Heat Pump, maintenance & how to live with them

[PMG]

We just bought a house with a heat pump and are needing some advice. We’ve done some googling, but most of what we’re finding is put out by heating companies. I haven’t been able to find our model numbers manual yet.

Forgive me if I use the wrong terminology!

It’s in a small town, I called around and found the company that installed our unit in 2014.  They said there hasn’t been a service call on it since. “Isn’t that great! Perfect machine!” I asked about filters, we’ve found and changed the intake filter located in the house, but the air handler is in a tight dirt crawl space.  My spouse crawled back in and found that the filter door is screwed shut and it’s obviously never been changed.  I asked about it and the gentleman told me that it doesn’t need changed (is empty), they intentionally set it up to just have the one filter in the house.  He was looking at the data on our machine and knew what size the filter should be.  Then I asked about routine maintenance and he assured me that if we weren’t experiencing any issues then we didn’t need to do anything.

Our googling tells us that we ought to have the outside unit (and perhaps the inside air handler) cleaned and serviced annually.  When the gentleman from the company was so emphatic that it didn’t need anything I certainly wasn’t going to offer to pay him to come out and tell me the same thing!  I can call the other company in town, but I know they are usually very careful not to poach customers from each other.  I’d be ok with pushing them to work on our machine if they responded to my questions with “Oh! yes, we clean the coils and check the fan and the thermostat…” etc. 

1.) Is it something we can DIY?  I found a youtube video showing how to turn the power off, remove the cover, clean things.  It looked pretty doable, but I don’t know enough to know how to spot if something is wrong.

2.) Is the following normal? We think it is functioning fine. It blows air and turns on and off and the auxiliary heat is not on so it must be the pump that is moving heat. We set the house at 65 and have a separate thermometer that shows it is indeed 65. But, it is so uncomfortable!  It’s been in the 20s at night, which from our googling shows that the heat pump isn’t very efficient at those temps and that it has to work to keep up, so it keeps blowing constantly. The one night we had in the 40s was much nicer! We’ve added little directors to reroute the air and that’s helped a bit, but this isn’t pleasant heat! Our last couple places have had gas heat and this has been a shocking change!  Is this normal? Do we just have to suck it up and get used to it?! I understand that the air coming out is warmer, and feels cool because it’s cooler than my body temperature. We’re expecting twins and the thought of two little babies sleeping with cool air blowing on them all winter next year just doesn’t sound nice at all!

3.) How does a heat pump work with back up heat? We’ve talked about some day getting gas logs in the fireplace.  Some day might come quickly due to how little we like this heat, and maybe with kids in the house it’s prudent to have an emergency heat source in case of power outages. Anyone have input on how the two would work together?  I assume the thermostat measures the actually temperature in the house and adjusts how much the heat pump runs according to that, so back up heat would mean the heat pump automatically runs less without adjusting it.

Thank you. We're gonna be a little anxious until we get the power bill!

[nereo]

The heat coming out of a heat pump is not going to feel "warm" to you, especially if you have it set at 65ºF.   Unlike resistance-coil heating or a furnace/HVAC system, the air that exists is the temperature you want the room to be (+ 1-2ºF).  You aren't blowing hot air into the room and having that mix with the cold air to ultimately get the temperature you desire.  Instead, heat pumps are circulating more air, more often.
Many people are used to the heat resulting in a blast of hot air from vents - instead heat pumps try to make the entire room be exactly the same temperature by circulating the air.  It's waaaaay more efficient, but might not be what you desire.

As you've already done, you can redirect the air somewhat. Beyond that the original placement matters a lot.

As for your baby daughters... I really don't think this is anything to worry about.  There's nothing unsafe about a 65ºF light breeze going over an infant's body.  One nice thing about heat pumps is they act as a whole-room air filter and humidity control unit as well.

You can certainly use supplimental heat, but almost everything (unless you have hyour own supply of firewood) is going to cost considerably more.  If you use a gas stove to 'heat up' the room your heat pumps simply won't kick on.  You can put them in 'fan' mode to circulate the air around your house, but again you don't seem to like that feeling.  FWIW we use a pellet stove which puts out a ton of heat during cold days, and have air circulated by heat pumps.  Then when we aren't home or at night after the stove goes out the heat pumps keep it at a nice temperature (we use 62ºF).

As for cleaning - you'd need to look at what your specific model ios, and read what the manufacturer says about it.  Ours came with a free cleaning at year 1 as part of our install deal, so we haven't needed to do anything.  In general they need very little maintenence when installed correctly, but I'd give it a once-over each year per the manufacturer's recommendations.

[Sibley]

I've lived with heat pumps in the past, and the biggest thing I noticed was that I felt cooler than I expected to at times. What you describe is exactly what I remember. So I put on a sweater or blanket. I know you can't put blankets on infants, but you might want to be prepared to add an additional layer onto them in whatever way is safe. Might not be needed, but if the baby is cold they're not going to be shy about letting you know.

