Mega Flo vs Thermal store

[shambolic]

This looks like an Albion Mainsflow(uncased) thermal store.
Thermostat on side should be set to 78 and if you have hot water control on timer it should be on constant.
There were two versions.
One had a primary coil from boiler (sealed system boiler) but these usually never had a pump on primary as the boiler had one in it.
The main store water at 78 degrees also circulated round the rads and the main problem was lack of inhibitor as the store held 200 litres and further 100litres on heating circuit.
Also the primary and boiler in sealed coil would need inhibited separately.
There was a second coil that the domestic water went through.
Major problems were slugged primary coil(slushed on inside and also on outside of coils), cylinder does not get to 78 and boiler cycles as it can't transfer heat to store. So store is too cold, when you put rads on then the store cools down and boiler can't get it back up quickly enough so if you run water it is colder!

Second problem was furred up(on outside) of domestic water coils this leads to a short blast of hot water from coils them almost stone cold water as no transfer from store to coil.
I personally would take it to scrappy and put in a decent unvented cylinder. Just problem of running the blow off from it to outside and ground level from attic!

 

[SimonH2]

Second problem was furred up(on outside) of domestic water coils this leads to a short blast of hot water from coils them almost stone cold water as no transfer from store to coil.

I'm still at a loss to figure out where all this scale is supposed to come from. By your own calculations, there's only 300l of water in the system, and it's not exactly changed every day ! Given that hardness is usually quoted in mg/L, with very hard water of 200mg/L there's only a total of 60g or so of scale in the entire system.

I can see the DHW coil scaling up inside, but this shouldn't be too difficult to deal with. Mike the Boilerman mentions this here/. I do like his comment at the end though : "Thermal stores seem to spook many repair engineers"

I personally would take it to scrappy and put in a decent unvented cylinder.

Yup, seems to be the standard answer - second only to "<suck> wouldn't have fitted one of those, you need a combi mate"

for the OP - how hard is your water ?
Ah, looking back I see you give your location as London, and this page says that will be hard water. Putting Mike the Boilerman's comment "There is a major problem in hard water areas.... Over a year or three, the copper coil gets blocked with water scale" and the fact that you've had this in for 5 years, there's a good chance the coil could do with descaling. In the back of the installation manual for the Gledhill Torrent (same general arrangement as yours) they include descaling instructions - basically remove the mixer valve, slot a connector block in it's place, and then let the descaler pump circulate the fluid for a while.

 

[D_Hailsham]

its made by this company and I think this is their current version

http://www.albionwaterheaters.com/product-combination-cylinders.html[/QUOTE]
That's a link to their combination cylinders. I think you mean this link: Mainsflow Thermal Store

 

[indus]

Thanks for the great replies

1) Yes the thermostat is set to 78 and the hotwater is set to constant.

2) Simon H2 that's a very good idea about checking the pipe temp. I can't get hold of the thermometers but will try but hand. I won't be able to get up into the loft again until Monday when the builders are back.

Basically if the pipe leaving the TS runs cold then there must be an issue with the TS right? Either it's malfunctioning due to scale or it was never up to the job?

3) The pic is an old one and is of the TS BEFORE it was moved. I will also take a fresh pic on Monday

4) I live in a hard water area and don't have a water softener.

5) You mention checking flow rates. If this is the issue then what can I actually do about it?

6) The contractor who moved the TS said the system was full of muck. I have no idea whether he was telling the truth or was he just trying to sell me a power flush??

7) I was told you can't descale the crap on the outside of the inner coil, is this not true?

Thanks again for all your help

 

[JonasX]

Fit a Fermox type of filter on the CH return to the thermal store then sludge will not build up.

Megalflows are not compatible with thermal stores as Megaflows do not do CH and run at high pressures. This is ignorance on the part of not very bright plumbers. Thermal stores enhance the boiler operation.

Was the Albion thermal store OK in using two taps, then it went wrong?

Most new thermal stores are stainless steel, which is far better. This Albion appears to be copper.

Plumbers who do not know what a thermal store is are not educated, time served college educated plumbers. Avoid them. Even I can understand them.

Thermal stores are not old hat.

Plumbers who cal thermal stores sludge buckets should give up the game.

Thermal store can be de-sludged/descaled.

Inhibitor, about 3 cans of X100, should be used every 4 years.

What is the fuss?

 

[DeltaT2]

Fit a Fermox type of filter on the CH return to the thermal store than sludge will not build up.

Megalflows are not compatible with thermal stores as Megalows do not do CH and run at high pressures. This is ignorance on the part of not very bright plumbers. Thermal store enhance the boiler operation.

Was the Albion thermal store OK in using two taps, then it went wrong?

Most new thermal stores are stainless steel, which is far better. This Albion appears to be copper.

