Supplier for small registers and boots for ducted minisplit?
whitenack
| Posted in Green Products and Materials on
Hi all,
I have a completed manual J, S, D, & T. Now I have to find the different parts an pieces.
Because of the small loads in the house, the ducts and fittings are smaller than what I see in stock at the local big box suppliers. For example, I need 4×4 and 4×6 duct boots and register grilles. Where can I find those size fittings?
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Replies
Clay,
In general, ducted minisplit systems require a low static pressure, which means low-energy fans and big ducts. If anything, your register sizes should be larger than usual, not smaller than usual. Even if I am wrong, oversizing your registers incurs no performance penalties.
Martin,
Thanks for the extra advice. I farmed these calculations out to HVAC Design Pros (formerly Home Energy Partners), so I am trusting that the design is correct. We are going with a Fujitsu 12RLFCD, which I understand has a higher ASP than typical ducted mini splits. The rooms that have the small registers are small-load rooms...rooms that need 50cfm and less.
Good to hear that I can oversize the boots and registers. That was going to be a pain trying to track down those items.
Sometimes it's necessary to narrow down the duct at the supply register boots to increase the velocity, enhancing the "throw" for reasonable air mixing within the room (particularly at lower blower speeds.) Discuss that with your duct designer.
For the return ducts that is not an issue- oversized registers will always be fine.
Thanks Dana. If it turns out that I need these small sized supply boots, where would I get such an animal? Is that going to have to be custom fabricated?
You should have an easier time with 6" round. Note that stratification is a function of throw and the delta-T between the supply and room air. The delta-T should be low with your mini-split - but you can block part of the grill to increase velocity/throw.
John Semmelhack is probably the right guy to recommend specific vendors. See his pictures on this thread:
https://www.greenbuildingadvisor.com/community/forum/mechanicals/93846/mitsubishi-minisplits-horizontally-ducted
Stratification is also a result of heat and air leakage of the envelope. If you have a good envelope, that's another reason not to worry about throw and mixing and such.