Central heating system design/House construction

yes, a boiler is just a way to make hot water and you can have your header tank above it and all the radiators below it.

One way to do this is with what they call a "monoflow" system. This is a run of hot water in an insulated pipe and you tap out water at any point, run it through the radiator and back in to the pipe.

look in this forum

http://www.boilerroom.com/wwwboard/homeforum2.html

Thanks for the lead aurizon , but what I'm after is a configuration that is seemingly impossible - the heat source (boiler or whatever) being the highest component in a 'wet' system . I'm told air-locks make this impossible . What I want to know is if anybody knows a way of achieving my desired configuration.

Kris,

As long as you have room to run the boiler output and return lines up a few feet higher than the boiler before dropping down again, and install air separators (or "air scoops") with automatic vents on them at these high points you won't have any air lock problems. Install your circulator pump (or pumps) on the output side as close to the boiler as practical, and below the high point where the air bleeds are, rather than on the return side of the boiler, everything will be fine. Additionally, I would install some form of low water cutoff to prevent any possibility of the boiler running dry in the event of a leak in the piping at lower elevations. On my boiler I use a pressure switch as a low water safety cutoff because my basement heat loop is below the boiler level.

I have provided a link to a Taco brand air scoop. in the threaded hole, visible at the top, you install an automatic air bleed. A hole in the bottom allows the installation of a bladder type expansion tank. On my system I have one of these air scoops on the return, and one on the output, with an expansion tank on one of them. I did this because I wanted to be able to immediately purge my system of air if I refilled it based on past experience with hydronic systems that were troublesome to bleed. While my air scoops are only at a local high point above my boiler, and two zones are at higher elevations, they have automatic bleeds (but no air scoops) at their high points also.

Just remember that any high point can trap air, and while a fast enough flow can sometimes push the air to the system high point, I recommend automatic bleeds at each local high point for trouble free, quiet operation with the least hassle, and this is particularly true if you use monoflow tees to radiators/convectors, but also true in straight series run baseboard loops.

You don't mention how much lower your low points would be below the boiler water level, but a minimum system pressure (measured at the boiler) of 10-12 psig (cold) would be fine, and you could even go a little less, but I wouldn't go below 8 psig cold (the pressure will rise when the boiler heats up). If the boiler will also be providing domestic hot water using a "tankless" coil, I would use a similar scenario of running the pipes up over the boiler before dropping back down, with some provision of air venting at the high points.

As a final point, make certain the necessary structural support is present to mount the boiler in the loft.

http://www.taco-hvac.com/en/products/Air+Scoops%26reg%3B/products.html?current_category=123

Regards, Greg

Is a boiler your only option? I wouldn't recommend installng it in the attic. Boilers can spring leaks, pumps can leak, fittings and auxilary equipment can leak. In addition you would need to run your fuel supply and water supply to the attic. Also, an air vent would need to be installed to provide combustion air to the boiler. If possible install the boiler and its equipment in your garage or in an out-building rather than in the attic.

On the other hand, a warm air furnance can easily be installed in the attic, needing only the fuel supply and air vent. From a discharge plenum on the furance, run outs to each room can be installed, all in the attic, with openings through the ceiling with ceiling registers to distribute the air. In most instances, a single return air would suffice, but more could be added if necessary. The return air would be ducted back to the furnace.

Good luck

If you get a careful worker, who tins all his joints and ends and hot wipes them so they fit you will not have a problem with leakage. Most plumbers just flux and connect and rely on solder being drawn into the joint. Open up a few joints done this way and you often get only 50% filling of the joint, especially with a hasty worker.

You can transfer 1600 times as much energy per unit area with water versus air, so water pipes 1" in diameter can be as good as large ducts. It is a lot easier to retro fit water pipes than fit ducts in walls. Surface pipes are visble, but smaller than surface ducts.

