DX Split Hot Gas Reheat
DX Split Hot Gas Reheat
(OP)
I have several 20T (two stages) DX splits installed on gym. I need to improve dehumidifacation which I plan on doing by adding Hot gas bypass(rawal device) and hot gas reheat. I desparately need your help with the following questions/concerns:
1.Should I do on/off reheat or modulating? I'm a bit concerned that with on/off temperature swings my be enough to cause discomfort in the space. However, the simplicity of the on/off is the way I'm leaning.
2.Every Hot Gas Reheat installation I've even done has been on packaged equipment where I route my hot gas/liquid leaving the HGRH coil back to the discharge line. However, this being a split I'm considering routing it back into the evaporator. I've been told, by several people, that routing hot gas/liquid to the evaporator will lessen my ability to dehumidify by reducing coil temperature. This seems counterintuitive to my but I would like to ask your option.
3.And the final question. I did a search on this forum before posting and someone has suggested adding a liquid line receiver when doing HGRH. Why is it needed?
Thanks in advance for your help,
D





RE: DX Split Hot Gas Reheat
When I use hot gas for this type of application, I prefer it to be on off, and such that there is not a lot of difference bewteen the entering and leaving air temps when it is engaged. -- like it blows 77 or 78F air that is dry
I also use hot gas on situations where the latent load is big enough that it is pyschrometrically impossible for a cooling coil alone to give you the correct dry bulb and wet bulb. Example a load with lots of people, (even active ones like a gym or pentacostal church) and lots of outdoor air.
In this case I usually use a small dedicated compressor with an evap and condenser down stream of the main cooling coil. This extra evap gets the dewpoint down to what I need and fan heat (pulling air through three coils) and the hot gas reheat seem to give me a 64 or 65F discharge temperature with a 50 dew point.
Only ever looked at a rawal to modulate capacity on a big oversized constant volume system having a classic part load dehumidifaction project.
Addison seems to be into modulating hot gas.
The way we build has a far greater impact on our comfort, energy consumption and IAQ, than any HVAC system we install
RE: DX Split Hot Gas Reheat
RE: DX Split Hot Gas Reheat
The way we build has a far greater impact on our comfort, energy consumption and IAQ, than any HVAC system we install
RE: DX Split Hot Gas Reheat
RE: DX Split Hot Gas Reheat
this one was made in Calgary
4 trane scrolls on the big coil get air down to about 52F
copeland is connected to an additional evaporator and condesner in series down streams,pulls the air down to about 50 on a dehu call, with fan heat it blows about 65F dry air
The way we build has a far greater impact on our comfort, energy consumption and IAQ, than any HVAC system we install
RE: DX Split Hot Gas Reheat
The way we build has a far greater impact on our comfort, energy consumption and IAQ, than any HVAC system we install
RE: DX Split Hot Gas Reheat
I have a couple units like that in operation down here as well
The way we build has a far greater impact on our comfort, energy consumption and IAQ, than any HVAC system we install
RE: DX Split Hot Gas Reheat
I cannot add another compressor/evap/condenser due to $. My plan is to have humidistat make the dehum call based on space. If there is not cooling call at the time I would turn stage 1 on and cycle reheat to satisfy the space. If stage 1 is already 'on' on cooling call, i would bring on stage 2 and cycle reheat as above. Do you see any issues with that theory?
Also, do you think liquid line reciever is necessary in this situation?
RE: DX Split Hot Gas Reheat
Basically add a second condenser coil down stream on the stage 2.
On a dehu call run both compressors but send the gas for stage 2 through the new inline condenser rather than the condensing unit coil.
Look at the "alternate reheat function" on page 7
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The way we build has a far greater impact on our comfort, energy consumption and IAQ, than any HVAC system we install