Questions about GSCH for a Victorian terraced house

Hjb

Hi, I’m wanting some advice and opinions
I currently live in an old Victorian terraced house, it’s a 6 bedroom house with internal 75mm kingspan on all the walls (except the lounge). And secondary glazing on most windows

We currently have an old gas system boiler, and it needs replacing I think ground source heat pumps are the way forward, greener and better.

But opinions, has anyone got one in an older property, Also we would need to have vertical bore holes. Anyone had a system like this fitted and if so how did it go and what sort of running costs do you now have?

Thanks

H

Smiley_Dan

It doesn't matter whether it's an old property or not. What matters is the heat loss from the house, and the nature of your emitters (rads or UFH). Heat pumps, running at lower temps, generally need larger emitters, but then it depends on the heat loss.

You don't have much insulation so you could improve that, your windows sound rubbish and you didn't even mention the air tightness so I'm guessing that's poor too.

You should fix the above, then see what you need to do. By then you could get away with a small cheap gas boiler or an ASHP, both far cheaper.

Cardew

Welcome to the forum.


IMO nobody who has mains gas should contemplate getting a heat pump.


It is highly unlikely that running costs will be lower with a heat pump than gas. Also the cost of a Ground Source Heat Pump with vertical boreholes will be huge; although RHI will offset some of the installation costs.



You will also probably need more, or bigger, radiators and be prepared to run the heat pump for long periods each day; 24/7 in winter.

todayisagreatday

We are considering heat pumps (likely water source) but if I had gas available (we don't) I would never be considering it at all. Gas will always be cheaper than a heat pump purely because gas in cheaper than leccy.

Skools_Out

todayisagreatday wrote: »

...Gas will always be cheaper than a heat pump purely because gas in cheaper than leccy.

Unfortunately it is not as simple as that.

Gas is burnt to produce the heat.
GCH itself uses electrically powered pump(s) - although admitedly not as large.

A heat pump simply extracts & pumps the heat that already exists (such as in the ground) to another place.

Cardew

Skools_Out wrote: »

Unfortunately it is not as simple as that.

Gas is burnt to produce the heat.
GCH itself uses electrically powered pump(s) - although admitedly not as large.

A heat pump simply extracts & pumps the heat that already exists (such as in the ground) to another place.

Agreed.


However even a very good Heat Pump installation will not have a COP* above 3.0 averaged over a year - including hot water for a tank.


*For those who don't know COP is the ratio of 'Energy in' to Energy out'. e.g. with a COP = 3.0, 1kWh consumed produces 3kWh heat.


Currently electricity costs roughly four times as much as gas; typically 14p/kWh to 3.5p/kWh. So at those prices and a COP of 3.0 gas will be cheaper.



There is another important factor. A heat pump's output is much lower than a gas boiler; for efficiency it needs to run with water at a lower temperature than a gas boiler. Hence it needs to run for long periods - even 24/7.



With a gas boiler people who are out during the day can have their heating switch on, say, 30 minutes before getting home and return to a warm house; similarly it can be set to come on 30 minutes before getting up in the morning.


The above cannot be done with a heat pump as it needs to be producing heat when 'not needed'.

Skools_Out

Cardew wrote: »

Agreed.


However even a very good Heat Pump installation will not have a COP* above 3.0 averaged over a year - including hot water for a tank.


*For those who don't know COP is the ratio of 'Energy in' to Energy out'. e.g. with a COP = 3.0, 1kWh consumed produces 3kWh heat.


Currently electricity costs roughly four times as much as gas; typically 14p/kWh to 3.5p/kWh. So at those prices and a COP of 3.0 gas will be cheaper.



There is another important factor. A heat pump's output is much lower than a gas boiler; for efficiency it needs to run with water at a lower temperature than a gas boiler. Hence it needs to run for long periods - even 24/7.



With a gas boiler people who are out during the day can have their heating switch on, say, 30 minutes before getting home and return to a warm house; similarly it can be set to come on 30 minutes before getting up in the morning.


The above cannot be done with a heat pump as it needs to be producing heat when 'not needed'.

I got excited when I saw "There is another important factor. "

I thought you were going to mention that gas boilers are not 100% efficient. Mine's probably less than 60%, but I accept newer ones are more efficient. But sadly not 100% or anywhere near it.

Hence it's not as simple as you suggest either.

todayisagreatday

We will be remodelling our bungalow and building up as our and a new heating system is needed. I've done so much research so far as mains gas isn't an option for us. We've been lucky so far since moving we haven't had our heating on just been boiling a kettle for washing dishes and electric shower so not used oil.

We both work full time and although I work from home two days a week I'm used to timed heat, e.g. gas but as we don't have it I'm dreading oil. We will need to fill out tank up at some point as our renovations won't start til spring.

As we want underfloor heating throughout we are tempted with heat pumps, and our most likely option is water source which is likely to be a little more economical than air and with the RHI we are hoping it will pay for itself something we can't get with a new oil system..... But the though of leaving it on 24/7 really doesn't make sense, paying for something we aren't using.

If gas was an option. I'd be jumping up and down but we can't get a gas pipe over a canal bridge!

lovesgshp

With the original post, the borehole option is the most expensive of all. We used to use a compact collector system as a option, but that does require a recharge system to be added. We have stopped installing these in Italy, though they may still be available in the UK.
In answers to other questions:
Yes it is preferable to have it operating 24/7 due to heat lapse if switched off for too long.
There is a lack of knowledge regarding indoor house temperatures. It is no good turning your indoor thermostat down by 5C overnight and expecting to have the original temp back up with a few minutes of getting up. It should only be the pump flow temp adjusted by very low gradients depending on whether underfloor or rads. It can be up to 24 hours just to get a 1C rise in cold conditions.
With underfloor, try to restrict the amount of carpet and if possible use mainly a tiled floor, as the above or wood is a insulator.
Recommended operating temp for UFH is around 19C as the heat rises, unless it is blocked by a type of factor as above.
There is not always the need to change rad sizes, but it is recommended to have diverter valves fitted if using thermostatic valves, so as not to restrict flows.
Domestic hot water. Tanks come in a number of sizes depending on your usage. Average is 20% DHW to heating requirement even with a 300ltr tank.
HTH