Dream Air to Water Heat Pumps

[PCW]

Hi
Has anyone got any experience of these. I especially need to know how noisy they are from practical experience, not from Db figures which I don't understand. Also how reliable?
It will most likely be an 8KW model to run just the UFH only which is set at around 35 C.
They are cheap, maybe too cheap?
Any help much appreciated.
Many Thanks

 

[oz-plumber]

Post the specs of the unit and a rough figure or % of how much cheaper they are from well known brands.
What is the warranty of the unit?

 

[PCW]

Post the specs of the unit and a rough figure or % of how much cheaper they are from well known brands.
What is the warranty of the unit?

Thanks for replying, Looking on line they are a lot lot cheaper. Most likely made in China so dont expect a lot and warranty probably not worth the paper it's on. Main thing I need to know is how noisy are they? Thats always been a problem with ASHPs . So any user feedback would be appreciated.

 

[Brambles]

The Dream range for dehumidifying swimming pools are (I think) fairly good. The majority of the kit is installed inside. Sourcing spare parts is an issue - the importer Better Bargains or some such name is not very responsive.

The single phase air to water range is a bit flimsy - if you see one next to an Aquarea the difference is quite dramatic - but then so is the price.

With respect to noise, they are all very similar - if you want to minimise the “drone type noise” floor mount the external unit on rubber feet bolted into a concrete slab that is not adjoining the property. Wall mounted units sometimes generate vibration within the wall cavity.

As always with Air Source heat pumps see one in operation before you buy - A lot of my potential customers change their mind once they have seen the size of the unit (both inside the house and outside) and heard the noise.

With the latter it is often consideration for the impact of noise on neighbours that is a concern.

When you look at the design, consider using a buffer tank - it will probably increase the COP and make the installation more effective during sub -5 degree temperature spells.

 

[PCW]

The Dream range for dehumidifying swimming pools are (I think) fairly good. The majority of the kit is installed inside. Sourcing spare parts is an issue - the importer Better Bargains or some such name is not very responsive.

The single phase air to water range is a bit flimsy - if you see one next to an Aquarea the difference is quite dramatic - but then so is the price.

With respect to noise, they are all very similar - if you want to minimise the “drone type noise” floor mount the external unit on rubber feet bolted into a concrete slab that is not adjoining the property. Wall mounted units sometimes generate vibration within the wall cavity.

As always with Air Source heat pumps see one in operation before you buy - A lot of my potential customers change their mind once they have seen the size of the unit (both inside the house and outside) and heard the noise.

With the latter it is often consideration for the impact of noise on neighbours that is a concern.

When you look at the design, consider using a buffer tank - it will probably increase the COP and make the installation more effective during sub -5 degree temperature spells.

Excellent, Many thanks for the reply and taking the time.
It will be going into the bottom of a 350 litre vented thermal store. Plan is to have it running 15+ hours a day so I want to size it for that, finger in the air guess really given the kind of crazy weather we get now. 8KW should keep it busy and on really cold days can be topped up with Imerssion heater. With a COP of around 4 that will cost max £3 on a cold day most often a lot less at anything over 8/9 degrees outside. It's a big house with 6 UFH zones and approx 700 meters of UFH pipe. The house is in the countryside so no neigbours, the problem is my partner has convinced herself they are noisy, Plan B will be install away from the house and pipe it back, added expense and complication though so not prefferred.

 

[Brambles]

A couple of points:

700m of underfloor heating pipe for living space (@175mm spacing) is around 120m2 or 6kw of air source.

If you can go to ground source - it is nearly silent - you would need a 5kw heat pump and around 55m of “slinky pipe” externally buried at around 1.5m deep - depending on the ground type - it may need to be a little deeper, rarely more than 2m.

From a sizing perspective ( particularly air source) oversizing causes two problems:

The floor area will heat up quickly - using a lot of power, driving down the COP - once at set temperature, it may have difficultly holding it, without a lot of relatively short off / on cycles.

In really cold weather if the cycles (on / off) are too short, the pump probably won’t defrost properly - leading to progressively reduced performance - this is more likely in really cold weather when the defrost times are longer.

The key to a heat pump for long life and low operating costs is for it to be sized to operate for long periods at a low output. Every time the pump switches off, upon restart it will ramp up to full power. Sometimes an inverter controlled variable speed pump is a preferable solution, nut that is dependent upon the system design - summer hot water demand is an influencer in that respect.

In an earlier post, I cited Dream as being a decent option for a swimming pool - that is because they are fixed speed, virtually always on and you have an enormous heat dump to mask any design inadequacies. If they fail, it is not such a big deal if there is a lengthy wait for parts ( as once happened to me with a customer).

