Posted By: Water Systems
That is whole point - there is no need for unvented cylinders.

Wrong and right. It is clear there is no need for unvented cylinders. In fact there isn't even a need for hot tap water; most people in the world live without it.

It's not the whole point though; as Paul said everything is a tradeoff. What's the cost/benefit?

Posted By: Water Systems

Posted By: ralphd

Posted By: Water Systems
That is whole point - there is no need for unvented cylinders.

Wrong and right. It is clear there is no need for unvented cylinders. In fact there isn't even a need for hot tap water; most people in the world live without it.

You are being silly now. If you read what I wrote, I emphasized that there is a risk free alternative that costs no more - in fact may be less.

Emphasize != provided evidence.
I posted before that my 270L unvented cylinder (with 2 4500W elements) cost under CAD330. There are NO annual service costs; annual service is not required by the mfr or by the National Plumbing code of Canada.
http://irc.nrc-cnrc.gc.ca/pubs/codes/nrcc47668_e.html
http://www.gsw-wh.com/

I can't even find a source for vented cylinders here from hardware stores.
www.homedepot.ca
www.kent.ca
www.rona.ca

Posted By: JohnhI've been studying this thread and crusoes comments on another thread in the hope of using a couple of wood fired boilers(plus solar at a later date) to heat a thermal store/heat bank.

Then WS says this -
"we have no alternative to gas, oil and elec'."

Eh? Are you (WS) saying that all your comments are based around using TS/HBanks with non woodfired/biomass systems?

My comment in that context was more an example. We don't need to use open coal fires as we have superior fuels and appliances that are much, much safer with far lower risks.

Posted By: Water Systems

Posted By: ralphd

Posted By: Water Systems

Posted By: ralphd

Posted By: Water Systems
That is whole point - there is no need for unvented cylinders.

Wrong and right. It is clear there is no need for unvented cylinders. In fact there isn't even a need for hot tap water; most people in the world live without it.

You are being silly now. If you read what I wrote, I emphasized that there is a risk free alternative that costs no more - in fact may be less.

Emphasize != provided evidence.

I wrote: "You are being silly now. If you read what I wrote, I emphasized that there is a risk free alternative that costs no more - in fact may be less."

Anyone with the slightest inkling of engineering nous can see that. Note: "risk free alternative".

Derogatory remarks about my inkling of engineering are not evidence that vented cylinders cost no more than unvented.

Posted By: Water Systems

Posted By: ralphd

Derogatory remarks about my inkling of engineering are not evidence that vented cylinders cost no more than unvented.

The point is near risk free vs a risk that could take down your house. You appear not to see it. If you can't just take mu word for it, a vented heat bank will not take down the side of your house.

I do not dispute the risk. Based on the number of documented cases in North America and the number of installations, it appears to be less than one in a million.

I disputed the cost claims. And I won't just take your word for it. I don't ask people to take my word either; scientists believe data not people.

-Ralph

Posted By: ralphd

Posted By: Water Systems

Posted By: ralphd

Derogatory remarks about my inkling of engineering are not evidence that vented cylinders cost no more than unvented.

The point is near risk free vs a risk that could take down your house. You appear not to see it. If you can't just take my word for it, a vented heat bank will not take down the side of your house.

I do not dispute the risk. Based on the number of documented cases in North America and the number of installations, it appears to be less than one in a million.

I disputed the cost claims. And I won't just take your word for it. I don't ask people to take my word either; scientists believe data not people.

-Ralph

I can't speak for costs in N America. A risk free DHW only heat bank giving the same DHW delivery performance as an unvented cylinder costs no more in the UK. Then put in the other clear advantages, there is only one choice.

Posted By: ralphdWater Systems: saying it costs no more doesn't make it true.
CAD330 is roughly ÂŁ185. Many of the north american products are made in Asia, so landed cost in the UK would be similar to here. So the cost of a vented cylinder with a 270L capacity should be equal to or less than ÂŁ185. Given your reliance on assertions instead of facts, I suspect the cost is much more than ÂŁ185.

