General: Back boilers and sealed systems - the truth!

61 to 85 of 85

- CommentAuthortom.harrigan
- CommentTimeJan 21st 2009
Bobo

You're right, and I'm most definitely wrong! A vented system won't run dry. I can't believe I actually typed that! (What was I thinking?) But you do highlight a possibility. Since we are discussing extreme and unlikely situations, why not include a water failure in the scenario? Or a stuck ball valve?
- CommentAuthorMike (Up North)
- CommentTimeJan 21st 2009
Hi,
The miss-terminology is creeping back in. The primary system is either sealed or unsealed, if we are debating connecting a WBS to a sealed system then it does not matter if the DHW cylinder is Vented or un-Vented as they both contain a tube which is the heat exchanger for the primary side, the term UV is for the secondary potable side - they are both in-direct cylinders.
A vented - conventional gravity cfed ylinder can run dry is as in my case the loss of power also loses the water supply pump from my well. To provide an emergency heat dump one could have simply turned on the hot tap to dump hot potable water to be refilled by cold incoming mains water, which I could not do.

Cheers, Mike up North
- CommentAuthortom.harrigan
- CommentTimeJan 21st 2009
Bobo

By the way, if my name was Crusoe, I'd be riding a donkey/bull hybrid and calling you level 1 incompetent (unconsciously incompetent) and inviting you to become level 2 incompetent (consciously incompetent), despite the fact that you are 100% correct and that I was 100% wrong.

Thank you for highlighting my error and stupidity.
- CommentAuthorcrusoe
- CommentTimeJan 21st 2009
Wow - an admission of error...you may reach stage 2 yet Tom :)

You remind me of the Fonz, trying to say he was 'wrrooo...' in Happy Days. He couldn't say he was wrong, when he so clearly was. And everyone competent to understand the issue knew it. You are playing politics.

Can't understand why I should call Bobo incompetent when he agrees with my own training and the experts listed. Can you explain?

Not having met people, I have to make a judgement as to their technical ability based on the validity of their comments. On his comments thus far, bobo may be a plumber, or have educated himself to the facts. I have no way of knowing. But I can spot an incompetent a mile off...based solely on their comments.

I also score the person themselves on their reasonableness and willingness retract an invalid comment when faced with valid points contrary to their own view, or at least acknlowledgement of those points. On this basis, until you change your attitude to a more reasoned one, you don't pass muster on either count I am afraid.

And simply changing your mind to accept the principles of make-up in a vented system - one of a number you have failed to appreciate so far - is not tantamount to an admission of error, it is an admission of corrected ignorance by bobo.

Nothing wrong with ignorance, it's a position to learn from. What I can't forgive is your confusing other, equally incompetent members (by their own admission - in this field) by your polemic, apparently expert stance. You talk as if from a position of in-depth knowledge of this subject, yet that position is fatally flawed by your comments. Digging a hole. Egg on face. I tried to ask you to refrain...in a moderate manner sadly lacking in your own posts.

Bluffers are eventually found out Tom. I sent an email to OSO the other day. Today, An OSO spokesman in their technical dept confirmed that none of their tanks is approved for, and should not be connected to, a woodburning stove. Of ANY kind. That's your system.

So it's not a surprise to me that you avoid the issue of sharing your (obligatory) certification with us. This is a notifiable installation, no matter how loudly your YOUNG (telling comment that one!) plumber laughs.

I tell you what, so as no hard feelings, we are due to do a rugby tour to middle England shortly. Between matches, I'll pop in, no charge - as a LEGALLY recognised expert on both WB and unvented (your opinion of me doesnt count here, sorry) and if I Do find the system is safe, according to HETAS, B Regs, Unvented guidelines and good practice, I'll issue such without charge...

As and when part G of the B Regs is revised, this MAY involve an approval of a modified unvented woodburning combination - it is certainly being discussed, and has been mooted for some time. Until that point, installation of ANY such is, according to the manufacturers of your cylinder, and the illegal in the UK. One of my original points. And even if it is, people with long experience in WB/SF 'meltdown' scenarios will need some convinving....