Then water can freeze and it can leak, so yu create your ways to channel leaks safely down. Steam is even better than hot water, and that is why they use it a lot in large systems, but it has it's own drawbacks. Insulation is a good way to avoid buying heating and I have never seen insulation leak.

I want the heat source to supply hot water for the kitchen/bathroom and to feed heat to 'wet' Central heating.

Unless convenience is a concern with the North or South Pole as the location, a corn stove is recommended as the low cost option in most locations on the earth. See www.cornstove.info

Whole kernel shelled corn fuel is the local low cost globally renewable environmental friendly fuel with only a few isolated exceptions. With proper selection of corn stove model number to match the facility design, a ducted HVAC system is not required unless each door has a gasket type air seal.

Thanks , but I really don't think this is a viable option in the roof space of a house in the UK . It was interesting to find out about Cornstoves though.Kris

Kris,

You do not say what your source of energy is - electicity or oil or gas - it makes a difference.

You could just install a wall mounted gas condesning boiler with balanced flue in the kitchen like most people have now. It takes less than the space of one wall cupboard.

If you really need to put it in the attic, use a fully presurised system which uses an air reservoir to keep the pressure up and heats on demand - thus no header tank, but it is generally better if the air pressure reservoir - the size of a small football - is at the highest point.

Do you have a local heating and plumbing centre you can visit? They will be pleased to show you all the data sheets.

Hugh Mattos

Chartered Engineer

kris, if you only require some hot water supply your kitchen room and bathroom, why not consider to install a simple solar energy collector? it has higher efficient and convinient. even on the cloud day in the winter, it can offer enough hot water for use. we have a gas heating wall stoven but more family begin to use this kind of solar engery conlllector. (we cannt install it because we live in a flat and no fit space for it) very save Ive sent a pic to Gwen. you can ask him for pic if you are interested in. you can install it on your attic.

I could certainly consider adaptions for water that is to be heated purely for use at the tap ( I think the general term is "potable" water ). My house is what is known in the UK as "mid-terrace" (imagine a house that shares a common wall with a house on either side) . Solar may be a potential add on - my roof has 2 pitches , one facing East and the other West. This is the worst alignment for collecting Solar (at least I think so , but I will do some quick calculations later ). Also , I expect the price of solar cells should hopefully drop in the future. In my overall scheme I would like to retain the option to incorporate it.

For your general interest I have also been looking at heat pumps . A relatively new use of them is with boreholes , but this would not be practicable where I live.

I have a lot of different jobs to do in this house , and various factors mean that things will not get done in the optimum order. That is one reason I am looking for a flexible design . This may add to the end cost , but I am learning some very good stuff along the way. Eventually I'd like to get my hands on a renovation project that I don't have to live in whilst doing it - then I can use a good work schedule. This is a 'hobby' rather than a money making venture . I just hope the dust will not kill my poor computer before I get there !

Another issue I'm looking at is collecting rain water to use to flush the toilet - The UK has a developing problem with water supply/cost (despite the reputation of our weather )

I am trying to improve my 'hands-on' skills whilst keeping up with other demands in life . I also like the saying "never ask someone to do something you would not try yourself ".

Regards , Kris

I know this kind of house from tv, books, magzines, in our country there are also these type house, but most of them has less gradient pitch than yours do. in shanghai and other big cities, most of such europe style house is existing as well. of cuase the pitches is eastward and westward direction, because the gate is southward to get more sun light. Our people place the collector on the eastern pitch or place on ground and raly on tap pressure to get hot water.the unit can be 2Mx14; 2x16... they are about 200--500eud for your budget reference.
I dont know the hot pumper you metioned, is it so called heat tube? or heat pipe? it has very high heat exchange efficiency. but its very expensive. decade ago I bought one for my apparatus as sinker. as I make a bad touch surface result in bad heat transportioon. so pay attention to its technology. I know only this.
as to solar cell, its very expensive for our home use, but your european can afford to. the going price on the market is about 3--5 europedollar per watt depend on different silicon type. 2kw will spend about 10 thousands eud with accumulator. of cause its a very good selection energy resource form. even brazil begin to use them as their electric supply.
you reconstruct your water system. wonderful, although your bt is rainning frequently.
Im out of door to decorate. I cannt give more information only but a little electric experience.

