Heat Pumps and Electric Heating - 2 questions: blowing cold air and cost options
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Cold in NC
02-14-06, 06:28 AM
What a great forum! Thanks for the help to everyone.
I have two questions. I've never had a heat pump before and so far, have mixed feelings about it. I've asked around here and my experiences seem to be typical so it doesn't sound like my heat pump is doing anything unusual. So, first question:
1) During the winter, when my heat pump isn't using the electric backup to heat the house, unless the temperature is at or above the desired home temperature, it blows cold air through the vents. Most houses around here have heat pumps and I've asked lots of people if this is normal -- they all say it is. In the interest of cost, I try to keep the house set at about 65 degrees. When I had forced air (oil) heat, this was more than enough to keep us warm (as a matter of fact, we usually kept the heat set at 60*, lived in the Northeast, and wearing just a normal sweater to add to warmth, it was absolutely fine unless it was below about 15 degrees out). It feels freezing in this house with the cold air blowing! In the interest of costs, we really don't want to set the temperature higher. Would closing vents in the rooms we're using help so that cold air isn't blowing right on us, or would that be a mistake?
2) Our heating bill was pretty high for the last couple of months, though from what I've read & heard, it's low compared to many. The highest bill was $216 (1500 sf house). I had always heard that leaving a house at a constant temperature was more economical than turning the heat up and down to warm and cool the house. Which is true? Because our heating bills were higher than we wanted, we switched this month to just leaving it set at 65 degrees. We were turning it way down at night and up in the morning to heat the house up. By using a constant temperature setting, will we be in for a rude shock on our next heating bill or is this a good idea?
Thanks!
Anne
I have two questions. I've never had a heat pump before and so far, have mixed feelings about it. I've asked around here and my experiences seem to be typical so it doesn't sound like my heat pump is doing anything unusual. So, first question:
1) During the winter, when my heat pump isn't using the electric backup to heat the house, unless the temperature is at or above the desired home temperature, it blows cold air through the vents. Most houses around here have heat pumps and I've asked lots of people if this is normal -- they all say it is. In the interest of cost, I try to keep the house set at about 65 degrees. When I had forced air (oil) heat, this was more than enough to keep us warm (as a matter of fact, we usually kept the heat set at 60*, lived in the Northeast, and wearing just a normal sweater to add to warmth, it was absolutely fine unless it was below about 15 degrees out). It feels freezing in this house with the cold air blowing! In the interest of costs, we really don't want to set the temperature higher. Would closing vents in the rooms we're using help so that cold air isn't blowing right on us, or would that be a mistake?
2) Our heating bill was pretty high for the last couple of months, though from what I've read & heard, it's low compared to many. The highest bill was $216 (1500 sf house). I had always heard that leaving a house at a constant temperature was more economical than turning the heat up and down to warm and cool the house. Which is true? Because our heating bills were higher than we wanted, we switched this month to just leaving it set at 65 degrees. We were turning it way down at night and up in the morning to heat the house up. By using a constant temperature setting, will we be in for a rude shock on our next heating bill or is this a good idea?
Thanks!
Anne
TigerDunes
02-14-06, 07:45 AM
Cold in NC
A couple of questions and observations.
You live in an area of the country that has a moderate climate that is perfect for a heat pump. Tell us about your system- age, model, brand, size. When was unit last serviced? Are you changing your filters regularly?
1.When you say unit is blowing cold air, what is the supply temp at your vent and what is outside temperature? (you can purchase an inexpensive digital thermometer to get these readings.) Take these readings over a period of several days in the early AM, mid day, late afternoon, and before you go to bed to build a little history. Note if aux heat is in operation-this should be indicated on your thermostat.The newer HP systems give you a supply temp in low 90s minimum and should be warm to your hand. It is true that a heat pump's supply temp is not as high as a forced fossil fuel system like oil or gas. Keep in mind this is mechanical heat produced by a refrigerant. Your electric rate in NC should be very favorable. I don't like the idea of closing vents-usually false economy and might cause damage to your system.
2. Tell us about your home's insulation properties-good or above average? I agree that $200+/mth electric bill seems high for a 1500 sq ft home. How many people live in home? Heat pump's aux strip heats are usually engaged when operation in normal mode can not maintain stat temp-this outside temp is called your balance point. This occurs on those extra cold days and/or cold mornings. However, the SE has had above average winter temps this year. If you set your stat back in the evenings 2 or more degrees, heat strips are also normally activated in the recovery mode.
My initial thought is your system's refrigerant charge may need to be checked. Is this your first winter in this home?
My opinion.
A couple of questions and observations.
You live in an area of the country that has a moderate climate that is perfect for a heat pump. Tell us about your system- age, model, brand, size. When was unit last serviced? Are you changing your filters regularly?
1.When you say unit is blowing cold air, what is the supply temp at your vent and what is outside temperature? (you can purchase an inexpensive digital thermometer to get these readings.) Take these readings over a period of several days in the early AM, mid day, late afternoon, and before you go to bed to build a little history. Note if aux heat is in operation-this should be indicated on your thermostat.The newer HP systems give you a supply temp in low 90s minimum and should be warm to your hand. It is true that a heat pump's supply temp is not as high as a forced fossil fuel system like oil or gas. Keep in mind this is mechanical heat produced by a refrigerant. Your electric rate in NC should be very favorable. I don't like the idea of closing vents-usually false economy and might cause damage to your system.
2. Tell us about your home's insulation properties-good or above average? I agree that $200+/mth electric bill seems high for a 1500 sq ft home. How many people live in home? Heat pump's aux strip heats are usually engaged when operation in normal mode can not maintain stat temp-this outside temp is called your balance point. This occurs on those extra cold days and/or cold mornings. However, the SE has had above average winter temps this year. If you set your stat back in the evenings 2 or more degrees, heat strips are also normally activated in the recovery mode.
