I am trying to sort out my badly installed woodburner with back boiler plumbed incorrectly.
Fitting a Dunsley Baker Neutraliser would be very difficult, and as an alternative I am exploring the use of normally-open motorised valves.
Is there such a thing as a non return valve available for 28mm copper pipework? I think this would help get a better result. If so, could someone post a link and/or the proper name for me?
Keith
Yes one version is mentioned in the instructions for an Aga/Rayburn, which has a particularly low pressure to open requirement. From memory it was called a featherweight check valve. Keep in mind the heat input from a solid fuel fire and what will happen if there is a power cut for whatever reason. Gravity circulation to an adequate heat dump is a basic essential to deal with this eventuality
What's the problem, is there another boiler or a pump in the same heating system?
Yes, there are swing-check (hinged flap, closes under it's own weight, observe fitting orientation) and spring-check (spring assisted, can usually be adjusted) types. I'm dubious that they'd fix the problem, but that depends on what the problem is. There shouldn't be any valves in the pipes between the boiler, open vent, heat dump radiator, cold feed.
The problem is that the woodburner back boiler feeds and returns have been simply plumbed into the main central S plan heating arrangement with plain T joints - at some considerable distance from the oil boiler. The result is of course that the oil boiler ends up heating the water in the back boiler (along with long runs of 28mm pipework) as well as the rest of the house . I discovered this problem when balancing the radiators after replacing several of them using one of those clever infrared temperature thingys. The input temp at the radiators was 5 degree C or more less than it should be.
I solved the problem initially using simple ball valves on the woodburner flows and returns and remembering to open them when I lit the woodburner - highly unsatisfactory (and potentially dangerous). I had a heating engineer round about fitting a Dursley Neutraliser. He seemed to know his stuff but couldn't really work out a way to sort it without considerable expense.
The point is that we never need to use the oil boiler and woodburner together. Also the woodburner is rated at a much lower output than the oil boiler, and procuring and lugging into the room all the wood needed to keep the woodburner going at full tilt simply does not really fit in with our lifestyle. It isn't really necessary anyway - it is a big house, but having the oil boiler running for up to 4 hours in the morning, with perhaps the occasional topup during the day, is adequate to keep it reasonably warm. The woodburner is in the room we sit in at night, and a fairly small fire is enough for our needs.
The only fail-safe answer I can come up with is using 4 "normally open" motorised valves, wired so they close when the boiler comes on, but these cost a minimum of =A365 each for 28mm valves as far as I can see. So I was toying with the idea of just fitting two on the central heating side of the woodburner pipework and somehow working out if I could make do with non-return valves on the HW side - if such things existed - hence my question.
At least I know they do exist now, I just haven't quite yet got my head round where I should fit them and whether they would help.
Keith
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Keefiedee saying something like:
You don't need two of anything. Just the one would do, but as a general rule, nothing that could stick closed should be put into a gravity loop. It works, that I do know - I've come across it, but I wouldn't do it, just in case. Have you seen the results of a steam explosion in a house?
I can't get me 'ed around the requirement for four and then dragging the HW circuit into the equation. I guess there could be a second loop from the wood burner to a coil in the HW cylinder...
As for spring valves I doubt very much that gravity would have enough 'umph to open them. A biased open(*) flap valve that closes when the pump for the oil boiler tries to cause flow through the woodburner loop might work.
But still doesn't avoid the problem of no flow through the woodburner. At least with only one valve the woddburner boiler would still be open but could still boil, Maybe adding another vent vertically close to the woodburner with a whistle on the end... B-)
(*) By orientating it so gravity makes it open.
Our woodburner in a similar set up has a motorised valve and pump on the pipe that links the woodburner's boiler to the main heating loop and these are controlled by a thermostat on the flow pipe by the burner. For safety reasons that are two radiators that are directly linked to the woodburner to dissipate any excess heat.
Jonathan
In both boilers the CH and HW circuits are connected - i.e. each have two loops from the heating chamber - thus four pipes. My concern was that it might be possible for the return flow from the radiators, which is connected by a T-junction to the return flow of the woodburner, to not just go back to the oil boiler but also to go through the woodburner CH return, through the woodburner boiler and then through the woodburner HW return and generally lose heat where it shouldn't before finding its way back to the oil boiler return.
I imagine one could argue that the suction effect of the CH pump is likely to draw the water flow back towards the oil boiler and so it's not likely to flow towards the woodburner CH return, but a little experiment I have just done - switching on the oil boiler and closing the feeds but not the returns to the woodburner for a short while - soon resulted in a small, but significant increase in the temperature of the woodburner CH return. So as far as I can see, 4 normally open valves would be needed to completely stop any possible flow throuhg the woodburner boiler.
I assume standard normally open motorised valves cannot stick closed and are normally used in solid fuel systems and fail safe in the event of a power failure.
And to reassure the guy concerned about a steam explosion, although the plumbing of the woodburner has generally been bodged, they did at least fit a steam release valve!!!
Keith
In both boilers the CH and HW circuits are connected - i.e. each have two loops from the heating chamber - thus four pipes. My concern was that it might be possible for the return flow from the radiators, which is connected by a T-junction to the return flow of the woodburner, to not just go back to the oil boiler but also to go through the woodburner CH return, through the woodburner boiler and then through the woodburner HW return and generally lose heat where it shouldn't before finding its way back to the oil boiler return.