Plumber who do not know what a thermal stores are not educated, time served college educated plumbers. Avoid them. Even I can understand them.

Thermal stores are not old hat.

PLumbers who cal thermal stores sludge buckets should give up the game.#

Thermal store can be de-sludged/descaled.

Inhibitor, about 3 cans of X100, should be used every 4 years.

I call them 'sludge buckets' mate, but I don't see what reflection that has on my skill & experience. They are sludge buckets, most are poorly installed in spec build houses & they need loads of inhibitor.

 

[SimonH2]

5) You mention checking flow rates. If this is the issue then what can I actually do about it?

Well I was just thinking that if you came back with some very high flow rates, we might be able to say it's something as simple as too high a flow rate = low flow temperatures, just as it is with combi boilers.

6) The contractor who moved the TS said the system was full of muck. I have no idea whether he was telling the truth or was he just trying to sell me a power flush??

Quite likely it was. See below

7) I was told you can't descale the crap on the outside of the inner coil, is this not true?

I would have thought it ought to be possible, but not by the usual means of hooking up a descaling pump and pumping a small amount of concentrated descaler around. I find it hard to believe that no-one does something that can be poured into the system and which will slowly descale it even in a weak solution. Given that I think most of the descalers are acidic, so they chemically react with the scale, then it may be difficult finding the right combination that dissolves the scale without dissolving parts of the system

I call them 'sludge buckets' mate, but I don't see what reflection that has on my skill & experience. They are sludge buckets, most are poorly installed in spec build houses & they need loads of inhibitor.

Most people call them sludge buckets as a term of abuse - they are looking for anything to criticise them for because they've a blinkered view that anything other than a combi or indirect open vent cylinder is just wrong. If you don't have a thermal store, do you then call the rads "sludge traps" in general conversation ? No ? thought not. It would be just as logical.

The store doesn't make the sludge, but by being the place where the water gets to be slow moving then it's where the fine stuff gets to settle out. Most of it is going to be coming from the rads. In any case, up to a point, does it actually matter if there's an inch or two of sludge in the bottom ? It does mean that it's not in the bottom of your rads or boiler and making them ineffective.

And lastly, is it the fault of the thermal store if they are incorrectly specced or fitted ? That statement is pretty well acknowledgement that the industry is full of ignorant cowboys who don't know their stuff and don't care that they don't know. As JonasX says, they aren't difficult to understand if you want to. FFS, people install Y plan and manage to wire those up, yet I don't hear too many complaints about those - perhaps these are people who just "plumb/wire by numbers" and have no idea what they are actually doing.

 

[JonasX]

I call them 'sludge buckets' mate,

That implies all of them sludge up irrespective. They do not. The thermal store experts say they can be isolated from the iron rad loops to prevent all this sludge. They tell me they need about 3 cans of X-100 every 4 years.

I looked right into them when researching UFH. Most are now stainless steel units.

 

[JonasX]

Most people call them sludge buckets as a term of abuse - they are looking for anything to criticise them for because they've a blinkered view that anything other than a combi or indirect open vent cylinder is just wrong. If you don't have a thermal store, do you then call the rads "sludge traps" in general conversation ? No ? thought not. It would be just as logical.

Good point. The thermal store makers echoed exactly that to me. I think it is a superb way for CH and main pressure hot water. I like the way it enhances the boiler operation, getting the best out of the boiler. After much more research I homed in the on the 1 to 10 kilowatt Geminox boiler heating only UFH at a very low temperatures. And then maybe using a combi's water section only or multi-point for hot water needs. It works out quite cheap to do it this way. I have been doing some figures. Improved boiler technology makes matters simpler in design and expense.

If rads were involved as well as UFH. I would use the CH section of a combi, with no efficiency reducing auto by-pass valve. And still keep the Geminox running UFH. If I needed very high flow for hot water then the thermal store would need to be revisited. One in which the rad loop is isolated from the thermal store to keep sludge out of the store.

The store doesn't make the sludge, but by being the place where the water gets to be slow moving then it's where the fine stuff gets to settle out. Most of it is going to be coming from the rads. In any case, up to a point, does it actually matter if there's an inch or two of sludge in the bottom ? It does mean that it's not in the bottom of your rads or boiler and making them ineffective.

Excellent point. It keeps the sludge, if it occurs, out of the rads and boiler, keeping these expensive items running clean and efficiently. Some UFH people use pressurized thermal stores saying sludge rarely builds up in these. They do not need the complex and expensive pressure controls that unvented cylinders use, only simple, cheap, standard, blow off valves at the boiler and cylinder. They said having two gives backup.

Can sludge cocks at the bottom of a thermal store be fitted connected directly to a drain? Then all you do is open it every few years and get rid of it. Will Fermox de-sludger soften hardened sludge? This could be used and then drain via the sludge cock.