And I am willing to chip in for a new pair of shoes for you - they must be full of holes from all that shooting yourself in both feet. But because you started a thread on the subject, and want everyone to do this to justify your own position doesn't make it right.

Kindest regards

Crusoe
- CommentAuthormrswhitecat
- CommentTimeJan 21st 2009
Crusoe - your German copperschmidt becomes a chaudronnier in France (from the word 'cauldron') but you go to the same chaudronnier guy for boiler making as well as witches' tools of trade.
- CommentAuthorMike (Up North)
- CommentTimeJan 21st 2009
Hi,
The new cills / edges to my upper windows, the gullys at the roof valleys, and many other joints etc etc are all lead and are soldered. For this I use a plumber not a roofer.
Cheers
Mike up North
- CommentAuthorbobo
- CommentTimeJan 21st 2009
It's called lead burning Mike.
I was a dab hand at it in my early days as a plombier especially with a nice herringbone pattern.
I now prefer servicing gas boilers in a nice warm environment for a grand a week...lovely
- CommentAuthorcrusoe
- CommentTimeJan 21st 2009
mrswhitecat

Merci mademoiselle (?)

Witches' tools huh - You sure that's not a black cat you got there? :)

bobo

Smelt you out! It wasn't your correct answer that did it, but (the misus tells me) the flux and boss white aromas never go away! :))

To answer Tom's question in his last post, a water shortage won't make any difference to a vented system, as the tank has water in it sufficient to replace any that boils off.

A stuck ball valve is a possibility, in which case said system will be low on water and will, like a kettle, boil away merrily (vent pipe is the spout), at atmospheric pressure or thereabouts.

In this scenario, a little water (less than if the system were full) will be vented as hot water or steam into the F&E tank, but an open vent means pressure cannot be built up and therefore steam is kept to a controllable level. It can be frightening, but in a properly designed system (note caveat), there is inherently little danger.

Regards

Crusoe
- CommentAuthorGotanewlife
- CommentTimeJan 22nd 2009 edited
Crusoe, golly this thread moves fast! Awfully grateful to you for addressing my specific concern, there is at least one other person dealing with my precise issue on another thread, so, whilst I am sure I will take you up on your most generous offer of further advice idc, I think others will gain from my dare I say it conscious incompetence!

Can't seem to quote you from previous page - You said
Living in Italy - You lucky FOD! :)) Sorry for the horrible pun, but as an amateur film-maker in my spare time I happened to be asked to video the 1998 St Mawgan International Air Day. And found out what FOD was - and when you said you were RAF, well....it just clicked. Which part are you? I have been looking at properties in Umbria - great value!! - MY COMMENTS: Umbria but see thread in members area about How I have a New Life NOT a New Wife - incl pics of both!!

You said: Anyway, to business: If the Italian law (apparently like the French - see mrswhitecat's comments - also requires a header tank (we are getting more of an international consensus than we expected!!)), then the advantages of direct flow of heat into the store rather than heat transfer through a coil are to be commended to you. - MY COMMENTS: other than safety, are there any other advantages, obvious not having a heat exchanger might make it more responsive and frees up a coil but apart from that I assume the advantages are wholly safety related??

You said: From your description, I am not sure if the cylinder (potable, DHW) is vented, but I suspect that it is mains-fed. I have been going on about the evils of unvented, whilst also acknowledging continental designs were far advanced to what we are talking about in this post. Chalk and cheese. (education from the very few systems of this kind we fitted over here). MY COMMENTS: The potable DHW tank, inside the TS, is mains pressure (supplemented by a whole house pump) with a back-up CW storage tank. I had not even considered this part of the system - I imagine the 340lt 'baby' tank will have its own pressurised expansion vessel but my heating engineer hasn't given me detailed drawings yet....???

You said: I don't like unvented and woodburning, period. For reasons discussed. But if you have a system with an open vented primary, a quenchcoil/heatdump arrangement in place, AND a fail-safe valve in place to allow heat out of the store by thermo-syphon then a 2000 litre tank is intrinsically safe. It will never boil due to it being 2 tonnes of water! I have never heard of a 1000l tank boiling - and I have fitted several - let alone 2000l. MY COMMENTS: ahhhhhhhh so this is where the heat dump thing comes in, and it has to thermo-siphon - there has been no mention from heating engineer about this part yet - so for the purposes of total clarity and helping me to judge just how hard to go in at my Heat guy - Is there a system of vented primary WB and unvented secondary TS that you would consider 'safe' without a thermo-siphon heat dump?? (I guess I just fit a dedicated radiator next to (up high!) the TS for this purpose, otherwise).