Prepare for the possible event of leakage by creating the upper room for the heating system with sealed ceramic flooring, an oil-based paint on the walls, and good drainage. Then do your best to ensure no leakage will happen anyway. I really like the idea of your proposed HW heating system.

Mark

If space is so limited that you don't have room for a boiler - they are usually about the same size as a kitchen wall unit - would an electric system not be easier? We are all electric, and total utility bill is no more than the neighbour who uses gas - and we don't have the annual maintenance to worry about.

Slimline heaters take up the same space as a ratiator, and hot water produced overnight with top-up during the day if needed.

That's interesting , down here in the South of England gas is the norm yet everyone I've spoken to tells me gas is far cheaper to run. The price differential is sure to close , but the additional servicing may make me go in favour of electric.The concern I have with electric is that this perceived cost problem exists - a potential buyer would freak out. I'm slowly renovating this house (very slowly ) and would like to get the heating issue sorted. The space limitations are diabolical , and whilst I could live with a boiler in the Kitchen , the space I'll loose will cost money when I come to sell in a couple of years (the limitations are that bad). If I did just say to a fitter go ahead and set it all up with a boiler in the kitchen (feeding rads), I may find it impossible to relocate the boiler later.

I think all the "gas is much cheaper" assumptions came when the first electric systems were introduced in the 70s. My mum had one of these, as she would not have gas in the house - having known someone who came off worst in an accident. The units were half the width of the hall, and took three days to heat up/ cool down. Only two fitted in a 3bed bungalow, 4kW each. Costs were much more than the current models.(6 units from 0.5-2.0kW). A big advantage is that any repairs tend to be the replacement of elements, and the rest of the system works even if one element is faulty (3elements in 15 years).

The one in the kitchen is only used when the temperature falls below freezing through the day - not at all this winter - and all rooms can be adjusted to the desired temperature at the unit.

The worst system we ever had in a house was a hot air distributed gas system. The ducts were uninsulated, and heated more of the space under the floor than the rooms - we were on the ground floor.

I think that we have to accept that there is a straightforward comparison of energy cost per KWhr. In my case the gas cost is lowest, then oil - depending upon a rapidly fluctuating price - but electricity is double the gas at my rates. You need to consider the efficiency of the conversion form source to room, and also from a global perspective the very low efficiency of electricity generation

That said, if you can get a good deal electric can be good offpeak, and the installation costs are much lower, and as you say the servicing is much easier.

Hugh Mattos Chartered Engineer

Agree with all you say, my electricity is on a special contract, giving 3 readings (day, night & control - the heating circuit, inc. water with additional boost as required)

For a small property, the cost of the boiler is split between fewer rooms, so is more likely to be dearer over the life of the system. One benefit, though would be that adding a solar heater could be cheaper and easier using direct water heating, where the electric system would need PV cells.

BUY A COPY OF DAN HOLIHAN'S 'PUMPING AWAY' ONLINE VERY REASONABLE. FOLLOWING THE SIMPLE DETAILS IN THE BOOK WILL PREVENT AIR LOCKING AND A HOST OF OTHER PROBLEMS YOU WOULD NOT THINK OF UNTIL THEY ARISE. YOU WILL NEED AN INEXPENSIVE VACCUM BREAKER TO PREVENT THE BOILER FROM DRAINING BY SIPHON WERE A PIPE TO BREAK BELOW. IMC REQUIRES INSTALLATION OF A DRAIN PAN UNDER THE BOILER INSTALLED OVER FINISHED SPACE AND ASME NOW REQUIRES LWCO ON ALL BOILERS. IF YOU GO BY DAN'S INSTRUCTIONS, YOU WILL GET THE MOST FOR YOUR MONEY AND HAVE THE MOST EFFICIENT SYSTEM POSSIBLE. PS( I PERSONALLY DON'T LIKE THE MAN BUT THE BOOK IS THE BIBLE FOR HYDRONIC HEATING).

