Which ASHP model / brand to go with...

[Deleted User]

rogerblack wrote: »

Nope.
I feel a site visit is relatively unimportant.
I believe ASHP (or GSHP) can work, and can be cheaper (a little to a fair bit) than gas.
However, efficiencies in various installations vary considerably, meaning one can make sense, and the other not.
A site visit is unlikely to help, unless they happen to have the exact model of heatpump, external temperature profiles, and internal water temperatures are similar.
I'm perhaps somewhat unusual in that I'm only considering ASHP only because it has the potential to be very much cheaper than gas, in the case of a system running (for most of the year) entirely on economy 7, with a very large buffer store.

The considerable initial outlay is something I'm still running numbers on.

Are you on mains gas?

rogerblack

jeepjunkie wrote: »

Are you on mains gas?

I am.
The sums do, in principle work, even against gas.
The numbers would of course be vastly better, if i wasn't.

Cardew

rogerblack wrote: »

I am.
The sums do, in principle work, even against gas.
The numbers would of course be vastly better, if i wasn't.

Interesting idea using E7 - how big a tank?

In your sums do you allow for the lost interest on the capital required to install the ASHP? e.g. cost £10k would mean £400 a year after tax in lost interest(more if you borrow)

You can buy a lot of gas for £400(compounded)

rogerblack

Cardew wrote: »

Interesting idea using E7 - how big a tank?

In your sums do you allow for the lost interest on the capital required to install the ASHP?

Several tons.
This would be a bargain basement system, with me doing all the work myself, or supervising unskilled labour and sourcing a lower end pump intended for swimming pools.
Running it from 45-35C or so.
This is as a part of dramatically upgrading the property thermally, so some of it gets easier - for example UFH is lots easier if the whole floor is getting ripped up anyway.

ROI is - to some degree - not the point.
The point is being able to feel freer to use the heating, without worrying about the cost.

I'm on, and likely to remain on benefits for the foreseeable future.
Unfortunately, I cannot freely save, as that will involve me hitting capital limits on benefit, so that alters things a bit.

Cardew

Thanks,

However the issue of lost interest on installation costs, which seem to be on the wrong side of £10,000 for most people is a huge factor - not so much ROI, but running costs.

zeupater

rogerblack wrote: »

Several tons.
This would be a bargain basement system, with me doing all the work myself, or supervising unskilled labour and sourcing a lower end pump intended for swimming pools.
Running it from 45-35C or so .......

Hi

You've obviously costed it all out but for the benefit of others 2 Tonnes = 2000l of storage which would cost between £2k & £3k for insulated buffer tanks .... Assuming a house temperature of 20C the potential heating capacity of the 2 tonnes would be around 40kWh at 40C but due to deminishing transfer of heat as the flow cools I would expect that only around 30kWh would be of any use ..... so the question really now revolves around whether this would provide the daily heating demand and at what point the heat being transferred to the house has depleted the heatstore and the pump is consuming as much/more energy during the day as the heatstore is providing ....

Could seriously do with a HP engineer to interject on this one ...

HTH
Z

[Deleted User]

As I understand it you are looking to heat a huge volume of water soley by an ASHP using cheap rate electricity then pump it round rads/ufh during the day?

Would this not give you the same disadvantages as storage heaters? You have gone to the bother of heating all that water that may not be used/needed...

Whereas if the ASHP was simply connected to fan convectors you have a system with very fast startup/heat times like GCH. Obviously you are using more expensive electricity but vastly less water to heat...

Personally if I was on GCH I wouldn't bother making the change.

Cheers

lovesgshp

wiffola wrote: »

I'm looking to retro-fit an air to water air source heat pump for all of our heating and hot water needs. We live in an 1895 cottage 90m2.

We'll be using oversized radiators on 15mm pipework, ideally without a buffer tank due to internal space issues.

All I would like is some advice on brands of ASHP. They all seems to have different COP's but I'm not sure whether they are all tested in the same conditions, and also how relevant these are anyways.

These are the units we have been quoted for...

1. DanFoss AQ 9kw

2. Daikin Altherma High temperature (Not sure what wattage - cant find the quote right now)

3. Mitsubishi Ecodan 8.5kw

This isn't a thread to talk about if it's the right option or not - been there done that and appreciate all the help people on here have given.

Any recommendations?

Might be worthwhile checking the price on the new IVT premiumline ASHP in the UK. New model released this year. It may be marketed by Worcester Bosch, as their heatpumps are the IVT models.

lovesgshp

jeepjunkie wrote: »

As I understand it you are looking to heat a huge volume of water soley by an ASHP using cheap rate electricity then pump it round rads/ufh during the day?

Would this not give you the same disadvantages as storage heaters? You have gone to the bother of heating all that water that may not be used/needed...

Whereas if the ASHP was simply connected to fan convectors you have a system with very fast startup/heat times like GCH. Obviously you are using more expensive electricity but vastly less water to heat...

Personally if I was on GCH I wouldn't bother making the change.

Cheers

You also have to take into account the max temp you are putting into the heat bank from the ASHP. If for UF then circa 35C or rads 50C. If UF the COP would be reasonable, but this would also depend on the temperature delta, room thermostat setting and how often the pump needs to activate. We had a small buffer tank here initialy, (0n a GSHP), but after testing, removed it as pump running times increased.Currently with outside temps getting to 0C we are running circa 8 hrs a day, with house temp set @ 18.5C.
If you are on GCH then I would stay with it, as payback will be far longer as JJ states.

rogerblack

zeupater wrote: »

Hi

You've obviously costed it all out but for the benefit of others 2 Tonnes = 2000l of storage which would cost between £2k & £3k for insulated buffer tanks

I should have expanded on this.
I happen to have a fair number of plastic barrels, which I know are good up to the temperature I desire - I've seen them used as hot water tanks for 65C maintained for several months.
I will not be going that high.
This, and an insulated box made of kingspan round them is a fair bit cheaper than 2-3K.

This would only work for UFH - and a UFH system which is designed for low loop temperatures, with a house that is fairly low loss.
In most other circumstances, it would be prohibitive.