Just some thoughts about how to get round any potential negative problems.

 

[SimonH2]

The store doesn't make the sludge, but by being the place where the water gets to be slow moving then it's where the fine stuff gets to settle out.

Excellent point. It keeps the sludge, if it occurs, out of the rads and boiler. Can sludge cocks be fitted connected directly to a drain? Then all you do is open it every few years and get rid of it.

I doubt it would work - you'd need to stir it up, otherwise you'd just drain a little hole and leave the rest in situ.

The only practical way I could think of doing it would be to drain down the whole cylinder (close the isolation valves to stop the rad circuit draining as well ?), and then stick a hosepipe in through the vent pipe connection and somehow swish it about inside to stir up the sludge and let if flow out of the drain cock. Otherwise, it's a matter of disconnecting all the pipework so you can rock the tank about - I'd just let it live there, unless you've got many inches of sludge then it's not going to interfere with anything.

Getting back to the OPs problem, perhaps this could be combined with a periodic descaling - throw in some descaler and sludge softener, let it run round the system for a while, then drain it down and flush out. Since it's not a huge quality required, it could be worth collecting some rainwater to refill the system with so the DHW coil can't scale up (externally) again.

 

[D_Hailsham]

How can a system which requires the water temperature to be a constant 78°C (implying a return temp of 58°C to 68°C) be considered "efficient"? The boiler will be permanently running above the temperature at which condensation starts.

Albion don't like modulating boilers either as they say: The use of a modulating boiler may increase recovery times.[/quote]

So you can forget about weather compensation.

My feeling is that thermal stores are a relic from the past when boilers had cast iron heat exchangers, ran at temperatures up to 85°C and the last thing they should do is condense as the condensate would eat into the heat exchanger.

 

[DeltaT2]

I know exactly how any heatbank or thermalstore works son. Would you like to call me a cowboy to my face?

They gather any sludge from a system, therefore they are sludge buckets.
By there very nature they can't transfer enough heat to the non ferous part of a radiator system. So all the sludge gathers in that primary water. Pyshics can't change that. You two are not Water Systems aka Dr Drivel etc etc by any chance?

 

[JonasX]

Sometimes, with thermal stores or heatbanks, you can get a blending valve fighting with a thermostatic shower mixer, that results in a cold shower,

How come? The blending valve only provides a constant temperature. then the shower mixer trims to suit. The shower mixer may not a need thermostat in it, as a constant temperature of hot water is supplied.

A neighbour fitted a non-thermostatic mixer as his combi was set to a constant output temperature. He said it works well and no breakdowns of replacement mixer cartridges. He has a high flow hot water combi with the hot and cold to the shower uninterrupted by other tee offs.

 

[JonasX]

I know exactly how any heatbank or thermalstore works son. Would you like to call me a cowboy to my face?

I probably would. Your view counters what the UFH experts say, who make these thermal stores. Your views fall in line with the so called plumbers that indus had around. You seems to have only come across poorly designed and installed systems, by your own admittance, and using your limited experience of them as a consensual view of these products.

They gather any sludge from a system, therefore they are sludge buckets.
By there very nature they can't transfer enough heat to the non ferous part of a radiator system. So all the sludge gathers in that primary water. Pyshics can't change that. You two are not Water Systems aka Dr Drivel etc etc by any chance?

"By there very nature they can't transfer enough heat to the non ferous part of a radiator system."

Can you elaborate on this. This is new to me and maybe something that is unknown.

I am not in the market for a thermal store, as other solutions are cheaper and easier for my needs. If I need higher hot water flows I may be back in the thermal store market. I really like they way they enhance the boiler's performance. So simple and elegant.

Us two?

 

[JonasX]

How can a system which requires the water temperature to be a constant 78°C (implying a return temp of 58°C to 68°C) be considered "efficient"? The boiler will be permanently running above the temperature at which condensation starts.

Albion don't like modulating boilers either as they say: The use of a modulating boiler may increase recovery times.

Stratification will ensure that the temperature at the bottom of the thermal store will be way lower than the top and sometimes a 40C difference. I searched on SimonH2's name on this forum and he has built a thermal store that returns water to the boiler at 25C or so. That appears very efficient condensing boiler territory to me. I will let him come in on that as he made it.

One maker told me that using slightly over-sized hot water plate heat exchanger and no internal hot water coils the thermal store temperature can be as low as 65C when running UFH. With a boiler on a 20C temperature differential that is 45C return.

Albion's claims say may. Say that is true, and I am sure it is the case with some boilers, the efficiency of the condensing boiler will probably increase, saving money?

I do know that there are many versions of thermal stores and the best sing along. One maker said, "you can't generalize with them".