UPDATED: Air Source Heat Pumps/Air Con - Full Info & Guide, is it cheaper to run than mains gas?

spinaltap

Has anyone considered the Daikin Altherma HT airsource heat pump?

It's designed as a direct replacement for conventional heating systems with conventional radiators - with a water flow rate of 80c and COP of 3.

albyota

Very good piece of equipment, yes it uses two refrigerant gasses, R410A in the outside unit, then R134 inside the hydrobox......it is an ANIMAL.... but you still need outside space, and more space inside....errrm... it is very heavy so dont even think about a first floor site....leave it on the ground floor....garage or utility room, is fine or even a basement.

aimed at very large houses and commercial (or Off gas Medical practices etc...) boiler replacement, or where Radiators cannot be upgraded.

Pincher

I have been reading up on air source heat pumps that do heating and cooling, but can't seem to find the configuration that can be incorporated in the way I would like.

In summer, when the heat pump is cooling the house, I want to use the waste heat to heat the domestic hot water (thermal store cylinder).

In winter, when the heat pump is warming the house, I want it to draw the heat from the thermal store cylinder. An optimisation is to use a solar thermal store, which stores some heat during the day in winter. The thermal store never freezes because it should call on the gas boiler if it gets cold. This way, the heat pump NEVER needs to defrost.

Essentially, I want an outside unit that has an enclosed radiator, with 150mm in and out duct connections. This part cools the fresh air coming out of a conventional heat recovery unit. The other side of the heat pump is connected to the thermal store, via flexible hoses through a top to bottom coil. When heating the thermal store, the refrigerant should flow in from the top, and come out cold at the bottom. For drawing heat from the thermal store the refrigerant should flow in through the bottom, and come out hot at the top, so it needs a reversible pump.

Obviously the thermal store cannot reliably supply hot water, so I would need a conventional cylinder that is heated by gas boiler, or some sort of instant hot water combi. A thermostat on the thermal store would control a three port valve, so domestic hot water is drawn from the thermal store when it has hot water, otherwise use the backup cylinder, which is heated once a day, and manually boosted as required.

On really hot days, and cooling is required all the time, the thermal store will boil. To prevent this, a thermostat will control a release valve, to dump some hot water into a rain water saving tank, which has a large overflow into the drain. When the heat pump is on, the solar panel flow should be disabled. It is envisaged that "really hot days" only happen two weeks a year, so the water wasted is negligible. Most of the time, the cooling heat pump is not switched on, so the solar panel is heating the thermal store. Whenever the thermal store has hot water, it is used in preference to the backup cylinder.

When the gas boiler breakdowns in winter, the heat pump/heat recovery system is the backup. To prevent th thermal store from freezing, the immersion element has to be switched on manually.

I think the problem is the central heating paradyne is based on a single heat source, whereas what I want is a ring topology, with multiple heat sources and heat sinks: some devices are both.
The control system should have an outside sensor to know what the ambient temperature is, and compare it to the set point (target temperature). It should then work the most cost effective way to achieve that set point using the devices on the ring.

Will somebody please develop this heat pump and associated controller please.

richardc1983

Pincher wrote: »

I have been reading up on air source heat pumps that do heating and cooling, but can't seem to find the configuration that can be incorporated in the way I would like.

In summer, when the heat pump is cooling the house, I want to use the waste heat to heat the domestic hot water (thermal store cylinder).

In winter, when the heat pump is warming the house, I want it to draw the heat from the thermal store cylinder. An optimisation is to use a solar thermal store, which stores some heat during the day in winter. The thermal store never freezes because it should call on the gas boiler if it gets cold. This way, the heat pump NEVER needs to defrost.

Essentially, I want an outside unit that has an enclosed radiator, with 150mm in and out duct connections. This part cools the fresh air coming out of a conventional heat recovery unit. The other side of the heat pump is connected to the thermal store, via flexible hoses through a top to bottom coil. When heating the thermal store, the refrigerant should flow in from the top, and come out cold at the bottom. For drawing heat from the thermal store the refrigerant should flow in through the bottom, and come out hot at the top, so it needs a reversible pump.

Obviously the thermal store cannot reliably supply hot water, so I would need a conventional cylinder that is heated by gas boiler, or some sort of instant hot water combi. A thermostat on the thermal store would control a three port valve, so domestic hot water is drawn from the thermal store when it has hot water, otherwise use the backup cylinder, which is heated once a day, and manually boosted as required.

