DIY ventilation heat exchanger - Page 20

AC_Hacker · 01-06-12, 12:45 AM

Quote:

Originally Posted by ThomSjay

The 'stale air' temp drop improved to 30 deg F., but the 'incoming air' DeltaT got worse. Why would that be? Previous to that the DeltaT was approx. 20 degF on both. Go figure.

There were so many thing that were changed between experiments that it would be pretty risky to compare results from one day of testing a particular HX to another day of testing a completely different HX.

Perhaps we will repeat the experiments with an effort given to minimizing variables.

I'm planning to make another HX for testing, and I wouldn't be surprised if Mike intends to test other configuration(s) too.

-AC_Hacker

ham789 · 01-06-12, 01:36 AM

I want to measure differential air pressure near zero.
I have a pressure gauge, but it has a resolution of only
0.01" of water.
I tried building a gauge using a resistor heat source with a thermocouple
on either side connected in a bridge. Stuffed that into the side of
a plastic tube. Air flow causes differential heating in the thermocouples.
It sorta works. I get about 200mV of bridge imbalance for a differential
pressure of 0.04" water. But the time constant is half a minute.
It's not temperature compensated, it drifts. I could use it to measure
zero, pressure balance...but I'd like to make it better if it's easy.

What do you guys use to measure low pressures?

ham789 · 01-07-12, 09:37 AM

I stuck an experimental HRV through a window in an unused bedroom.
The bedroom opens into the hallway just beneath the gas furnace
return vent and the thermostat.

It's a small coroplast unit about 4" square by 2 feet long.
I'm guessing it's 15-20CFM. Air velocity varies considerably
over the port area. I'm gonna have to build some kind of
"air straightener" tube before I an get an accurate flow
measurement.

AC Hacker posted some pix of it last week.

Since I turned it on, the place smells less stuffy. I like the effect.
Problem is that I feel COLD!!!
Temperature is still 64F. Humidity still about 50%.
I even turned the thermostat up to 65F. Better, but I still feel cold.

I figured it was all in my head, 'till my neighbor came over and commented
that the place felt colder than usual.

Inside temperature and humidity have not changed.
We're having record warm weather outside.
What mechanism can make it "feel" colder when the numbers are the same???

MN Renovator · 01-07-12, 09:44 AM

It's weird that you mention that because yesterday I had my windows open and the temperature was 3 degrees higher and the humidity was 1% lower but it felt like it had gotten colder. It aired out the afternoon bacon frying smoke though. Is it a draft thing? I wonder if the air continues to move at a faster rate than normal after the windows are closed because now its the next day and things feel normal and not cold again even though its below the temperature it was yesterday in here.

Xringer · 01-07-12, 10:03 AM

Welcome ham789 and have a Great 2012!
73,

MN Renovator · 01-07-12, 10:11 AM

I know a few people who use BP meds or other meds that can reduce blood flow who say it makes them feel more susceptible to cold. If you are warm with a workout, it sounds like a blood flow thing. ...then again same thing can happen if you are cold too since moving around can warm you up pretty quickly.

ThomSjay · 01-10-12, 10:17 PM

Quote:

Originally Posted by MN Renovator

It's weird that you mention that because yesterday I had my windows open and the temperature was 3 degrees higher and the humidity was 1% lower but it felt like it had gotten colder. It aired out the afternoon bacon frying smoke though. Is it a draft thing? I wonder if the air continues to move at a faster rate than normal after the windows are closed because now its the next day and things feel normal and not cold again even though its below the temperature it was yesterday in here.

Were you comparing out door air to indoor air?

I have noticed that in the shade it feels cooler because of the larger amount of moving air that moves the heat from you. Indoors the heat would slowly move away from you into the space (small) that you are in. And there is no solar effect.

AC_Hacker · 01-11-12, 12:29 AM

This thread is about building a Heat Recovery Ventilator...

The Billard Room would be the perfect place to discuss subjective effects of blood pressure meds, etc.

-AC_Hacker

MN Renovator · 01-11-12, 09:19 AM

Quote:

Originally Posted by ThomSjay

Were you comparing out door air to indoor air?

I have noticed that in the shade it feels cooler because of the larger amount of moving air that moves the heat from you. Indoors the heat would slowly move away from you into the space (small) that you are in. And there is no solar effect.

Yes, indoor air after the windows were closed, so its fresh air that recently came from outside.

abogart · 01-18-12, 08:56 AM

I like the dehumidifier idea (posted near the beginning of this thread). What about placing the evaporator coil in the cold/stale air going out, and the condenser in the cold/fresh air coming in? Basically putting a small HP on the outside air portion of the HRV system. Dehumidifiers don't use much electricity. It seems to me like that would greatly improve energy recovery. The HP would not only be using the heat energy from the incoming air from outside, but also the heat that the HRV doesn't recover. To me, it seems like this system would produce much more heat than an air-air HP located outside. Ductwork could be made to reverse the system during the warmer months.

