Oil and Multi fuel Stove Linkup - Part 1

[Gray0689]

It's another of those threads I gaze at with morbid fascination!

It amazes me john that when someone asked for advice
Then just totally does the opposite lol
Sure let them do what they want it's not my house lol

 

[Nostrum]

Can't quite see how the second heat distributing heat exchanger will work effectively. The cold water will cool the heat exchanger, but the stove will carry on heating the store? The heat loss will be negligible.

unless the bottle of cheap 'meal deal' champagne I'm drinking is hindering my reading abilities?

 

[Gray0689]

Can't quite see how the second heat distributing heat exchanger will work effectively. The cold water will cool the heat exchanger, but the stove will carry on heating the store? The heat loss will be negligible.

unless the bottle of cheap 'meal deal' champagne I'm drinking is hindering my reading abilities?

Vintage krug it is then lol

 

[Nostrum]

Smart price bollinger I think.

 

[dlm4473]

Can't quite see how the second heat distributing heat exchanger will work effectively. The cold water will cool the heat exchanger, but the stove will carry on heating the store? The heat loss will be negligible.

Hot input to heat exchanger is main gravity flow - cooled output to gravity return . Valves stays open as long as water temp >95 degrees. Cooled return will speed up gravity flow which in turn speeds cooling. A 50KW heat exchanger will cool 5 times faster (with sufficiant flow) than the stove (10KW) can heat. This method will ensure the water cannot boil - which a a heat leak can only "help" to prevent.

This system is already incorporated into off the shelf thermal stores - xcel heat bank is one that i know of. wont let me post links but youl find it on heatweb. To quote from their site

"Another unique aspect of the Xcel Heat Bank (again, patented by us so unavailable anywhere else) is its ability to protect from overheating, even during a power cut. This system was designed primarily for systems connected to a wood burner. It is needed because wood burners provide a large amount of energy, and they don't turn off, even when there is a power cut. As such they easily have the ability to boil the water in a thermal store if there is no other form of protection.
The standard approach is to use a heat leak radiator - located higher than the wood burner so that heat generated in the wood burner circulates naturally (thermo-syphon) to the radiator where heat is dissipated and the cooled water drops back into the wood burner. This is fine providing:

1. 
   [*=1] The wood burner is thermostatic, and slows its burn rate down when it gets hot.
   [*=1] The heat leak radiator is large enough to dump the output of the wood burner.
   [*=1] A location can be found above the wood burner for a dedicated heat leak radiator.

The problems start occurring when not all of these criteria can be met, and given that most wood burners are not thermostatic and have an output of approx 9kW to water, the chances of dedicating 9kW of radiators (three large double convectors) to this function becomes impossible.
The protection system on the Xcel works on the basis that the heat can circulate from the wood burner to the Heat Bank naturally using thermo-syphon (gravity) circulation. The Xcel is fitted with a heat exchanger in the top, and if the temperature of the water in the store ever goes over 95°C then a mechanical valve opens up to allow cold mains water to pass through the heat exchanger and out to drain, cooling down the stored water as it does so. The heat exchanger can extract over 12kW of heat and as such is suitable for all types of wood burner, and in many instances is the only way that the latest building regulations (now covering vented systems) can me met when using a wood burner."

Hence the reason i am confused at the advice being given - i'm not ignoring anyones advice i'm trying to understand it.

 

[Dotty]

The advice is get someone in who knows what they're doing. You don't need to understand the system.

You just need faith in it. And what you're looking to do I wouldn't put faith in if I were you.

 

[dlm4473]

The advice is get someone in who knows what they're doing. You don't need to understand the system.

You just need faith in it. And what you're looking to do I wouldn't put faith in if I were you.

