Heat pump
- Thread starter martyheat
- Start date
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Forget that idea unless you or your cust have money to throw away
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I have an oil system costing £50 a week in the cold spell ,which is to much for a 3 bedroom 9" solid wall.I would like to insulate outside walls but my
wife does not want the mess.
Well Tony my thinking is that any input heat as from a heatpump at 40c
would mean the oil boiler i have would only be required to heat at 40c
to give a 80c output ??????
Are you suggesting that you think by having a heat pump pushing out water into the system at 40ºC and the oil boiler doing the same this will result in an 80ºC c/h temp? The result of the above will be a c/h temp of 40ºC, adding a second heat source will cause it to heat up faster, but not get any hotter.
To prove this if you don't believe me, take two saucepans and put an equal amount of water in both. Heat them both on the hob (or one in the oven if you want a different heat source) to 40ºC. Now pour the contents of one into the other. The mixed water will not jump in temperature to 80ºC, it will stay at 40ºC.
Apologies if I've misunderstood your post but from what I can tell you've misunderstood your physics.
Most standard heat pumps require bigger rads as the rated KW output of any given rad decreases with a decreasing flow/return temp.
To prove this if you don't believe me, take two saucepans and put an equal amount of water in both. Heat them both on the hob (or one in the oven if you want a different heat source) to 40ºC. Now pour the contents of one into the other. The mixed water will not jump in temperature to 80ºC, it will stay at 40ºC.
Apologies if I've misunderstood your post but from what I can tell you've misunderstood your physics.
Most standard heat pumps require bigger rads as the rated KW output of any given rad decreases with a decreasing flow/return temp.
I think the OP was suggesting the heat pump be used to pre-heat the water before it goes through the boiler. However, it sounds totally unworkable to me. Either get a heat pump and larger radiators installed (and probably go to electric immersion heaters for your DHW), or stick with the oil boiler.
Oil fired Boiler would still do all the work as once over Heat pump working temp, the Boiler would be doing 100% of the work, also have you any idea just how expensive heat pumps are at present? 
A heat pump would probably cost you in the region of 10 - 15K to install and they are not all they are cracked up to be. They may claim to be 400 odd % efficient (my rse) but they work off electricity which is more expensive than oil. Running costs are about on par with oil so you have no real saving. When you read stuff about how good or how cheap to run these things are, that applies to homes that are so well insulated and airtight if you sparked a match the house would be warm all day. They best way to cut down on the oil bills is insulation. Fill every space in the house with it. Some houses are knee deep in the stuff in the attic! If the boss don't want the walls done think about external and rendering
The best most energy efficient way to save on your fuel bills is get a couple of wooly hats and some thermals and turn the heating off . Oh and plant a couple of trees for the planet
Edit above cost was ground source. Air cheaper
OK, somebody needs to stick up for heat pumps. I'll do it because I'm not busy right now
The basic answer you got is correct. Heat pumps generally don't provide hot enough water (or air!) to run a standard system of radiators. You may be able to put in over-sized rads or fan-assisted ones to extract enough heat from the low temperature flow. Good systems for heat pumps are underfloor heating with water or ducted air.
If you don't have access to mains gas then a heat pump becomes a viable alternative to heating with oil or directly with electricity. They are borderline at best competing with mains gas despite recent price increases. Some of the prices mentioned here sound like gold-plated systems, massive ground source pumps, etc. You don't have to spend that much. A simple air source heat pump is really not expensive, although the modifications to your heating system may bump up the price. The best argument of all is if you also want air conditioning in the summer, since a heat pump can also give you that. Ground source pumps have advantages, but its a lot of work and probably only viable if you or a mate can do the digging, or perhaps as part of a large new build.
The lack of wall insulation does sound like a problem. Heat pump output is not huge unless you buy a ridiculously massive system, they work best by producing a steady flow of heat nearly continuously. With leaky single walls you would probably need a backup system, for the coldest days if for nothing else.
The basic answer you got is correct. Heat pumps generally don't provide hot enough water (or air!) to run a standard system of radiators. You may be able to put in over-sized rads or fan-assisted ones to extract enough heat from the low temperature flow. Good systems for heat pumps are underfloor heating with water or ducted air.
