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Author Topic: Open Vented WBS to Pressurised Thermal Store over distance  (Read 573 times)
tinsoldier
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« on: January 11, 2019, 10:16:43 AM »

Apologies for asking another layout question- theres lots on here but I'm not sure mine will work over distances involved


The situation at the moment is that I have self built a large single storey extension (with 4m high ceilings in living space and a loft) (135m2) attached to an old 135m2 farmhouse.

within the old farmhouse, on the ground floor I have a 500 lt pressurised/sealed thermal store, complete with appropriately sized expansion vessel.
This is powered by a 30kw oil boiler and heats the house through conventional radiators.

In the extension I have an underfloor heating manifold connected to the thermal store which provides ufh throughout.

I have a new boiler stove- an Arada Stratford 25HE Ecoboiler Wood Burning Multi Fuel Boiler Stove, which requires an open vented system, and as such I was thinking of a load valve or loadunit/plate exchanger etc.

I am yet to purchase anything that would go between woodburner and thermal store


I have plumbed in and insulated 28mm flow and return pipes from the thermal store to the woodburner, which is roughly 20m away on the same level, but the pipes route up and through the ceilings.

I have plumbed in an overflow pipe from loft above thermal store down and out through wall

I have access to mains cold water in loft above woodburner

I would have ample room in the loft above the woodburner to install any equipment




I would appreciate advice on whether a laddomatt type install would work (picture attached)
also would a load unit/load vale be able to be placed in loft 4m above WBS - level with plate heat exchanger 4 m or does it have to be level with WBS



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Countrypaul
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« Reply #1 on: January 11, 2019, 01:24:46 PM »

Just a couple of comments as I am not an expert on this sort of setup by any means.

In principle imo it looks as though it would work but there are a lot of assumptions that you may want to explain rather than have everyone making their own rather than using what you plan.

Looking at your diagram you appear to have the two bottom connections on your WBS connected together and the two top ones likewise. It appears that normal practice is to connect bottom at one side and top at the other only when you have a single circuit - I believe this is because the longer route to the stove can result in boiling as water from the pump takes the shorter route only.

You have not indicated and air bleed valves which would obviously be essentail on both circuits as pass the high point.

I presume the NO 2 port valve will be closed when there is power and the loading system is working.

The stove is 12kW I believe but you don't indicate how large the heat leak radiator is, given that during a power failure the radiator will need to be relied on to dissapate the heat from the WBS obviously there needs to be a certain amount of matching.  If the connection to the radiator is a bottleneck (they usually are) then you may need more than one radiator just to take the flow from the WBS under gravity situations.

Will the heat leak radiator be activated by opening the valve if the thermal store gets upto a predefined temperature?
Will the pump in the loading valve be activated by a thermostat on the water exit pipe from the WBS or some other way?
How will the pump on the store to the FPHE be activated?
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tinsoldier
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« Reply #2 on: January 11, 2019, 01:34:09 PM »

CountryPaul

thanks very much for your comments, appreciate the feedback

yes air bleed valves will be installed, as will a draincock.


just realised the pic has both ports linked - the diagrams I stole and modified from something I found online, yes it will be as you describe one port on each
yes the valve will be closed when power is there, open when not

The stove outputs 22.5kw to water - I've not bought, nor sized heatsink radiator, but I've plenty room to put multiple rads

I was planning a pipestat or flue pipe stat to kick off the pump in load unit


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tinsoldier
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« Reply #3 on: January 16, 2019, 08:01:08 AM »

Does anyone have experience of alternative systems such as heat genie?
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offthegridandy
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« Reply #4 on: January 16, 2019, 09:04:03 AM »

Hi TS,

I expect that you've thought of this but just in case.

On your diagram it says 15mm feed and expansion to the header tank. I think the expansion pipe would need to be at least 22mm and ideally all in copper not speedfit plastic.

Apart from that I think your layout should work.  Don't know about heat genie I'm afraid.

