Heat bank & boiler connections

[SimonH2]

Having a combined feed and expansion pipe off the top may cause the cylinder to implode if it boils over. Tee of the combined pipe at the top off the cylinder and take a pipe to the bottom of the cylinder. Have a non-return valve in this new pipe. This tops up the cylinder at the bottom but prevents circulation through pipes. When blowing off water gets back into the cylinder. Cheap and easy.

This is the most dangerous thing I've ever read on here, by far!! It also would not comply with the Water Byelaws. Please don't take this nutters advice.

But at least someone is actually trying to answer the OPs question - unlike the rest of you spending 10 (yes TEN pages) pages bickering.
I'll offer some constructive suggestions to some of you - though I suspect those whom it's aimed at will fail to recognise themselves. I don't think it's too much of an exaggeration to say that the perception of plumbers amongst the general community isn't very positive. Plumbers are those people who arrive late, take one look at an installation before have a big "suck" and stating that something very expensive needs to be ripped out and replaced, turn up without the material they need even when they've already been and measured up, and so on - and I've met some of these people. I know there are a great many plumbers (the majority) who aren't like this, who know their stuff, charge fair prices, etc, etc. But people don't remember those.
There are a number of people posting in this thread (and others) with posts that make themselves appear completely and utterly untrustworthy. When someone makes a statement that they will never ever consider a particular technology no matter what, then that says that they are not prepared to offer a customer what is best for that customer's requirements - instead they will offer something that may well be second (or third) best. To go on at length that <some technology> cannot ever work when clearly it does for a great many people simply makes you look stupid and ignorant - see above about not being able to select the best option for any particular set of requirements. Also, when you have that attitude, people are likely to think that if there is a genuine reason for changing the system - that you are just doing it because you can't be arsed trying to understand what's already there.
There is a saying that if you can lead, lead; or if you can follow, follow; otherwise get out of the way. Adapting that, I'd suggest that when someone posts asking for help on something you don't want to be involved with, instead of getting in the way, just stay the f**k out of thread and let others who are prepared to help, help. Ten pages of old arguments is just getting in the way.


And I'm interesting in the original question because it is relevant to a future project where it will be a long run to the F&E tank and the opportunity to reduce the amount of pipework required would be welcome.

I am curious about the statements made by JonasX. I don't see why tee'ing the pipe to top and bottom of the tank will make any difference. If the tank boils then expansion into steam will push steam & water up the vent pipe (in the absence of a separate feed pipe). When the boiling is no longer sufficient, water will come back down that pipe and if it's cool then it will quench the boiling - at least to some extent, it depends on the quantities involved, and the capacity of the heat source that's causing the boiling.
The pipe is the same size whether it connects to the top or bottom of the tank, and I fail to see why tee'ing it into two tank connections will avoid potential problems if a large quantity of steam collapses quickly. I can see how letting the cold in at the base will reduce rapid quenching of the boiling, but the arrangement suggested doesn't prevent cold water also entering the tank at the top.

But the mention of it does bring to mind an amusing anecdote. If anyone doesn't want to read it then I won't be offended - just skip ahead and ignore it, don't complain about it because I'm not forcing you to read it.

Someone I know sells pumps for a living ...
Anyway, one job he got involved with was for a marmalade manufacturer. Marmalade and jam is often cooked in a partial vacuum to allow cooking at a lower temperature and avoid boiling off some of the aromatic oils. At one place, they'd had this big vacuum cooking pot built, and it had a poxy little valve in it - clearly they were only considering that they needed to admit air as fast as the vacuum pump could suck it out under fault conditions.This error was pointed out, but the "experts" claimed to have considered everything ... They didn't allow for a sudden temperature drop and associated condensing of steam, which they soon enough had - apparently it took some doing cleaning an industrial quantity of marmalade off the inside of the factory

 

[Onetap]

But at least someone is actually trying to answer the OPs question - unlike the rest of you spending 10 (yes TEN pages) pages bickering.

