufacturers and suppliers that I could browse?  Just for interest, specification would be up to the consultant.



Has anyone any further thoughts on my radiator "design".



If anyone has any experience or knowledge of the Mini-tube system could they comment on it's suitability in this application please?  I am a bit unclear about how it is possible to use such fine tubing when the "Dead Men" called for much larger diameter pipes.  Presumably such details as the valve sizing may differ, for venting at least, as well as such details as pipe slopes?  Do any of Dan's books cover this type of system?

Snail

Been a bit quiet here

Hope the weekend may turn up some interest?

Snail

Anyone got any ideas?

Hope late tonight there is something,   Bedtime already here.

moneypitfeeder

How about a crazy answer

Hi, while I am a huge steam advocate, I wonder if in your case there might be some cost effective alternatives out there for you. You mentioned on one of your answers that wood is practically free for you, have you ever heard of a rocket stove mass heater? See link: http://www.richsoil.com/rocket-stove-mass-heater.jsp I have looked into a lot of alternative heating options having an off grid cabin in a cold climate. This is a design I keep going back to but have not had direct experience with one. You haven't told us how big your house is, how many floors, etc. so it's hard to make a lot of suggestions. If you are bent towards steam it is certainly possible, but you would have to be willing to do a lot of legwork, and educate your installer. A lot of the steam systems in the US were originally installed when people didn't insulate. Example, my house is 3000 sq ft, 3 floors in central PA, drafty windows, with no insulation in the main house (there is an insulated addition) and only a smattering of insulation in the attics ceiling joists, and my system is pretty efficient for my area. I have large convector style radiators, and a few column rads. I have a 2 pipe vapor system and operate it at ounces of pressure. I really don't think you need to go the route of installing a rad overhead. They radiate, it's what they are designed to do, everything around them will heat, and heat rises...put them on the floor, and they will heat the room from the floor up ( where you want to feel the heat). I think your biggest problem would be finding reasonably priced radiators. For a steam system to really work as it efficiently in a drafty place I think you really need heavy cast iron rads. The thermal mass of the metal will continue to heat the room long after the boiler has shut off. Which is why steam feels so comfortable, the heat doesn't just stop with big rads. BTW, any mention I have seen of overhead rads was for industrial applications, or basements ( mainly to provide heating to the floor above, but I think some were for heating basements?>?) If you dig around the library here, I think there might be some articles about overhead rads but I could be mistaken.