Dream Air to Water Heat Pumps

[quality]

I agree with the not over sizing and comparing gas or oil. Heat pump air or any other source is the future. Brambels makes some good points there

 

[PCW]

Some good comments, thanks again.
I have a 350 litre Thermal Store and can always top up with a wood burning back boiler and two immersion heaters if it gets very cold which is rare these days. We are in Gloucester.
The Dream units are fixed speed so undersizing it slightly I think would be better so it runs longer. Total house load is 18kw excl DHW I worked out. That's heating every room to standard temperatures. Reality is some will be off and there is only two of us so DHW requirements is minimal and my partner doesn't like it too hot anyway. It will need to run a few radiators too so I think I'll go for a 10kw.
Good point re summer use, I'll do that.
Have you got experience with these units, are they reliable?
Thanks again for your comments.

 

[Brambles]

That is far too large a heat pump for your loading.

I would advise you to have a proper design undertaken to properly determine the required pump size, COP and Seasonal Adjusted Factors before committing.

With respect to Dream, I have used them in pools for heating the pool and dehumidifying the atmosphere. They are ok. I have not used them as a domestic heat pump - the parts back up ( lead times) is not at a level that I would deem acceptable.

 

[PCW]

My gut feeling was to go for an 8kw and you suggested a 6kw. Since they dont do a 6 I've decided to take your advice and my feeling and oted for an 8kw which is being deliverred today.
If it turns out too small I can allways get a 5kw machine to run in parrallel and cut it when the bigger machine is struggling, if it's too big I'll turn on a few extra rads.
Apparantly the return stat is set at 58 degrees so will cutout then. I think that is too high for any decent effeciency on cold days so will lower it and experiment. I really only want this running UFH at 35 so have plenty to play with.
I'll post the outcome later.
Thanks again for all your comments, very much apreciated.

 

[Brambles]

Good luck. If you are installing it yourself run it initially will all the external valves fully open and the external thermostatic controls disabled. IE. it is operating in an unrestricted mode. Leave it for a week (or longer ) to settle down and see what the performance is like.

Thereafter, introduce the minimum number of controls needed.

The logic behind this is that air source heat pumps need high flow rates - which UFH systems are really good at providing. If the flow is too restricted they will cut out - you don’t want that behaviour confusing the situation whilst you set up the system.

Even a motorised valve opening too slowly can cause an air source machine to trip.

 

[PCW]

Well its been running nearly a month with the compressor on almost non stop. My calculations seem to have been OK as when it is 7 degrees or more outside it heats the whole house and the thermal store using around 1.6/1.8 kw from a 3 pin plug. (haven't wired it in properly yet). Generally it averages about 30kw a day which I measure through a SONOFF POW. Turns out I think it is more noisy than Partner does, it's a bit like the sound of a boiler exhaust and a wall silences a lot of the noise when out of direct sight.

When outside drops to 4 and below it starts struggling to keep up so I light the wood burner with back boiler which adds another 5 or 6kw to the thermal store tank. Nothing happens quickly though as normal with UFH so you have to plan a bit. One day the whole fin assembly frosted up so I had to reset the auto defrost to cut in at -5 instead of -13 and it's been OK since.
I'll keep it as is for this winter and test a bit more but at the moment considering getting another unit to work in parallel for very cold days.

Quality seems OK and I've had no problems...yet? so with two I have a standby in case needed. Apparently spares are held in the UK, hopefully I wont need to find out anytime soon.

I'm getting some evacuated tubes being delivered this week and will be building a solar thermal system shortly for more heat input to the tank during sunny winter days and DHW in the summer.

 

[bestoday]

Hi PCW
I've been following this thread and your posts, and am wondering how the dream heat pump is working out for you,
6 months on? I have an electrical back round and have been considering DIY installing an air to water heat pump for a while now, in parallel with the oil fired system that I currently use. I'm hoping this will cut down on fuel bills & CO2 emissions. (Ironically Kerosene has dropped in price recently)
I'm planning to keep the oil fired burner as a back up, and to give me more flexibility during cold spells.
I've noticed your central heating system and load seem similar to mine, with approx 700 meters of UFH pipe in the main living area on the ground floor, (on 24/7 Sept to April) and radiators in the bedrooms, mostly upstairs, which are only ever turned on occasionally when it gets really cold. (Heat rises). Hot water is heated indirectly and stored in a180 litre cyclinder with an electrical immersion heater in summer. Is a DHW tank what you mean when you talk about a thermal store?
Anyway, problem is, good quality Heat pumps here in Ireland are extremely expensive, especially with certified installation to get the current government grant. Sums just don't add up at the moment and it could take 10 years or more, if ever, to get the costs back and then it would probably need to be replaced at that stage with a new one.
Currently, I can get an 8kw Dream heat pump like yours sent over from UK for £1250 inc. (Shipping 20% of cost)
That is why I would really appreciate your thoughts and advice to see how it has worked out for you?
Thanks
DJ

 

[Sparkgap]

Always a bit wary about ASHP performance in cold weather as most are tabled at 7C. Had a commercial installation with 70kW of load however when I queried the performance at design conditions (-4C outside) the manufacturer bumped their ASHP unit up to 100kW which screwed up the spare capacity from the supply transformer changeover which was being done at the same time. GSHP is preferable if you can go for it as conditions are more stable.