My initial thought is your system's refrigerant charge may need to be checked. Is this your first winter in this home?
My opinion.
Cold in NC
02-14-06, 12:00 PM
Many thanks for your help! Of course, what it really points out is how little I know about this stuff. Ugh....I have a Ph.D. that is totally useless when it comes to anything involving mechanics, physics, etc.
I'll go buy a thermostat to take the readings you suggested. Though I do live in NC, I live in the mountains of Western NC (which I should have pointed out). We have, indeed, had a warm winter. Many days the temperature indoors was mild with no heating used at all -- with the thermostat set at 60, the indoor temp still ranged around 66* and none of the cold air blowing on me while I work in my office. But it does get cold at night, often down to the 20* range (and some nights/early mornings even below 20*).
We're trying to avoid much use of the aux heat -- we understand that use of it makes the cost go up. (I note that I went into the bathroom last night and wasn't pleased when I felt warm air coming out of the vent! The thermostat was set at 65* but I believe the outdoor temperature went down into the 20's.) The green light (indicating aux use) is rarely lit when I check it if we maintain the constant temperature, but I do often get the cool air blowing out of the vents, making it feel colder in here than it actually is. (I note that I just gave up and turned the heat up because I was freezing.....the aux heat wasn't on for long, now the house is at a comfortable 68*, and the cold air has stopped blowing on me. It's a sunny 48* outside now.)
Wish I could tell you more about the insulation. It's a new home, all on one floor. There is a cathedral ceiling in the living room area (living, dining, kitchen). Most of the windows are double-glazed, double-hung tilt. A couple are casement. Though we would have liked more windows in the house, from an energy perspective, we're happy with the number we have. The front of the house faces south and the majority of the windows are on that side, though there are two sets of French doors on the back of the house. The whole house gets sun all day, though. (Amazingly enough, our A/C bills are quite low, again thanks mostly to being in the mountains and having few above 90* days.) The NC insulation/energy code is the "International Energy Conservation Code" if that helps. I'd say the insulation is good, though knowing the builder, he didn't go over and above code. There are only two adults living in the home (and 2 dogs). Neither of us likes the house hot!
Definitely won't close vents based on what you said! I'll have to run out later and check the make of the pump (I've forgotten at this point). Since I'm supposed to be preparing a report, better get back to work!
Many thanks for your help! When I get the readings, I'll come back to see if we can figure this out. Thanks again!
Anne
I'll go buy a thermostat to take the readings you suggested. Though I do live in NC, I live in the mountains of Western NC (which I should have pointed out). We have, indeed, had a warm winter. Many days the temperature indoors was mild with no heating used at all -- with the thermostat set at 60, the indoor temp still ranged around 66* and none of the cold air blowing on me while I work in my office. But it does get cold at night, often down to the 20* range (and some nights/early mornings even below 20*).
We're trying to avoid much use of the aux heat -- we understand that use of it makes the cost go up. (I note that I went into the bathroom last night and wasn't pleased when I felt warm air coming out of the vent! The thermostat was set at 65* but I believe the outdoor temperature went down into the 20's.) The green light (indicating aux use) is rarely lit when I check it if we maintain the constant temperature, but I do often get the cool air blowing out of the vents, making it feel colder in here than it actually is. (I note that I just gave up and turned the heat up because I was freezing.....the aux heat wasn't on for long, now the house is at a comfortable 68*, and the cold air has stopped blowing on me. It's a sunny 48* outside now.)
Wish I could tell you more about the insulation. It's a new home, all on one floor. There is a cathedral ceiling in the living room area (living, dining, kitchen). Most of the windows are double-glazed, double-hung tilt. A couple are casement. Though we would have liked more windows in the house, from an energy perspective, we're happy with the number we have. The front of the house faces south and the majority of the windows are on that side, though there are two sets of French doors on the back of the house. The whole house gets sun all day, though. (Amazingly enough, our A/C bills are quite low, again thanks mostly to being in the mountains and having few above 90* days.) The NC insulation/energy code is the "International Energy Conservation Code" if that helps. I'd say the insulation is good, though knowing the builder, he didn't go over and above code. There are only two adults living in the home (and 2 dogs). Neither of us likes the house hot!
Definitely won't close vents based on what you said! I'll have to run out later and check the make of the pump (I've forgotten at this point). Since I'm supposed to be preparing a report, better get back to work!
Many thanks for your help! When I get the readings, I'll come back to see if we can figure this out. Thanks again!
Anne
Pendragon
02-15-06, 03:24 PM
I'll go buy a thermostat to take the readings you suggested. Though I do live in NC, I live in the mountains of Western NC (which I should have pointed out). We have, indeed, had a warm winter. Many days the temperature indoors was mild with no heating used at all -- with the thermostat set at 60, the indoor temp still ranged around 66* and none of the cold air blowing on me while I work in my office. But it does get cold at night, often down to the 20* range (and some nights/early mornings even below 20*).
Anne
Just guessing here, but it sounds like your heat strips are working, but only in aux mode. They should also come on when the unit is defrosting, that may be the cold air you are feeling, the unit is defrosting but the heat strips aren't on.
Next time you feel cold air, go outside and listen to the unit, is the fan _not_ running? If it's not running, it's probably in defrost and the heat strips should be on.
Anne
Just guessing here, but it sounds like your heat strips are working, but only in aux mode. They should also come on when the unit is defrosting, that may be the cold air you are feeling, the unit is defrosting but the heat strips aren't on.
Next time you feel cold air, go outside and listen to the unit, is the fan _not_ running? If it's not running, it's probably in defrost and the heat strips should be on.