If in any doubt, get a local specialist to design the system for you. You will get a better result and probably save the cost of the design in reduced electricity consumption over the first winter.

 

[PCW]

A couple of points:

700m of underfloor heating pipe for living space (@175mm spacing) is around 120m2 or 6kw of air source.

If you can go to ground source - it is nearly silent - you would need a 5kw heat pump and around 55m of “slinky pipe” externally buried at around 1.5m deep - depending on the ground type - it may need to be a little deeper, rarely more than 2m.

From a sizing perspective ( particularly air source) oversizing causes two problems:

The floor area will heat up quickly - using a lot of power, driving down the COP - once at set temperature, it may have difficultly holding it, without a lot of relatively short off / on cycles.

In really cold weather if the cycles (on / off) are too short, the pump probably won’t defrost properly - leading to progressively reduced performance - this is more likely in really cold weather when the defrost times are longer.

The key to a heat pump for long life and low operating costs is for it to be sized to operate for long periods at a low output. Every time the pump switches off, upon restart it will ramp up to full power. Sometimes an inverter controlled variable speed pump is a preferable solution, nut that is dependent upon the system design - summer hot water demand is an influencer in that respect.

In an earlier post, I cited Dream as being a decent option for a swimming pool - that is because they are fixed speed, virtually always on and you have an enormous heat dump to mask any design inadequacies. If they fail, it is not such a big deal if there is a lengthy wait for parts ( as once happened to me with a customer).

If in any doubt, get a local specialist to design the system for you. You will get a better result and probably save the cost of the design in reduced electricity consumption over the first winter.

Clearly you know heat pumps, many thanks for your comments.
It is at 150mm centres, interesting rule of thumb calculation you did for KW requirement.
I would like ground source but too much work, this has been a renovation that has long overextended so need to be finished. I wish we had a stream nearby, that would be perfect.
UFH does all the tiled areas, hall etc, there are radiators in the bedrooms so I'm looking to have something that gives a residual heat and can top up with radiators if required.
You say to run at low loads, I thought better to have it at max design load?. I would like this running at least 15 hours a day.
You say Dream are a fixed speed, I guess that also accounts for why they are cheaper so maybe it's better if I get a slightly bigger one? I'd value your opinion there as it looks like you have experience with these "Dream" Heat Pumps. They say max outlet temp is 60 degrees. Seems high to me, guessing that must be under absolute ideal conditions. I was going to be happy with 40 degrees as UFH is set at 35 degrees anyway.
I'm not concerned about summer, that requirement will be by solar collectors mainly with some PV panels back up into the Immersions heaters.
Ultimately the PV panels. plus a wind turbine into batteries will run the Heat Pump also so when that happens it will run 24/7 through winter only then shut down for the summer.
Once again many thanks for your comments, very much appreciated.

 

[Brambles]

The most efficient way if operating an air source heat pump is in “unconstrained” operation - then direct the heat to where it is needed. The pump runs continuously at or near full capacity and defrosts as and when. That is how you would configure a system in a public / commercial area. In a domestic environment that is not generally realistic unless you have s large heat dump ( a decent size thermal store, pool et al).

So to replicate this in “constrained operation” the heat pump needs to thermally sized to match the installation and expected outside temperatures. This is normally achieved by correctly sizing the installation ( radiators and ufh thermal demand - match this as closley as possible to a heat pump and balancing the output with a suitably sized thermal store. The thermal store size is absolutely key to getting the system to perform. You have very little leeway with the UFH flow temperatures ( it has to match the installation type) - too cool it is useless and too hot, it is both uncomfortable and will probably over time damage the floor coverings / furniture et al. For tiled screed, I would not go much above a 45 degree flow temperature.

The second form of control is to use a heat pump with an inverter - so the compressor is in effect a variable speed drive. These are very effective (and efficient) in areas where you anticipate reasonable periods of sub zero external temperatures and /or you are using the system with comfort cooling chillers in the summer. However, they are not too good if you are using the system for hot water production in the summer.

So, in summary, if you oversize in a domestic environment, it will only run on an intermittent basis (and that may cause ongoing operational issues ) if you try to run it for longer periods you have to be able to use the heat.

My recommendation would be a fixed speed pump sized to match your system with a decent ( 600litre) thermal store. Some summer use is desirable, heat pumps generally don’t like being static for long periods.

Try not to compare these systems with gas or oil ( where oversizing is often eliminated either by the boiler modulating or the in the case of oil the output being reduced) one kW of an over sized air source heat pump is a lot of heat to disperse.