I answered the OP's question on P1 and I have read nothing to change my opinion. I've used thermal stores and would do so again if they were advantageous. They are not in the OP's application; the TS is a pointless complication for him and prevents him making full use of the condensing and modulating efficiency features that are built into his boiler.
He would be best advised to scrap the thermal store.

Dan Robinson is a thermal store enthusiast and is incapable of recognizing or admitting their disadvantages. Although he fits them, he didn't know why they were liable to produce sludge until he was told on P7; strangely, immediately after that, he announced that he fitted mainly sealed TSs.

As for JonasX/DD/WS, well, what can you say other than ignore him?

I believe this is Dan Robinson's picture of his thermal store; maybe he could explain it.

Untitled

• Dan Robinson
• 8 Oct 2011
• 3

 

[Onetap]

You have been bleating on and on about legionellas for days now, then finally acknowledge L8 doesn't apply to anything in this thread.

I suggest you look back at P2 (I think) when I first mentioned L8; I said then that it didn’t apply to domestic installations.

L8 (Legionnaires’ disease; The control of legionella bacteria in water systems, Approved Code of Practice and Guidance) contains guidance on the relevant legislation and on the code of good practice to prevent LP proliferating in water systems, as the title suggests. The legislation is based on the H&S at Work Acts and so is not applicable to domestic installations. The code of practice consists of simple, common sense precautions that are relevant to all water systems, commercial and domestic.

You should read it.

Or are you suggesting every dwelling in the land is chemically treated to eliminate Legionella a few times a year?

No. I’m suggesting that water, at pasteurising temperatures, should be regularly drawn off from all outlets for sufficient time to kill any bacteria within the system. In the case of a PHX based system, like the one for which you posted the specification, you could only achieve an adequate temperature by drawing off the water at a reduced flow rate. In practice, this is done by people simply using basin and sink taps. A problem arises with faulty and neglected systems, both storage and instantaneous, where pasteurising temperatures are not reached.

PS I posted the quote about the 100mm dead end simply because I found it interesting and surprising.

The other reason why TSs have earned the nickname of 'sludge buckets' is because they heat the DHW up towards the temperature of the stored primary water, usually 80 degC or so, and then blend it with a TMV on the outlet of the PHX or internal coil. Heating the water to a high temperature causes the precipitation of a lot of limescale from hard water, compared to a 60 degC water storage cylinder.

 

[Dan Robinson]

To paraphrase tenacious D - I just made the best post ever - then lost it because ipod screens do weird things in hot steamy bathrooms. Don't gloat, I only lost the post - the ipod is fine.


Anyway.

Whilst running said bath I was pouring my usual large G&T. Thought I would check the store - or Apollo as it has become known. As you can see it is indeed unvented. And as far as I recall the only one of its type I mention installing. As all the other TS's I have fitted have been open vented.

Next to it is "Little Brother" the EV. Named in homage to the game Bioshock.

The lagging is looking a little shabby because I had an underling install some cold (softened) and hot water taps outside so I can wash the car. Probably the nearest thing you will get to a dead-leg in my house I can assure you.

Now, whilst running my bath I noted the top temperature was hovering a little above 80, the bottom, 42 (according to a READ500005 temperature probe). Various JET thermometers gave the expected readings for stratification. the flow rate according to my Ultra 9 softener were 22.5 litres per minute.

DHW off the plate was 75. Blended (according to a READ500005 temperature probe) temperature to the house was 47.5 degrees.

Boiler flow invariably peaks at 82 - 84 depending on whether the heating is running at the same time as the bath.

Unfortunately my house has 10mm pipe work for the heating. However, in the next 12 months we are doing some extensive renovations, which will involve re-piping the heating upstairs in plastic back to a modified UFH manifold. Downstairs will - subject to me finding a clever way to eliminate downward heatloss - will be UFH.

Perhaps I will find a funky way to implement WC through the manifiolds. Should be too hard.