You said: Localised boiling is an issue at 40KW, even with a thermostatic stove, in power-fail conditions. I guess at this size you will have a SAMSON-style immersion stat rather than the dreaded coil and chain - MY COMMENTS - food for thought I have never heard of either of these terms, however, my heat man will be using the legally certified products because an system over 35.5Kw should be authorised by an inspector working for the Govt - obviously at 1500 Euros we, along with everybody else, won't get the certificate, but we will use the right products just in case we get caught out....

You said: As the DHW temperature is a function of the store (you don't have a shunt, I take it, but straight thermal transfer), then your DHW temps will mimic your store temps. 60 deg c should be about the max. MY COMMENTS. Yes, direct thermal transfer BUT 60 degrees no, I understand we will be looking at 80-85 - indeed all sizing has assumed this - 45-60 gives just 15 degrees to 'play with' from the TS being fully hot to fully depleted (ie DHW too cold for nice morning showers!!) - please say your 60 was a typo, if not can you explain why??

So, PROVIDED the thermo-siphon heat dump issue is resolved, AND the right quality parts are used AND caveated that this is 'theoretical' and system diagram unseen, you think it might work safely?

A WORD on 'safe' - which might help illustrate this part of the debate: I have regular powercuts (but never yet that cause water supply cuts), I have regular water cuts, I will have a large CW tank and a pump to supplement mains pressure. Except for last line of defence pressure blow out valves, I do not intend to require a design that copes with no water supply and no electricity. Yes the parts will be good or excellent, the design without error, and the installation appalling DIY (but then checked and fixed!!!) and if the worst happens I will end up with slightly molten WB, a large Cappuccino maker and dirty underwear.....but no dead people - that's my definition of 'safe' and, properly informed, I am entitled to make that decision. Thanks again. and sorry about going for the longest post record.
- CommentAuthorcrusoe
- CommentTimeJan 22nd 2009
Gotanewlife

You're welcome. Conscious incompetents ask for help - and get it, where unconscious incompetents don't know they need it. Keep asking...conscious competence beckons... :)

Mmm, well, I am going to say that I will need a mfr and model - plus a system diagram - to confirm what you ask....and possibly some Italian techie I can ask questions of!!! While I understand the principle you outline, I am not familiar with the operation of this type of kit (conscious incompetence in this area!).

My comment at 60 degrees C was for a 'typical' thermal store using renewables - with DHW you need higher temps (we have them from 50 C on HPs up to 85 C on WBs) so you are right, with a big WB you will - depending on your combustion pattern - approach 85 C + at times. This is a bit of a trap though, any design having to keep the store that high. It won't stay at 85 Cfor long, so I would be sure you get kit that WILL allow you nice hot morning showers. Saving grace appears to be the size - it won't drop too quickly hopefully.

Taking DHW off this directly raises a few issues: When the store drops below 85 C, will the mixing equipment (TMV for DHW) still give you 50 C + at the taps?

How is the DHW protected from reaching 85 C when the outer tank is - I presume a thermal cut-out of some kind?

A 40KW woodburner at full chat is a sight to see - and I doubt if it will gravitate completely in a power-fail (plumber speak for thermo-syponage, which is a bit of a mouthful), so thermostatic operation of the boiler is essential, as is AS MUCH THERMO-SYPHON TO THE TANK AS IS POSSIBLE in one of your frequent power-outages. A single large rad - 2KW typically - is not going to do much to prevent boiling, whereas 2000l of thermal store just might.

But your heat guy - if he is competent in this arena - and familiar with the kit - will have his own way of doing things - ask him to explain. And cover the extremes - what happens in a boil-up, a power-fail, etc.

Conversely is DHW temp high enough that it will disinfect for legionalla - 65 C for short periods regularly? If this is a reputable product I expect it will be though.

