Community: Mechanicals

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1 Answer

Manual J, D, S

I am working on a major remodel of my 1950s house. The existing ducts are metal. I am looking for someone who can advise me on whether my existing ducts are properly sized and who can perform a Manual J and S since I will be replacing the air conditioner and furnace. I am outside Houston. I would prefer a 3rd party consultant over an HVAC company. I see some companies perform this service without a site visit.

Do I need a local company who can come to the house or can they perform these calculations accurately without visiting my house based on the floorplan?

Asked By Kasey Doggett | Jul 25 17
9 Answers

Vented dryer depressurization and it's effects on radon levels?

Has anyone studied the effects on radon levels caused by running a dryer, or other unbalanced ventilation equipment, in a well sealed home?

Asked By Calum Wilde | Jul 24 17
0 Answers

Want to install mini-split need advice

Hi everyone!

Our master suite has only 1 small ac vent, none in the closet or bathroom, this makes it very uncomfortable in the summer in Florida. We have a large slider window and a really small double hung window in the bathroom. This makes windows units not a good choice as I've tried to install many without success.

We have a flat roof over this part of the house so we can't run more ac to the other rooms.

3 walls are outside walls, one wall is concrete the others are basic construction, minimal insulation and no insulation on the roof. Both windows are double pane.

Asked By jgraeff | Jul 22 17
7 Answers

What is minisplit short cycling? Turndown?

I understand that a "somewhat" oversized mini split will generally run at a more efficient rate, as opposed to an undersized mini split, which will run full-out, and therefore be less efficient. It sounds as if the problems with oversized mini splits would be 1) wasted money on oversize equipment, and 2) decreased dehumidification, due to the equipment not running enough. Am I about right, so far?

Asked By Ben Rush | Jun 25 17
3 Answers

portable dehumidifiers

Are there any that are as efficient as Santa Fe? And durable/reliable too? I need something that extracts about 40 pints a day.

Asked By charles CAMPBELL | Jul 21 17
2 Answers

Humidity and negative pressure

A customers home (zone 4 non-marine) has condensation problems (summertime) on a particular HVAC duct. Upon inspection the %RH was at 60%. There is a whole house dehumidifier hooked in with the HVAC System (Fan runs at low speed continuously) Bathroom exhaust fans are backflowing and letting in a significant amount of heat, and when opening the front door one can feel the hot air entering the house. There is no ductwork in the attic, it is all in the basement.

Asked By Jeff Classen | Jul 20 17
3 Answers

Venting for multiple appliances

Hey GBA,

I wanted to reach out to the community for a thought experiment.

The home I am building will have the following :

High efficiency Gas furnace
High efficiency Gas water heater
ERV
Central vacuum

All of these require exterior intakes and exhausts.

The house is a row house, so the majority of the side walls are attached to another house. Thus, this only leaves one spot where I can place the multitude of vent pipes. (which is pretty much a small alcove at the rear between the two houses) see attached image.

Asked By Jamie B | Jul 21 17
6 Answers

Thermostats and weather compensation in a well insulated tight house

Trying to figure out a heating strategy for the following house:
- climate zone equivalent to 4A (continental Croatia, Europe)
- 170m2 net, ground floor + 1st floor
- ~35kwh/m2 a, so well insulated
- Zehnder ERV
- underfloor radiant heating + gas boiler (also used for warm water tank)

I am trying to figure out two things:
- do I need thermostats in several rooms?
- do I need weather compensation thermometers and a regulation system that supports it (most do)

Asked By davor radman | Jul 18 17
20 Answers

Tankless, tanked, or both?

I'm in the process of trying to figure out what i'm going to do for hot water on a new custom home I just broke ground on. I don't want to say money's not an object but it's definitely not my first consideration.

A colleague of mine recommended that I explore doing a tankless gas water heater with a 10 gallon standby tank. In exploring this option I came across a Rinnai RH180 hybrid tank-tankless water heater.

Does anyone have any experience or thought about this unit...good, bath or otherwise? Thanks!

Asked By Michael Winn | Jul 7 17
7 Answers

Advice on minisplit inspector approval

I'm building a new home with Mitsubishi mini-splits. There are three units total, two 9K units and one 12K. Manual J was done and came it at 24K for heating in zone 5. The house is a simple stacked square 2 story of 847 sq. ft. each floor and a 550 sq. ft finished work shop with one 9K unit. The 12K unit is on the bottom floor and the last 9K unit is at the top of the stairs. The building inspector is not wanting to sign off on the HVAC system because he does not think that the one upstairs 9K unit will get heat into each of the bedrooms, he thinks that I need a unit in each bedroom.

Asked By Jeff Towson | Jul 14 17
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