Monday, October 10, 2011

DIY HVAC with Plans!

Okay, How Crazy am I???

I'm going to do my own HVAC!!!

It's really not that I want's just that I don't have much choice.

Right now there is one forced air unit in the basement that supplies air (poorly) to the two basement apartments AND the main floor of the house....with the thermostat (t-stat) on the main floor of our house...

This has to change of course.

There needs to be two separate forced air systems: one for the new legal 3-2 apartment in the basement and one for just the main floor of the house...

I talked to a couple local 'well respected' HVAC places, but what I got from them was not encouraging....they both were going to do the system completely using flex duct and just use basic rules of thumb to size the equipment and place the registers...which means to me that I was going to get a non-optimized system sized incorrectly...this matters because what usually happens is they size the furnace too big and you get short cycling...where the furnace cycles off-on in quick succession...bad for the equipment, and the larger furnaces always cost more.

An Aside On Local HVAC Contractors
I've come to the conclusion that the vast majority of CA HVAC types (at least in this area) are fricken lazy and mostly inept. In the SF Bay area..where it really never gets super cold (Think a winter in the North East for comparison) or super hot (summer in high humidity Georgia) I believe this has caused the HVAC types to become lazy...

They can throw together a system using b.s. rules of thumb and over sized power plants and it's okay..nobody's going to freeze to death...and the local building dept isn't requiring people to show real HVAC plans either...

In other parts of the country to get a building permit, the HVAC contractor needs to do a manual J load calculation and a manual D duct calculation. The manual J is where they actually calculate the heating-cooling load of the home based on its size, construction, location. A manual D is where they then calculate the placement of the heat registers and size of the ducting.

I talked to like eight local HVAC guys and they ALL acted like I was crazy for wanting the Manual J & D's done...we don't do that place referred me to an engineer that wanted $1200 to do it!?!?!
End Aside

To The InterWebs!
I found a place online that will do the Manual J,D calcs for you, for a fee of course.
Its kinda got a lame name... PerfectHomeHVACDesign
The guy that runs it seems pretty reasonable and I like what he's sent me so far.
You send him the floor plan, window-door schedule and what your existing equipment is (if you have any) and he sends you back A LOT of info...most of it you don't need except where he spec's the equipment and the duct maps.

Here's what the HVAC plan looks like.
For the basement.
Take a look at the plan. Some things I've never seen on a local HVAC install. The outside air vent and the jumper vents between rooms. It seems like that around here they just say the space under the door will work.. I asked the designer about that and he said that you'd have to make sure that there was 1.5" clear under the door! How many people have that much clearance?

For the Main Floor.
We have the ducts shown for both as he had to move some around to make them both work.

Here's just the register locations

What he did was use two existing registers and the existing intake for the return air for this floor. I will have to add registers to a lot of places like the bathrooms and whats called the study (really the kids play room) on the plans. Not super fun but we're taking the ceiling down in the basement anyways so it will all be open...gotta do it now.

I think it will be nice to have a house with a correctly designed forced air system.

The single unit that's currently heating the area is a 100Kbtu, the software says that we only need a 45Kbtu for each level..and even then those are on the big side...but its the smallest size unit generally made. We had to get multi-stage burner and fan speed units to keep them working correctly (not short cycling).

Parts List From Hell
I went through the above diagrams and I believe I've figured out how many widgets I need to buy.

Anybody want to check my math?

Wow HVAC stuff is expensive.
Just did an online order (free shipping and no sales tax!) for the two different heating units, special venting supplies, thermostats, and supply and return air plenums...I think all the big stuff and I spent over $3000!!! Holy Fricken Moly!

I still have to buy all the widgets above! Speaking of..

Does anybody know of a DIY friendly local store that carries this kind of stuff?

I don't think Home Despot does but who knows....I can buy a lot of it online but that seems kinda silly, no?

I've gotten the impression that HVAC places that stock this kind of sheet metal are pretty anti-DIY...or am I wrong about that?

Next up....Halloween!!!!


Jim said...

While that design may be good from an HVAC perspective, those jumpers and return design look suboptimal from a sound isolation perspective, unless there is some sound dampening technology in those vents. Jumping the MBR and a bedroom directly to the family room seems like an unwanted implementation of the sound tubes you see at playgrounds.

Do you think that will be a problem?

The MadScientist said...

thats a good question...

Don't know...the designer was pretty adamant that I needed to pull the return air from the MBR and the hallway...ya..hmmm...need to look into that...maybe some right angles thrown in?

Anonymous said...

Agreed on your assessment of the local HVAC contractors. Levine & Co. did NOT impress with the quality of the work they did at my place.

A finished basement room is not the place to use a saws-all to open two gapping square holes then loosely drape flex-duct between them. The duct work is round. You use it all the time. Is it too much to ask that you invest in either a tool or the skill to cut a circular hole of the same diameter as the ducts you install?

Balance was bad too. Over heated one bedroom, under heated the second, even with all the doors wide open. Had to do a lot of my own rebalancing by trail and error. It's a standard 2-1 bungalow. They must see hundreds of them. How hard could it be?

I redid some of the work with material from Pacific HVAC Depot on Teagarden St. in San Leandro. I'm obviously not in the trade, but they were quite friendly and completely willing to spend time answering my questions. Just don't go during one of the busy times of day.

No idea if they are price competitive, I didn't shop around other than so see that Home Depot didn't have what I needed.

The MadScientist said...

Thanks, I went by the local home despot and they didn't have anywhere near enough stuff to do the job...

What would be HVAC Depot's not busy time?

I haven't been there recently but I also know that Sincere Plumbing in Oaklands Chinatown has a decent supply of hvac sheet metal.

The goal for these installs is no flex duct!!!

Anonymous said...

Hi, this is "anon" again.

As a DIY home-owner, my general strategy when going by the trade specific warehouses is to go in the mid-afternoon.

I figure the pros go early in the morning, stocking up for the work they've already got planned out for the day. Don't want to muck up the flow of things with a business's regular customers, or get in the way of the pros, who likely have a job site crew waiting for them. Generally the sales folk have been more than willing to help as long as you aren't preventing them from doing their primary job.

I went to the place in San Leandro around 2PM in the mid-afternoon and was the only customer in the warehouse.