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Energy Surveys

Project Management

Gas and Oil Heating

Electric Heating

Office Lighting

Carbon Trust Loans for Energy Efficiency

Renewables

General Lighting Stuff

LED's

Compressed Air

Voltage Power Optimisation

EPC's

Water


P F C

Refrigeration

C R C

Energy Awareness Training

CCA / ECA

H V A C

The Green Deal

Home Owners Page

Stewart

My Opinion

Client list

Links

Contact Me
Energy Surveys

Project Management

Gas and Oil Heating

Electric Heating

Office Lighting

Carbon Trust Loans for Energy Efficiency

Renewables

General Lighting Stuff

LED's

Compressed Air

Voltage Power Optimisation

EPC's

Water


P F C

Refrigeration

C R C

Energy Awareness Training

CCA / ECA

H V A C

The Green Deal

Home Owners Page

Stewart

My Opinion

Client list

Links

Contact Me
Energy Surveys

Project Management

Gas and Oil Heating

Electric Heating

Office Lighting

Carbon Trust Loans for Energy Efficiency

Renewables

General Lighting Stuff

LED's

Compressed Air

Voltage Power Optimisation

Energy Performance Certificates

Water


P F C

Refrigeration / Cooling

C R C

Energy Awareness Training

CCA / ECA

H V A C

The Green Deal

Home Owners Page

Stewart

My Opinion

Client list

Links

Contact Me

Heating

Boiler fuel saving technology     and     Underfloor heating (a discussion).

HeatKeeper radiator panels

I can help cut anything from 10% to 30%+  from your heating bills......

Boiler Management Control

"Back in the day" as they say - I used to sell something called the IFC FuelSaver - a clever wee box of electronics designed to cut fuel consumption of indirect fired warm air heaters. 

I persuaded the makers (BBC Industries) to build a boiler control unit using similar control algorithms and return flow sensing and we sold masses of them - a fantastic piece of kit that basically inhibited the burner circuit until it was actually needed - as determined by suitable drop in circulating water temperatures. 

Sadly BBC Industries took a very different direction a few years ago (Bob now sells very good cheese and wine so if you are interested email me) and so for years I have been waiting for someone else to take over in this key area of energy efficiency.  That time has arrived - but what am I talking about - why do we need boiler controls?

Lets take a typical example of something I come across all the time - but this is an actual quantified case study if you like.  Three boilers were surveyed as part of an audit of a major secondary school for one of the Scottish Councils.  The boilers were observed to fire up when Return Flow reached 165oF or 74oC, which represented a very small drop from the output temperature of 170oF and is indicative of a phenomenon known as ‘dry cycling’.

Dry cycling is common in boilers operating an On/Off cycle controlled by the boiler thermostat and occurs when the central heating system is not demanding any heat.  Heated spaces could be up to temperature or the time clock could have stopped the circulating pump on the DHW (domestic hot water) system.  There is no useful load for the boiler to meet and in theory it should stay shut down until the next call for heat.  In practice however the boiler loses heat from its own outer surfaces, from flue losses and from circulating losses and when it has cooled even slightly the thermostat sensing boiler internal water temperature operates to bring on the burners and raise the temperature again. This cycle is often repeated over and over even although there may be no true demand and therefore no useful export of heat from the boiler.  During dry cycling the efficiency of the boiler is zero.

Instead of keeping the boiler permanently at the thermostat setting there is no reason why it should not be allowed to stand idle until the next demand for useful heat.  It may cool down significantly but the heat lost will be considerably less than that incurred through frequent firing and cycling.

Whenever this situation is found I recommend the M2G fuel saving system, which has been evaluated by the Carbon Trust and given ECA (Enhanced Capital Allowance) approval.

These units are much more than just simple clockwork timers that you may have come across before to eliminate dry cycling.  The logic behind the systems is water temperature intelligence.  A fuel saving unit is required for each boiler and strap on sensors are attached to flow and return.   An internal microprocessor collects water temperature values from the flow and return every ten seconds and averages these readings out every minute.  If the boiler thermostat or BEMS (Building Energy Management System) calls for heat the M2G will evaluate whether or not the burner needs to fire at that precise moment.  The M2G will be able to detect the exact type of demand based on water temperature fall versus time and will fire the burner when its intelligence instructs it to do so.    The software parameters for water temperature intelligence are the result of 1700 on site tests resulting in a database of 69 million water temperature readings.

  The software also holds in memory the flow and return temperature the last time the boiler terminated its fire and uses this template for all future fires combined with the temperature readings every ten seconds.   If a zone valve opens the return temperature drops and the software will watch this drop until eventually the boiler terminates that fire and the M2G will hold in memory the satisfied flow and return water temperature values as the current system condition.    The control continually monitors and regulates the system through loading demand temperature variations.    Its intelligence can never be more than nine seconds old and its "decision making criteria" can never be more than one minute old.