If you don't have access to mains gas then a heat pump becomes a viable alternative to heating with oil or directly with electricity. They are borderline at best competing with mains gas despite recent price increases. Some of the prices mentioned here sound like gold-plated systems, massive ground source pumps, etc. You don't have to spend that much. A simple air source heat pump is really not expensive, although the modifications to your heating system may bump up the price. The best argument of all is if you also want air conditioning in the summer, since a heat pump can also give you that. Ground source pumps have advantages, but its a lot of work and probably only viable if you or a mate can do the digging, or perhaps as part of a large new build.
The lack of wall insulation does sound like a problem. Heat pump output is not huge unless you buy a ridiculously massive system, they work best by producing a steady flow of heat nearly continuously. With leaky single walls you would probably need a backup system, for the coldest days if for nothing else.
D
DeltaT
You could always stick in a couple of these split units in your house, cheapest ASHP I've seen & they're great at heating any room;
http://www.cooleasy.co.uk/product_wall.htm
We've one in our showroom & one in an office, they'll give you a COP of about 3.5 if the outdoor temperature is not too low. Stick a couple of TRVs on the rads that are in the same room, that should save yourself a few bob. And any DaftyDIY'er could fit it!!
We fitted a 3KW split unit for this tight auld cnt. He had an open fire at one end of the house & the split unit at the other. It was a two bedroom 70's timber frame type house & I was amazed how warm it was!!!
http://www.cooleasy.co.uk/product_wall.htm
We've one in our showroom & one in an office, they'll give you a COP of about 3.5 if the outdoor temperature is not too low. Stick a couple of TRVs on the rads that are in the same room, that should save yourself a few bob. And any DaftyDIY'er could fit it!!
We fitted a 3KW split unit for this tight auld cnt. He had an open fire at one end of the house & the split unit at the other. It was a two bedroom 70's timber frame type house & I was amazed how warm it was!!!
Ground source heat pump installations are very expensive and are around 400% efficient
Air source heat pump installations are cheaper but the efficiency drops to around 300% but can drop even further dependant on what the outside temperature is and what temperature you are heating the water to.
In ther ground at about 1 to 1.5 meters deep the temperature is relatively constant at somewhere around 5-9 degrees c. So the temp range means the Ground source heat pump will be more efficient than an air source.
Air temperatures fluctuate a lot more so anywhere say between -10 and 10 degrees. When its very cold outside your heat pump efficiency can drop to 150 to 200%. The running costs then massively increase at the time of year that you need heating and hot water.
Whether its Ground or Air source, radiators need to be oversized due to the lower temperatures that they produce. Insulation should be upgraded in the property also before installing a heat pump. A heat loss calculation will also need to be done.
Heat pumps up to around 12 KW can work on a single phase supply, but anything larger will need three phase power so that can add to the installation costs.
Systems can be designed so that Heat pumps can work with boilers, these are called bivalent systems. The system should be designed in such a way that the boiler only ever provides the short fall of what the heat pump cannot provide.
Air source heat pumps will give you 75% of the efficiency of a groud source heat pump but at 50% of the cost.
Regards
Air source heat pump installations are cheaper but the efficiency drops to around 300% but can drop even further dependant on what the outside temperature is and what temperature you are heating the water to.
In ther ground at about 1 to 1.5 meters deep the temperature is relatively constant at somewhere around 5-9 degrees c. So the temp range means the Ground source heat pump will be more efficient than an air source.
Air temperatures fluctuate a lot more so anywhere say between -10 and 10 degrees. When its very cold outside your heat pump efficiency can drop to 150 to 200%. The running costs then massively increase at the time of year that you need heating and hot water.
Whether its Ground or Air source, radiators need to be oversized due to the lower temperatures that they produce. Insulation should be upgraded in the property also before installing a heat pump. A heat loss calculation will also need to be done.
Heat pumps up to around 12 KW can work on a single phase supply, but anything larger will need three phase power so that can add to the installation costs.
Systems can be designed so that Heat pumps can work with boilers, these are called bivalent systems. The system should be designed in such a way that the boiler only ever provides the short fall of what the heat pump cannot provide.
Air source heat pumps will give you 75% of the efficiency of a groud source heat pump but at 50% of the cost.
Regards
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