Heat recovery for water heater

[cec39466]

I have been thinking of ways to save power as the cost of everything is going up. I have bought the energy saving light bulbs, turn out lights when not in the room, ect... I thought about installing a heat recovery unit on my a/c but I have a heat pump and was wondering how much it would affect my heating. I live in southern Mississippi so our cold spells don't last to long. I have installed them on straight cool systems with great results. I also could install two valves to bypass the recovery unit during heating but was hoping for a little input from someone who might have already installed them on a heat pump.

Equipment
Heil Condencer# H4H430GKD 14 SEER R-410 A
Heil FXM4X3600A AIR HANDLER WITH TXV

Thanks in advance

[cartercrew]

Haven't actually done it, but was thinking the same thing about winter operation. I don't see why a relay couldn't be installed by the contractor installing the recovery unit, wire it to only run the circulation pump when the reversing valve is powered (unit is in cooling mode).

[cec39466]

Yea I thought about that but even in Ms. We get a few freezes. I don't think I can post a link but I found one with a 20 year warranty and comes on when outside sensor reaches 35 degrees to prevent pipes from freezing. I would have to look again but entering refr. temp 170 degrees into heat recovery with I think 120 degree leaving refr. temp. Standard 125 starts pump with a limit of 140 on water side. Freeze protection starts at 35. Two year on the little 2 gpm pump. Also not sure if Heil energizes reversing valve on cool or heat mode but that doen't really matter because it will take out freeze protection. I can't believe more contractors aren't pushing heat recovery units when they are selling the high seer units for energy savings. They aren't hard to install if you have fairly easy access to the water heater. Could it be I missing something or are they just installing on straight cool units?????????

[beenthere]

Most of those desuperheaters have a stat in them, that when the hot gas temp is below X degrees, they shut down the circulator.

[icemeister]

I've had a heat recovery desuperheater on my home's 4-ton heat pump for over 15 years. Although my heating requirements are minor as compared to most folks, I've never noticed any significant loss of heating capacity from it.

In normal operation, these desuperheaters are maintaining the water temperature solely with the discharge superheat of the refrigerant, not the latent heat. The superheat amount to about 15% of the total heat of rejection, so when in the heat mode, the indoor coil gets the other 85%.

I set my water heater at 100ºF and the desuperheater cuts out at around 120ºF. My R22 heat pump typically runs around 200 psig in heating, so can see there's normally very little if any condensing going on in the desuperheater.

I'd leave it enabled, even in the coldest weather. The amount of heat you get per KW from the heat pump will always be more than straight resistance heating.

[cartercrew]

I was also thinking that any heat put into the water and not the house balances with the electric heat in the unit. I mean electric heat is electric, right? If the desuperheater takes enough out of the refrigerant that the strips come on, it is offset by the heat being put into the water heater and keeping the elements off. Am I missing something?

[cec39466]

Icemeister can I ask what brand you chose, and did the 85% going to house keep the heat strips off. By the way guys thanks for the responses.

[CraziFuzzy]

I think it would all depend on your runtimes whether it is worth it or not (how much of the year are you heating with the heat pump, how often are you cooling). If you are cooling most the year, then the desuperheater would likely pay for itself quickly. If you do a lot of heating with your heat pump, then it may not actually be all that useful to you. In which case, if you DO use a lot of hot water, and are stuck on electric only, it might be worth looking into a heat pump water heater. Their prices seem to have dropped significantly over the last few years.

[rickboggs]

This is the first time I have ever heard/read the term desuperheater.

[CraziFuzzy]

This is the first time I have ever heard/read the term desuperheater.

It's basically a heat exchanger on the hot gas line to recover some heat for useful purposes instead of throwing it away in the condenser coil. It is most often used for domestic water heating, or pool heating.

[rickboggs]

We just called them ECUs or heat recovery units... same thing?

[SBKold]

I too have a HRU in my personal house on a 10seer rheem.

I haven't been here long....but am presently enjoying free hot - well ok sometimes warm water (if ac isn't running much)

My only concern for you is generally the high efficiency 410a compressors run cooler than their predecessors.

I also have mine running in heat and it does take some btus from inside but as others stated it still saves over resistance heat.

I actually had scalding water when temps dropped below freezing here for a whopping 2 days here this winter. Due to the longer run times.