Understanding a reversed TMV for cylinder loading

[Greenbeast]

Can someone help me get my head around using a reversed TMV for loading a cylinder from the top down?
I've been searching and have seen mention of such use but could really do with a decent diagram or explicit description of operation

[SteveH]

 I'm also interested in this subject.
 
 I have a 14m (each way) run of 15mm pipe from my boiler stove (8kw) to the accumulator & DHW heat store. I really don't want to run ½ that volume of cold water through either store. I would much rather send it around the pumped pipe run until it gets to a reasonable temperature, say 50°C...

 Steve...

[SimonHobson]

It's simple enough.
Remove any non-return valves from the TMV "inlets" as they'll stop your flow.

Connect the flow from your boiler to the "outlet" of the TMV, the hot inlet to the boiler return (tee'd into the pipe form store to boiler), and connect the cold inlet to the top of the store.

In operation, while the water is cold, the TMV will go hard over - in normal use this would pull 100% hot water. The result is that the flow from your boiler will bypass the store and circulate back to the boiler. As the flow heats up, the TMV will change over, and once above the setting it will end up hard over the other way - in normal use it would be trying to pull 100% cold water as it's too hot.

Ther eis a band where the valve will be part way, and so it will regulate flow (partly to the store, partly bypassed back to the boiler) according to what temperature the boiler can put out.

[Greenbeast]

I meant i terms of diverting flow between two coils, but perhaps i have misunderstood the posts i have read in the past

[A.L.]

hello,

I meant i terms of diverting flow between two coils, but perhaps i have misunderstood the posts i have read in the past

No, i think your O.K. - connect the flow from the solar panel to what would normally be the output of the TMV, if the flow is above the mix temp of the TMV the water will come out the cold input of the TMV and if the flow is below the mix temp it will come out of the hot input. There will be a small range of flow temps around the mix temp where it will come out of both.

[Greenbeast]

thankyou

[SimonHobson]

I meant i terms of diverting flow between two coils, ...

Not sure you can do that with a TMV in reverse.

What is your heat source for that ? From what I've read, many solar controllers have an output that can be used to drive a diverter valve.

The problem I see is that with solar, as the sun comes out you will have low grade heat - you can put that through a lower coil to heat the store bottom up but then the loop temperature will stay cool and you'll not get to switch to top loading via the upper coil. Alternatively, you keep keep the pump turned off (or slow it down if variable speed) to allow the loop temperature to climb so that you can top load your store through the upper coil.
You'd need a thermostat/temperature sensor half way up the store to control the system with as well.

The method I described is for use with a boiler etc - and prevents you pumping cool water into the top of a previously stratified store - thus killing the stratification. It will prevent flow into the store until the supply is hot, and thereafter would regulate the flow temperature (by indirectly controlling the temperature of the water going into the heat source) if the heat source was unable to maintain output temperature at full flow rate and available input temperature.

[Greenbeast]

Yes i'm familiar with that technique and have that planned

I think i probably don't need what i originally requested. you're right, the controller can handle the solar switching coils, if needed.