I will mention in the interests of fairness that, store temperatures are only taken a few inches from the outside. the core temperatures will no doubt be a degree or so higher. thankfully on my system the dhw draw off is via an elongated baffle and extracts heat from the core. I have always meant to ask how many of the other tappings have that. But it wold probably be as easy for me to check personally.,


Whilst I think about it - perhaps Mr Onetap would be kind enough to answer another question. OSO have a cylinder - of which I am a fan - that has a blending valve set to 55 degrees IIRC. Makes your bleating about legionellas even more pointless. And yes. You brought it up first. It was pretty apparent that it was a rather fatuous thing to mention, so why you carried on for so long still escapes me.

Where was I, Oh yes.


So a pretty good performance. Part of the renovations will be moving my office downstairs next to the garage where the TS is. This will enable me to permanently hook up my Picolog doo dah to a networked PC. Which sadly enough I am quite looking forward to as it will also mean the boiler can be hooked up to the same PC for direct comparison. You can follow the chronicles in the CC when the time comes (planing permission permitting).

Oh wait. I don't think you can.... What qualifications do you have out of interest?

All I would need to do is find a way to measure the true gas consumption of the boiler. Which I am sure I can do through the software.

recently I added a shed load of sensor pocket to my TS. Whilst dumping the water down the drain I sampled some water. Now, my TDS gadget was dead, but, I still had courtesy of our friends at Sentinel (you remember them Mr Onetap? they know their beans according to you) my turbidity tube. that's right. that little measuring cylinder with 2 O-rings at the bottom. If you can see them then the system is pretty much OK. If you can not see the two rings, then it needs attention.

Whilst not perfect, my system water was fine. Which considering the state of the water when I took out the phucked Ideal heat only boiler and open vented system and installed this one (without a proper powerflush) is pretty good going.

I am sure your expert eyes will have spotted the boiler I have used on the system; and therefore know how sensitive it is to system debris clogging the pressure sensor. It uses this sensor to chek for appropriate flow through the primary system. It also uses temperature rise, but that is secondary.

Whilst a heat only boiler I have it set to think it is heating a cylinder as if it was a 4-pipe boiler,. Which it isn't.

I have also set a number of other parameters through the software to make it do things it normally wouldn't. But I fear that would probably boil your brain to well beyond legionella killing levels to comprehend.


Oh and before you get too enthusiastic about this revelation. I have a letter from Gas Safe to say that it is OK.



Now, anymore questions at the back? No? Good - the dude is back from the land of the rising sun he has jet lag, and has decided it is the morning and wants to play with trains. I have also had some rather good news regarding my retirement. So one is feeling rather stoked

Let's hope the kidneys last that long

 

[DeltaT2]

Get a grip Danny Boy, do you really advocate the installation of something like that in people's homes?? Man, you're as mad as a box of frogs, just like WS/DD/BB. This is what is termed as over-engineeeeeeeeeeeered,
KISS is the watchword in Plumbing & Heating son.

 

[DeltaT2]

This cowboys thinks stopping a cylinder implosion will be dangerous. Who employs this sort. Only the unweary.

That statement just goes to show why you're so barking mad. You may be considering the danger of the cylinder imploding, but ignoring the biggest danger; of it exploding!!!!

Thank gawd the BBA never employed the services of people like you when they approved un-vented cylinders in this country. To date, un-vented cylinders have a 100% safe record in this country.

 

[Onetap]

P 10

As you can see it is indeed unvented. And as far as I recall the only one of its type I mention installing. As all the other TS's I have fitted have been open vented.

P7

My TS is sealed. Those I fit generally are.

Enough.

 

[JonasX]

I am curious about the statements made by JonasX. I don't see why tee'ing the pipe to top and bottom of the tank will make any difference. If the tank boils then expansion into steam will push steam & water up the vent pipe (in the absence of a separate feed pipe). When the boiling is no longer sufficient, water will come back down that pipe and if it's cool then it will quench the boiling - at least to some extent, it depends on the quantities involved, and the capacity of the heat source that's causing the boiling.
The pipe is the same size whether it connects to the top or bottom of the tank, and I fail to see why tee'ing it into two tank connections will avoid potential problems if a large quantity of steam collapses quickly. I can see how letting the cold in at the base will reduce rapid quenching of the boiling, but the arrangement suggested doesn't prevent cold water also entering the tank at the top.

