Newhouse Farm

Neil_J · Posted: Fri Jul 17, 2009 11:42 am Post subject: ASHPs more info needed

Hi all.

I'm new to this post but I've been following Andy_WSM's experiences with great interest as we're on the verge of buying an Activair 5kW and this is the first real world experience of it I've found in weeks of searching. What I'm really interested in, as it seems to be working so well, is the rest of the setup. And is it still working as well a few months down the line?

You say at the beginning, Andy, that you've put a new tank in the loft, but what sort and size is it? It sounds as though you have fairly standard domestic plumbing wares, but I thought that wouldn't really work particularly with radiators and a small heat pump. I've been recommended a Gledhill thermal store, which I can't really afford at present and had been thinking of using one of their solar coil tanks instead. Is even that necessary? We only really need DHW for two people and maybe some heat to a couple of bedrooms.

On the subject of radiators, are yours oversized? I'd been led to believe you could only really use underfloor successfully, or oversize the rads by 33%, but it sounds like you're getting away with pretty regular stuff. Or am I misreading between the lines? I'm also a little concerned about this loft cooling effect. Have any polar bears found their way into your roof yet? We have no alternative in our listed 18th century cottage but to put it in the roof that's also the reason we're going down the ASHP route as we have no suitable roof area for solar and no outside space to mount any other kit at all.

Any further details would be really appreciated before I invest in the unnecessary.

Thanks in advance.

Neil J

Andy_WSM · Hazel Seedling Joined: 20 Feb 2009 Posts: 24

Hi Neil!

As luck would have it I had email notifications enabled for this topic as I haven't been on this forum for a while.

With regards the heat pump - yes, still chuffed to hell with it!

Installation wise - I have a Fortic style 120L hot water tank in the loft, with a booster pump on the outlet to serve the domestic hot water and shower - so I effectively get a power shower too.

I've had the heat pump in for about 7 months now. It works faultlessly. During the hot weather, as you can imagine, my loft was VERY warm and the heat pump was able to heat the entire hot water tank from cold in about 40 minutes. I also have the towel radiator plumbed in to heat all year round. I have 2 bedrooms, both with radiators, hall way, living room and a convector blower in the kitchen. None have been uprated and all work sufficiently well to keep the rooms warm (22C living room, 21C bedrooms / kitchen).

The loft has suffered no adverse effects, no damp, condensation, anything really and the heat pump remains clean and free from dust - which was another concern, that it might stir up / draw in dust from the loft.

I'm in a bit of a hurry as in works time, but if I think of anything else to say, will update later.

All the best,

Andy
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Neil_J · Posted: Fri Jul 17, 2009 12:53 pm Post subject:

Thanks very much for the information, Andy. That's really helpful and suggests that I can maybe cut the costs down a bit further than I'd been told.

Can you just tell me if the Fortic tank has a regular coil or a special solar one I believe some are available. I've got a lot more options if I can get away without the solar type, although I guess it'd be more efficient. I'm also pretty tight for space and pipe run options because of the nature of our old house dodgy timbers etc. so a combination tank could be really useful.

Thanks again for your time.

Neil

Andy_WSM · Hazel Seedling Joined: 20 Feb 2009 Posts: 24

Just a regular tank. I was on a tight budget at the time, so really put this in as cheaply as possible. To my relief I haven't suffered as a consequence!
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AidanB · Hazel Seedling Joined: 10 Nov 2008 Posts: 24

Generally when talking about ASHP I say that they are only worth using when mains gas isn't available or where there is underfloor heating.

My reasoning is that a COP of about 4 at 7 degrees is just about ok and saves you about 46% of the CO2 you'd previously have used (assuming grid electricity is .422kgCO2/KWh cf gas at 0.194 kgCO2/kWh), and 15% from the bill (using electricity at 13.6p and gas at 4.0p).

However, when you really need your heating, and the outside temperature is below freezing, if the COP drops down to say 3 then by your crude calculation above you're actually paying more (13.6p compared to 4p).

Is this fair?

What is the measure COP of ASHP at say -2C, a cold, but highly normal winters day?
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DMc · Posted: Tue Aug 18, 2009 7:22 am Post subject:

I haven't checked your figures but your reasoning is similar to my (untested) logic that a GSHP could be better when it is cold, whilst an ASHP could have an advantage in the warmer part of the heating season.

I am a bit puzzled by this statement:

Andy_WSM · Hazel Seedling Joined: 20 Feb 2009 Posts: 24

DMc · Posted: Tue Aug 18, 2009 8:44 am Post subject:

Andy_WSM · Hazel Seedling Joined: 20 Feb 2009 Posts: 24

Ecocentric · Posted: Tue Aug 18, 2009 3:01 pm Post subject:

Andy, it might be useful to factor in ambient temps in your data.
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Andy_WSM · Hazel Seedling Joined: 20 Feb 2009 Posts: 24

Ecocentric · Posted: Tue Aug 18, 2009 4:12 pm Post subject:

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200 yr old farmhouse and land - a few hundred £k. Livestock, more buildings and kit - a few more £k. Greener business and lifestyle - ***king priceless.!!

martin w · Posted: Wed Sep 02, 2009 9:36 am Post subject:

I'd be very interested in your data too!

I'm interested in the tranco 3kW or 5kW unit to possible patch into my themral store. I already have solar and will be putting in the wood burner soon (honest!). The back boiler on the wood burner is 2.2Kw output and the store links to 2x rads as heat dumps.

I probably won't conside the ASHP until next year anyway as I need to see how the wood burner pans out first, but it might be a nice addition.

I have a theory (probable completely wrong) that as I would be plumbing in the ASHP into the bottom of the thermal store it might only be needed ot heat the water from 30-40°C, with the wood burner above it heating from 40-55°C. Would the ASHP be working at a greater COP as the water temp will be lower due to the woodburner also heating the system?

The ASHP would be direct on the thermal store (two tapping at the very bottom of the Store, The wood burner will be on a coil above the solar coil and the ASHP tappings. (damn wish I put more tappings in now!)

The hotwater coil and dump rap take offs are at the top of the store.

What are people thoughts on this therory?

MrC · Posted: Wed Sep 02, 2009 9:44 am Post subject:

Yes you can do that no problem, you will have to link some controls so the heat pump will not run together with the wood burner.
The cop will be higher although in the spring to autumn you should rely on the heat pump for all the water heating, giving around 4 cop.
Mike
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"Cooling & Heating Solutions for Your Needs"
Air source heat pumps with over 500% efficiency and cop of 5.4.

DMc · Posted: Wed Sep 02, 2009 9:52 am Post subject:

I think I would put the solar at the bottom of the tank rather than the ASHP, but other than that it looks OK. It does rely on good stratification within the thermal store, and that may not be so easy to achieve, especially with so many inputs/outputs/flows, but I don't know what you can easily do about that.