Personally, I would fit a separate cylinder for DHW cos I wouldn't want to keep 2000l hot all summer JUST for DHW - unless it was a British summer, which we can tell by the slightly warmer rain...but you know all about that which is why you gotanewlife, si?

I am sure this doesn't asnswer all your questions. Keep heat guy on your side (he's hopefully unconsciously competent!) and ask the questions - if you are unsure, I may be able to help with principles.

E&OE

Regards

Crusoe
- CommentAuthorJohnh
- CommentTimeJan 29th 2009
Just spotted this on another thread regarding Dunsley's Yorkshire Boiler Stove -

"Have found a local plumber who is actually a rocket scientist. He has persuaded Dunsley to let him install their stove on a closed system. We were going to be the guinea pigs, but as we are waiting till next winter someone else gets to take the risk first."

Any comments?
- CommentAuthorleemind
- CommentTimeJan 29th 2009
I was just typing a response to another thermal store question, and after I hit return I realised I'd throw this out there

I really want this store: http://www.evinox.co.uk/docs/swppdmanual.pdf and if you see on pages 13 & 14 it shows a direct connection to the store from a solid fuel boiler -- two setups, one for >10kW and one for <10kW. Interesting thing is, this thermal store is pressurized -- See page 2. So clearly the continentals are fine with it???
- CommentAuthorFree spirit
- CommentTimeJan 30th 2009
Posted By: leemindI was just typing a response to another thermal store question, and after I hit return I realised I'd throw this out there

I really want this store:http://www.evinox.co.uk/docs/swppdmanual.pdf" rel="nofollow" >http://www.evinox.co.uk/docs/swppdmanual.pdfand if you see on pages 13 & 14 it shows a direct connection to the store from a solid fuel boiler -- two setups, one for >10kW and one for <10kW. Interesting thing is, this thermal store is pressurized -- See page 2. So clearly the continentals are fine with it???

I could be wrong, but I think that both diagrams are showing direct heating of the cylinder water by the wood fuelled boiler, with the following 3 tier protection:-
1 - Thermal (thermic?) Mixing valve to isolate the return from the tank to the WF Boiler if the return temperature is too high.

2 - Pressure relief valve on flow from wood fuel boiler (possibly pressure/temp relief valve, not very clear)

3 - Thermic Discharge Safety Valve on flow from wood fuel boiler

if 3 is engaged the discharge of hot water will allow cold water from the mains to flood into the bottom of the tank until all the hottest water at the top of the tank that's at or over the cut in temp for the thermic discharge valve has been forced out through the valve.

also I'm pretty sure there's an electronic safety system via the underfloor heating loop to take hot water from the top of the tank and circulate it via the underfloor heating loop, which would operate before any of the above safety systems providing the electricity is on, and everything's working right.

Pretty sure that's how it works, and it looks safe enough to me, but I'll leave it to crusoe to say if it would be allowable under UK regs. I'll bow to his wisdom on it no problem btw as I'm trained but inexperienced, whereas he's obviously an expert in the field... actually thinking about it, I'm kinda hoping he'll say this meets uk regs as it would fit the bill nicely for a project I'm working up.
- CommentAuthorFree spirit
- CommentTimeJan 30th 2009
ah good, just checked back through the thread and the disagreement has been about systems that have both an unvented tank, and a sealed indirect heating loop from the wood fuel boiler...

The above linked system has a direct heating feed from the wood fuel boiler not a sealed indirect heating loop, which when combined with the above safety features should presumably mean that the concerns raised in this thread aren't applicable to this system, and *crosses fingers* should be allowable in the UK?
- CommentAuthorMike (Up North)
- CommentTimeJan 30th 2009
Hi,
This is the normal set up for this kind of large thermalstore/buffer/accumulator in that it is direct, it is connected to the boiler primary flow directly and it is sealed. Obviously you end up with an expansion vessel (sealed so thats not a header tank) that is quite sizable. This would typically be 100-150lit so the expansion vessel is the size of some peoples DHW cylinder. If you have to have an unsealed loop from a solid appliance that would have to transfer heat into this thermalstore indirectly via a coil (no where near as effective as a direct connection).
Cheers, Mike up North
- CommentAuthorFree spirit
- CommentTimeJan 30th 2009
glad you said that Mike, I was starting to doubt myself for not being able to spot what was wrong with it.
- CommentAuthorMike (Up North)
- CommentTimeJan 30th 2009
Hi,

If any one would like some sketches of various set ups I can email them if you send an email to m_up_n at btinternet dot com.