[Ecky]

There is indeed basically no maintenance for a heat pump, other than cleaning the filter. Just as an example, when was the last time you maintenanced your car's air conditioner? That's also a heat pump, and in those you basically just clean the evaporator filter and, if it leaks, get the leak fixed and fill it back up with refrigerant. If the fan or thermostat fail, you'll know it, because it will stop working.

Modern and highly efficient heat pumps have variable speed pumps in them and are designed to run 24/7 rather than cycling on and off, because it's more efficient.

I suspect your sensation of comfort has most to do with relative humidity and the constant movement of air (rather than short bursts of much warmer air), but I'd like to hear others' opinions.

As for cost, heat pumps can vary drastically in efficiency. Central units tend to be less efficient than mini-splits, presumably due to the large overhead of large fans and the heat loss through ducting. New units can be as much as 2-3x more efficient than older ones, and a lot of improvements have come in the last 5-10 years.

I have a spreadsheet that calculates the cost of various heating methods based on local prices. We have high-ish electricity costs (around 16 cents per kwh) and it tends to be that a very good heat pump is (based on average efficiency) marginally more expensive than natural gas and around the same as wood. Oil is around 50% more expensive, propane costs around 2.5-3x as much to heat with, and electric resistive is a little more than propane.

~

Anecdotally:

When we bought our mini-split last year it was the most efficient one on the market. It's responsible for the heating of half of our house, with a pellet stove covering the other half. Our home is in Vermont and around 1250sq ft, and built in the 60's without heavy emphasis on insulation.

During the transitional seasons (when it's most efficient) we didn't even notice a change in our electricity bill - keeping the house 10-30F warmer than outside was $x per month at most, and we didn't fire up the pellet stove unless it dropped below 40 outside.

In winter, our electrical bill has increased $80-100, with outside temperatures typically being between 10-30F and with some days being as cold as -10F. The pellet stove by comparison burns $100-120 in pellets during the coldest month. The side of the house with the heat pump is considerably more pleasant than the one with the pellet stove - the pellet stove is not controlled by a thermostat but cranks out pretty consistent heat, is noisy, requires the addition of fuel every day, and needs half an hour of cleaning soot and ash weekly. Its fan circulates a lot more air in the room which can feel a bit chilling to exposed skin. If we planned to stay here forever I would not hesitate to put a second mini-split in and reserve the pellet stove only for those weeks below maybe 10F.

[lhamo]

Don't have a heat pump but I love our gas fireplace!  It is saving me from freezing at the moment because DH just returned from China and -- out of an abundance of caution -- doesn't want us to use the central heat just in case he's been exposed to Covid-19 and it MIGHT get into the vents (he's self-quarantining in the basement).  It has also been great to have a source of heat that continues to work during the occasional power outage -- we've only had one or two, but we were able to sit warmly by the fire with a bunch of candles to wait them out comfortably.

I know many people are advocating getting rid of gas heat and cooking due to climate change concerns, so maybe look at efficient pellet systems, too.  But I do love the convenience of gas so while we have it in our house already I will continue to use it.  We drive pretty minimally compared to most people and have a hybrid, so at least we are doing something right.

[PMG]

OP here.  Thank you all for taking the time to respond. 

This makes a lot of sense. I found the units manual and it doesn’t have cleaning instructions, but the website for the maker does suggest at least annual cleaning/maintenance.  We’ll keep reading up and see what we decide!  I did get a good look inside the outside unit yesterday and it looks really good.  I could spot some grass clippings that I think would wash out with just a spray with the garden hose, but in general it was clean and there is no encroaching shrubbery. 

In truth it took a bit of talking to get my partner to 65*! He’d been set on 62* for the first several days and I just couldn’t handle that. 65 is muuuuch more doable! I’d like to get him up to 68!  We generally kept our old house around 65, but that was gas heaters and very easy to warm it up for an hour or two in the evening and let it cooler at night or if we were gone all day.  This heat pump is a different beast.

Our main motivation for gas logs is largely because we’re coming from gas heat and there’s an empty fireplace where it would look lovely and is so quick and easy! Whatever we get would have to be tank/delivery, so we need to see what is available.  Pellet stove is an interesting option.  I may do some research. A regular wood stove seems like a lot of work, and we’d have to get a full out chimney added on, or the special pipe, so it seems like it could be expensive start up costs.  We don’t have access to our own wood. 

Last night the temps were right around 40 and I didn’t notice the heat pump at all.  Could be because I was exhausted and slept like a log, but I think it ran a lot less, I expect we’ll be a lot more comfortable as spring comes.  Then come summer. Neither of us likes AC... but I am really looking forward to having the heat pump combat humidity.  Even in winter, that’s wonderful!  Our rental house always seemed to have damp corners. 
 
Again, thank you for explaining things and good ideas.