Cheers.

Andy
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tinsoldier
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« Reply #5 on: January 16, 2019, 10:26:16 AM »

Yeah noted 22mm for feed and expansion
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eabadger
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« Reply #6 on: January 16, 2019, 05:15:26 PM »

we have an open vented wood burner no ladomat or store, heat leak radiators directly above stove on landing, 22mm feed to expansion tank in copper 22mm vent to outside.
sensors detect temp on gravity feed and return and at preset start pumps and valves to unvented DHW cylinder, when the temp of dhw is near satisfied the valves to radiators open.
i would advise a scrubber type thing in flow to get crud out, we have one with a magnet and a drain point to drop all the crud every couple of months

steve
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26kw wood stove back boiler to underfloor heating and dhw
tinsoldier
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« Reply #7 on: January 22, 2019, 12:43:35 PM »

so the last part of my question is key for me

would a load unit/load vale be able to be placed in loft 4m above WBS - level with plate heat exchanger 4 m or does it have to be level with WBS
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Pile-o-stone
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« Reply #8 on: January 22, 2019, 01:01:28 PM »

Yeah noted 22mm for feed and expansion

To save on pipework, you can have a combined feed and expansion. 22mm expansion pipe up to the loft tank, 15mm feed from the bottom of the loft tank, T-ing into the 22mm expansion pipe.



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Pile-o-stone
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« Reply #9 on: January 22, 2019, 01:15:35 PM »

CountryPaul

thanks very much for your comments, appreciate the feedback

yes air bleed valves will be installed, as will a draincock.


just realised the pic has both ports linked - the diagrams I stole and modified from something I found online, yes it will be as you describe one port on each
yes the valve will be closed when power is there, open when not

The stove outputs 22.5kw to water - I've not bought, nor sized heatsink radiator, but I've plenty room to put multiple rads

I was planning a pipestat or flue pipe stat to kick off the pump in load unit




The rule of thumb around the size of a heatsink radiator is 10% to 20% of the WBS output to water. So 2.25kw to 3.3kw in your case. This radiator should be always on when the WBS is, so that you don't have an explosion if a valve on the heatsink rad freezes up from non-use. We had our overheat rad in a cold hallway. Most of the hot water will be pushed past the radiator feed and into the heatstore anyway, so you wont lose too much heat to the overheat radiator.

We had an overheat problem with our WBS and it sounded like Odin's hammer smashing around the house. The boiler in the WBS cracked and flooded the kitchen. I would always size the rad correctly and definitely wouldn't have a valve between the wood burner and the overheat rad (like we did, to our cost).

The article below bears out some of what I have said and seems a decent resource:

https://www.stovefittersmanual.co.uk/articles/heat-sink-radiator/
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offthegridandy
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« Reply #10 on: January 22, 2019, 08:26:50 PM »

Hi Tinsoldier.

Given that both of the elements in your proposal are pumped not gravity fed I can see no reason why the heat exchanger shouldn't be separated from the WBS by the distance indicated.  You may need to experiment with pump settings and obviously insulate the pipe work meticulously to avoid heat losses.

To be sure, I would telephone the product manufacturer and ask to speak to their technical department.  In my experience these guys are usually very helpful as they are not directly involved in sales.

But no valves between heat source and heat dump radiator.  Always assume the worst will happen and plan accordingly. Ie fire roaring away and a power cut so no pumps or valves operating; make " fail safe" the basis of the design not an after thought.

Andy
« Last Edit: January 22, 2019, 08:29:02 PM by offthegridandy » Logged

8 KVA Lister TS2 Startamatic Genny
24 Volt 1000amp battery bank
Outback VFX3024
4.6 Kw PV array permanently ground mounted
Outback Flexmax 80
2 X Flexmax 30 PV CC
2.5 Kw wind turbine H Piggot design 4.5 Mtr Dia
12 Mtr free standing Tower.
u/floor heating from oil boiler cross linked to 12 Kw
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