On really hot days, and cooling is required all the time, the thermal store will boil. To prevent this, a thermostat will control a release valve, to dump some hot water into a rain water saving tank, which has a large overflow into the drain. When the heat pump is on, the solar panel flow should be disabled. It is envisaged that "really hot days" only happen two weeks a year, so the water wasted is negligible. Most of the time, the cooling heat pump is not switched on, so the solar panel is heating the thermal store. Whenever the thermal store has hot water, it is used in preference to the backup cylinder.

When the gas boiler breakdowns in winter, the heat pump/heat recovery system is the backup. To prevent th thermal store from freezing, the immersion element has to be switched on manually.

I think the problem is the central heating paradyne is based on a single heat source, whereas what I want is a ring topology, with multiple heat sources and heat sinks: some devices are both.
The control system should have an outside sensor to know what the ambient temperature is, and compare it to the set point (target temperature). It should then work the most cost effective way to achieve that set point using the devices on the ring.

Will somebody please develop this heat pump and associated controller please.

U will need to ask this on the following forum as engineers there will be able to tell you if such system is available:

http://www.refrigeration-engineer.com/forums/forumdisplay.php?f=78

To be honest I dont think it is... it sounds awfully complicated and unless you get someone to design the system for you I dont think any such system is available.

There are units that recover the heat from the refrigerant in summer cooling months and this can be used to heat hot water/heat other parts of the building etc but something as complicated as what you are putting fwd sounds awfully complicated.

Why would you have the system boiling over in summer why not just have the system not divert heat to the tank when it has reached temperature... this way the outdoor unit would dissipate the heat to the outside air when you no longer require it elsewhere... otherwise you are wasting time setting up rain water to cool the store down?

Seems very complicated and I doubt such system exists to your exact specification however such systems do exist that will use the waste heat to contribute to your hot water. Examples of such I do not know of but the forum link I provided should help.

albyota

what.... like this?........

However, it really seems like you have got carried away with trying to over engineer this ...when you would be spending a lot of money on trying to do what a standard ASHP with a twin coil heat pump cylider and then use a MHRV unit to recover 90% of normally exhausted stale air.

Not sure about the Ecocent system as pictured as I have not used or spec'd one. sometimes pincher, (and I have been there) you can get so caught up in your own thought process that common sense goes out the window. I now have a ASHP and twin coil cylinder and solar. The solar is soon to be decommissioned and removed. where I can get a much better yield from the heat pump through both coils.

rhubarbe

Just a thought, but since we're taling about the two very hottest weeks in any year, isn't the ambient cold supply likely to be so warm that you'd be able to get it to 60C with a couple of candles held under the tank for five minutes?

I know I am being flippant, but...

richardc1983

albyota wrote: »

what.... like this?........

However, it really seems like you have got carried away with trying to over engineer this ...when you would be spending a lot of money on trying to do what a standard ASHP with a twin coil heat pump cylider and then use a MHRV unit to recover 90% of normally exhausted stale air.

I think he is trying to recover the heat that is exhausted from condenser coil this air is usually quite hot so there is a lot of heat in it.

However systems that reuse the hot refrigerant before it goes back to the compressor to start the cycle again do exist. VRV systems for instance can send the hot gas from one unit to another indoor unit that perhaps requires heating, or they can send the refrigerant to a hot water cylinder.

albyota

Rich I am well aware of the kit available i.e Daikin VRV and Mitsi et al VRF Heat recovery, using BC controllers etc. hot gas sent to a cylinder as you describe would have to go through a heat exchanger like the Altherma kit, what I thought pincher was getting at, was ducting off the outdoor unit with 150mm flexy duct to the cylinder.... thinking about it though, using solar, and a gas boiler indicates to me that it would be utterly uncontrollable and inconvenient.

albyota

rhubarbe wrote: »

Just a thought, but since we're taling about the two very hottest weeks in any year, isn't the ambient cold supply likely to be so warm that you'd be able to get it to 60C with a couple of candles held under the tank for five minutes?

I know I am being flippant, but...

I keep getting the DEATH STARE off the missus when I start messing with candles and pans of water with a stopwatch and thermometer.
apparently I have got to grow up.....:eek:

richardc1983

albyota wrote: »

Rich I am well aware of the kit available i.e Daikin VRV and Mitsi et al VRF Heat recovery, using BC controllers etc. hot gas sent to a cylinder as you describe would have to go through a heat exchanger like the Altherma kit, what I thought pincher was getting at, was ducting off the outdoor unit with 150mm flexy duct to the cylinder.... thinking about it though, using solar, and a gas boiler indicates to me that it would be utterly uncontrollable and inconvenient.

I agree, good idea to combine them all but there would be no way of controlling it all.

I dont think Solar is that good either in this country its just not sunny enough!

Perhaps maybe you could suggest what he could possibly set up with some links to the equipment?