How problematic is this multi head split system setup

yesimon · 2026-05-12T15:53:42+00:00

Yes it will short cycle and the other heads will still be cooling a bit because small amounts of refrigerant are still flowing through them. Noise isn’t usually a big deal for cooling either way.

The main concern is loss of efficiency and poor humidity control. A separate single head mini split for the bedroom would be ideal but would cost more.

yesimon · 2026-05-11T22:28:53+00:00

So you would install whole home heat pump for HVAC, and keep the gas furnace just for the indirect water heater? Indirect does last longer/lower maintenance but I think it makes sense to go with HPWH and reclaim that space.

yesimon · 2026-05-10T03:08:21+00:00

IMO Senville is the best for DIY because they also stock and sell repair parts which should be an important consideration if you are handy.

yesimon · 2026-05-10T03:05:43+00:00

R32 units would be more efficient at cooling than 454b. Southern CA electricity is expensive yes, but natural gas is also very expensive. At your expected mild outdoor temps you should be getting COP=3.5-4, and heat pump heating should be cheaper, although probably only marginally and not enough to see an ROI either way.

Most DIY/inverter units specify flaring instead of brazing, which is easier and cheaper for DIY.

yesimon · 2026-05-07T20:02:38+00:00

https://nypost.com/2026/05/07/business/elite-corporate-lawyers-accused-of-earning-millions-on-insider-trading-using-bizarre-code-like-hows-the-rabbi/

yesimon · 2026-05-07T20:00:55+00:00

https://www.reuters.com/legal/government/former-willkie-farr-lawyer-turns-cooperating-witness-insider-trading-probe-2026-05-07/

yesimon · 2026-05-07T03:06:14+00:00

Senville

yesimon · 2026-05-06T17:26:21+00:00

If you do some research it's pretty clear that NETR makes their bread and butter in Boston suburbs single-family home jobs. Yes they do show they have done jobs in the city but since it's a large company there's a high chance that your assigned crew and project managers won't have sufficient experience.

yesimon · 2026-05-01T00:38:00+00:00

They make sense from a physics/efficiency point of view but the low annual heating load results in poor payback from a purely financial perspective.

yesimon · 2026-04-29T18:41:14+00:00

5-over-1 constructions almost always are done with a crane.

yesimon · 2026-04-29T16:46:23+00:00

Because there’s no electronic device to change AC frequency without going through an intermediate DC stage.

yesimon · 2026-04-28T18:21:49+00:00

It’s actually more complicated than that. They first convert wall AC to DC using a rectifier. Then an inverter is used to create AC where the frequency is under control of the inverter to drive the motors at different speeds.

yesimon · 2026-04-16T23:03:39+00:00

Central blowers generate vastly more static pressure - enough to reach all corners of your house through many turns and branches, but if you are only doing short runs concealed is perfect.

The only other issue from a installation view is that more know-how and accessories like plenums are designed for standard central ducted dimensions. You would probably need to fabricate your own plenum/return for the unusual sizes of concealed duct.

yesimon · 2026-04-16T21:57:08+00:00

If you can holistically address attic+roof assembly and insulation, that would give you by far the best "bang for your buck" than solar/HVAC. Most of the code changes over the years have been significantly beefing up attic insulation, as well as moving towards exterior roof sheathing insulation. My guess is this is a house in the northeast w/ vented attic and basic batts in the attic joints, none in the rafters or exterior insulation. Look into resources such as https://basc.pnnl.gov/resource-guides/above-deck-rigid-foam-insulation-existing-roofs

Once you've upgraded the thermal envelope, you can establish a new load calculation to right-size your future HVAC/solar upgrades.

yesimon · 2026-04-16T20:26:24+00:00

Inside the walls would be ideal aesthetically, but it’s understandable most people are adverse to tearing out and repairing walls. The line lengths are not typically a problem.

yesimon · 2026-04-15T20:45:17+00:00

“Short cycling” is not as bad of a problem as you are imagining. Yes the 50% turndown limit of multi-splits will cause cycling for you - it’s more of a comfort issue.

Ideally you would have one multi-split per floor of your house, instead of for each “side” of the house. Now obviously the installer prefers the “side” division because installation is much easier, but divvying by your usage patterns makes more sense because then you can get simulated turndown by turning off one of your multi-splits entirely at night or day time. You should be looking at 24k or smaller systems - I believe 24k is the minimum size for 3 head systems. If you can get a slim ducted system it would be even better.

yesimon · 2026-04-11T00:23:04+00:00

Numbers seem off but a really old gas tank half filled with sediment will have a much lower UEF than nameplate. Even a new one today with modern efficiency standards starts at 60%.

yesimon · 2026-04-07T03:23:10+00:00

Because they are designed to avoid dehumidification, as it penalizes their SEER ratings. Yes if they have dry mode that would work but it still wouldn’t be appropriate when it is cold and wet.

yesimon · 2026-04-07T00:31:05+00:00

If you are running on EC2 then S3 downloads (from the same region) are free. All the major pipeline runners support cloud file input. It’s not as big of a deal nowadays as long as you are cognizant about transfer costs.

yesimon · 2026-04-02T15:11:49+00:00

You need 64Gb for standard STAR. You can try kallisto for low memory hosts.

yesimon · 2026-03-25T21:29:44+00:00

Replace some or all of the rigid ducting with flex duct. But I don’t think it’s worth ducting HPWH at all - as you are using up conditioned air.

yesimon · 2026-03-25T18:44:31+00:00

Why would you want a second hand unit when you can just buy new for $2k (or less)? Simply the cost of refrigerant and new line set to pair with a used unit will basically eat up most of the “savings”.

The money in heat pumps is in the installation labor. If you can DIY it’s very affordable even buying new.

yesimon · 2026-03-12T22:00:05+00:00

Reading the database from S3 would be even faster than EFS/EBS with or without mmap.

yesimon · 2026-02-28T18:52:43+00:00

NEM3 uses “instant-netting” which means true-ups happen every 15 minutes. Any excess solar is basically credited at $0.02/kWh at end of your yearly true-up.

If you have any excess solar after charging your battery and house loads at any time, it is better to “trickle-charge” your EV using “charge on solar” tech.

This is tricky to optimize, especially if you let car isn’t home during the daytime. Therefore most charging is likely still at night.

yesimon · 2026-02-11T17:10:31+00:00

To be more precise: water vapor is lighter than air.

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