A tee off the one vent pipe back to the bottom of the cylinder will put some water back into the cylinder and prevent negative pressure in the cylinder and an implosion. I forgot to add that installing at mid to bottom of the cylinder an anti-negative pressure vale (an anti-vacuum valve). This acts like an air admittance valve on a drain, and when negative pressure on the cylinder side it open up allowing air in preventing an implosion.

In this particular setup the boiler must have a high limit stat as well as a normal run thermostat. Then the cylinder stat(s). The immersion must have a backup stat as well, which they all do these days.

Onetap:
You were put in your place re: Legionella. You do not fully understand thermal stores. Your advice was childish and totally uninformed. In your home you installed a normal boiler modulating to around 7 kilowatt minimum, that cycles when the system is up to, or near, to temperature, and needs a by-pass valve reducing efficiency like a heavy lead weight. The boiler will not last as long with constant clicking of the controls and restricted flow through its heat exchanger. A waste of time.

Dan:
Great thermal store. Your cylinder is packed with temperature sensors, so they normally do not look like a space rocket. Yes, your figures do prove they operate at very low condensing temperature. They do not cause sludge when properly designed and installed, as your figures show.

It is simple to get a foolproof highly efficient store:

a) Have CH taken from coil in the cylinder or have the cylinder pressurized to avoid sludge build up.
b) Have a boiler that modulates sensing the return temperature.
c) Have an Alpha modulating pump on the CH loop and no central room stat. Each room is fully independent temperature-wise.

Only having a) above will stop sludge. The rest will make a system that gives far better comfort conditions and far more efficient than a direct boiler rad system and gives mains pressure hot water with minimal risk of Legionella.

It is a no-brainer. Even SimonH2 figured all this out way above the heads so-called professionals here (Cowboys really, a disgrace) .

My Plans:
Well my UFH will be run directly by the only boiler sold that modulates down to 0.9 kilowatt. The boiler will not heat the DHW. Simple and cheap to do. The DHW will be instant amy maybe an Intergas combi running as a multi-point. I have done the figures, it is cheaper this way. If I decide to have rads, then the thermal store comes into play. Or have higher DHW flow rates then the thermal stores come back into play. The Intergas combi gives 13 litres per minutes of DHW which is OK for me right now. I will have to keep this in mind before making a decision.

Although I am looking at some low modulating Geminox boilers again that may do both, but these multi-temperature boilers are complex inside. I prefer to separate the functions: DHW, UFH, rads, and have simple less-complex setups for each. A thermal store does that. Not finished yet, still looking.

 

[SimonH2]

I believe this is Dan Robinson's picture of his thermal store; maybe he could explain it.

Untitled

• Dan Robinson
• 8 Oct 2011
• 3

It's not too clear (and not all the pipework is visible), but I can see, first of all, that it's not a "thermal store", it's a "heat bank". Both store therms, but they are fundamentally different in the way they heat DHW.
The pipe at the top to the left of the JB is the primary outlet for DHW heating, it goes down through the PHE, then through the silver/grey pump partially hiding behind the EV, and into the bottom of the store - it looks like the return is the one lower right below the one with the thermometer on it.

At the bottom, if you follow up from that flexible loop, there's a Y strainer, a flow switch (to trigger the DHW primary loop pump), then it tees off - branch into the PHE, straight through into the TMV. The other inlet to the TMV is from the top of the PHE, and the outlet goes off to the left and up the wall where there's some lagging missing. It's hard to see, but I think the cold water supply is into the tee just below the strainer, and the flexible loop will be the filling loop for the system.

I think the pipe where the multimeter is sat will be the CH takeoff, and up to the left is what I assume to be a Grundfoss Alpha modulating pump. There's a Magnaclean on the CH return, and I assume it then goes back into the tank where the thermometer is on the pipe.

Pipe top right will be the hot flow from the boiler, can't see where the return to the boiler is coming from - I'm guessing it's hiding behind the EV.

Add in a bunch of thermostats, thermometers, immersion heaters, and so on ...