EDIT: oops, got my condensers and evaporators confused

01-06-12, 01:36 AM	#192
ham789 Helper EcoRenovator Join Date: Dec 2011 Location: tigard, oregon Posts: 42 Thanks: 0 Thanked 4 Times in 4 Posts	How do you measure differential pressure? I want to measure differential air pressure near zero. I have a pressure gauge, but it has a resolution of only 0.01" of water. I tried building a gauge using a resistor heat source with a thermocouple on either side connected in a bridge. Stuffed that into the side of a plastic tube. Air flow causes differential heating in the thermocouples. It sorta works. I get about 200mV of bridge imbalance for a differential pressure of 0.04" water. But the time constant is half a minute. It's not temperature compensated, it drifts. I could use it to measure zero, pressure balance...but I'd like to make it better if it's easy. What do you guys use to measure low pressures? Attached Thumbnails

01-07-12, 09:37 AM	#193
ham789 Helper EcoRenovator Join Date: Dec 2011 Location: tigard, oregon Posts: 42 Thanks: 0 Thanked 4 Times in 4 Posts	Why do I feel cold? I stuck an experimental HRV through a window in an unused bedroom. The bedroom opens into the hallway just beneath the gas furnace return vent and the thermostat. It's a small coroplast unit about 4" square by 2 feet long. I'm guessing it's 15-20CFM. Air velocity varies considerably over the port area. I'm gonna have to build some kind of "air straightener" tube before I an get an accurate flow measurement. AC Hacker posted some pix of it last week. Since I turned it on, the place smells less stuffy. I like the effect. Problem is that I feel COLD!!! Temperature is still 64F. Humidity still about 50%. I even turned the thermostat up to 65F. Better, but I still feel cold. I figured it was all in my head, 'till my neighbor came over and commented that the place felt colder than usual. Inside temperature and humidity have not changed. We're having record warm weather outside. What mechanism can make it "feel" colder when the numbers are the same???

01-07-12, 10:03 AM	#195
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	Welcome ham789 and have a Great 2012! 73, __________________ My hobby is installing & trying to repair mini-splits EPA 608 Type 1 Technician Certification ~ 5 lbs or less.. Last edited by Xringer; 01-11-12 at 08:15 PM.. Reason: Foolish reason

01-11-12, 12:29 AM	#198
AC_Hacker Supreme EcoRenovator Join Date: Mar 2009 Location: Portland, OR Posts: 4,004 Thanks: 303 Thanked 723 Times in 534 Posts	This thread is about building a Heat Recovery Ventilator... The Billard Room would be the perfect place to discuss subjective effects of blood pressure meds, etc. -AC_Hacker __________________ I'm not an HVAC technician. In fact, I'm barely even a hacker...

01-07-12, 09:44 AM	#194
MN Renovator Less usage=Cheaper bills Join Date: Nov 2010 Location: Minneapolis, MN Posts: 939 Thanks: 41 Thanked 116 Times in 90 Posts	It's weird that you mention that because yesterday I had my windows open and the temperature was 3 degrees higher and the humidity was 1% lower but it felt like it had gotten colder. It aired out the afternoon bacon frying smoke though. Is it a draft thing? I wonder if the air continues to move at a faster rate than normal after the windows are closed because now its the next day and things feel normal and not cold again even though its below the temperature it was yesterday in here.

01-07-12, 10:11 AM	#196
MN Renovator Less usage=Cheaper bills Join Date: Nov 2010 Location: Minneapolis, MN Posts: 939 Thanks: 41 Thanked 116 Times in 90 Posts	I know a few people who use BP meds or other meds that can reduce blood flow who say it makes them feel more susceptible to cold. If you are warm with a workout, it sounds like a blood flow thing. ...then again same thing can happen if you are cold too since moving around can warm you up pretty quickly.

01-18-12, 08:56 AM	#200
abogart Efficiency Afficionado Join Date: Jan 2012 Location: Michigan, US Posts: 68 Thanks: 21 Thanked 6 Times in 4 Posts	I like the dehumidifier idea (posted near the beginning of this thread). What about placing the evaporator coil in the cold/stale air going out, and the condenser in the cold/fresh air coming in? Basically putting a small HP on the outside air portion of the HRV system. Dehumidifiers don't use much electricity. It seems to me like that would greatly improve energy recovery. The HP would not only be using the heat energy from the incoming air from outside, but also the heat that the HRV doesn't recover. To me, it seems like this system would produce much more heat than an air-air HP located outside. Ductwork could be made to reverse the system during the warmer months. EDIT: oops, got my condensers and evaporators confused