how to protect heat pump compressor
Just had Mitsubishi Hyperheat pump system installed in Minneapolis condo (Climate zone 6B). Works like a charm, very efficient, heats quietly and very economical. However like all good things in life, it presents a challenge in unusual situations. The inverter is located on condo balcony 7 stories up so the condensation in the heat mode (running about 4+ gallons daily in recent high humidity cold) has to go somewhere. Not a problem if in your back yard but we don’t have that luxury. Best I can do is have a 4 gallon flat pan under the compressor to collect it before it spills over the balcony edge. An onerous task to empty and dispose of, to say the least, and not all that guaranteed, in that it does tend to overflow the pan and/or freeze on the deck.
My basic question is: does anyone have any ideas to handle the condensate in a secure, efficient manner? This system is too good to have a seemingly insignificant problem intrude.
Thanks,
Longjohnsilver
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Replies
Vaporize it! get a little misting pump and spray it out finely into the air. maybe it’ll even turn to snow.
Where does water go when it rains? Send the condensate there.
Balcony under roof 0f condo above; rain does not fall on our balcony. Actually, its only in heat mode that it condenses on outside appliance, i.e. your rain is then snow.
Do all the units have heat pumps on the balconies?
Walta
Nope. I'm an early adopter on heat pumps in this complex. Hard to believe that with all the complaints of high electric bills I hear.
Do you have bath vents, a dryer vent or kitchen vent exhausting near the balcony? If so, you may be able to use the same pathway as the ductwork to bring a condensate line into the condo and connect it to the condensate line at the air handler, or have it drain near the washing machine or dishwasher (if allowed.) Or, do you have an air conditioning duct hidden behind a soffit that dead-ends at the outside wall near the balcony? If so, you may be able to hide a condensate line in that soffit. I’m assuming that the floors of the building are concrete and that all ductwork is hidden behind soffits, and not between the floors. Is the outside unit sitting on the balcony, or is it mounted to the wall? If sitting on the floor, it might be challenging to get the condensate to go up a vertical pipe. You could use a condensate pump but it would be subject to freezing conditions. It would be ideal if the outside unit was mounted high enough to get the condensate inside via gravity. Edit: If you have a non-load bearing wall abutting the balcony, you could bring the condensate line into the condo via that wall, if you can run it to a suitable drain.
outside condensate is going to be ice in minutes, then melt when the temps rise. I would probably try a shallow pan that extends to the outside edge of the balcony
There’s a chance that this would cause a problem with the condo association. There are 6 condo units below this unit, as well as whatever is on the ground, which may be landscaping, a sidewalk, or parking. One solution would be for the association to get onboard with some kind of downspout that all of the units could tie into in order to convey the water to a safe place at ground level. But my guess is that the OP is an early adopter of heat pump technology in his building and the association is not at the point where they need to invest in a solution for heat pump condensate.
Precisely correct on all points!
That would be fine with me but not the neighbors (nor Association) contending with ice on sidewalk below. As temporary stop-gap I am collecting condensate directly from compressor and yes, it does freeze fairly quickly. Switching pans, thawing 4 g chunks of ice and still contending with icy balcony deck is a pain.
All terrific speculations and suggestions. The inverter compressor is on the balcony (concrete) floor and the HVAC installers have tried to persuade against trying to pump condensate through piping via duct soffit in the unit due to freezing (as you point out). Heating coil in pipe, etc. is a hazard they say is to be avoided (the condensate pump/pipe traverses 8' vertical and ca. 17' horizontal before entering unit). I've been searching for appropriate evaporation pans with heating coil to go under compressor to collect condensate and evaporate it with heat/compressor fan. That, so far, seems to be the most effective, economical and non-intrusive add-on to system.
It takes 8000 BTU to evaporate a gallon of water. You could well end up using more energy for that than for heating.
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Have the condenser pan hole drain into a small condensate pump. Run hose from pump discharge to wherever you want to dump condensate- best is through a hole in the wall to inside of condo. Wrap outside pump and hose with temp activated heat tape so the whole contraption does t freeze when pump is not running.
Thanks for suggestion, however, the Association would not accept another hole (beyond the present connection from outside compressor to inside air handler in apartment).
When hauling water in batches it seems like a lot, but usually it is just a drip. Obviously if it lands on the sidewalk it is a problem, so can that be avoided? Where does rain naturally drain? People keep talking about water, but in a month this is ice. Big block of ice
You are correct to say that condensate comes in drips but adds up to gallons over the day/night. The Association does not accept ANY alteration/addition to exterior of building. The rain/snow falls where it does, no drain system. Adding a drain system is out of question, and "draining" the condensate over the edge of balcony will only accumulate on neighbors window sills/balcony or further down on sidewalk and driveway.
Have you talked to your condo association? You seem to be assuming a lot about how they're going to respond.
I think your best bet is to find he closest spot where rain falls and send the water there. Sending it inside is a mistake.
I think you're right about sending it inside. Yes, I have spoken with Association in addition to going through the application process. Their rules are iron-clad. See my #18 response re: rain.
I know this forum specializes in building advice and not legal advice, but you may want to read your actual condo agreement and possibly even consult a lawyer. They may be overstepping.
If you have the right to install the unit, giving the water a place to go is part of the installation.
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Usually the issue is with the condensation from the air handler on the inside.
DC,
I don't know where my head was. Long day.
Agreed. However, our hyper heat pump in heat mode needs condensate relief. The system in a/c mode is no problem since the indoor air handler has condensate drain close at hand. Only problem there would be due to lax maintenance and clogged condensate line --- which I intend never to happen.
