Heat Pump Shopping List

[rjsimmon]

Hi,

I'm building my own heat pump system. I've selected the compressor, the condenser, the evaporator, the TXV, reversing valve, the refrigerant and fans.

The heating capacity is 220W, its a small system for a scale model of a Eco house.

What's bothering me is, do I need anything else?

Do I need an accumulator, filter drier, check valve and metering deveice?

Do I need a check valve and metering device on the vapor line and the liquid line?

Any feed back would be great!

Cheers, Rob.

[Brian_UK]

Yes, you need an accumulator and always a filter/drier

You also need two check valves, one for each TXV.

As a matter of interest, what is the refrigerant that you are going to use?

Plus, of course, you'll copper tube and insulation as well as OFN.;)

[rjsimmon]

Cheers Brian!

The cost of my project is mounting! Luckily, my university is paying for all the equipment. Think it 's comming to around £450+! I hope it works.

So no metering device is needed? I take it that's only needed if I want to meter something, lol.

My choice of refrigerant is R-134a.

If you want to know anything else about the project please ask.

Cheers, Rob.

[Brian_UK]

Maybe I'm missing something but you said that you have TXV - that is a metering device.

Oh Yes, one other thing that you need is a Refrigerant Safe Handling Certificate.

[Brian_UK]

Hey Rob, have a look here for a system layout...

http://www.books4hvac.com/refrigeration_basics/800x600/heat_pumps1.htm

[rjsimmon]

Ah, my bad. Being new to this game I'm not too down with the refrigeration lingo and now, looking back at my book, I should have realised that a TXV is also refered to as a metering device. I feel kinda stupid now.

The truth is I've been focusing most of attention on the heat exchanger design, as that is the main part of my project. I've designed and I'm about to build the condenser and evaporator, exciting stuff!

There's a technician at my uni who's certified for handling refrigerants, lucky for me.

Cheers for the link, its got some good info very similar to one of the book I've been using, 'Heat Pump Technology' by Billy C Langley.

Thanks again for the info, much appreciated.

Rob.

[rjsimmon]

I've now decided that I'm not going to make my system reversible. It will only be used to heat.

So just to check through the shopping list again:

Compressor x 1
TXV x 1
Filter/Drier x 1
Accumulator x 1
Condensor x 1
Evaporater x 1
Copper Pipe, varius sizes
Silver Solder

Is this ALL I need to construct the circuit? Is there anything else I should add to the circuit?

It has now been established that the refrigeration technichian at my Uni has retired, only in January (sods law), so I'm going to need an external fridge guy to pressure test and charge the system.

Is it likely that a company will charge the system for me, even though it is not your 'standard' job? Are they going to want to see something on the circuit that I haven't included???

Cheers, Rob.

[taz24]

I've now decided that I'm not going to make my system reversible. It will only be used to heat.

Is it likely that a company will charge the system for me, even though it is not your 'standard' job? Are they going to want to see something on the circuit that I haven't included???

Cheers, Rob.

For the parts list if your using a TEV then you need a receiver and if its a system built from scratch a sight glass will help to determin correct gas charge. Also you need copper to copper brazing rods as well. Silver solder is for disimilar metals.

If you involve sombody from the outset then they will be able to controbute to the project. At the least they would need to strength test it and then leak test it. Charging the refrigerant is the easy bit.

I'm sure someone onthis site would be able to help out.

Cheers taz.

[Brian_UK]

Further to Taz, you can lose the accumulator as it's no longer a heat pump.

Also you'll need OFN, oxygen free nitrogen and a pressure regulator for purging during brazing.

[frank]

If the cold coil (evaporator) is going to be outside during winter then you also need to consider some kind of defrost mechanism.

What part of the UK are you in?

[Brian_UK]

Just a thought, but as this is a scale model of an eco house are you planning to build it all indoors ?

[rjsimmon]

Just a thought, but as this is a scale model of an eco house are you planning to build it all indoors ?

