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

matt_drummer

One issue is the liquid circulated in the ground.

I know it's called brine, but that isn't what it actually is, is it?

It is actually water with glycol?

If so, not as good as transferring heat as pure water.

Most ashps use pure water.

A gshp should really be better than an ashp and they were but ashps have caught up.

There is one gshp on heatpumpmonitor.org with a SCOP of 5.70 though which is the best by far

However, there is so little in it between the two generally, you could do as well, or almost as well with an ashp

In view of the installation costs there is no reason not to go for a top quality ashp install over a gshp.

Reed_Richards

Strummer22 said:

Wouldn't the higher heat capacity of the ground source can transfer more heat energy to the brine and then to the refrigerant than can be transferred from air at the same temperature? 

Something went awry when writing this sentence and I am struggling to figure out what you meant to say.   

michaels

Presumably GS is quieter?

Strummer22

Reed_Richards said:

Strummer22 said:

Wouldn't the higher heat capacity of the ground source can transfer more heat energy to the brine and then to the refrigerant than can be transferred from air at the same temperature? 

Something went awry when writing this sentence and I am struggling to figure out what you meant to say.   

Ah, the first "can" is superfluous. Parentheses might also have helped.

Wouldn't the higher heat capacity of the ground source transfer more heat energy to the brine (and then to the refrigerant) than can be transferred from air at the same temperature?

Reed_Richards

Strummer22 said:

Reed_Richards said:

Strummer22 said:

Wouldn't the higher heat capacity of the ground source can transfer more heat energy to the brine and then to the refrigerant than can be transferred from air at the same temperature? 

Something went awry when writing this sentence and I am struggling to figure out what you meant to say.   

Ah, the first "can" is superfluous. Parentheses might also have helped.

Wouldn't the higher heat capacity of the ground source transfer more heat energy to the brine (and then to the refrigerant) than can be transferred from air at the same temperature?

More heat per unit volume almost certainly, so that means you need to pass air over the heat exchanger in the ASHP faster than you need to pass "brine" over the heat exchanger in the GSHP; that doesn't seem very hard to do.  On the other hand, if you are working a GSHP really hard you might start to cool the ground surrounding the buried pipes whereas with an ASHP in open air you are not going to cool the air supply.

fizio

Thanks for all the feed back and I will add ASHP to my enquiries - I had the impression they were not great in terms of efficiency and ability to heat up the building but that seems untrue. The basic figures I worked off are that a gas/oil boiler will deliver 0.9kw of heat for every kw of fuel used where as a ASHP will do 2kw for every kw of electricity and GSHP will do 4kw. Very rudimentary I'm sure but was my starting point. 
The cost/benefit is very much against GSHP as it will be a single low energy user living in the property and likely every room will be a separate zone so that only the key rooms are heated fully during the winter. The time taken to recoup a 30/40k investment will be 2-3 decades as a rough guess. Underfloor heating is not really an option given the historic nature of the building and the costs involved in raising the floors etc.
The ASHP financials are likely to work better if the grant is used and I suspect I will need some backup heating (wood burning or electric etc). 

I will know more once I have some quotes and discuss this with listed building consent folks to say what conditions they places on doing something like this and the added cost implications.

Will be a shame if, despite trying to be energy and enviromentally efficient it turns out the most sensible course of action is to spend money to insulate the property best I can and then stick in an oil back boiler

matt_drummer

Heating systems using heat pumps are designed very carefully to heat the whole house and everything is sized to do just that.

You cannot then just choose to heat one or two rooms to save money, that is not how they work.

They need to the full system in operation to work best.

Heat pumps are not like a gas or oil boilers where the efficiency is pretty much fixed and operating costs are determined mainly by how long the boiler is working for.

You need to do some more research.

Perhaps you should also think of the future, an oil boiler may (or may not) be cheaper today but may not be for much longer.

Reed_Richards

Unless your internal walls are well insulated (which would be unusual) then if you try to heat a single room you will lose a lot of heat through those walls to the unheated parts of the building.  To compensate for this you will need a bigger heat source in the room you are trying to heat; that is a bigger (or larger surface area) radiator.  And you will probably have to run that radiator hotter than if you were heating the surrounding rooms.

Most oil boilers don't modulate so if you keep your oil boiler it will run full on or off.  You may have to raise the output water temperature to make your one radiator hot enough but the return water will likely quickly overheat and cause the boiler will cut out and by this means cycle on and off.  You will need suitable controls to make sure those cycles are not too short, because short cycling is bad for the oil boiler.

The situation will be similar with a heat pump but not so bad.  The heat pump should be able to modulate down its power output so its not adding as much heat to the leaving water as an oil boiler typically would.  But even so it's still likely to cut out and cycle.  And you will need to ensure that the volume of water being heated meets the heat pump requirements (by using a volumiser or buffer tank in the system).  Again you will probably need to turn the heat pump up to a high output temperature, which will adversely impact its operating efficiency.  Or to avoid this, when specifying your heating system you could oversize the radiator in that one room you want to heat compared to the size you would use if heating the whole house.

No boiler or heat pump that is specified to heat an entire house will like being asked to heat a single room.  I think with a little care, it is perfectly possible to do.  But it will reduce the operating efficiency so may not save you as much in heating costs as you expect.

       

FreeBear

Reed_Richards said: No boiler or heat pump that is specified to heat an entire house will like being asked to heat a single room.  I think with a little care, it is perfectly possible to do.  But it will reduce the operating efficiency so may not save you as much in heating costs as you expect.      

Running a heat pump (or gas/oil boiler) to maintain a relatively low temperature of say 17°C throughout the house and then using a wood stove to boost the temperature in one room could be an option. It is a strategy that I'm using here, but it isn't a sprawling mansion (just a typical post war semi), and the stove is enough to heat the whole house at times.

fizio

Reed_Richards said:

Unless your internal walls are well insulated (which would be unusual) then if you try to heat a single room you will lose a lot of heat through those walls to the unheated parts of the building.  To compensate for this you will need a bigger heat source in the room you are trying to heat; that is a bigger (or larger surface area) radiator.  And you will probably have to run that radiator hotter than if you were heating the surrounding rooms.

Most oil boilers don't modulate so if you keep your oil boiler it will run full on or off.  You may have to raise the output water temperature to make your one radiator hot enough but the return water will likely quickly overheat and cause the boiler will cut out and by this means cycle on and off.  You will need suitable controls to make sure those cycles are not too short, because short cycling is bad for the oil boiler.

The situation will be similar with a heat pump but not so bad.  The heat pump should be able to modulate down its power output so its not adding as much heat to the leaving water as an oil boiler typically would.  But even so it's still likely to cut out and cycle.  And you will need to ensure that the volume of water being heated meets the heat pump requirements (by using a volumiser or buffer tank in the system).  Again you will probably need to turn the heat pump up to a high output temperature, which will adversely impact its operating efficiency.  Or to avoid this, when specifying your heating system you could oversize the radiator in that one room you want to heat compared to the size you would use if heating the whole house.

No boiler or heat pump that is specified to heat an entire house will like being asked to heat a single room.  I think with a little care, it is perfectly possible to do.  But it will reduce the operating efficiency so may not save you as much in heating costs as you expect.

       

Interesting points and need to be considered
1. The walls will all be insulated with wood fibre boards as thick as possible and floor and ceilings will also be insulated as much as poss
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.

All learning at this stage and probably 6 months from making major decisions and even longer before pipework etc gets done. Exciting project regardless