Hello. I have absolutely no knowledge of back boiler systems. But I would like to know is it possible to run 2 radiators in 2 bedrooms off a backboiler stove directly below the rooms without a water tank? What is the most basic system possible? Thankyou
back boiler no tank
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It would be best if you supplied a basic drawing or schematic in a post, or gave a better description of the term "back boiler." I'm guessing that you are describing a thermosiphon coming off a solid-fuel burning stove with a water heating coil or tank on it. It is certainly possible to heat two radiators on the floor above that. BUT…you need especially to provide for overheat scenarios. Definitely you must have a temperature/pressure relief valve on the system. It would be good to have the amount of radiation match well with the BTU output of the heating unit.
maple1
Minister of Fire
'Without a water tank'.
You will need some sort of tank for expansion of the water when it gets hot. And the above mentioned overheat protection. Have no idea what this back boiler is you mention, but if it works off a stove I likely wouldn't count on keeping very much space very warm with it.
You will need some sort of tank for expansion of the water when it gets hot. And the above mentioned overheat protection. Have no idea what this back boiler is you mention, but if it works off a stove I likely wouldn't count on keeping very much space very warm with it.
Wood cook stoves on this side of the pond commonly were fitted with coils to heat a tank of water for domestic use. Back in the day that those cook stoves were burning all day long they could heat a lot of water. But they were famous for sooting up (the coils or plates) and eventually leaking. Those I've seen weren't pressure tight but were topped up as water was used by pouring water in at the top of the tank.
A simple thermosiphoning system probably could be rigged up to get some heat upstairs but it would be a devil of a calculation to guess how much heat, on average, could be managed. A simple circulator pump would help a lot but it would not add to the simplicity.
My intuitive guess would be that a hole in the ceiling with a floor grating above in each room would let in more heat as long a the bedroom doors were left open to let the warm air circulate back down the stairs. That's how my grandfather's place did it. Kept the frost off the window panes, anyway.
Not what your interior decorator wants to see, I bet.
A simple thermosiphoning system probably could be rigged up to get some heat upstairs but it would be a devil of a calculation to guess how much heat, on average, could be managed. A simple circulator pump would help a lot but it would not add to the simplicity.
My intuitive guess would be that a hole in the ceiling with a floor grating above in each room would let in more heat as long a the bedroom doors were left open to let the warm air circulate back down the stairs. That's how my grandfather's place did it. Kept the frost off the window panes, anyway.
Not what your interior decorator wants to see, I bet.
Here's the best book I've found on the subject ;
http://www.archive.org/stream/kitchenboilerco00unkngoog#page/n6/mode/2up
Reprints are available on Amazon.
A gravity system is the simplest. That requires the heated water to rise out the higher water outlet on back boiler, continue to rise to radiation and drop back down as it cools and becomes heavier to the lower water inlet on boiler. This uses the lighter expanded hot water for circulation instead of a pump. An expansion tank with relief valve is required when you heat water since it expands and builds up pressure. Overheating the water will produce steam with explosive force, so expansion and safety relief is necessary on any closed system.
http://www.archive.org/stream/kitchenboilerco00unkngoog#page/n6/mode/2up
Reprints are available on Amazon.
A gravity system is the simplest. That requires the heated water to rise out the higher water outlet on back boiler, continue to rise to radiation and drop back down as it cools and becomes heavier to the lower water inlet on boiler. This uses the lighter expanded hot water for circulation instead of a pump. An expansion tank with relief valve is required when you heat water since it expands and builds up pressure. Overheating the water will produce steam with explosive force, so expansion and safety relief is necessary on any closed system.
Some of the basics are a water pressure regulator on feed line, 3/4 stainless pipe water back is the best and ALL piping should be 3/4 or larger. This cuts down on resistance and will circulate as well as a small circulator pump. With proper pitch up and back down, (1/4 inch / ft.) depending on system resistance, length and materials used, it may require a throttle valve to slow the flow. At the highest point of system there should be an automatic vent that has a small float that releases any air out of the system. There are all sorts of air separators, scoops mounted horizontal on the outlet, and spiral separators, but the float type at top is all that is necessary. It allows you to fill the system venting air out the top as well. A manual boiler drain at the top works, but for the cost of a float type, it's well worth never bleeding the system manually. Heating water causes tiny air bubbles which is the separation of oxygen from the water. This needs to be purged and will rise to the highest point in system. When this air bubble gets large enough it will stop flow, overheating water in boiler causing the relief valve to open allowing more cold water into system. So all these components are necessary.
Tubing, if Pex or poly tubing is used, must be the type for heating systems with oxygen barrier. This is not covered in the book since it is new technology. Nature will balance itself and when the oxygen is removed in the water, oxygen molecules go through regular water tubing replacing the oxygen that has been removed. If a circulator pump is used or not, always allow rising hot water to flow AWAY from the expansion tank, never towards it since higher pressure on hot side, or pump outlet side will push into tank. These small tanks have a bladder inside like a balloon for expansion. Older tanks without bladder rely on keeping an air space above water and loose this air bubble becoming water logged. Relief valve starts to operate as water expands...... Stick with a newer tank with bladder. Circulator pump should be at return side, pumping into boiler as well. For gravity flow, (thermosiphon) the less elbows the better, flexible tubing with minimum 3/4 ID is the secret for good circulation. If copper is used, insulate the hot lines to prevent heat loss and keep the fluid expanded and light to continue to rise. Let it cool uninsulated on the way back in returns. If it sounds like a babbling brook, there is air in the system. Don't mix materials such as copper and zinc galvanized fittings. Dissimilar metals create electrolysis or a minute electrical current flow between dissimilar metals. With stainless coil (boiler) the entire system can be copper, iron, or galvanized, but don't mix the materials in the system. If you already have an iron water back, and iron radiators, use poly between them. With proper material selection, corrosion can be eliminated without the use of chemicals. Those are the basics to follow.
Tubing, if Pex or poly tubing is used, must be the type for heating systems with oxygen barrier. This is not covered in the book since it is new technology. Nature will balance itself and when the oxygen is removed in the water, oxygen molecules go through regular water tubing replacing the oxygen that has been removed. If a circulator pump is used or not, always allow rising hot water to flow AWAY from the expansion tank, never towards it since higher pressure on hot side, or pump outlet side will push into tank. These small tanks have a bladder inside like a balloon for expansion. Older tanks without bladder rely on keeping an air space above water and loose this air bubble becoming water logged. Relief valve starts to operate as water expands...... Stick with a newer tank with bladder. Circulator pump should be at return side, pumping into boiler as well. For gravity flow, (thermosiphon) the less elbows the better, flexible tubing with minimum 3/4 ID is the secret for good circulation. If copper is used, insulate the hot lines to prevent heat loss and keep the fluid expanded and light to continue to rise. Let it cool uninsulated on the way back in returns. If it sounds like a babbling brook, there is air in the system. Don't mix materials such as copper and zinc galvanized fittings. Dissimilar metals create electrolysis or a minute electrical current flow between dissimilar metals. With stainless coil (boiler) the entire system can be copper, iron, or galvanized, but don't mix the materials in the system. If you already have an iron water back, and iron radiators, use poly between them. With proper material selection, corrosion can be eliminated without the use of chemicals. Those are the basics to follow.
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