Heat Pumps and Electric Heating - Choosing a new thermostat or is this normal
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haydenm315
02-04-09, 11:34 AM
I think I'm in the market for a new thermostat. I installed a Righttemp digital wrong temperature a couple years ago and I'm not happy with it. I have 3 separate issues with it, but I'll only go into the current one here. I'm looking into purchasing something more high end like a Honeywell. I have a heat pump with aux heat.
We recently had a good cold spell where the heat pump alone couldn't keep up. The thermostat has a jumper for auxillary heat to come on when the house temp is 2,3, or 4 degrees away from the configured setting.
If the house can't get up to the set temp without the help of aux heat, why does it shutoff a configurable amount from the set temperature and just let the heat pump run for all eternity? This doesn't seem energy efficient to me.
I think there should be some sort of logic to determine how long the heat pump has run and if it's made up any ground. If not, boost the heat pump with the aux heat until the set temperature is reached. My thermostat isn't smart enough or my thinking is incorrect.
My thoughts are that I'm blowing money when it's cold because the heat pump runs all day making up no ground, as opposed to getting the aux heat boost, reaching the set temperature and having a chance to rest. Do I have a point, or am I somehow flawed in my thinking?
I'm looking for suggestions on a thermostat upgrade. Thanks.
We recently had a good cold spell where the heat pump alone couldn't keep up. The thermostat has a jumper for auxillary heat to come on when the house temp is 2,3, or 4 degrees away from the configured setting.
If the house can't get up to the set temp without the help of aux heat, why does it shutoff a configurable amount from the set temperature and just let the heat pump run for all eternity? This doesn't seem energy efficient to me.
I think there should be some sort of logic to determine how long the heat pump has run and if it's made up any ground. If not, boost the heat pump with the aux heat until the set temperature is reached. My thermostat isn't smart enough or my thinking is incorrect.
My thoughts are that I'm blowing money when it's cold because the heat pump runs all day making up no ground, as opposed to getting the aux heat boost, reaching the set temperature and having a chance to rest. Do I have a point, or am I somehow flawed in my thinking?
I'm looking for suggestions on a thermostat upgrade. Thanks.
badtlc
02-04-09, 01:16 PM
The heat pump is not a waste while running all day. Even if it isn't maintaining the temperature, it is supplying BTUs at a MUCH cheaper price than the fossil fuel backup or electric strips. It also helps lengthen the time between when the Aux. has to be engaged.
haydenm315
02-05-09, 08:56 AM
Last month I changed the jumper from 4 degrees to 2 degrees, meaning aux heat will come on when the temperature is more than 2 degrees off the set temperature. My bill was huge. It didn't help that the utility company decided to estimate usage and overcharged by 600kwh.
I run the EPA program which drops the stat to 62 while I'm sleeping or out and 68 when people are around. It's been 10F cold so it's made it to 62 overnight or while at work and the aux has come on a lot when getting back to temp.
What you're saying is it's costing me more money to get up to temp with the aux heat as opposed to running the heat pump all day with little to no aux heat?
My friend who does HVAC... mostly freezers says it's more cost effective to use the aux heat than have the heat pump running all day and doing little more than holding it's own. Maybe he's wrong? After all, he has a furnace and stokes a fireplace. I'm not fortunate to have a cheap alternative heat source.
My wife and baby were out of town for 4 days, so I experimented with what the heat pump could handle in the cold. It was near single F digits for the majority of time. When I saw my heatpump running for a long time at a temperature, I dropped it a degree. I got all the way down to a set temperature of 60F and the heat pump was still losing ground slowly or never able to take a break.
When it's 5-10F outside, what can a heat pump maintain given that the house is plugged up good and the system is the correct size. How much above outside temperature can a heat pump handle? 40,50,60F?
I run the EPA program which drops the stat to 62 while I'm sleeping or out and 68 when people are around. It's been 10F cold so it's made it to 62 overnight or while at work and the aux has come on a lot when getting back to temp.
What you're saying is it's costing me more money to get up to temp with the aux heat as opposed to running the heat pump all day with little to no aux heat?
My friend who does HVAC... mostly freezers says it's more cost effective to use the aux heat than have the heat pump running all day and doing little more than holding it's own. Maybe he's wrong? After all, he has a furnace and stokes a fireplace. I'm not fortunate to have a cheap alternative heat source.
My wife and baby were out of town for 4 days, so I experimented with what the heat pump could handle in the cold. It was near single F digits for the majority of time. When I saw my heatpump running for a long time at a temperature, I dropped it a degree. I got all the way down to a set temperature of 60F and the heat pump was still losing ground slowly or never able to take a break.
When it's 5-10F outside, what can a heat pump maintain given that the house is plugged up good and the system is the correct size. How much above outside temperature can a heat pump handle? 40,50,60F?
badtlc
02-05-09, 10:07 AM
Yes, using the setbacks is costing you 2x (maybe more) more $$$ than running the heat pump. Setbacks only work with a heat pump when the heat pump can recover on its own.
Considering you have electric strips, you'll save much $$$ by setting the t-stat at one temperature and let it be.
The heat pump probably cannot maintain the house temperature at any reasonable level below temperatures around 20-25F. These temps make it almost essential that you leave the setpoint set and do not use setbacks. This allows the t-stat to utilize the heat pump as much as possible while using the aux. heat ONLY when necessary to maintain the temp.
Considering you have electric strips, you'll save much $$$ by setting the t-stat at one temperature and let it be.
The heat pump probably cannot maintain the house temperature at any reasonable level below temperatures around 20-25F. These temps make it almost essential that you leave the setpoint set and do not use setbacks. This allows the t-stat to utilize the heat pump as much as possible while using the aux. heat ONLY when necessary to maintain the temp.