Domestic Biomass CH

[difflock]

At least since the Mrs. retired 10 year ago, we have got better value from the very slow reacting but stable temperature holding, high thermal mass underfloor heating.

But even when we were were both working, the radiators came on for a quick blast in the morning (all bedrooms are radiator heated), and the underfloor was set to kick in about 14:00/15:00 to have the house warmed for our return from work.

One did not have time to register the lack of proper cosy heat in the morning!

I have only ever heated the underfloor once per 24 hours, for 1 or 2 or up to max 3 hours depending on outside air temps, I could keep the 25kW-30kW oil boiler running constantly during this time.(from recall, I seem to remember reducing the jet size in the boiler and tweeking the pump back to reduce heat output, for this very reason )

Which I intuitively understood to be the most efficient way to run an oil burning boiler.

And seeing as we were heating 3600 sq ft of 1990's std insulation build, on about 2500 l of kero a year (plus the big Morso stove), probably correct.

[cornish wood burner]

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.

Most of our works heating is underfloor but I use a slightly different system for timing. The office MUST reach a tropical temperature for long enough to warm chairs,cups and pens before occupation so it runs from midnight to just before end of play. The production staff are more forgiving so the concrete slab gets a couple of hours before start of work to melt the ice so all is well then.

 

Best advice I can give to Mac and anyone installing biomass is make sure your heat store is big enough. It will give you much more flexibility to run the system as you want.