These are just sketches and do not show any safety devices or any thing else they just show the various combinatuions of boilers and tanks etc. In the sketches B = Boiler and could be any boiler / heat source. Obviously in the picture of sealed system it would ahve to be ok for the heat source to be in a sealed system, and some of the combinations would be pointless. I may have missed some combinations and some vital points - they are jsu sketches. I have numbered then so we know which is which.

Cheers, Mike up North
- CommentAuthortom.harrigan
- CommentTimeJan 30th 2009
As I have repeatedly said, my back boiler is connected to a sealed system. The installation was done by a firm of heating engineers who have done many such installations. It is the same firm of heating engineers that performed this installation:

http://www.40percent.org.uk/40-percent-exemplars/case-study-1-an-18th-century-cottage/

It turns out that they have performed many such installations, are strong advocates of sealed pressurised heating systems and the integration of biomass into them. The stove they install on such systems are invariably HCC Heat Demons, as the manufacturer allows this, subject to certain safety precautions. Indeed the manufacturer is a strong advocate of such systems.

The safety features of my sealed system are:

1. Stove is thermostatically controlled
2. 3kW radiator on a gravity circuit
3. Pressure relief valve on gravity arm of circuit
4. Pressure relief valve on pumped arm of circuit
5. Some other pressure/temperature relief gizmo I've never seen before.

The two pressure relief valves are set to 3bar, and have piping to safely vent to the outside. The other thing does not. Should that ever go off, steam will be released into my fireplace.

Furthermore, the latest standards and regulations allow for such systems. The standards, being ENs leads me to suspect that such systems are covered by the regulations throughout the EU. The critical factor being the manufacturer's specifications.
- CommentAuthorcrusoe
- CommentTimeJan 30th 2009
Free spirit

'Expert'? Please refrain - 'Ex' is a has-been and 'Spurt' is a drip under pressure. :)

Took a look at the link - not all bits working,very slow, and couldn't find the diagram you mention. BUUUT, Geminox have been around in the UK for donkey's years (just keeping the horsey thing going...) and are pretty good kit, not sure if the WB boilers have moved on much (ie not gassification) as they seem exactly the same as the ones we used to fit more years ago than I care to remember, along with the original Scanfield, Farm 2000 and the Danish Passat straw-bale burners.

You may by now just have got a slight feeling that there is disagreement on this topic. And everyone is welcome to their opinion of course. Just don't install it at my place... :) I know what the majority of solid-fuel trained plumbers would do.

Mike is right - direct thermal transfer (if endorsed by mfr) is far more effective than heat exchange via coil.

I can't tell you if your particular installation is safe without a definitive diagram (as opposed to one of Mike's sketches) but if you have one I'd be happy to take a look. Please note that this is open to manufacturer consent, and is a notifiable installation for safety reasons (vessel and appliance mfrs) but my understanding of the HETAS requirements is that this does not meet their guidelines, not being open-vented. Having said that, as per my orginal comment at MarkH's thread on this subject, the continentals have been doing this far longer than we have, so should by now have a workable system if they can show just cause why theirs will pass muster in the UK.

But in principle It IS a Thermal Store, so, given that you have a size suited to your installation, it is intrinsically safer than an Unvented cylinder connected to a WB - in several respects:

1. It's at a significantly lower pressure
2. There is more room for thermal shock and absorption of same with what can be an uncontrolled appliance - like Tom's new Rayburn 300, these things DO run away at times, which is when, with a boiler model, you just hope the engineer knew what he is doing, he likely being in sunny Barbados by this time..
3. Even in a runaway situation, any store can be set to dump heat into a part of the system by temperature actuation.
4. It should provide a virtually unlimited thermo-syphon heat-dump in a power-fail situation, at least with a batch-fed boiler, which can after all only contain 'this much' wood.

