Replacing LPG boiler sytem advice

wiffola

Hi All,

We want to get rid of our dependancy on LPG for heating and hot water.

We are not on mains gas.

Here is some info about our house:

Semi detached
88m2 floor area
3 rooms downstairs
3 bedrooms
loft conversion

LPG Gas
Or whole house runs off 4x47kg cylinders. We use about 20-24 bottles a year running heating very lean.
We currently have a Vaillant eco tec 831powered by LPG - heating and hot water.
We are low hot water users, 2 adults and 2 young children. We have a mixer shower straight off the boiler.
In the winter months the heating is on most of the day at a low temperature - usually at 50 degrees on the boiler and 20 degrees on the thermostat.
We have 7 double panel double convector radiators throughout the house and a large towel radiator in the bathroom, which we only turn on now and again.
A few radiators have thermostatic valves installed.
We have mainly 10mm pipes to the radiators, 12mm to others.
We have an LPG gas hob.

Electricity
We have a 2kw PV solar system on the roof.
PV array since installation has produced 1000kw (16th May 2011 to 4th October 2011).
We have a dishwasher (cold feed), washing machine (cold feed), tumble dryer. All A rated apart form the tumble dryer.
We have an electric oven.

House and Insulation
The house was built in 1895.
Thick stone wales - no render or insulation.
2 external doors, not brilliantly insulated.
Original single glazed sash windows, windows in main living room are secondary glazed.
We have a loft conversion which is insulated with 50mm king span rigid insulation. But not brilliantly done - installed 10 years ago.
We have good insulation everywhere else in the roof - this was done professionally this year.
The roof has no felt with bare tiles on battens. Apart from the solar panel side of the roof which is now felted.
One velux window in the loft. roughly a metre square.
The down stairs floors are concreted.

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I've done lots of reasearch and go round in circles.

I've had quotes on air source heat pumps - Danfoss AQ with Danfoss unvented concealed tank seems the best product IMO (about £12k though). However I've heard bad things about ASHP on here in general and am being put off this approach.

I keep wondering about air to air systems and keeping lpg just for water demands? We dont use much hot water and we will still need lpg for the hob.

We havent got space for biomass indoors, but we do have space for things outside.

Any suggests most appreciated.

Budget of £8-10k.

thanks

david29dpo

I would stick with what you have but get a bulk tank.

wiffola

Thanks for the reply.

We haven't got space for a bulk tank. Unless we give up our back garden completely. Don't get me wrong, we have space as I said but the regulations for bulk tanks are just crazy. No structures within 3 metres an we only have a small garden.

One option is to have an underground tank, but to spend a few thousand to do this just doesn't make sense with LPG just going up and up.

We want to invest in a technology which is going to bring down our monthly cost and push us in the right direct for the future, hence why we have installed our PV array.

Also, when you work the cost difference, it's actually very similar between 47kg cylinders and bulk. This is because of the tank standing charge is around £100 per year.

Any more thoughts would be gladly received.

Thanks

wiffola

Thanks jeppjunkie.

Lovely to hear some positive feedback on the ASHP plan. This is really what I want to do. To get rid of LPG and claim back some boiler space would be brilliant for us.

As for UFH or fan convectors, that sounds like a huge job. Partiularly as our house is in quite a finished state - as lovely as it would be. The company we plan to go with for the DanFoss AQ basically said that to retro fit UFH just wasnt a feasable option for our house. We have concrete floors throughout downstairs.

He recommended oversizing the downstairs rads by at least 30%. This can be quite easily done (only 3 rads) by installing stelrad k3's with thermostatic vavles. This will actually create more than a 30% oversize which he says will benefit us with our current setup as well as on an ASHP.

I understand what you are saying on the UFH i.e. that it will get the best results from an ASHP, but I just can't see this making financial sense in our situation.

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Regaring the PV's. We have a 2kw system (8 monocrystaline sharp 245w with sunny boy inverter). We've covered the roof completely.

We've had them for 5 months. The summer has been average and we live in Wales which is rain central!

So far we have produced 1000kw so roughly £450 from the FIT.
Best day so far (mid june) = 16kw in one day.
Worst day (yesterday rained all day) = 1.1kw in one day.

We're are pleased with them. It's hard to judge at this stage how it will impact our electricty bills. I'm estimating we will save 1/3 throughout the year. We are high consumers of electricity though - tumble dryer, dish washer, elec oven and 2 small kids!

The effectiveness of the PV array is also down to how you use your electricty. We now stagger appliance use and make sure something is running when the suns out. It's great feeling sitting in the sun, knowing that the dishwasher is running for free!

The feelings I have 5 months on, is that without the FIT it just wouldnt be worth it financially. From a green c02 persepctive it would of course.

If you're a bit of geek like me, I take great satisfaction from reading the meter on the inverter everyday - it's a very satisfying past-time! I also personally think it looks great on the roof, although our neighbours probably beg to differ.

last thing to note on the PV. We had to have our roof felted before installation - just the south side. It cost around £2k. The solar company wouldnt install without the roof being in tip top condition. Despite that being a big kick in the balls...I'm so glad we did it. It cost more but while you have scaffolding up it makes sense. Plus we have a lovely new roof of welsh slate - which u can't see!!

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The overall plan was to get the PV array and then combine them with an ASHP. The reality is though that a PV array of this size probably wont touch the sides of an ASHP. Maybe it would in the summer when the ASHP is replenishing the DHW but not in the winter.

What do people think on this?

I would love to learn more on your ASHP installation jeepjunkie. i.e. how do running costs compare, how many kw it uses when it's running the heating and how many for DHW. Any more info would be brilliant.

As you can tell I am as keen as mustard!

Thanks for your help everyone.

wiffola

Thanks JeepJunkie - very interesting indeed.

Also very interesting to hear about your fan convectors combined with wet central heating. Although I imagine in my situation this would mean extra expense.

We have been assured that our mixture of 8-10mm microbore wont be a problem. By 2 independant installers. I am still wary of this though.

I quite like the idea of fan convectors, as space is a premium and would dearly love to get rid of all the rads.

How many indoor fan convectors do you have and how much of a messy job is to connect them all to the ASHP?

Also, how noisey are the indoor units?