The only problem there croppie is that I would struggle to have faith in the people that say they "know what there doing" when they ;

1) cant answer a simple question i.e. how does a 1KW heat leak rad dissapate heat from a 10KW stove
2) Whilst professing how knowlegable they are - are apparently unaware that this system is fitted to off-the-shelf thermal stores - presumably (but i could be wrong) passing all relevant standards inc. building control and WRAS.
3) Appear to think that Danfoss (and other manufacturers) who designed and made these valves specifically for use with heat exchangers for overhead protection on solid fuel heating systems are "silly" and don't know what they are doing.

Would you have faith in that person ? or the system they installed ?

 

[Gray0689]

The only problem there croppie is that I would struggle to have faith in the people that say they "know what there doing" when they ;

1) cant answer a simple question i.e. how does a 1KW heat leak rad dissapate heat from a 10KW stove
2) Whilst professing how knowlegable they are - are apparently unaware that this system is fitted to off-the-shelf thermal stores - presumably (but i could be wrong) passing all relevant standards inc. building control and WRAS.
3) Appear to think that Danfoss (and other manufacturers) who designed and made these valves specifically for use with heat exchangers for overhead protection on solid fuel heating systems are "silly" and don't know what they are doing.

Would you have faith in that person ? or the system they installed ?

Yep probably more than you

 

[dlm4473]

Can't quite see how the second heat distributing heat exchanger will work effectively. The cold water will cool the heat exchanger, but the stove will carry on heating the store? The heat loss will be negligible.

Hot feed to Heat exchanger is on gravity flow (as is sensor) Cooled water from exchanger returns to gravity return. Difference in temp will increase gravity flow (which would just about stall at 95 degrees) more cooling performed by exchanger the faster gravity flow through exchanger - the faster cooling takes place. When temp goes below 95 in top of gravity flow circuit (hotest part of circuit) the sensor shuts off the valve.

 

[Gray0689]

Dlm
What is your profession

 

[Killy Bing]

Hot feed to Heat exchanger is on gravity flow (as is sensor) Cooled water from exchanger returns to gravity return. Difference in temp will increase gravity flow (which would just about stall at 95 degrees) more cooling performed by exchanger the faster gravity flow through exchanger - the faster cooling takes place. When temp goes below 95 in top of gravity flow circuit (hotest part of circuit) the sensor shuts off the valve.

.......so at 95 degrees on one side of the heat exchanger.....you intend to flush the other side with mains water to reduce the temp?

correct?

 

[dlm4473]

Yep probably more than you

I thought you were "out" if your going to nothing but critisise why keep posting ? You gave me advise to check out with building control - which I've done - but you can't even wait for the response before you say the system and me are incapable of doing the job !

You havn't even attemped to respond to any of the three questions above - that would be giving advice! so tell me how does a heak leak radiator of 1KW stop the water boiling in a system that is outputing 10KW ?

 

[Gray0689]

.......so at 95 degrees on one side of the heat exchanger.....you intend to flush the other side with mains water to reduce the temp?

correct?

Yep think he does
So let's sat you cool hex without busting it from the shock of the incoming cold mains
So hex gets cooled
What cools the stove as it is sitting at 95
Fire still lit still producing uncontrolled heat
It starts to boil then flashed to steam as the hex is not dissipating the heat
Increasing its volume by (come on op you should know this one)

I wouldn't like to be to near it myself

 

[Gray0689]

I thought you were "out" if your going to nothing but critisise why keep posting ? You gave me advise to check out with building control - which I've done - but you can't even wait for the response before you say the system and me are incapable of doing the job !

You havn't even attemped to respond to any of the three questions above - that would be giving advice! so tell me how does a heak leak radiator of 10KW stop the water boiling in a system that is outputing 10KW ?

Because I don't need to tell you
YOU should already know that answer
Plus it's not 10kw radiator
Check your facts

 

[Gray0689]

I thought you were "out" if your going to nothing but critisise why keep posting ? You gave me advise to check out with building control - which I've done - but you can't even wait for the response before you say the system and me are incapable of doing the job !

You havn't even attemped to respond to any of the three questions above - that would be giving advice! so tell me how does a heak leak radiator of 10KW stop the water boiling in a system that is outputing 10KW ?