North American and EU unvented cylinders are banned in the UK, as they do not have enough safety devices and other aspects as well. UK unvented cylinders require approved men to install and service. Not a DIY thing.

Crusoe / WS, I've been (trying) to pick out the useful information from this thread as I'm seriously thinking of a new heat bank and have a couple of questions:

1 - sounds like a heat bank with an external heat plate X is the way to go - can you drink the hot water generated as it is mains fed and not stored? If so, then a good way to fill the kettle and save electricity?

2 - sounds like larger stores are better as they give you longer between re-heats - if I go for a 500 or 1000ltr store it will be heavy and need to be located on the ground floor - my concern is the time it might take to get hot water out of the plate X and upstairs to the bathrooms - is there anyway to minimise this as it is a waste of water plus a long dead-leg of hot water left to go cold between bathing?

3- also, if the store is located at ground floor level and I have a WB with a boiler on the same level would it need a pump (lattdomat?) as I assume it could not be gravity fed?

Thanks for all the expert advice

Lots of strong opinions and SHOUTING in this thread.

Clearly any given heating system will not be appropriate for all possible circumstances. If you only intend to heat your home and hot water with a condensing gas boiler then a thermal store or heat bank might be viewed as overkill. However I would point out that if your aim is to use just a condensing gas boiler, you're possibly in the wrong forum.

If you intend to use a combination of heat sources (say solar, biomass and either gas or electricity as backup), particularly ones that are 'bursty' and perhaps even unpredictable, then a thermal store makes a lot of sense regardless of a few points of efficiency either way. For some forum posters, the obsession with numbers perhaps overrides practical considerations of how a system might be made to work in the real world.

If your heat bank looses energy, I would hope that your home is sufficiently well insulated, and the heat bank is sited to keep that energy within the living envelope?

As for the people requiring evidence and legal documents, it seems to me that the posts from those who are very happy with their heat banks / thermal stores speak for themselves. Good technology does the job required of it.

So why are you all getting so angry at other people's decisions?

Tuna

I totally agree that thermal stores have a very valid role and I would very seriously consider installing one myself and very much in the manner you describe.

I think heat losses from high static temperatures are an issue and return temperatures to condensing boilers but as you say with biomass and multiple heat sources in particular they could well be a very good solution.

However this thread is being dominated by someone who has more than a passing personal interest and is using the forum to promote the benefits of a technical solution to the detriment of other possible solutions.
My objective is actually to see if the claims being made actually stack up. The evidence so far suggestions there are claims being made and no substantive information being provided to support those claims.

In doing so does not denigrate the decisions others have taken for their own reasons to install Thermal Stores.

Posted By: nigel

Posted By: crusoeTo get back to the main thread of this debate, despite his undoubted ability to ruffle feathers, Water Systems has it pretty well-nailed. You can use a TS/HB?Accumulator/Buffer Tank/Thermal Battery - call it what you will - in most cases. It gives you the ability to connect many different types of appliances (JohnH - incl Solid fuel/ woodburning) and alter that mix to suit developing fuels and technologies.

Well I don't agree he has nailed anything. There is no such thing as the perfect solution and there is no point preaching that Thermal Stores are a perfect solution for every situation because neither you or Water Systems have produced any EVIDENCE to support your claims.

We abundantly have. If you can't accept them for some illogical reason or - or just clearly do not understand, then you think you are right.

Water Systems claims that using a thermal store is more efficient than a modulating boiler, with weather compensation, to supply space heating.
He claims Cranfield have researched this but no one can find it and he will not provide a link to it.
Does it exist?

Do a google. A TS can be used with a modulation boiler using weather compensation. Read back on my posts and it gives the details - it has to be a dual temperature boiler, like Broag.

It is my view that a well designed heating system using a gas condensing boiler is likely to be more efficient measured over a season than the thermal store.

You are just plain guessing and think unvented cylinders are 100% safe and all that.