  In multi boiler applications installed M2G units are linked together so that they "talk" to each other passing intelligence information and boiler activity data from unit to unit.  One boiler will pass information to other installed boilers relating to when it has fired and its associated water temperatures.  The other M2G units will be informed that a boiler has fired and the non firing boilers through their installed M2G units will closely monitor the water temperature rise from the burner fire.  If the fired boiler is unable to raise the water temperature effectively and efficiently then the next boiler will be allowed to fire to help the load demand.  This induces a second level of both compensating and sequence control to the boilers. 

In the case of the secondary school cited above a recommendation has been made that M2G controls should be fitted to the three boilers.  Given annual gas costs of £27,000, even a modest 10% saving is worth £2,700 per annum, which against investment of around £3,000 offers payback just over 1 year.

Now - there is one other very good reason that I like the M2G - and guys at Sabien who make it.  They sell ethically and therefore it doesn't matter whether you save £100 or £10,000 with your M2G installation - the price of the unit control - fully installed - is exactly the same!!!!  I like that approach to sales.

Get in touch to discuss your boiler installation

Underfloor Heating (UFH)

Space heating energy use constitutes a major proportion of total UK primary energy consumption - at least 60% for example in the domestic sector.

Despite improvements in energy efficiency (better insulation etc) energy use in our homes is increasing.  The number of homes is increasing too and we keep our home warmer than we ever used to (average 16oC in 1990 rising to 18oC in 2004).  So how do we maintain this drive for more and more comfort whilst reducing our energy burden - is UFH the answer?

UFH comes in two forms - wet and electric.

Lets look at wet systems first - fed by the circulation of hot water through pipes under floors.  These systems warm the floor structure by conduction causing the surface to radiate heat into the space above and the primary source of heat is typically a boiler - although many other options now apply which i will deal with later.  The boiler heats water to 40-50oC and this is distributed in plastic pipes to one or more manifolds each of which comprises a flow and return header from which loops are taken to serve areas of the building to be heated.  In a simple two-storey office for example there would be one manifold serving the ground floor and one for the first each feeding UFH loops in the individual rooms on that floor.

Getting good conduction between the UFH loops and the floor structure is the key to success. Different methods of transferring heat from the pipes are applied for different floor structures.  The pipes are usually fixed to the floor insulation and a concrete screed poured over them further to which floor tiles, carpets or other surface finishes are applied.  Where floor tiles are used heat radiates into the "treated space" at roughly 100W/m2.  The design output achievable with suspended timber floors averages slightly lower at 70W/m2.  Note the use of the word radiate - UFH is more akin to radiant heating than is for example the use of radiators which are mostly convection.  Radiant heat means less rising heat lost to the roof void as convection - indeed with UFH the reverse is probably true - that is temperature inversion where the floor is hotter than the ceiling.    All of this means that the boiler operates at a lower temperature which promotes good combustion increasing efficiency.  Typically a condensing boiler serving UFH would be operating at 90% compared to 87% for the same boiler feeding radiators.

These low operating temperatures also means that UFH is the ideal partner for "renewables" such as ground source heat pumps and air source heat pumps (where the heat exchanger carried out an air to water transfer).  Why ideal - well simply these systems tend only to be capable of heating water to 40-50oC and although some people like to boost this with a small boiler or an electric immersion element it seems a bit daft to me so I prefer to use the water at the temperature the heat pumps produces it in UFH systems - but heck what do I know?

Pro's and Con's of Under Floor Heating

Pro's Cons'
Lower running costs and CO2 emissions Slower response time
Optimises thermal comfort Heat output limited to 100W/m2
Enhances decor by concealing heating Supplementary heating may be required in small rooms & bathrooms with two external walls, small conservatories and corridors with large glazed areas
Flexible for use with renewables and CHP Remains a "novel" technology, despite recent growth which tends to lead to uncompetitive pricing
Ease of access to manifolds for maintenance Can restrict floor finish
Concealed heat emitters improve access for cleaning floors and skirtings Pumps can be noisy so need sound damping or remote siting to avoid nuisance to occupiers
Enhances property value Deep floor required to accommodate pipework and insulation
Common on continent - becoming more popular in UK Not really much of an option for existing properties unless flooring is being replaced
Extended warranty of up to 25 years available on pipework loops of most UFH systems Risk of damaging pipework if flooring is penetrated, leading to potentially costly repair works

Conclusions:  if you are building a new property then potentially great in terms of using new renewable technology.  Initially expensive in terms of material costs and requires specialist labour (not just any old plumber can fit this stuff) but long term your running costs are likely to be substantially lower than with traditional boiler fed systems

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