These are some of the reasons why many WB mfrs like Thermal stores but NOT unvented. Likewise unvented mfrs themselves -(OSO and RANGE are the two I spoke to to clarify the issue) confirmed they DON'T recommend their product be connected to a SF/WB system.

That won't stop some people connecting their product, but it does beg the question 'why' when it is not something they endorse, or that you are likely to be able to pass easily through your local building control - a significant consideration before you part with your hard-earned.

Crusoe
- CommentAuthorFree spirit
- CommentTimeJan 31st 2009
Crusoe - cheers for the offer, I may well take you up on that at some point. I realised after posting that this install is probably going to be a pumped groundwater system rather than mains, so the set up I was discussing in my previous post wouldn't work (would be unsafe in a power cut), plus the cold tank gives back up water supply in a power cut.
- CommentAuthortom.harrigan
- CommentTimeFeb 3rd 2009
Just to clarify things a bit further relating to mains pressure cylinders and back boilers. I finally managed to have a chat with the MD of Sterland and Elgar Ltd. It turns out that OSO do permit the connection of their cylinders to sealed CH systems incorporating solid fuel, provided the system is installed by a competent heating engineer. If one wants to verify this, you'll probably have to talk directly with someone in OSO's engineering department. Sterland an Elgar have a very close relationship with OSO (they seem to always specify their cylinders), so as an alternative you could chat to them. The MD has also promised to get me some documentation from OSO since I'm so interested in the matter.
- CommentAuthortimevans2000
- CommentTimeFeb 3rd 2009
A lot of this debate seems to hinge around what Building Regs say or donÃ¢â‚¬â„¢t say. Just remember that the Approved document is only a model way of meeting the Regulation. The actual regulation is normally a single page none specific document.
If you can demonstrate an alternative method of safe operation, you have qualifications to demonstrate you are competent then you can submit an alternative proposal to Building Control. They may refer the proposal to a qualified consultant for a professional opinion.
We have done this on several aspects of Building Regulations on many commercial projects
- CommentAuthortom.harrigan
- CommentTimeFeb 3rd 2009
The building regs have nothing to say on the matter. I've got such a system, and so have quite a few others. Apparently they are all illegal.
- CommentAuthorjonny50
- CommentTimeFeb 5th 2009
I just read through this thread- an epic! I just wanted to throw in a possible solution to anyone considering connecting a wood burner stove to an unvented cylinder.

Consider the use of a heat exchanger http://www.ejbowman.co.uk/products/InPlateHeatExchangers.htm between the pumped heating circuit and the cylinder

I used one of these on a old house to great effect to presurise a section of someone's underfloor heating system (as they didn't want the muc much older (buried) part of the system to be presurised. Yes in the case of the DHW cylinder it would utilise another pump, but you could use laing eco pump with its lower running cost. http://www.alternativeenergystore.co.uk/item/item/9001003/1/0/Laing-EcoCirc-E6-Vario-Pump.htm -

the DHW unvented system now would be protected from overheat as its not directly connected and relies on the pumping through the heat exchanger - electrical failure would result in no heat (virtually) going to the coil in the cylinder. In the situation i used it the heat transfer rate/effeciency is superb and no air problems with the vented open side of the system (so far, been 9 months now)

Just a thought. Until i read this thread I (my first on the green building forum - i was actually lokking at underfloor and got side tracked) i had always assumed that Unvented and solid fuel were a complete no go and hadn't relaised that it wasn't illegal, i remeber the videos at college and being given clear instructions never to fit solid fuel to an unvented cylinder

Jonny
- CommentAuthorPeter C
- CommentTimeFeb 21st 2009
Hi,

Very good discussion however for the benefit of the average consumer I would like to point out that all wood burning stoves Do Not have thermostatically controlled air supply.

I have five different stoves with boilers on display only one has this feature as standard and another has it as an optional extra.

That said I would never advise a customer to install a wood burner using a sealed / pressurised system in fact I would prefer they buy the same appliance elsewhere as I do not want to be held even partially to blame for what may happen.

We are in the real world where real property can get damaged and real people can be injured or killed by water at high temperatures especially when combined with high pressure.

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