Thermal store or not?

Relying on gravity-feed only isn’t an option as the pipe runs will have to run up-down-and back up again in some places



In most houses this is never a problem, even in France.
But these Dark Arts are not for sharing with DaftyDIYers or anyone else that think they know Gravity Central Heating systems.
Churches, Skools, Houses, Offices........etc, etc...........Done them all with gravity systems son.

Oh, these systems are never that bonny - to the untrained eye or *******.
DELETED
*******

But they'll work in the many Frog Power Cuts...........

gaswizzard said:

LondonChap said:

0.6 bar to zero down the pipe. . Work it out from that.

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Seems your struggling with the answer , I asked for the "circulating pressure" , this being in proportion to the temp difference between flow/return , the answer being 6.2 mb.

What is an 'open vented' system?

I think I know what 'one of those' is.

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Oh you've got a ********** on the end of your line GW.............
I think they're all *******?? This forum & the Navitron forum are *********, they're a complete ****!!........

DeltaT2 said:

I think they're all retired teachers or goaty beard stroking, oilly rag engineers?? This forum & the Navitron forum are poluted with them, they're a complete PITA!!........

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Does that mean they can think things out better than you?

DeltaT2 said:

But these Dark Arts are not for sharing with DaftyDIYers or anyone else that think they know Gravity Central Heating systems.
Churches, Skools, Houses, Offices........etc, etc...........Done them all with gravity systems son.

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Spill the beans on your dark art. We all await.

I did see a 3 bed semi on gravity heating. Done in the late 1950s. A 28nm (1" then) pipe went upstairs to the gravity cylinder from the boiler. Also a 28mm pipe went upstairs as well. This dropped to 22mm under the floors feeding in the upstairs radiators. The return was 22mn and dropped down to the boiler on the far side of the house and back to the boiler under the ground floor. The ground floor radiators used this return pipes as well. A 22mm flow pipe to each ground floor radiator was dropped down from the upper floor. Pipes everywhere, but it worked on a small Powell Duffryn (sp?) conventional flue cast iron boiler with NO electric controls using a gas relay valve.

To turn on the radiators the user turned large handled wheel vale on the CH flow. They could gauge the heat given by opening the valve to suit. In spring only half opened.

Simple, effective but downright ugly.

Delta-T must be very old if he put gravity systems in. They are rarely used these day and haven't been for about 40 years. That doesn't mean by me that they don't have a place.

DeltaT2 said:

Do you seriously think I'd share that with DaftyDIYers??...........

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Yes you would share if you knew.

LondonChap said:

The problem with you is that you think you are cleverer than what you are. .

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You'll notice I don't post in here that often due to the googlers/know it-alls , anyway thanks for the inverted compliment.

LondonChap said:

Delta-T must be very old if he put gravity systems in. They are rarely used these day and haven't been for about 40 years. That doesn't mean by me that they don't have a place.

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Not necessarily old, but is unlikely to be some young guy - I doubt if there are many people below a certain age who know much (if anything) about gravity systems.

Funnily enough, the subject of gravity systems came up in conversation only the other day - incidentally it had worked around from problems my brother is having with a "not very good" plumber. A work colleague of my father's back in the 40s or 50s was buying a new house and insisted on a gravity system, and a boiler with no electrics. Even back then he really struggled to find a plumber who could install one - and it didn't work properly either (part of it needed to be pumped in the end).

I can see where DeltaT2 is coming from - if you don't have reliable power, then you try* and design a system that will work without it. That was the reason dad's colleague wanted the system he did - before my time, but apparently we were no stranger to power cuts in the UK back then.
But that does not excuse DeltaT2's attitude.

* The OP may or may not have a setup where a gravity system is practical. "Possible" does not equal "practical". Possible doesn't necessarily fit in with what's aesthetically acceptable (to the OP, or perhaps to the "other half"). Nor does "possible" fit in with desirable from the POV of how the system works and the user actions required.



If the OP hasn't been frightened off by the bickering, it might be worth him expanding on the information he's posted so far. Number of floors, location of stove and cylinder, other people involved (and their attitude to manual system operations), etc.

LondonChap said:

DeltaT2 said:

Do you seriously think I'd share that with DaftyDIYers??...........

