Does a GSHP make sense in a Grade 2 listed building in need of complete renovation

FreeBear

fizio said: 2. On a gas boiler it's perfectly fine to have the radiator thermostat turned down in unused rooms and the boiler copes fine. I dont know enough about oil boilers and heat pumps  to understand why they are different.

A modern gas boiler can modulate its output down to supply heat for just a few radiators. Although there are one or two oil fired boilers that can modulate, the majority will only run at one setting. Without sufficient radiator capacity to use the heat being generated, the boiler will start to short cycle. This reduces the average heat output at the expense of increased wear & tear along with a drop in efficiency.

Heat pumps, depending on make & model, can modulate down, but the output range is limited - a 4:1 range is (I believe) typical, compared to the 10:1 range of a decent gas boiler. If you have say, an 8kW heat pump with a 4:1 modulation range, you will need a minimum of 2kW of radiator to avoid short cycling. The other issue is that heat pumps require a minimum water volume circulating through the system. Some can be as little as 20l, others could be 60l or more. Volumisers and/or buffer tanks can be fitted to compensate for a lack of water volume circulating through the system, but this adds to installation costs and may reduce overall efficiency.

Reed_Richards

@FreeBear has given most of the explanation.  But also:

Modern gas (and oil) boilers are condensing and that improves their efficiency but they only condense if the return water temperature is below 60 C.  A boiler heating a single radiator and making it hot enough to keep the room warm is unlikely to be able to maintain a return water temperature less than 60 C so it won't be running as efficiently as it could.  

fizio

Freebear/Reed_Richards, very useful information and I didn't realise these 'limitations'. I am not expecting to just heat a single room but more likely have a luke warm temp in unused rooms and a decent temp in lounge/kitchen/bathroom etc. Surely minimising energy use is a good thing rather than heating an entire house just because thats how the equipment works - seems like heat pumps have a way to go yet to give the flexibility of gas boilers. More pondering needing as I lean more about these technologies..
My other corner about GSHP is that the pace of technology change is likely to be rapid so in the next decade will there be stuck with 'old equipment' that may for may not still be serviceable etc? This is true with any product but works easier when the sums involved are lower so moving to a new boiler etc is not a huge hit to the wallet versus GSHP.

Very much appreciate the education so far and none the wiser as what I should do
 

FreeBear

fizio said: My other corner about GSHP is that the pace of technology change is likely to be rapid so in the next decade will there be stuck with 'old equipment' that may for may not still be serviceable etc? This is true with any product but works easier when the sums involved are lower so moving to a new boiler etc is not a huge hit to the wallet versus GSHP.

Heat pumps have been around for a surprisingly long period of time. 1928 saw the installation of a heat pump to heat Geneva City Hall, and in 1945, Norwich City Council used one to heat some of their buildings (with a SCOP of 3.4). So heat pump technology  is well established - Much of the recent developments have been around the refrigerant used and a push towards higher flow temperatures.

Shifting expectations of users and better education of installers are going to be areas where we will see changes - For my part, I've been looking at how well my heating system works (currently powered by a gas combi boiler). Last few weeks, been running with a flow temperature in the 30-45°C range. At times, it hasn't felt as if the radiators were working, and the room temperatures don't shoot up in an instant. Even so, the house is staying warm despite the boiler running for longer periods but still using a little less gas in the process. I had doubts about low flow temperatures, but the data tells me that it is working (could do with a couple of larger radiators though).

Reed_Richards

fizio said:

 Surely minimising energy use is a good thing rather than heating an entire house just because thats how the equipment works - seems like heat pumps have a way to go yet to give the flexibility of gas boilers. More pondering needing as I lean more about these technologies..
 

1. A lot of gas boilers share a common control interface called OpenTherm.  There is no equivalent for heat pumps and that is certainly something that is lacking.  It means that if you are to get the most out of a heat pump you need to use the manufacturer's own controller.
2. The efficiency of a heat pump is more sensitive to its operating conditions than is the efficiency of a gas boiler.  This means that it takes more effort to get a heat pump operating at near its best efficiency, although once you have done that you can set it and forget it.
3. The range of heat outputs from a gas boiler is greater than the range you can achieve from a heat pump.  