As to whether there's a coil for the CH or whether the CH shares the same water, unless there's a separate filling point and EV then I'd assume it's shared (no coil).

I've never seen this installation before, nor have I actually seen a heat bank "in the flesh" as it were. But really, are you suggesting that any [/i]competent[/i] plumber would not be able to understand that ?

 

[Dan Robinson]

Well it was rather late/early.... just checked my work database and it is roughly 50/50. So I was not totally inaccurate with my "general" statement. A few I have fitted were supplied as unvented but fitted OV due to problems with G3 discharge rules and goal posts being shifted. UV was often selected because of boilers not being suitable for OV applications (like mine).

My TS/TB is rather large as it was the only one they had in stock and my time constraints were such that I got that 350 litre monster rather than the 250 one originally sized.

TS/TB are a very small part of my business as you quite rightly pointed out, it is not for everyone. i had a lovely garage and easily accessed pipes to play with. Of the ones I maintain mainly Gledhill's older models) I have very few troubles apart from the iffy electronics on the All electric models. Strangely the only trouble I seem to have with BM2's are the TMV valve.


It is not over engineered by any means. Certainly no more son than an S-Plan and Megaflow. remember I added the extra pockets and probes to satisfy my own curiosity.

Simon has correctly pointed out pretty much what everything does, as should any heating engineer (especially as I labeled everything too ). The radiator return is the one below the boiler return (which has the thermostat on it). There are several other tappings blanked off for other heat sources and there is a 1m3 coil in there should i wish to hook up a solar panel. What you might also note are the two anti-gravity valves. the one on the DHW was more an experiment than anything else, but the CH one was essential. Who would have thought Microbore would have worked under gravity alone? Especially considering how the CH return was re-worked during the installation - I was a little surprised that the ground floor rads worked at all .


As the boiler is directly sensing the store (sorry) TB temperature, the two cylinder stats that buffer the firing periods are not used. which eliminates all but the hot water side of the wiring - which is a simple flow switch and pump. So you can ignore pretty much all the wires the zone valve head was there to act as a vol free relay for the boiler before I decided to wire it directly.

A simple time switch could be used to interrupt that control wire to offer some further control.

I note there was no mention of sludge in Puller's last posts?

We will wait to see if Mr Onetap has any thoughts on unvented cylinders being sold with TMV's blending the water temperature down at source later?

 

[Onetap]

But really, are you suggesting that any [/i]competent[/i] plumber would not be able to understand that ?

View media item 38700

 

[JonasX]

Well it was rather late/early.... just checked my work database and it is roughly 50/50. So I was not totally inaccurate with my "general" statement. A few I have fitted were supplied as unvented but fitted OV due to problems with G3 discharge rules and goal posts being shifted. UV was often selected because of boilers not being suitable for OV applications (like mine).

Dan, Nu-heat supply unvented heat banks and now pressurized thermal stores fall within G3, from this month, Oct 2011. This mean an annual service for the thermal store/heat bank. A vented version with a CH take-off coil needs none, so unqualified Joe Plumber can fit them. Nu-Heat issued an info leaflet:

https://system.netsuite.com/core/me...nN5AXdHTd_r&vid=XsJmvnN5AbJmM_El&cktime=96627

EnergyMaster Thermal Store – G3 implications for thermal stores
In October 2011 Part G of the building regulations was
re-issued. Previously, unvented thermal stores such as
the EnergyMaster were outside of the scope of Part G3.
However now they must comply, and are therefore
a notifiable work.

The basic idea of G3 is unchanged, in that the cylinder
temperature must not exceed 90°C, and that there must be
three mechanisms to prevent this.
With a conventional unvented cylinder the three
mechanisms are:

1. The control thermostat operating a normally closed
zone valve
2. A manually resettable over-temperature cut-out (limit
stat) also operating the zone valve
3. A temperature & pressure relief (T&P) valve.

So, trying to apply this to a thermal store; items 1 and 2 are fine, but the T&P valve is not satisfactory. The latter prevents over temperature by discharging hot water, and replacing it with cold water from the mains, thereby lowering the overall temperature.
With a thermal store the main volume is primary water, and therefore there is no permanent connection to the mains water supply, and consequently a T&P valve will not serve to cool the cylinder.