The Eco House will be built indoors but then put outside. We've designed it to split in half and to fit into a Transit Van so it can be easily moved, as long as theres a few helpful hands around.

It will be monitored for about a year until the next project superseeds it!

All the brazing is being looked after by a brazer friend of mine in the Uni. Lucky for me the Uni have all the gear needed for brazing, including OFN.

To Frank:
I'm located in Sheffield. The defrosting of the evap will be done by a deicing agent if its bad. It will only be ON in 12 hour periods, so the ice build up should be minimal. Fingers crossed.
As I've designed the heat exchangers as the main part of my project, the difference in air temp from inlet to outlet is approximately 1.5 degrees C. Minimal, so ice build up will be kept at bay for a while I hope.


Brian you quoted; "Further to Taz, you can lose the accumulator as it's no longer a heat pump."

I'm confused, the system will only be heating, not cooling. Is it not a heat pump then?

So do I need a suction line accumulator, a liquid line reciever, or both?

Sight Glass x 1
Reciever x 1......?

Now on the list, cheers Guys!!

[taz24]

The Eco House will be built indoors but then put outside. We've designed it to split in half and to fit into a Transit Van so it can be easily moved, as long as theres a few helpful hands around.


Now on the list, cheers Guys!!

So its a glorified mobile home for the little people:D

taz.

[Brian_UK]

Brian you quoted; "Further to Taz, you can lose the accumulator as it's no longer a heat pump."

I'm confused, the system will only be heating, not cooling. Is it not a heat pump then?

So do I need a suction line accumulator, a liquid line reciever, or both?
No, it isn't a heat pump as the term is presently known. We call them heat pumps when it is possible to change from heating to cooling.

Technically you are 'heating' inside but you are actually 'cooling' the outside air and expelling the heat adsorbed into the inside of the building.

An accumulator is needed in a heat pump because when the reversing valve operates there is a sudden change of direction by the refrigerant and the condensed liquid can be directed straight into the compressor. The accumulator allows the liquid somewhere to go and the compressor to only receive vapour.

The receiver 'receives' liquid from the condenser, inside coil, and ensures the the TXV only sees liquid and hence qorks correctly.

[rjsimmon]

Cheers Brian, point noted.

Do I need any valves especially for charging purposes?

Cheers Rob.

[Brian_UK]

Yes, you'll need some Schraeder access ports, these are often made up with a short stub of 1/4" tube aleardy fitted and you braze them into the system wherever you want.

Some items, such as the receiver, may come with service valves which incorporate an access port, but you'll need to check this.

Have a look at Parkers literature here http://www.parker.com/ead/cm2.asp?cmid=1567
to see what some of the kit looks like.

[rjsimmon]

Cheers again Brian you've been a big help.

I do believe the reciever has the access ports required.

Now to order the stuff!

Thanks again.

[Brian_UK]

Now to order the stuff!

Thanks again.We await the next post which asks the question:-

"Anybody got a spare fiver" :D

Fiver:- 5 GBP, 5 dollars, 5 euros - you get the meaning;)

[Peter_1]

Sheffield, isn't that the birth place of Joe ****er?
Or is this completely wrong?

[Peter_1]

Sheffield, isn't that the birth place of Joe ****er?
Or is this completely wrong?

I meant Joe C O C K E R

[Brian_UK]

That's the place,

http://www.nndb.com/people/557/000022491/

[taz24]

To Frank:
I'm located in Sheffield. The defrosting of the evap will be done by a deicing agent if its bad. It will only be ON in 12 hour periods, so the ice build up should be minimal. Fingers crossed.
Now on the list, cheers Guys!!

If you are in Shefield I am willing to help and give you any practical assistance you may need.
I have had a keen intrest in heatpumps for years so I am very interested in your project. If you do not need help thats fine, I would like to see it when it is running. If you require the use of tools I can organise that. As for the refrigerant side again I would be prepared to help out if you want.

taz.

[Brian_UK]

Thanks Taz, that's a nice offer.