The Thermal Stores solution requires a body of water to kept at a static temperature to be used to produce space heating and DHW.

No. The stored CH water can vary to the outside temperature.

According to Gledhill this should be kept at least at 70c - regardless of outside temperature.
So there is continuous heat loss from this store which given its high temperature will be significant.

There will be little from a Gledhill as their insulation is brilliant.

There is also the question of return temperatures to the boiler which have never been answered.
Gledhill quote 11c temp drop which gives a return temperature of 59c.
Water Systems tells this out of date does not point us to an updated specification or an alternative product.

A directly heated Gledhill will give very low temps and the boiler condense. If you size rads for a 20C drop then it will work well with a Gledhill.

A similar concept to thermal stores is used in modern district heating systems where a heat main is kept at a high temperatures and plate heat exchangers are used to supply space and dHW to individual properties. These require a flow temperature of 80c for the plate heat exchanger to provide the required performance.

This seems to be a common concern about thermal stores which makes them LESS EFFICIENT in many situations.

District heating tends not to have TS's. Just individual stations in each home.

For the last time provide some EVIDENCE of thermal store temperatures and boiler return temperatures or we will all just assume you have not got any.

Read this thread again. All is there. We can;t just go around in circles because you can't grasp it.

Posted By: jezza22Crusoe / WS, I've been (trying) to pick out the useful information from this thread as I'm seriously thinking of a new heat bank and have a couple of questions:

1 - sounds like a heat bank with an external heat plate X is the way to go - can you drink the hot water generated as it is mains fed and not stored? If so, then a good way to fill the kettle and save electricity?

Usually mains fed, but can be off a tank.

2 - sounds like larger stores are better as they give you longer between re-heats - if I go for a 500 or 1000ltr store it will be heavy and need to be located on the ground floor - my concern is the time it might take to get hot water out of the plate X and upstairs to the bathrooms - is there anyway to minimise this as it is a waste of water plus a long dead-leg of hot water left to go cold between bathing?

Fit in a secondary circulation loop, using two check-valves and a bronze pump and a pipe stat and timer.

3- also, if the store is located at ground floor level and I have a WB with a boiler on the same level would it need a pump (lattdomat?) as I assume it could not be gravity fed?

A vented T Store can be gravity fed.

This is a very disappointing thread.

Agreed. I've heavily researched this topic and would probably be interested in some of the views. Unfortunately I don't have the time to wade through all the counter-quoting. Also there's not much referencing to external reviewed sources so a lot of it looks like heresay.

Dragging on a bit, this one isn’t it?

I feel I should respond as Tom said a few pages back regarding my set-up…

“30l/min is good, but it's not as good as an unvented cylinder.”

So. It’s 30l/min at 45 deg rise because that’s the flow the shower is designed for, and that’s what I asked the store manufacturer (who supplied the plate heat exchanger) for.
That’s 30l/min at what, 40 to 45 degC. So some of that 30l could well be blended cold water. What my accumulator pushes out, I have no idea, I’ve not measured it.
But it’s enough to almost hurt under the kitchen tap. I can now bounce hot water (almost hot enough to brew tea with) clean out of the bottom of the kitchen sink and a good 8 feet away onto the kitchen floor if I give the heat exchanger’s thermostatic blending valve a tweak into the danger zone first, so it does the job regarding showers. Trust me.
An unvented (with the same essential accumulator) would produce exactly the same effect, maybe even better, as a plate heat exchanger might have a slight restriction to flow? Not that I’ve noticed. But you’d be out of water pretty sharpish at 30 litres a minute using a 300l cylinder.
So the 30 litres doesn’t depend on the technology, it’s what is pushing it through the system – an accumulator or a good mains supply. But we knew that. Didn’t we?

Tom also said

”Two showers in the winter before your water gets chilly may be acceptable to you, but I think it may be totally unacceptable to others. It's nowhere near the performance of an unvented cylinder of comparable size!”

