dual system..for the expert!!

[Bernie2]

Hi! Buffy

Sorry for slow reply, could not work out what was going on. In the basics a free unobstructed vent with a good cold feed path seem to cover safety, it may be worth adding a blow off valve on the boiler, you never know the vent and cold feed could freeze.

The waste heat is a problem but I feel sure you know that anyway. Up and over systems are terrible for trapping air but you seem to have worked that out as well.

 

[justlead1]

Hi. There are a number of issues here,
1. Pumped primaries on solid fuel should not be used. On a cold windy day when the stove is working at max, is the time power failure is most likely to happen. The stove will almost bounce around the room and the noise omitted will frighten the life out of you. 14 kw is a lot of energy, along with the noise etc the roof space will be converting the steam back to water, staining ceiling etc. (pipes in loft frozen is another story?
2. Using a drop system on primaries to cylinder will result in parasitic circulation of hot water up the primary flow into the roof space, when the stove system is not in use. Resulting in the waste of stored water heat/energy waste.
3. When gravity primaries were used extensively, and over heating occurred. The fire could be shoveled out and the hot taps through out the house turned on to introduce cold water into the cylinder to find the heat produced something to do with it self.
4. Why not just heat the room with the stove? Its a safe option. Good Luck

 

[Renewable M]

Sorry if you didnt like the tone of my previous answer, but crumbs, what you are trying to do, as many people have explained, is not in any way good. It's got nothing to do with my ego. I didn't create the laws of physics or building regs. Honestly!

Some of the guys have spelt out some very, very basic principles that any heating engineer should know, like the basics of thermodynamics, that's all. Heat is heat, whether produced by gas, oil, wood, heat pumps. The biggest issue with a stove is the lack of control. Thats why you need to follow the regs to the letter. They are there to prevent disasters and you dont want your phone ringing with an unhappy customer each time the stove gets hot and there is nowhere for the heat to go.

The f&e tank is not an acceptable repository for the surplus energy either.

What you are trying to do is quite frankly, well dodgy.

Anyway, hope it goes well.

 

[Bernie2]

Yes it probably will be a nightmare system. I wouldn't do it. And yes it probably will vent into the f and e and possibly bounce around.

But if there are no alternatives?

Could always put the pump on a by pass circuite and retain primaries integrity, using the pump as an aid to circulation rather than the prime circulator perhaps.

Its all very dodgy.

 

[buffy27]

thanks guys .. listen renew m i do understand pretty much every thing u said to me ..my problem was the tone u took with me ..read back now in hindsight ..u were a bit ott in your approach...now as i have said i have done nothing yet and am still unsure..i rang a plumber who told me he has a stove in his house which is up and down ..too much hassle to cut floor he said...he put 3 bar blow off on boiler which is piped to outside..he vented from 1' to 3/4' while rising and then had 2 air vents just for commissioning.. he said it works grand...now he said its not to the book but its safe !!!
if u have a situation where the coil on cylinder is below the level of the stove.general rule of thumb is 18 ' between flow hight in stove to coil inlet.any one come across this even !!

 

[migoplumber]

i'm one of them who still thinks it can be done. closed loop circuit up over and down, when the flow gets hot, yes convection will send the hot up the flow pipe. but it dosn't stop there. stove constantly heating water. flow carry's on getting hot and rising. as pointed out before basic physics. but in closed circuit, nobody remebered to point out flow in one direction will create a flow in the other! the forced flow through convection will also force the water down the return pipe, and back into the stove - making the closed circuit circulate.
the system can work - easily.
and i also agree it could also go very pair shaped, but dont question the physics involved!
buffy has my blessing right or wrong!

 

[buffy27]

cheers ..like. ye must know by now that i have some bit of a decent head for this plumbing lark..been on here a good while now. lads this really is a kinda dark area in plumbing .i just wanted to bounce idea s around...now,i understand there must be a cut off point regarding regulations etc and i am not challenging them. but i cannot see how a bomb can be formed..open vent ..feed adding cold water down return and a 3 bar blow off on top of stove..there will be a natural convectional circuit if the pump fails,from the expansion back down through the feed on return!!the f & e would be well supported all around with the expansion dropped into a hole in the cover of the tank.../not plastic.. any input appreciated ..cheers

 

[migoplumber]

buff, just could i think it can be done, dosnt mean it should!! there are lots of points (most of which have been covered here) which if not followed through could lead an explosive combination. i think the point earlier raised about pressure and temps is concerning. as i recall over pressurize steam vapour returning to water increases in volume by about 1100 times. thats a big bomb. just be carefull, research it for another week or so before you go back to site.

 

[buffy27]

what if a larger stainless f& e tank was used ..wouldn t this help as a heat dump in this extreme overheating cases..

 

[migoplumber]

nope, cant use an f+e tank for heat dumping!!
i read that posted website sucking up info willy nilly, was dead good. do the same

 

[justlead1]

Hi To achieve gravity circulation the parameters are very tight. The cylinder needs to be as near as vertical above the boiler as possible an as high as possible. Long horizontal runs and the friction they provide, will slow circulation to a stop. What makes the water move is the circulating head, which is measured in parts of an inch. Developed by the weight difference between water in say 12" length of the flow and return pipe. The weight difference being the amount of water displaced with a temp difference of say 20 degrees is minimal. I would also challenge whether the coil/heat exchanger within the cylinder is capable of converting 14 kw per hour through this apparatus?

 

[peteheat]

Hi,

I would really love to be able to say this will work safely because I sell stoves !

There are stoves designed to work as part of a pressurised system, I have not come across one made by a UK manufacturer yet and I seriously doubt any of the Chinese models (including Stanley, Mulberry etc) have caught up with the design.

Please do not try to take elements of both open and pressurised systems to try to make the system work.

A 3 bar safety will be a total pain (constant call backs) because it will most likely be either blowing off or definitely weeping on a regular basis.

Forget what your plumber told you about his system he was not working for a consumer likely to panic when the pipes start banging.

The cylinder will use about 4 > 6 Kw of the heat when it is cold, as it heats up the return will get hotter, if the stove can produce 14 Kw you would need a heat dump (buffer) with a capacity of approx 700 litres.

 

[buffy27]

is a thermal store not pressurised ..seen stoves worked with 500l thermal store cylinders.

 

[peteheat]

Hi buffy,

Not neccesarily like most large cylinders buffers, thermal stores, accumulators can all be plumbed to suit the heating appliance.

Coils can be fitted to add or take out the heat, some are used as pre-heat cyinders.

In all cases the standard multi fuel stove should have the old fashioned header F&E tank for safety.

 

[Renewable M]

Hey pete, when you say the f&e for safety you mean the open vented aspect rather than a heat dump I'm sure.

p.s. what stoves do you sell. are you a shop? pm me if you like