heat pump and water cylinder installed away from the house, pros/cons

[alex567]

I'm planning to get an air source heat pump (ASHP) installed and I'm considering my options about the location of the water cylinder as I live in a small house and space is a premium. I was thinking about building a small insulated shed about 20 to 25 metres away from the house to put the cylinder with the buffer tank and expansion vessels, and the ASHP right outside this shed. Then use underground insulated pipes to carry DHW and heating pipes back to the house.

What are your thoughts on that? I'm wondering how much efficiency I would lose by this long underground pipe run. The Vaillant Aeroterm plus states the max run is 20m, so I guess I would be just at the limit of what it can do. The reason to heave the heat pump also further away from the house is that it uses R290 refrigerant, so it cannot be close to windows or air bricks as I have suspended beam and block floor.

Has anyone tried something like this? Does it work in practice?

I'm even considering giving up on the ASHP and go for a Viessman 222-F and have it installed on the back side of the house outside, as it is relatively "smaller" than the water cylinder used for a heat pump, I could get it right at the back of the house:

 

[oz-plumber]

The problem with having the cylinder so far away from the the house will be that you will be waiting minutes for hot water to come through to the taps.
Particularly bad when you want to wash your hands in a basin or a small squirt of hot water from your kitchen sink.

It wouldn't be so bad if you had the cylinder installed where you have marked.

Keep the ASHP away from the house and as far away from the neighbours as possible.
They do run very often / almost continuously and cause noise issues.

We have one next door to us and it's about to get a crowbar through it.
Effing thing runs all night.
They had the thing installed on the opposite side of the house to their bedrooms, which is closest to our bedrooms.

 

[ShaunCorbs]

In the loft ?

 

[alex567]

The problem with having the cylinder so far away from the the house will be that you will be waiting minutes for hot water to come through to the taps.
Particularly bad when you want to wash your hands in a basin or a small squirt of hot water from your kitchen sink.

It wouldn't be so bad if you had the cylinder installed where you have marked.

Keep the ASHP away from the house and as far away from the neighbours as possible.
They do run very often / almost continuously and cause noise issues.

We have one next door to us and it's about to get a crowbar through it.
Effing thing runs all night.
They had the thing installed on the opposite side of the house to their bedrooms, which is closest to our bedrooms.

Yeah very good point on the water taking ages to flow from the cylinder that far away. I was even thinking about a hybrid system for the taps with a electric tap just for these situation washing hands, but I'm not sure how the unit would work once the hot water comes in, are there units that can just switch off the electrical heating element? Perhaps this doesn't exist...

I'm leaning to keeping the cylinder at the back side of the house as per picture.

Do you mind sharing what heatpump brand they use if you can see? Just curious as I want to get the most quite model possible

 

[alex567]

In the loft ?

Adding the tank to the loft which I'm converting would be a last resort as I would not like to lose 1.5 m2 to have the tank and all other bits. I've not ruled it out, but I would like to avoid

 

[Knappers]

You could use a secondary return to avoid hw flow delays but would want pipes really well insulated. For external pipes underground I'd use the pre-insulated dual pipes but they need particular terminations and are awfully expensive!
Last time I priced for running heating pipes to an anex under a garden it worked out cheaper to fit a combi boiler and run gas pipe

 

[alex567]

I'm considering the whole hassle of working around this with a horizontal tank in the loft eaves. Yeah the external insulated pipes are pricey indeed, I'm trying to revert back to a simpler solution now.

If I manage to fit a horizontal cylinder, then I don't need anything outside the house. I'm trying to get more information about the losses of this method, but there is not that much information out there. I'm aware of the problems with a large stratification area, but then again, what are my other options? Not many so far I can see.

 

[ShaunCorbs]

Fit a destrat pump around £100 and you can use the full capacity of the tank for hot water

 

[Knappers]

Not sure how much of an issue stratification is on a domestic sized cylinder?

 

[alex567]

I'm also not sure how much it will affect the performance of the cylinder, I'm reading the technical documentation from gledhill, Telford and Kingspan. The guys from Gledhill were very helpful over the phone providing some further technical details. I may call them again Monday to double check some bits.

The destrat pump is a good idea, thanks for the suggestion