Domestic Biomass CH

[AardvarkTreeServices]

BUT

With current technology in our temperate climate, if starting from scratch, one should only require minimal heating, i.e. a log burner for both ambience and heat, with solar hot water panels to supply the DHW, backed up by a small modulating mains gas boiler.

marcus

 

Thats the set up we have but if PV FITs continue it may be a more efficient installation to spend your money on additional PV capacity rather than solar thermal. You can then use surplus electric to heat the hot water using an Immersun diverter and get additional FIT payments for the extra generating capacity. The RHI payments on the solar thermal are quite low relative to the PV FIT payments.

[drinksloe]

From the rumour my brother was hearing is they reckon pV FiT could be getting lowered again in the new years possibly as low as 1p, considering it was 42p and 21p in its early days. He was looking at fitting more but not worth it now.

If u've got heat pumps or a high elec use might be worth putting PV on for free elec even with no FiT

 

Not sure about tank size?

U will really need a plumber to access ur heating requirements for ur heating rads or UFH.

 

For a 150m2 house insulated with UFH they were quoting a 1000-1500l tank with a 18 or 25kw LGB, and that was an oversized tank for system.

I'd say 3000l is a pretty big tank (3T of water alone, bet tank will wiegh 1T itself) but if needing a lot of rads in an old unisulated house or high DHW demands u may be right enough

[AardvarkTreeServices]

The PV FIT rate is 12.5p til end Dec and then 12p til end if March/April. It was scheduled to drop to next to nowt at end of Dec but seems to have had a stay of execution for a few months. Whether the recent Paris climate summit will affect the rates is yet to be seen but at current rates a PV array should still give a 10% return over the 20 years of payments

[jamez654]

We have a Dunsley Yorkshire wood burning stove that feeds a 300L heat bank. Also have 2 X immersion heaters and oil boiler. The heat bank comes ready tapped for solar thermal although we haven't got around to fitting it yet. The whole system is integrated and oil only kicks in when required. TBH I'm very happy with the system

I am trying to get a system installed like this. Currently we have an oil boiler and open fire to heat an old poorly insulated 5 bed cottage. Planning to retain the oil boiler, replace the open fire with a large stove with back boiler, probably one of the following:

• Arada Stratford Ecoboiler 25 HE
  
• Arada Villager Boiler 20
  
• Brosley Snowdon 30
  
• Stovax Stockton 14HB
  

All linked up with a heat bank. Might add solar thermal at a later date. Currently waiting for a plumber to size the heatbank for me.

 

Although with the current low heating oil prices it seems debatable whether it is worth going to all the effort.

 

James

[cornish wood burner]

Ah - thanks for all responses to date - to be clear - no interest whatever in log, chip or pellet boilers. My main heat source is, and will remain, in the lounge with a set of glass doors so I can look at the fire.

 

The wet CH system is already installed and working fine, all I need to do is to install a buffer tank to the existing system in tandem with a planned changeout of the stove - and I might even line the chimney.

 

cheers

mac

Hi Mac

If it helps a 2000ltr tank will hold 47KWhr of heat with a flow and return differential of 20 deg. If you need more info on recharge times with a certain boiler running set load for a certain time etc, or even system resilience running a smaller boiler than the peak heat load please let me know.

[openspaceman]

Hi Mac

If it helps a 2000ltr tank will hold 47KWhr of heat with a flow and return differential of 20 deg. If you need more info on recharge times with a certain boiler running set load for a certain time etc, or even system resilience running a smaller boiler than the peak heat load please let me know.

 

This is where underfloor heating scores, not only do you have the thermal mass of the screed but that delta T could easily be as much as 50 deg C, effectively doubling the water heat store as long as DHW is separate.

[difflock]

Having forgotten to switch off the Underfloor pump, I have pulled my TS temp down to 30 deg, the house was well toasty by then.

