Why Rating a GeoExchange Heat Pump on Tonnage is a Bit of Bunk
We hear this all the time: “My heat pump is 4 tons”. “I need a 5 ton unit for my house”. This is based on the 12,000 btu’s…
We hear this all the time:
“My heat pump is 4 tons”.
“I need a 5 ton unit for my house”.
This is based on the 12,000 btu’s = 1 ton of heat pump capacity.
Also many manufacturers (almost all) label their units in a manner that suggests the unit capacity of their heat pump1:
Heat Pump Peformance Data
Two similar comparing units until you look closer at the specifications. In order to achieve 49,000 btu’s, the Waterfurnace requires 15.5C entering water temperature (EWT) while the Climatemaster only requires 10C EWT2. Big difference, but in either case, not really one that is achievable in my climate locally in winter.
In the thick of winter, the EWT may be 0C (depending on design). The Watefurnace now has a 37,500 btu capacity and the Climatemaster has a 38,300 capacity. Both now approaching 3 ton capacity.
I have shown two of the industries more efficient units and respected and proven companies. There are a multitude of other options out there and, in some cases, the manufacturer labelling is not a good representation of the heat pump output3. I can find units with labelling that only gets 45,000 btus (less than 4 tons) of heating out of 15.5C EWT.
If you are buying directly from a manufacturer as a building owner, you need to be very careful about this purchase. You can not size a unit, if the manufacturer only gives you the btu output based on one temperature. You need a broad range table that allows you to interpolate heat pump output correctly.
In summary, talking about the size of a heat pump in tons is good for generalities. But that is where the usefulness ends.
1 – I have roughly interpolated the heating side only, but used similar variables for both units.
2 – To be fair, the Watefurnace 7 NV048 series reaches 48,000 btu’s at 4C EWT.
3 – I should name some companies, but I’ll try and keep it civil. Chances are if you can purchase directly from the manufacturer without being an installer, you need to pay attention.
Pressurized flowcentres are a common method of pumping a ground loop to a heat pump.
On a recent job, I came across a flowcentre that leaked. It leaked internally and this is not a simple fix. In this case, we replaced the flowcentre and had the opportunity to take the old one and tear it apart. As we were curious in what was inside, I thought I’d take some pictures and share.
The Flowcentre after being removed.
Digging out the spray foam insulation on the back.
A pump, a coupling, and a 3-way valve.
In this case, the plumbing on both pumps was loose. We easily undid all the fittings by hand. No thread seal, teflon tape, or such was noted between the female coupling in the middle and either the pump or the 3-way valve. Also important to note, there is a combination of plastic and metal connections. So, in summary, yes these things can leak inside and you have a few choices:
Pulling it apart
In all cases, not a quick or cheap fix and a day of labour that nobody wants to pay for.
This is a larger geo-radiant system with an HRV unit that we are a few days in to installing.
Inside the mechanical room, we have built an angle iron frame for stacking the heat pumps. The plumbing to the left is the outside loop being tied in to a non-pressurized flow centre. Eventually a Wilo Stratus pump ECM pump will be circulating the fluids from the surface water loop to the heat pumps.
Keeping the radiant system plumbing nice and tidy.
Geoexchange pond loops are a cost-effective manner in which to heat and cool your building. Working in and around waterbodies requires due diligince on the contractor’s part. To ensure one requires the correct procedures and obtains the required permits one needs to complete and submit the following:
It is also important to read and be familiar with the Best Management Practices for lake installations.
The following is supplemental information one should be aware of as well:
Note this information is current as of the date on this posting. It needs to be explicitly stated that we are talking about the requirements within the Province of British Columbia.
Thanks to John Manning of Phoenix Energy Supply for sending me this graph. The chart clearly shows geoexchange coming out ahead (in New York dollars) over the long term.
On a personal note, I’m been very hesitant to write new postings as we attempt to filter 5 years of postings on our historic blog postings. This was good enough to get the juices flowing again.
Our beloved blog was hacked and we’re doing some damage control. In the meantime all the old methods of contacting us still work: Shine Energy Systems Inc. 4943 Uplands Drive Kamloops, BC V2C 6M8 250-377-1216 firstname.lastname@example.org