Topic: Hot water heat pump calculations

Re: Hot water heat pump calculations 

Pete,

yes and no.

You can not have it all. You decide what is your main priority and go from there.
My heat pump system is undersized for approx 80 hrs a year (10 days), I made the decsion i was not going to pay the extra 3K for the larger size, for 80 hrs of perfect heating. (not that it stops heating, it is just not as swelting hot, as I like it) I knew this (my job) so i am happy, If this had been explained to you no BS, which choice would you make, there is not a right or wrong answer.

Re: Hot water heat pump calculations 

hmm, I kind of hope I am making that same decision Frosty- While I may not be getting the 'optimal' performance and using the best HP at the moment we have wooden floors with sitting 300mm above the dirt-so it can only get better than that!

I would like to use a spiral coil but from what I have read the current config I have shown is the only one suggested for retrofitting on 18" joists. I think it is just plain easier to install.

I'll look at removing some of the loops from the walls - but yes I'm aware of the nailing issues. Thats why the east end (3 loops) are broken up from the rest of the house as that's where the extension will be going.

Re: Hot water heat pump calculations 

Hello pjimmy,

I may have missed this point in your posts, but understand you are post fitting on a Matai floor with a 300+ crawl space. If so, then what provision have you made for insulating the floor and have you considered ground water upward permulation and therefor a polythene vapour barrier protection?

Rex

Re: Hot water heat pump calculations 

hi Sceptics,
I plan to put polythene plastic down on the ground first. I believe you can get it from any harware shop. Comes in about 3+ metre wide rolls. This will make it easier to shimmy around under the house and will hopefully mask any bad odours from our cat. Most importantly it will inhibit the moisture.

There is no point going through this process unless the underside of the house can be insulated.

Had the plumber in over the weekend to look at the hwc and hp. He thought it was a good system to install although not sure about my ideas for plumbing in the underfloor heating to the system..
I don't have a lot of time for the next couple of weeks to make a move on this project so will keep chipping away and learning as best I can.
Thanks for all your advice -keep it coming! I do appreciate it.
Cheers
Paul

Re: Hot water heat pump calculations 

Re my comments about being too proscriptive.

Depending on conditions outside, an air sourced hot water heat pump will produce an amount of energy that can be stored as heat in a concrete slab. As long as the house is kept at the desired temperature, for as low a running cost as possible - heat calculations are irrelevant. All that matters is that the heat pump can keep up with the heat loss - so if an outdoor unit runs 24 hours a day under the worst conditions - and keeps the house temperature correct - you don't need to work anything else out.

Hence the trick is to overspecify the heat pump to some extent, but not too much as the costs escalate.

From experiments carried out over the last three years I know how much one of our 12kW units can do without calculating a single thing.

Due to a rat chewing through a controller cable, I had a customer here a couple of days ago. I initially fitted a 12kW unit in parallel with his 30kW diesel boiler a couple of years ago. 240sqm house, mud brick - two storey. After a couple of months he sold the boiler on trade me as he ended up never using it. Middle of winter he runs it 24 hours a day, costing about $250 a month - the house is warmer than with the ups and downs in temperture of the diesel - and it costs him a lot less.

No doubt conventional calculations would have said it wouldn't work.

When the living area goes over 220sqm we suggest fitting two of our outdoor units. As Frosty says there aren't right and wrong answers, just various solutions to heating a house - and calculating heat losses won't really help me.

Re: Hot water heat pump calculations 

Does anyone know where I can buy most/all of the equipment required for the UF installation? I'm after everything from pumps to PEX tubing and manifolds.
Lots of overseas companies, but not that many in NZ.
Cheers
Paul

Re: Hot water heat pump calculations 

We import all the major parts for our underfloor systems, and sell all the parts as well.

ie Pex pipe, manifolds and connectors, circulating pumps, heat pump outdoor units, expansion vessels, and control valves.

JK

kippingheating

Re: Hot water heat pump calculations 

Hi All,
Can anyone explain why I can't suspend Pex pipe below the floor (about 30mm) and create an air pocket for a more even heat distribution?

I have never heard of this but it was suggested by a building scientist.

The images below should explain what I mean.

The alternative (as shown in the other image) is more conventional and uses a aluminium diffuser. There are 2 reasons why I am not keen on this system:
1. It is expensive.
2. Although the response time will be better for heating, I am concerned about creating hot spots where the pex touches the wood.
Cheers
Paul

Re: Hot water heat pump calculations 

This is the conventional method:

Re: Hot water heat pump calculations 

Pipes under an existing timber floor are a heating system, not an energy storage system - hence some the benefits of using a hot water heat pump are lost (the heating has to be on when it's cold outside with a loss of efficiency).

I would suspect that radiators with a heat pump would be a lot easier to install and probably work as well. Anyone have such a system?

Bottled gas or diesel can work out expensive each winter.

JK