I imagine one could argue that the suction effect of the CH pump is likely to draw the water flow back towards the oil boiler and so it's not likely to flow towards the woodburner CH return, but a little experiment I have just done - switching on the oil boiler and closing the feeds but not the returns to the woodburner for a short while - soon resulted in a small, but significant increase in the temperature of the woodburner CH return. So as far as I can see, 4 normally open valves would be needed to completely stop any possible flow throuhg the woodburner boiler.
I assume standard normally open motorised valves cannot stick closed and are normally used in solid fuel systems and fail safe in the event of a power failure.
And to reassure the guy concerned about a steam explosion, although the plumbing of the woodburner has generally been bodged, they did at least fit a steam release valve!!!
Keith
Isn't this an application for injector tee's?
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Keefiedee saying something like:
One hopes it works :)
If they fitted it close to the stove, then fine.
It looks as if it could be venturi effect.
effect.http://www.google.co.uk/search?num=50&hl=en&newwindow=1&safe=off&pwst...>> Baz
Injector tee's sound promising! Are you suggesting I fit one at each of the four T junctions where the feeds and returns form the oil boiler are joined to the feeds and returns of the woodburner boiler - giving the oil boiler preference. Presumably this would be sort of the equivalent of fitting a Dursley Neutraliser. Or would you suggest I fit normally open motorised valves on the woodburner boiler feeds and injector tee's on the returns.
And yes the steam release valve is within 3 feet of the boiler!
Keith
stream is constant so, increasing the velocity (reducing the c.s.a.) causes a reduction in the pressure. The pressure can be reduced to induce flow from the tee branch &/or make a vacuum pump.
No.
But I don't think they will do what you want ie stop the flow through the woodburner loops when the oil boilers pump is running. Mr Bernoulli and/or the venturi effect will draw water from the stub of the T.
At anything they may make it worse by evening up the flows. The site says they are for use with Agas and Rayburns, things that are on and hot 24/7...
With the four pipes on both boilers(?) it does become a nightmare, as you say any incoming flow on any pipe could find it's way back via any of the other three pipes.
Injector tees are really meant for linking a gravity flow solid fuel boiler to a pumped central heating system. The gravity circulation works when the pump is off and the circulation through the solid fuel boiler is assisted when the pump is on.
The nuisance flow is caused by a pressure difference across the flow and return connections. The neutraliser works by ensuring that the pressure on all the flows and returns connected to it are the same. You would typically have a pumped input from an oil/gas boiler, gravity input from a solid fuel boiler, and pumped distribution(s) to a central heating system and hot water cylinder(s).
You can achieve the same effect witha low loss header; the header is a pipe that is large enough that the flow through it causes a negligible pressure loss due to friction along its length. Have a google for "closely-spaced tees" and "primary-secondary systems".
In your case, the heat distribution system could be a pumped primary circuit. The oil boiler could then be connected as a pumped secondary circuit through a low loss header. The circulation in the primary circuit is not affected by whether the oil boiler and pump is on or off. Similarly, no heat from the primary circuit enters the oil boiler's secondary circuit when the boiler pump is off.
Similarly, the wood burner could be connected ,as a separate independent system with a heat dump radiator and linked the primary distribution system via closely spaced tees. If the pipe sizes are calculated correctly, it will work by gravity circulation without a pump.
The primary flow has to be greater than the secondary flow rate or you get reverse flow in the common pipework.
The usual problems arise by connecting both boilers to the flow and return pipes in order to generate flow through them. This results in uncontrolled flow through unfired boilers and, usually, a major heat loss to the atmosphere.
Just picked up this thread. We have two wood stoves fitted to the cylinder. All gravity fed and with heat dump rads. We get backflow from ine stove to the other when we only light one and they tend to form a loop and bypass t he water when we light both. Thinking of fitting a non rerurn valve to help stop this but would welcome some advice. We know it's not conventional but the heat sink rads work well to prevent overheating we just need to stop t he flow heading off down the other 28mm at the T to the cylinder
cylinder. All gravity fed and with heat dump rads. We get backflow from ine stove to the other when we only light one and they tend to form a loop and bypass the water when we light both. Thinking of fitting a non rerurn valve to help stop this but would welcome some advice. We know it's not conventional but the heat sink rads work well to prevent overheating we just need to stop the flow heading off down the other
28mm at the T to the cylinderI'm going to assume that whatever you are replying to is a long gone thread and treat this as a new question. The problem with non return valves is that they tend to have both significant operating pressure and some flow resistance, and would probably stop the gravity circulation working properly.
Hopefully someone has a solution. One would be 28mm full bore electrically operated valves and temperature sensors. But, if they exist, they would probably cost more than the rest of the heating system, so I don't know.
+1
google "dunsley neutraliser". Essentially a sealed box with lots of pipe ports for the flows and returns of the various loops. The idea is to have everything at the same "level" and nothing sharing a pipe so that the only thing that drives circulation in a given gravity loop is the density of the water in that loop.
Needs to be fail safe without power or manual intervention. What's the point of having stoves if you can't light them when the powers off...
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.