You're advice to consult an attorney is well-placed. We had one review the by-laws before purchasing the unit and it clearly gives the association power over remodels, etc. However I find myself with a problem on my hands (condensate on the balcony) because the management company had not idea about the ins/outs of heat pumps, hence their green-flagging my application to association board. Contesting it now will be defeated by the by-law provisions on alterations to common areas of condominium (i.e., outside walls, no gutters, neighbors' units, etc etc etc).
They gave me the right to install the unit, but a by-law provision as innocuous as no balcony flower pots water dripping down on neighbors, sidewalks, etc. allowed.
Giving you permission to install the heat pump without knowing what it would entail was their mistake, they're trying to turn it into your problem. Keep that in mind as you proceed.
That said, here's the technical challenge you need to solve. Wherever you end up routing the water, it has to flow by gravity until either it reaches its final destination, or until it reaches an indoor place where you can have a condensate pump without it freezing. In order to flow freely, the pipe has to be sloped at exactly 2%, which is 1/4" per foot or 2cm per meter. Maintaining that slope is typically the principal challenge in routing a drain pipe. You probably also need at least a 1" diameter pipe to avoid nuisance blockages.
Where does that pipe go? It either goes to a sanitary drain, a storm drain, or a condensate pump that pumps it into one of those two places.
If you want to take it indoors, probably the best approach is to have a cabinet or other means of concealment, with a condensate pump as close to the outdoor unit as you can get it. Then pump the condensate to wherever the indoor unit drains. The hose used by the pump can be fished through the walls to a certain extent, but you're probably looking at some drywall work. How does the tubing from the outdoor unit get to the indoor unit? You probably want to follow that path if you can.
Here's a bit of information that I've left out concerning our condo building: its origins. This is the only residential building, I believe, in the U.S. which started its life as a concrete grain elevator back in 1916. It was developed as a residence in 1982-83 with exterior walls of 12"+ concrete. Hence, disturbing that profile is the last thing that will be permitted.
I agree with your advice to follow the path of the tubing going from outside inverter to indoor air handler condensate drain. My solution for the installation of the heat pump was to utilize a bizarre feature of the development of the condos: the ducted heating system (electric) sent ducts out through the concrete envelope under the balcony drop-down ceiling back into the building to interior rooms. This avoided disturbing concrete walls in the interior (you have to imagine the entire complex consists of 20' round rooms) which are obviously load-bearing for 12 floors. The adaptation to the heat pump bringing the heat via tubing into the unit was accomplished by drilling a 3" hole in the partition (non-concrete) next to the duct work for the tubing going out over the balcony under the drop-down insulated ceiling. This is the route I'd prefer. Once done, no muss no fuss with regular maintenance, just as in the case of A/C condensate. However, the resistance I'm getting is from the installer: they obviously would love to spread the word on heat pumps in buildings with expensive resistance electric heat. But their aversion to a failure of pumping potentially frozen condensate is a red flag for them. We'll see. I'm compiling a record of condensate discharge collected (most of it anyway) with daily temperature and humidity figures. In the three months of the current heating season, we've enjoyed steady, efficient and very economical heat roughly half of what we've spent for this period over the past 17 years. [warm el nino effect has helped] Cold climate hyperheat pumps are the future.
Nevermind. No need to even approximate doxxing.
So cool about the Silo conversion!! Thanks for sharing OP. Reminds me of a Grand Designs in which a family converted a 1955 concrete subterranean reservoir into a beautiful 4500 sqft home for under 150k quid. Wild. https://www.granddesignsmagazine.com/grand-designs-houses/grand-designs-hull-reservoir-conversion/
Thanks for shout-out. But solid concrete in a cold climate has its disadvantages. Any blame for deficiencies in the reuse of concrete elevators has to be laid at the feet of inexperience and a touch of short-cuts by residential developers. However, cold climate heat pumps master the tendency of concrete to capture below zero temps and hold it. They do so with the steady constant heat - a la hot water heat - with the added excellent air circulation. We've noticed the disappearance of that cold clammy feel the building gives off. At the end of the day, I don't think the future of conversions of concrete grain elevators to residential units is too promising in the Minneapolis-St.Paul area given the plethora of abandoned silos. Now, if I can just master the heat mode condensation....
If you do not want to send the condensate water indoors to a drain you could evaporate the water with a heater like the one in this link.
https://www.kasonind.com/index.php/products/evaporator-pans/energy-saving-evaporators
Walta
"Energy saving" or not, I don't see how you get around the fact that it takes 8000 BTU to evaporate a gallon of water and the poster is saying the compressor is producing 4+ gallons a day. That's got to be a big chunk of the heat pump energy consumption.
I agree it is less than ideal but there seems to be some reluctance to pumping water indoors and devising an system outdoor pumping system that will not freeze will have some energy penalty.
Walta
I think I laid out the options in post #26: either drain by gravity to someplace the water can go, or drain by gravity to a pump that is indoors and protected from freezing.
If going indoors, +1 on gravity drain and the indoor pump. It will be near impossible to keep a pump outdoors from operating reliability in cold climate.
Insulate the drain line install heat tape. Pumps can fail, so also install a condensate overflow safety switch to disable your heat pump (most have an input for this, sometimes at the indoor unit). No heat is better than flooding your neighbor.
My $0.02 would be to raise your outdoor unit high enough that all the drains can be gravity. Run to the kitchen sink tailpiece, washer drain, overflow on your tub or any floor drain. Bonus, raising the outdoor unit will free up space on the balcony.
+1 on raising the unit up. The description of solid concrete walls makes me worry that routing a drain through the walls might be difficult or impossible.