Therefore an alternative third mechanism has to be used, and the ‘Approved Document’ suggests a second manually resettable over temperature cut out (limit stat) controlling a second zone valve.
Because the over temperature protection should be staged Nu-heat has designed that the protection will work as follows:

1. The control thermostat operating a normally-closed zone valve will allow up to a maximum temperature of 65°C
2. A manually resettable over-temperature cut-out (limit stat) also operating the zone valve will switch off when the temperature rises to 80°C, and
3. The second manually resettable over-temperature cut-out (limit stat), operating the second zone valve will switch off when the temperature rises to 90°C. The second limit stat and zone valve are additional to the previous supply.

In practice 1 & 2 are combined into a dual-stat, which is internally wired in series.

We will wait to see if Mr Onetap has any thoughts on unvented cylinders being sold with TMV's blending the water temperature down at source later?

I believe ACV supply the blending valves as standard for their unvented cylinders. Apart from a pump and flow switch but no complex, expensive, pressure controls, a thermal store is little different to these unvented cylinders in DHW terms. Thermal stores have far less risk of Legionella.

 

[JonasX]

But really, are you suggesting that any [/i]competent[/i] plumber would not be able to understand that ?

View media item 38700

You cannot understand it for sure.

 

[SimonH2]

But really, are you suggesting that any [/i]competent[/i] plumber would not be able to understand that ?

View media item 38700

And what's complicated about that

But I find it really odd that people who claim to understand Y plan systems and combis have any trouble with a thermal store which has less moving parts than either, or a heat bank which is about on par with a Y plan but still simpler than a combi.

With a conventional unvented cylinder the three
mechanisms are:

1. The control thermostat operating a normally closed
zone valve
2. A manually resettable over-temperature cut-out (limit
stat) also operating the zone valve
3. A temperature & pressure relief (T&P) valve.

So, trying to apply this to a thermal store; items 1 and 2 are fine, but the T&P valve is not satisfactory. The latter prevents over temperature by discharging hot water, and replacing it with cold water from the mains, thereby lowering the overall temperature.

There exists a similar valve for a thermal store. IIRC it fits in something like an immersion heater boss and has a heat exchanger coil inside the store. A built in thermostatic valve allows mains water through the coil and down to drain if the tank gets too hot.

Wasteful, but better than overheating the store if you put too many logs on the stove
Incidentally, both rely on there being mains water available - which thankfully round here is normally the case.

I have memories of several houses where the owners instinctively drew off hot water when the gurgling and thumping started - usually because there's a solid fuel source in the system. The house I lived in until I was 5 has a coke boiler which (from the stories I've been told) could be entertaining/frightening (depending on your viewpoint) if lit and forgotten about

 

[Onetap]

OSO have a cylinder - of which I am a fan - that has a blending valve set to 55 degrees IIRC. Makes your bleating about legionellas even more pointless. And yes. You brought it up first. It was pretty apparent that it was a rather fatuous thing to mention, so why you carried on for so long still escapes me.

You're a big boy and you're responsible for setting the TMV. So you consider the risks (legionella and scalding) and available evidence and make your own decision.

"According to the paper "Legionella and the prevention of legionellosis," [15] found at the World Health Organization website, temperature affects the survival of Legionella as follows:

At 60 °C (140 °F) - 90% die in 2 minutes (Decimal reduction time (D) = 2)
At 50 °C (122 °F) - 90% die in 80-124 minutes, depending on strain

Other sources claim alternate temperature ranges:
60 to 70 °C (140 to 158 °F) to 80 °C (176 °F) - Disinfection range
66 °C (151 °F) - Legionella die within 2 minutes
60 °C (140 °F) - Legionella die within 32 minutes
55 °C (131 °F) - Legionella die within 5 to 6 hours."

Personally, I'd store at 60, distribute at 50 (DHWS R), TMV at point of use, when required.

In the event of a conflict between the recommendations of OSO and the WHO &/or HSE, which would you prefer?