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Yes you would share if you knew.

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Oh no I will not share my knowledge..............

I have been on holiday ( working ) in France and have not been scouring these forums.

But it does seem as if Delta T2 wants to be barred from the forum for a few months ( again ).

Apologies if I have missed who made the deleted posts and he is not the culprit as usual ( Give a dog a bad name.... )

As in the well-reasoned explanation of the gravity system, above, there are no time or temperature controls. This applies largely to thermal store based systems - you cannot have really effective control of a system based on a huge thermal mass, especially if it is partly heated by a hand fired solid fuel boiler, which must have gravity circulation available to at least part of its load. What was good in the 40s and 50s is still good, [and many thousands of people had free coal] but we now have far better boilers and controls. Our boilers now use far less fuel and cause far less pollution because they and their controls are better - and give us much more comfort. Going via a thermal store compromises this excellent controllability, which is not to say that it is always wrong. A thermal store has its place if you want to use a hand fired boiler as a significant contributor to the total heat input, and are happy with a much more complex layout than you would otherwise need. The other option is to have a dry heat-only stove in the main living room, and let the heat convect through the house in appropriate circumstances.

Solar input to the central heating does not make much sense in the UK climate; it is good for the Alps where you can get low air temperatures and strong sunlight at the same time, we don't get that very much here.

Finally, you can draw your own conclusions about the quality of the advice given by those who resort to abuse.

I agree with much of that, but there are bits I don't agree with.

The presence of a large thermal mass doesn't compromise controllability provided the controls are designed to suit. But if you take a system/controls designed without a big thermal mass, and then add a big thermal mass, then you would be right to say that it will compromise things.

So while the stove needs "uncontrolled" access to dump it's heat into the store, that doesn't mean there cannot be good controls on the output(s) of that store.
At one extreme you could have a gravity loop for rads with no controls other than individual valves on each rad. At the other extreme you can have a fully pumped system, with multiple zones, with weather compensated flow temp, and individual room temperature controls (eg TRV). In some ways this loop can be better controlled than with (eg) a condensing gas boiler as you can design it specifically for how it works in heating the rooms - and don't have to start compromising it to fit in with constraints imposed by the boiler (eg minimum flow rates).

But of course, if you go for a fully pumped and fully controlled CH system, then you need to consider a secondary means of extracting heat from the store (or stove) in overheat situations. This would still be the case with a gravity CH system since the user could turn all the rads off and still overheat the store.

Whatever combination of controls you choose, the store provides the needed buffer between uncontrolled input and controlled output. IMO it isn't a complex layout, even less "much more complicated". Compared with (say) an S-Plan setup with CH and DHW cylinder + bypass to keep the boiler from tripping or breaking, there's hardly any extra hardware involved.
Of course, if you want complex that that's also an option (combi boiler with it's complex flow sensors, diverter valves, heat exchangers, ... ? ) ...

Um.

Whatever you do here, it won't be as well controlled as a quality gas boiler with weather compensation feeding the radiators and cylinder directly. Interpose a thermal store, and nicety of control is lost. By all means do it if you wish, or need it for alternative inputs, but you lose some controllability.

But then whatever you do with "a quality gas boiler with weather compensation feeding the radiators and cylinder directly", it won't be what the OP is asking about, which is using an uncontrolled heat source and burning wood to heat his DHW and CH.

His CH can be exactly as well controlled if set up as discussed - with the limitation that its control will fail if the store temp is below the required flow temp. Actually, I'd argue that by interposing the buffer tank, the CH can be better controlled (no need for bypass or always on rads) - unless you know of a condensing gas boiler that is rated for arbitrarily low flow rates and/or arbitrarily high temperature differentials.

Actually, if you do know of such a boiler, then I'd be interested to know about it as it would be ideal for charging the thermal store in the flat. Even Atmos specify a substantial minimum flow rate (about the same flow/delta-T as other manufacturers) even though (I believe) they claim their boilers can survive dry-firing.

Yes, we are saying the same thing. A thermal store is only justified if there is a substantial uncontrolled heat input, the economies of which outweigh the loss of close control of the gas boiler.

The best condensing boilers have modulating pumps to reduce circulation rate in line with heat input.