Do I really need a Laddomat ?

[camillitech]

 Morning chaps,

I was intending doing without "the mother of all thermal bridges" (a chimney) as Eccentric Anomaly puts it  in our new 'off grid' 121m square hoose. However thinking back to last November and early January with a few weeks of below zero temperatures, no wind, snow on the solar panels and a frozen hydro turbine I'm thinking I'd be stupid not to have one as back up. I'm surrounded by trees and hopefully high insulation levels would mean it gets little use.

I'm going to heat a large thermal store with a combination of hydro, solar and dumped energy from the wind and PV. The wood burner will have to be capable (in worst case scenario) of supplying both UFH and DHW but do I really need a Laddomat  I understand that the back boiler will be more efficient and it will help stratification in my store but surely if I heat the store via a coil rather than circulating the store water it will do that anyway, or am I missing something 

It's not the cost of the unit that's bothering me but the thought of yet another pump making a noise and sucking the life out of my batteries.

I was thinking for long enough of doing the MHRV, ASHP, as well but that would mean another two motors running so now I'm going to stick to trickle vents and buy more PV with the money 

Cheers, Paul

[billi]

 

[camillitech]

Not helpful 

[Billy]

Paul,

personally I am one for no gadgets and even less pumps and motorised valves.  My gravity heating works just fine and it even works downhill but no lower than the boiler return of course.  I worried for some time about back end corrosion with cold water returning to the boiler.  The water is treated and the boiler is stainless and if it leaks I will have to weld it up.  Yes I get a cold fire at times but the gravity system seems to balance itself and a good burn soon burns the tar off.   

KISS - you have enough to do with maintaining all your other energy systems.   

billy

 

[qeipl]

Morning Paul,

My understanding is that the laddomat keeps the return water temp high enough to stop the bottom of the water jacket getting too cool, which is inclined to tar it up, corrode it or some such.
I can see the point of this in a pumped system where the water is moving through the pipes and, if someone runs a bath, the return temp could drop substantially sending a slug of cold water to the boiler.

In a gravity system the heat is moving through the water, which suggests much more gentle temperature gradients, especially if you have a huge thermal store.

I'd be inclined to do without the laddomat, but others may have a better understanding of the reasons for using one.

[camillitech]

Hi Billy'

I'm inclined to agree with you, I'll already require a pump for my UFH another for my solar and possibly one to raise the water pressure  A pump for a Laddomat and another couple of motors for MVHR and ASHP seems like three loads too many.

Hopefully the stove would not be getting much use, but when it does it's likely to be in sub zero temps with little renewable input and a set of batteries severely hampered by the cold  so I'd like to keep power usage to minimum at these times.

Cheers, Paul   

[dhaslam]

A typical woodburner  will make very little impression on a large store if there is a heating load at the same time.   If you are not using  a Laddomat  the boiler coil would need to be  high up in the store  to  concentrate the heat in the area needed for DHW.   

[camillitech]

A typical woodburner  will make very little impression on a large store if there is a heating load at the same time.   If you are not using  a Laddomat  the boiler coil would need to be  high up in the store  to  concentrate the heat in the area needed for DHW.   

What I was thinking of was an Akvatherm or similar of around 1000lts which would hopefully have a constant 900w of heat going into it from my new hydro. This would be supplemented by around 10Kwh per day on average dumped from my other hydro and wind turbine. There would also be input from solar hot water and a 6Kw immersion for when the genny is running, though I'm hoping to make Mr Lister redundant 

If a Laddomat is really going to make that much difference then I'm happy to fit one but I really would like to keep it simple.

What do you think about store size for a four bedroom single storey, of 121m square with UFH, three occupants and lots of insulation.

Cheers, Paul

[Billy]

Have you done your heat loss calcs, and how long do you want the store to last?  How hot do you want house?  Will you use WBS in sub zero to supplement?

Do you really need to have WBS connected to the store?  Might be a better back up on its own.  Cook on it too, ok the heat is a bit more localised with cooler bedrooms but hey.

billy

 

[Baz]

The world did seem to manage without a Laddomat until a couple of decades ago. Unless you wait until the store is stone cold before lightng the fire it won't be doing much, and to improve the fire all you need is a bit of fire brick or better still the modern insulating board to shield the fire from the bottom of the water jacket. While they do have their place it's getting to be a bit of an Aga type mantra.