But yes your correct and it's not criticism just my opinion
I'm out lol

 

[dlm4473]

Yep think he does

It starts to boil then flashed to steam as the hex is not dissipating the heat
Increasing its volume by (come on op you should know this one)

I wouldn't like to be to near it myself

ON A VENTED SYSTEM !!!!!!- WHAT DO YOU THINK WILL HAPPEN ! would it be exactly the same that would happen on a system with a heat leak rad when it boils ?

 

[Nostrum]

I'm not sure if radically cooling the middle of a gravity circuit will induce circulation at all. You'll have heat at top and bottom and a cool heat exchanger?

Would you not be better off with a coil in the buffer and pass cold water through this?

 

[Killy Bing]

Thermal shock......heat exchange goes bang bang.....

 

[Gray0689]

ON A VENTED SYSTEM !!!!!!- WHAT DO YOU THINK WILL HAPPEN ! would it be exactly the same that would happen on a system with a heat leak rad when it boils ?

Will it ok that's grand then

 

[Howsie]

Howsie - the heat exchanger IS the heat leak !

Whatever you say. Goodnight.

 

[dlm4473]

Thanks you Nostrum - some advice !.

yes i'm considering that as an option, but i prefered the external valve and exchanger for flexibilty - e.g. could change size of tank reasonably cheaply if its too small or too large.
fyi. that method uses exactly the same valves.

As for placement - valve and exchanger could be placed anywhere teed off gravity flow, there is some logic to having it as close to stove as possible and some in having it before tee for store.

I really can't see the hostility to the external approach - the heat exchanger will be subect to the same thermal shock as every other heat exchanger fitted to a thermal store that provides DHW.

 

[Nostrum]

I really don't think a cooled heat exchanger 'inline' will offer significant cooling.

When you think the boiler will still be lit, you may just stop gravity circulation dead and cause the stove to boil? I'm not sure if honest but I wouldn't want to try it.

you could still use the valve, but pass it through a coil in the store which would cool the store down rapidly and allow the stove to burn out and dissipate into the store.

the only additional expense would be the additional cost for a store with a coil, but you'd save on a heat exchanger and the potential for it not to work.

 

[Dotty]

The only problem there croppie is that I would struggle to have faith in the people that say they "know what there doing" when they ;

1) cant answer a simple question i.e. how does a 1KW heat leak rad dissapate heat from a 10KW stove
2) Whilst professing how knowlegable they are - are apparently unaware that this system is fitted to off-the-shelf thermal stores - presumably (but i could be wrong) passing all relevant standards inc. building control and WRAS.
3) Appear to think that Danfoss (and other manufacturers) who designed and made these valves specifically for use with heat exchangers for overhead protection on solid fuel heating systems are "silly" and don't know what they are doing.

Would you have faith in that person ? or the system they installed ?

Pray explain to me why we should go through the expense of training, certification and accreditations just so we can entertain your curiosity.

It won't work. It can, but not the way you're proposing.

The advice is get someone in because you haven't a clue and someone will get hurt by it.

 

[dlm4473]

only concern i have there is that the coil would be empty (although open to atmosphere) until (if ever) the valve is used, assuming valve pre coil ? If valve was placed after coil it would be unvented.

In your opinion would there be any issues having an empty coil in the tank ? What size of coil would you specify ?

btw I posted a jpg of what your talking about near the beginning of the thread.

 

[dlm4473]

Nostrum: finally found the origional plan that set me on this track . Copied from Heatweb site DPS MultiFuel Heat Bank Thermal Store - hope it clarifies what i'm talking about.

Anyway ;

"The following diagram shows a suitable circuit which allows both pumped operation to a thermal store, and also has a gravity circuit that comes into play when the pump is not running. During overheat conditions the TS130 valve opens up to allow the cold mains to flow through the heat exchanger, cooling the circuit and driving gravity circulation. This form of overheat works without power, although power will required to pump water from the store to provide central heating."


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