Advice needed - upgrading gas/electrics to power outbuilding

MrM83

I would appreciate some advice if I may.

I am currently undertaking some building work comprising of a new outbuilding/annex and renovation of our main house. The new outbuilding will be single story of about 800 sq foot, and will contain a home office, guest bedrooms and a bathroom and hence I need to supply utilities to it to heat and power it.

My understanding is our builder intended to take a separate gas connection off of our existing gas line and add an electrical connection via our consumer unit. We had a recent visit from a heating engineer who raised concerns that the gas pressure/volume would unlikely be sufficient to power the boiler in the house and a new boiler in the outbuilding. I would estimate the location of the new boiler would be approx 30m from our existing gas meter. We are unable to add a new connection as the outbuilding will not have its own address.

I have made an inquiry to Cadent who want approx £450 for a "non-standard application form" to be considered, whereby they will assess the situation and then quote for a solution of unknown cost. I am reluctant to part with this sum without even a ballpark idea of the cost we might be looking at.

I have also spoken to our supplier, British Gas, who claim they could increase the pressure "from yellow to amber" for a nominal fee. I am not sure if this would then be sufficient for our needs, but would appear a simple option if viable.

The second option is installing an electric boiler into the outbuilding which as a unit and as a fuel source would be more expensive. We would also likely need to upgrade to a "3 phase" supply, from what I understand, but am unaware of the cost in doing so at this time.

Lastly, LPG is an option, which would serve our needs. It is a little more inconvenient, but I am keeping this at the back of my mind.

If anyone has any experience of the matter and could provide advice I would be greatly appreciative? I am a little annoyed that this hasnt been given more attention until now, but will proceed to explore the various options and discuss with our builder.

Many thanks

jk0

Storage heaters?

MrM83

Sorry, I should probably elaborate on a couple of points. Given how the building would be used (infrequently except the office), we wont need to heat it regularly and so ideally a fast "on demand" heating style is what I am looking for. We also live in a conservation area so wont be able to install solar panels on the roof.

Owain_Moneysaver

A U6 domestic gas meter has a maximum throughput of 6 cu metre per hour which is a maximum of about 60 kW - which depends on the gas pressure and calorific value locally.

To upgrade the meter may require a new meter housing and also a new pipe from the street.

You may be able to get a free GT1 test to advise.

However the simple answer would appear to me to be to one of

• put two system boilers (non-combi) in, with an electrical interlock so they can't both operate at once,
• range rate the two boilers to limit there maximum demand,
• use the one boiler in the house to heat both buildings through an isolated heat transfer loop through heat exchangers in the house and outbuilding and insulated district heating pipes.

Before doing any of that your Gas Safe-registered heating engineer should check your existing pressure and flow available at your meter and actually calculate what gas supply and pipework is required. Anything less is speculative guesswork.

Owain_Moneysaver

Air source heat pump may also be suitable for some of your office space heating load and will provide cooling in summer too.

MrM83

Having had some feedback from our heating engineer it seems our gas supply would be insufficient for 2 boilers to work in the way we would like. LPG remains a backup option, but we are now exploring the possibility of installing an electric boiler to handle a wet central heating system and shower in the outbuilding. I have no concern about central heating, more so about the hot water supply for the shower. The irregular and unpredictable times in which the shower is likely to be used would ideally suit the heat on demand nature of a (gas) combi. Is it possible to achieve similar using electricity? What I want to avoid is having to heat water ahead of time (which may or may not be used), or having to constantly store hot water in case of use (which would drive bills that we dont need).

Any further advice welcome.

Gloomendoom

I think I would consider going all electric given the projected intermittent use. What would be the payback time for the gas option?

Robin9

The gas problem may well be more internal than external to the property. It is likely that you would need to run direct back to meter.

Your new-build will be super insulated so its heating needs will be quite low.

Consult the Gas Safe heating engineer.

Heedtheadvice

Given your description of intermittet use of the outbuildings and the ability of a new build to be super insulated I would agree with Gloomy to look at all electric.
Whilst electricity (and lpg) is expensive to run it is cheap to install. You perhaps need to estimate running costs (installation costs for heaters are quite small) versus high gas or extended wet central heating installation costs. Consider electricity is three to four times more expensive to run so 1000kWhours might cost you £150 per annum electricity gas maybe £50. If your gas install cost is £2k (maybe more from what you write) then the £100 a year saving would take 20 years (very approximately) to pay for itself. Add in servicing and replacement boiler costs and then.....
An electric shower is cost effective to buy, install amd run too (as is an on demand electric hot water heater for a sink) especially for very intermittent use and would add very little to running costs.


Very controllable too so can be set to run with background heating for most of the time and fast rise to desired temperature when required.



I am a fan of heat pumps too but unless being used for your main resicence as well would probably rule them out on installation cost grounds.


A lot depends on your time horizon to some extent and more importantly power requirement. f you needed 15,000 kWhours then that would be a different matter!!

MrM83

Thanks for your replies, very useful and its opening my mind to different solutions. I feel some further context would be useful at this point.

Our main residence is a listed building, but the new outbuilding is not, but we do live in a conservation area. The only impact this has is that we might struggle to house large fan units on the outside of the outbuilding if we were to install a heat exchange solution. That said, if we could hide it from view, it might be possible.

Our issue lies in the sporadic use of this building. My wife is likely to use the office during the week. The guest bedroom is likely be to used maybe one weekend a month on average, but might be used for longer periods on occasion. The bathroom is likely to be used when my wife uses the office and when we have guests to stay.

Given it should be well insulated and how the building will be used, I am hoping whatever fuel source we use, the running costs won't be too high. This is hopefully our forever home so I don't mind up front installation costs if savings are offered on ongoing costs.

Our gas safe engineer has advised that the current supply simply wont work for us. A new run from the meter would be about 30m in length and the advice is the pressure drop would be too much for 2 boilers to function. If anyone things differently, then please advise. I made some inquiries into a U16 meter, but this seems to then seriously restrict the number of engineers who are qualified to work on the system.

Stored LPG not an option as we have nowhere convenient to site a storage tank.

Bottled LPG (an expensive) option.

Air to air pumps - I need to investigate

Air to Liquid - Im worried about performance in the cold and ongoing maintenance costs

So right now electricity is the main contender and where I think I need to focus my efforts. An instant hot water boiler would suffice for the shower, given its infrequent use, but Id like to know the flow rate wouldnt be pitiful.

I am not adverse to electric radiators heating rooms as required, but would be nice to have some remote control of all units, so we can turn them on as required ahead of time if not in the house. Is this possible?

Fall back option remains a wet CH system with some facility to provide hot water. I spoke to Elektra and they claimed they have a true combi electric boiler that can provide hot water on demand, but have read mixed reviews...

Niv

If the shower is going to be that infrequently used. Why not just get an electric shower?