Some heat pump users can get hung-up on operating their heat pump at its best possible efficiency and lose sight of the fact that they might be able to operate it more economically by only heating some rooms.  You can certainly do that with a heat pump if you want to.  And most of the disadvantages of a heat pump compared to a gas boiler are even worse for an oil boiler compared to a gas boiler.    

Strummer22

Reed_Richards said:

fizio said:

 Surely minimising energy use is a good thing rather than heating an entire house just because thats how the equipment works - seems like heat pumps have a way to go yet to give the flexibility of gas boilers. More pondering needing as I lean more about these technologies..
.  

Some heat pump users can get hung-up on operating their heat pump at its best possible efficiency and lose sight of the fact that they might be able to operate it more economically by only heating some rooms.  You can certainly do that with a heat pump if you want to.  And most of the disadvantages of a heat pump compared to a gas boiler are even worse for an oil boiler compared to a gas boiler.    

This is excellent advice. You might find it's more "efficient" to have a heat pump without a buffer tank and heat all the rooms, but much of the heat would go to waste. Install a buffer tank to eliminate short cycling and heat only the rooms you need to. Install TRVs and put them low in your "unheated" rooms to keep them warm enough to prevent damp/mould. 

matt_drummer

I live in a 100m2 house with a 15m2 conservatory that I heat.

I get the zoning and trvs if I lived  in a sprawling mansion, but I don't.

I can't imagine which part of my house I would shut down to save money.

The reality is, we use all of the house, there isn't much of it to start with!

There are no savings to be made in shutting off radiators, the heat pump would still use the same amount of electricity per day whatever we did.

Our heating and DHW cost is about £1 a day at the moment, I don't think it's too bad.

Shutting off a room or two will not affect the overall cost, it will just make it less efficient.



There doesn't have to be a choice between efficiency and cost, you can have high efficiency and low operating costs.

A lot of people with inefficient installations use the cost of operation as some sort of justification for the poor efficiency claiming that they sacrifice efficiency for cost. In most cases that is untrue, they just have a bad installation or can't work out how to use it efficiently

fizio

I think I am coming round to the idea of a ASHP being the right choice if looking at a combination of cost/complexity/value/environment/etc. Given I started with GSHP or Oil, its been an interesting journey via this thread. Given it will be 6-9 months before I get to that stage, there is plenty of time to investigate further.

Reed_Richards

Octopus have been offering some very good deals on heat pump installations, although I don't think they yet cover all the UK.  They might be worth investigating.

fizio

I have had the quote below from Kensa. Not sure what this 'plant room' he is talking about is not has he said much about sizing or depth etc so I will followup.. Appreciate any comments on the Kensa email or anything else I should ask them. 

I have looked into the project details you have sent across and would anticipate a budget cost starting from:

£25,000.00

This cost is based upon the following:

·         Plant room equipment and necessary external infrastructure equipment supplied by Kensa.

·         A nominal cost for the installation of the plant room (not supplied by Kensa).

·         An estimated cost for the installation of a borehole ground array (not supplied by Kensa).

·         This budget is not inclusive of any upgrades which may be required to the distribution system. (Example: New radiators, upgrade of microbore pipework or upgrades to underfloor heating)

We have estimated the need for boreholes due to restricted space for a shallow ground array, typically to qualify for this we would anticipate a typical household needing 500m²+ of open land space with larger properties needing in excess of 1000m². They would need to be free of service pipes, tree roots, shade from tree canopies and anything else which might impede the digging of a trench or solar gains regenerating ground temperatures taken out by the system.

Please note:

·         The site for a singular borehole generally requires a minimum 8m x 8m plot of land with a 7m headroom free of trees and overhanging obstacles, this is due to the geological conditions of much of the country with some exceptions such as Cornwall, parts of Devon and much of Scotland.

·         The area needs to be accessible by a borehole drill which requires a 3m wide pathway.

·         Multiple boreholes are common for most typical GSHP projects whereby additional boreholes require a minimum of 8m spacing between them, increasing the ground requirements further.

Next steps:

If the costs above are a consideration for the installation of a ground source heat pump then the next stage would be for us to conduct a feasibility study for your project, the cost of this is £500.00 (+VAT) and will be inclusive of an MCS accredited heat loss report and a geological study, everything required to enable us to provide a concise quote and move your project forward. If this is something you would like to move ahead with, please respond to this email and someone will be in touch to assist you.