It’s fine for us.
That’s two long showers while the 15 or so radiators are all calling for heat.
In the dead of winter.
Incoming water rather cold.
With a 3 speed shunt pump set to ‘slow’.
I s’pose I could get the radiators to come on fifteen minutes earlier, turn the store ‘boiler off’ stat up to get to the design temp of 70-75 degC, or turn the shunt pump up to 2, or turn the ‘on’ stat up to get the boiler to fire a bit earlier in the store depletion cycle, but there’s no point, it does what we want as it is, without wasting too much gas.
Or I could do a lockout as water systems suggested for the space heating – circ pump stops when hot water is demanded. But I can’t be bothered – it’s not an issue.
You want better hot water for the days my wife washes her hair during the 2 weeks a year it’s a bit parky – get a bigger heat exchanger to suck the last little bit of energy out. Or a bald wife.
The 5 degree store water to tap water transfer sounds right – it seems very efficient from here.
As Cwatters says, it’ll tick over during summer at 55 degC or less, and perform fine shower/bath wise.
Gledhill state they need 70 degrees/80 degrees/whatever. I would suggest their plate X is undersized?
The stored water isn’t sprayed in your face with a store, so legionella isn’t quite so much of a problem (understatement!!) as a traditional cylinder.
How long does an unvented take to recover it’s heat? I’ve just googled it. Took a while to stop laughing to be honest, but that’s not important.
It’s 29 minutes to recover a 300l cylinder if you have taken 70% of the water and are replacing it with 15 degC water. I’m guessing there’d be a cold shower somewhere there.

Tom also said

“You have reinforced my view that small thermal (size now raised to 300l from 250l) are utterly pointless. You have a worse hot water system than an unvented tank in return for complexity”

Complexity – yes, there are extra bits, but all off-the-shelf stuff. Any old flow switch, a standard circ pump, standard stats and a cheapo relay, erm, that’s it.
Half of the extra bits are there to make the boiler cycling better – you’d do the same to any cylinder if the hot water performance could be maintained through a 20 degree storage range.
Want to go green with an unvented? You’ll be needing weather comp, and, oh… complexity. And the damn thing will STILL come on at the whim of a roomstat.

Thermal stores are crap, good, brilliant, and in between. Depends what you want.
Gas boiler, a bit of solar and a regular plumber = unvented. They’re great.
If you service your car and your boiler, get your cylinder done as well. If you can’t be bothered, well that’s just fine. In the UK, servicing is advised, same as being sensible on the stairs is advised.
But hang on, do you want a wood burner as well? Or you want your boiler to last forever? Or use solar to help heat your house? Maybe low temp underfloor heating? That’s where the decision gets tricky. I can’t comment, because my wood and solar aren’t here yet, but as far as the store goes, It Is Good.

Jezza22…
1 – yep, it is mains water, not stored water, kettles are more than happy with it.

2 – what WS or crusoe said – depends on the layout.

3- you would still need a gravity heat dump (eg rads upstairs??) even with a laddomat – maybe a normally open failsafe valve to close off the heat dump rad when the laddomat is running?

Regarding boiler return temps, my boiler shows 30-35 degrees up to 65 return at the end of a reheat. Most of the reheating is done at low return temps, mainly because the flow out from the boiler only just hits 82 (max) when the store stats call ‘enough’.
It condenses, mostly.

A little thing, but something I’m really impressed with is the space heating from stone cold. First thing in the morning when the programmable roomstats wake up, the radiators get hot. Quickly. And I mean within seconds, certainly full temperature within a minute or two. Not important in the scheme of things, but nice to have.

Listen to crusoe, someone who fits the damn (unvented) things…

“You can use a TS/HB?Accumulator/Buffer Tank/Thermal Battery - call it what you will - in most cases. It gives you the ability to connect many different types of appliances (JohnH - incl Solid fuel/ woodburning) and alter that mix to suit developing fuels and technologies.

In short, it gives you OPTIONS for the future. It will save you money too.”

Pointless ie without a point, a reason for being? No, that’s wrong. End of. See you again on page ten?