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Author Topic: Does this seem right? (Biomass thermal store connections)  (Read 6011 times)
Ivan
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« on: December 13, 2014, 01:23:09 AM »

I'm trying to design a very low cost biomass system. The boiler is going to feed a big tank directly, and the heatloads are also going to be connected to the tank directly. Can anyone advise me of the suitability of the connections I'm proposing (the diagram shows the actual positions of the tank connectors).

Is it ok to feed the boiler flow into the middle of the tank rather than the top?


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knighty
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« Reply #1 on: December 13, 2014, 01:36:06 AM »

why don't you just have 1 big connection top and 1 big connection bottom (say 2inch?)

then have a 'kit' which is essentially a 2inch T-piece and some reducers

users can tag on as many kits/connections/T-pieces as they like

boiler can suck from the return and pump back into the feeds, meaning it always sucks in the coldest water and returns heat where it's needed


production cost should fall more than enough to cover the T-piece and reducers

and users always have the option of adding more connections later on with ease ?


and to me (maybe I'm odd) that would be easier/neater to plumb up too ?
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Ivan
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« Reply #2 on: December 13, 2014, 01:50:14 AM »

I've already ordered the tank - the price is very low, but there's no flexibility on the inlets/outlets - they just produce what they think are 'standard' tanks. One thing that puts me off using some kind of manifold (eg the 2" tee with reducers) is that you can get flows obstructing each other, or venturi effects etc - in my experience, things that you never thought would happen, but somehow start to make sense after you've done all the plumbing and then found it's not working properly. The benefit of plumbing everything into the tank is that it acts as a really good neutral point, and you don't tend to get pressure effects (It's like having a 36" tee in the system!!).

I would have instinctively fed the boiler into the highest point and returned to boiler at the lowest point, but the fittings on the tank don't really work in this arrangement. I'm thinking there may be some logic to feeding the hot water into the middle of the tank (it will rise), but wondering if there's any fundamental reason why this won't work, that I haven't thought of.
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Countrypaul
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« Reply #3 on: December 13, 2014, 11:12:20 AM »

As shown you don't appear to be using the top part of the tank which would be the hottest water and therefore are potentially wasting the heat in the top 1/4 (?) of the tank. Hopefully it is just that some connections are not shown, otehrwise you may wish to move one of the outflows to take advantage of the hottest water at the top.

Paul
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julian
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« Reply #4 on: December 13, 2014, 12:35:50 PM »

your boiler connections -

just to be sure - are you injecting hot water mid way, or are you injecting at the base?

i think that you are sucking cold out of the base of the the store to the boiler, and then returning hot from the boiler to the mid way point?

that is the way that i would do it.  there is no issue with injecting it mid way.  radiators have both connections at the base, and the heat rises to the top.

in a tank with flow, im really not sure there will be much stratification anyhow, so i doubt it makes a whole load of difference!
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Ivan
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« Reply #5 on: December 14, 2014, 02:04:41 AM »

Yes, good point - I should use the connection at the top.

Yes, injecting hot water mid-way and taking cold water from the bottom of the tank back to the boiler.


I've witnessed one of these tanks in operation - and there is definitely stratification in the tank (you can feel the temperature change on the metal skin of the tank).
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sb79
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« Reply #6 on: December 21, 2014, 10:46:34 PM »

Assuming a loading unit (laddomat)will be involved (incidentally what make is the house brand?), then I would be loading from the top down. Admittedly this is a preference due to my use of smaller stores and using the different temp layers to do different things.

I would be using the top 6/4 (1 1/2 inch?) connection as primary flow.
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Ivan
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« Reply #7 on: December 23, 2014, 01:18:22 AM »

Yes planning to use a loading valve. Not sure what brands of loading system we sell,but it won't be a navitron one, as we're talking about a 200kW input, rather than domestic sized.

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