Air Source Heat Pumps

grahamc2003

Cardew wrote: »

Graham,

I have a couple of cages in my garden, one with a 2" mesh and the other with a 1" mesh.

In the weather in Dec both meshes were completely blocked with a combination of ice and snow.

Yeah, I don't think the filter could be made of any metal for those reasons. I expect there are some filter materials out there which would do the job - little restriction to airflow, slippery to snow and water, low heat conductive etc.

Also, a further problem seems to be the melted water runoff during defrosting refreezing in the drain holes in freezing weather, and simply building up that way.

All these problems are a bit surprising - I'd really have expected them to have been designed out well before they hit the market, especially from the Japanese manufacturers.

Cardew

grahamc2003 wrote: »

Yeah, I don't think the filter could be made of any metal for those reasons. I expect there are some filter materials out there which would do the job - little restriction to airflow, slippery to snow and water, low heat conductive etc.

Also, a further problem seems to be the melted water runoff during defrosting refreezing in the drain holes in freezing weather, and simply building up that way.

All these problems are a bit surprising - I'd really have expected them to have been designed out well before they hit the market, especially from the Japanese manufacturers.

Even an electrically heated mesh would work. 50 to 100w produces a lot of heat and isn't a lot of power to waste.

richardc1983

grahamc2003 wrote: »

I was thinking of something like nylon, as in tights, but stronger. I doubt snow would stick to any vertical nylon, which I expect would protect the side vents. I'd just be careful not to let the nylon get ripped and injested! But it would be a case of giving it a try - i think a physical barrier is necessary to stop snow and rain getting inside. Also, I think having the unit wall mounted instead of on the ground would help too.

It'd be really interesting to see how any air to air units worked in the very cold weather - Steve's electricity usage readings would be really interesting, as too his observations on how often his units froze up and whether his units' defrost strategy worked well.

I think the unit is mounted directly so wind is blowing all the elements at it. Wet snow will stick to any surface and nylon material it will stick to anything like velcro we have seen it ourself here. The snow if blown hard enough will stick to walls etc.

Removing the rear cover and making sure the unit is off the ground and water can drain will stop the ice and snow bridging the grill.

richardc1983

grahamc2003 wrote: »

Yeah, I don't think the filter could be made of any metal for those reasons. I expect there are some filter materials out there which would do the job - little restriction to airflow, slippery to snow and water, low heat conductive etc.

Also, a further problem seems to be the melted water runoff during defrosting refreezing in the drain holes in freezing weather, and simply building up that way.

All these problems are a bit surprising - I'd really have expected them to have been designed out well before they hit the market, especially from the Japanese manufacturers.

A plate heater mounted in the bottom of the drainage tray of the unit that comes on in freezing weather would stop it refreezing so it could drain away.

TiredGeek

All good points regarding tray heaters etc guys, however, even a low wattage, say 30w on for 24/7 for 6 months is gonna rack up the bills a bit

The company who supplied these units carried out a survey on the house and recommended where they should be fitted, and that's where they are.

Honestly, from reading various forums, I've come to the conclusion that these units are never going to be reliable at my place, whether it's due to their position, the low ambients or the high humidity in the valley or a combination of all, I don't know, but they ice up each time it drops significantly below zero. Where the house is that's anytime from early November through to April, and it can stay below zero for weeks at a time.

richardc1983

TiredGeek wrote: »

All good points regarding tray heaters etc guys, however, even a low wattage, say 30w on for 24/7 for 6 months is gonna rack up the bills a bit

The company who supplied these units carried out a survey on the house and recommended where they should be fitted, and that's where they are.

Honestly, from reading various forums, I've come to the conclusion that these units are never going to be reliable at my place, whether it's due to their position, the low ambients or the high humidity in the valley or a combination of all, I don't know, but they ice up each time it drops significantly below zero. Where the house is that's anytime from early November through to April, and it can stay below zero for weeks at a time.

They are not on 24/7 they just come on when the temp drops below 3C.

Have you got any where with the installers?

samtheman1k

TiredGeek wrote: »

All good points regarding tray heaters etc guys, however, even a low wattage, say 30w on for 24/7 for 6 months is gonna rack up the bills a bit

But may cost less than the reduced efficiency of the HP...

Cardew

TiredGeek wrote: »

All good points regarding tray heaters etc guys, however, even a low wattage, say 30w on for 24/7 for 6 months is gonna rack up the bills a bit

30w on 24/7 for six months is 131.4kWh - say £15.

Although I agree with your overall point that the system is not fit for purpose!!

lovesgshp

TiredGeek wrote: »

All good points regarding tray heaters etc guys, however, even a low wattage, say 30w on for 24/7 for 6 months is gonna rack up the bills a bit

The company who supplied these units carried out a survey on the house and recommended where they should be fitted, and that's where they are.

Honestly, from reading various forums, I've come to the conclusion that these units are never going to be reliable at my place, whether it's due to their position, the low ambients or the high humidity in the valley or a combination of all, I don't know, but they ice up each time it drops significantly below zero. Where the house is that's anytime from early November through to April, and it can stay below zero for weeks at a time.

My thoughts are that they should never have been positioned on a roof area, but on a side wall of the house, preferably south facing. External air sensor on the north wall.

zeupater

Cardew wrote: »

30w on 24/7 for six months is 131.4kWh - say £15.

Although I agree with your overall point that the system is not fit for purpose!!

Hi

As a rough rule of thumb, I calculate costs for items on standby etc as being £1 per Watt per Year ..... 30W for 6 months = £15 .... Agree.

HTH