[dhaslam]

The 1000 litre store  sounds right.   The  top third will always need to be reserved for  DHW  but that still leaves the best part of  1 kWh for every degree of variation in the rest of it.     Mine is nominally 1000 litres but  unless it is magic  it only holds 850 litres based on the measurements.  I  only have the DHW cylinder heated from the top third.    It heats at an average about 2 kW  for nine hours from the heat pump but  in cold weather the heat pump runs for  up to six hours in the afternoon.      The stove  adds about 2kW to the top of the store when it is running but it uses  4 kilos of wood an hour to do it so it's days are numbered. 

The stove is a more difficult  one.    A small very efficient stove that can run all day on  15 kilos of wood  and gives comfortable local heat  but    doesn't heat water is  a lot easier to operate than one that  heats water but uses three times as much fuel. 

[Justme]

My thinking is that the laddermat will only help during the start up & high load on the system phases. So I have left it out of our system as the boiler will be running almost constantly as its a low kw wet boiler & the load is low & even. Plus as its a non pumped system I dont rate the "fall back" mode if its in use full time.

[Brandon]

paul,

I would also advise considering using a dry back stove for local heat, if you can get it reasonably central in the building, it will do you proud, and be far easier to install, have no cold water worries, and be less hassle all round (I say this as someone who designs and installs systems using wood burners and thermal stores as the majority of my work.)

I live with a Morso squirrel with a wee 2.5kW boiler that runs 2 rads (little ones) as my only heat source in a 3 bed council semi, it heats the living room well, but on occasion I ponder the benefits of the boiler ( I can send the heat to the cylinder if the solar has let me down, and that is the plus side, that and the warm bathroom.

A small boiler on a large store can often appear to do little if nothing, and if you are to do it, then either directly tap it to the top of the store only (for DHW) or put it through a high level coil.

A couple of years ago I built a house for a couple, it is a barn conversion of 128m², and has a heat load of 3kW, the details were done with painstaking anality.  A wee stove could easily provide this.

If however, you are proposing to try and meet you heating demand, and therefore use a larger stove, it may well warrant the loading unit ( I would use an ESBE over a thermoventilier).

Hope that helps, feel free to PM me if you want to ask anything.

[knighty]

is the Lister air or water cooled ?

I'd be tempted... (if it's water cooled)

to plumb it into the heat store and then use that for power/heat when you're stuck ?

(seeing as it's just for the dead of winter etc... when your other sources of power/cheat fail)

that way you could charger your batteries up, heat the store with the immersion heater and with the hot water from the engine... all at the same time ?

[camillitech]

Morning all and thanks for the replies,

I'm hoping (perhaps dreaming) to have enough power for most of the year without needing it. Indeed I'm hoping that the only time it will be needed in earnest is if the hydro freezes. Like you say DH, the stove is a tricky one as I might end up lighting it just to look at it  but it will need to be big enough to at least provide DHW in the event of freezing, lack of wind/sun etc.

Billi, not very good at calcs  but I'm working on it  all I can say is that it will be insulated well above regulation requirements but I'll not get much in the way of solar gain due to orientation and planning constraints. It's a bungalow with no vaulted ceilings or roof lights, one door and no patio 

Baz, Justme, think I'm inclined to agree with you on the Laddomat front, I was not convinced with its ability to thermosiphon in the event of a power cut, though I've never had one for longer than it takes to re set an inverter or start a Lister 

Hi Brandon, I'm a great Squirrel fan myself, running two now for over twenty years (though I converted one to oil  ) but my concern would be the DHW, I'm sure I could live without the UFH for a week or two with a decent space heater. I was thinking of the Dove, do you have any experience of that stove ? I could I suppose heat the water via Lister and immersion but I'm determined to make the generator obsolete or at least put him into semi retirement.

Knighty, I'm afraid all my Lister's are air cooled and I have to say that I am really tempted to get a modern water cooled generator and do just as you say but I really want to use diesel as a last resort and veg oil is not really an option here. Though I've not ruled it out.

Cheers, Paul