Many thanks to everybody who's taken the time to let me know their thoughts on this .

Ive just had a chat with a guy who can supply a system that utilizes a vented boiler that can be located irrespective of where the radiators are located .I didn't really get the drift of this over the phone , so he's posting me some detail. If it's as good as it sounds it will give me the flexibility I want (it sounds like a fairly new innovation).

I'll get back and let you all know how it pans out when I've seen this guys idea and canvassed opinion from a local plumber who can see my house at first hand.I'll also be looking into the links you've provided. Very much appreciated folks. Kris

Those vented condensing gas boilers are great.I run one in the attic, it is the highest point in the system and it works fine. (5 winters now, no single failure yet)

A decent quality boiler has its own air purge. But attention, you need to open a valve or loosen a screw to enable the functionality. (a mistake often made)

If you are really in doubt of leaks you can install a drip pan underneath the boiler system. In the drip pan you can install a water detection system and you need to install a condensation evacuation system.

Freezing risk: a boiler system in an insulated attic, supplying heat for the central heating system will never freeze. You need to protect the lines against freezing, so the pump must be activated as soon as the temperature in the coldest room goes below 4°C, normally a boiler has a freezing protection that will start heating as soon as the water goes below 4°C. (At least the one I have does it that way)

The attic is also the perfect spot to connect the system to a sun heat collector. And last remark: the attic is the closest to the roof, small exhaust piping, reducing extra costs as long piping needs to be of a bigger size.

Gwen

You've made some good points . The data that is being sent to me incorporates a system schematic that enables a vented cylinder or boiler to be located anywhere. If I run some ( 'just-in-case') piping to the attic , I can initially have the heat source downstairs but move it to the loft at a later date . Hooking the thing up again (if electric ) to the rad system would not be that big a deal. Further explanation is pending the Postman .

Ok so no experts here. You need a minimum height above your storage tank for the expansion pipe (vent) of 6 feet, then fire regs may prevent the loft location. Gas regs are now much tighter as well. The next best proposition is to go for the storage heater option on what was the economy eleven scheme, new slim line heaters can be fitted in each room as required with individual controls for heat out put. as long as you get a good qualified electrition to give you an estimate or quote and ask your local council enviromental person about the best insulation and energy requirements you should be able to look after your heating needs. The tariff on the economy eleven was set so as to encourage usage of electricity out of normal hours. The times were set at 11:00 pm to 7:oo am. the storage heater would when set correctly give out enough heat to cope with the time inbetween. The gas solution is going to be expensive and don't use the condencing boiler option they are just trouble.

OK , The plan that seems best for my situation includes a dual-pressure system . In general terms a vented cylinder feeds the rads via a pump and non return valve , return flow to the cylinder is de-pressurised by a feedback control unit . This means that rads can be above the header tank and cylinder . I can get the advantages of a conventional pressurised system , but not the more extensive set-up hassles.

I'm not rushing this project , but when I've finished 'wall-bashing' etc and got everything up and running I'll post a project update.

Kris.

One possibility for the location of a boiler, if interior space is limited, is in a lean-to structure attached to the outside of the building.

The absence of air locks in piping has more to do with the piping design than the location of the heat source. Building Regulations may dictate where a central heating boiler will go, and will certainly dictate the design and layout of the plumbing needed to connect it to any hot tank and radiators. It is contrary to Regs to install a gravity feed hot water system these days. Building regs are available on the 'net, and the Planning office at the local authority is also a valuable source of advice worth tapping into.

As an aside, water can be raised to a higher temperature than 100degC by applying pressure to it, sometimes expressed as 'head': Westinghouse does this with the Pressurised Water Reactor in nuclear power generation. However, release the pressure and, well, er...