My conunderum is the fact that since my thick slab cum heat store underfloor slab requires time to both warm up and then start radiating heat, it needs to be on during the night, since we get up at 06:00, so despite being able to strip the heat energy from the TS, there is then not sufficient temperature for the DHW or bathroom/bedroom radiators from 05:30.

Only solution ud be a more expensive Froling type WGB that can be pre-loaded with fuel and left to light on a timer, about 04:30.

Or actually two TS'S run down alternately would be another solution.

marcus

[cornish wood burner]

Having forgotten to switch off the Underfloor pump, I have pulled my TS temp down to 30 deg, the house was well toasty by then.

My conunderum is the fact that since my thick slab cum heat store underfloor slab requires time to both warm up and then start radiating heat, it needs to be on during the night, since we get up at 06:00, so despite being able to strip the heat energy from the TS, there is then not sufficient temperature for the DHW or bathroom/bedroom radiators from 05:30.

Only solution ud be a more expensive Froling type WGB that can be pre-loaded with fuel and left to light on a timer, about 04:30.

Or actually two TS'S run down alternately would be another solution.

marcus

Have you tried just running the underfloor slightly over temperature by day and have a timer to turn it off by night. Depending on slab thickness it should retain a fair bit of heat for the morning. Probably not an ideal solution but if the morning and evening temperatures were bearable then no cost involved. I do something similar to this to reduce peak loads in the glasshouses.

[Westwood]

Hi

 

I have been running a Biomass boiler to heat a large detached house with good standard of insulation since 2005/6... Really sick about not being a legacy system for RHI without swapping out the boiler which I refused to do. Early adopters often lose out but there we are. I think there were only a handful in the country when we installed ours.

 

I have a 50Kwatt Baxi log boiler with 2500 litre thermal store and the usual Laddermat controls from Foundation Firewood. The unit is in a garage which holds a buffer wood store of about 9 cubic meters. The original oil boiler is still there for emergency use when the buffer is low but has only been used a couple of dozen times in nearly 10 years.

 

Operationally we burn about 30-40 loose cube a year of mostly hardwood from tree surgeons, forestry companies and ours and neighbours gardens. The wood is processed by ourselves and stored in Heras fencing bays with tarpaulins - fantastic drying system. Currently running 3 years old wood about 15-18% in the bays and 13/15% in the garage which provides final drying before burning.

 

Boiler has to be filled once a week in summer for hot water only and once a day for central heating in this current warm spell. When winter really sets in it is loaded 2-3 times a day.

 

Only repairs I have had are two sets of replacement fire box units and seals which are really a maintenance item. Obviously the boiler needs cleaning and de-ashing once a month or so.

 

It order to improve efficiency I have a Grundfos variable speed pump and Honeywell CH Zone electronic radiator valves for zoning the areas of the house we are actually using - both are pricey but give a great deal of control.

 

In rough terms we have replaced a £4-5000pa oil bill with about £1000pa of wood and a lot of hard work but had a lot of fun along the way - can recommend it particularly with what I read about the RHI.

 

If anyone would like to discuss our experience let me know. I also own a large woodland and can supply bulk containerised firewood if required PM me for info.

[openspaceman]

Have you tried just running the underfloor slightly over temperature by day and have a timer to turn it off by night. Depending on slab thickness it should retain a fair bit of heat for the morning. Probably not an ideal solution but if the morning and evening temperatures were bearable then no cost involved. I do something similar to this to reduce peak loads in the glasshouses.

 

You need to find the time constant of the slab, the time it takes to reach an equilibrium from a stepped input, so you can predict how long it takes the slab to cool to half its normal temperature , this coupled with a predictive programmer that compares outside and inside temperatures should be able to decide when to start pumping for the morning demand.

 

Whilst I have worked on installations using thermal stores and underfloor heating from wood firing I have never lived in one.

 

What I have discovered is that a high thermal mass underfloor heating system doesn't really suit a couple who both work away from home 11 hours a day. I'm thinking I may have to compromise and fit a kick space fan coil unit for the sitting room. This is in a gas fired one bedroom bungalow.