• Have you tried out dark mode?! Scroll to the bottom of any page to find a sun or moon icon to turn dark mode on or off!

diy solar

diy solar

Heat pump nearly doubled power consumption in one month, advice please

O

OM617YOTA

Solar Addict
Joined
May 27, 2021
Messages
552
Bosch/Mitsubishi heat pump(standard heat pump, not mini split) has been GREAT for years, then inexplicably in one month power consumption shot up.

Nov 2022
243kwh

Dec 2022
321kwh

Jan 2023
415kwh

Feb 2023
352kwh

Nov 2023
349kwh

Dec 2023
307kwh

(basically stopped burning wood here, Jan 2024 bump is expected)

Jan 2024
512kwh

Feb 2024
398kwh

Nov 2024
412kwh

Dec 2024
697kwh - wtf?

Jan 2025
661kwh

Feb 2025
529kwh

Monthly average temps have been the same year to year, less than a degree of difference. Only minor changes to house insulation - to ADD insulation. Air filter is kept clean.

Heat pump seems to turn on the compressor and air handler fan, run until house is up to temp, then the compressor turns off and the air handler fan keeps running until the house is cold again, then starts the process again almost immediately. Didn't used to do that. Non smart non internet connected thermostat.

Edit to clarify: Air handler fan does turn off, it just runs for so long after the compressor turns off that the house gets cold again, then turns off briefly, then restarts the process. Air handler fan probably running 30 minutes out of every 40 minute span, even when outside temp is 50F and inside temp is 67F.

Before I call a tech out to take a look, is there anything else besides double checking the filter that I should take a look at?
 
Last edited:
If its cycling on/off and not varying speed it could be a number of things. I'd call a tech out that can hopefully troubleshoot and repair the thing versus saying "I dunno, things broke, I'll sell you a new one"
 
timselectric said:
Sounds like the fan is set to on instead of auto.
On the thermostat.
Click to expand...

I wasn't clear, the fan does shut off, after continuing to run until the house is cold again. Then a very few minutes later it kicks on again and the process restarts.
 
going_commando said:
If its cycling on/off and not varying speed it could be a number of things. I'd call a tech out that can hopefully troubleshoot and repair the thing versus saying "I dunno, things broke, I'll sell you a new one"
Click to expand...

The fan doesn't vary in speed, but I can see the power usage on the compressor varying between 200w and 3kw based on output.
 
Thanks folks. I edited the OP for more clarity.

Edit: Air handler fan does turn off, it just runs for so long after the compressor turns off that the house gets cold again, then turns off briefly, then restarts the process. Air handler fan probably running 30 minutes out of every 40 minute span, even when outside temp is 50F and inside temp is 67F.
 
OM617YOTA said:
I wasn't clear, the fan does shut off, after continuing to run until the house is cold again. Then a very few minutes later it kicks on again and the process restarts.
Click to expand...
The fan on my gas furnace does the same thing, when the demand is high.
But if the temperature is similar to the year before, I would assume that the demand is also.
I can't think of another reason, at the moment.
 
Is the system a Mitsubishi inverter (mini-split style) outdoor unit with a conventional bosch air handler inside, or is it the Bosch IDS series heat pump with a more conventional style outdoor unit and an indoor coil?
 
The fan is 100% controlled by the thermostat, the heat pump and air handler only respond to the call for heat.

I would start with changing out the thermostat, its the lowest cost part.

This assumes it is a non-communicating system ( simple Y/W and reverse wires ). If its communicating type ( RS485 ) that would require a tech that has the tools to debug the issue.
 
Thanks folks.

going_commando said:
Is the system a Mitsubishi inverter (mini-split style) outdoor unit with a conventional bosch air handler inside, or is it the Bosch IDS series heat pump with a more conventional style outdoor unit and an indoor coil?
Click to expand...

It looks more like a conventional outdoor unit and indoor air handler. Looking up the IDS series, the outdoor unit looks very similar, the indoor unit doesn't. I can take a better look when I get home.

I think I remember the indoor air handler ramping fan speed up and down. That's definitely not happening now, and now with the Emporia Vue, I see the air handler run at a constant ~300w.

Interesting.
 
There is so many things that can cause what you are experiencing

Could be a new draft source bringing in cold air, broken or leaking duct, dirty coils, low refrigerant, failed thermostat, crank case heater thermal switch, reversing valve leaking or not cycling fully, weak compressor or bad valves, loaded up filter dryer, and many more.

I'd call a tech out to go over the system
 
OM617YOTA said:
That's definitely not happening now, and now with the Emporia Vue, I see the air handler run at a constant ~300w.
Click to expand...
That would seem to point to running in recirculation mode as its suppose to help even out the temperatures within the structure.

Has anyone changed the setting ( or the thermostat ) recently?

It could be a failure of the control board in the air-handler, One could temporally disconnect the fan wire ( usually green in the common heat pump ready thermostats ) and see what happens and yes, running that will create large heat loss as the duct work usually is something like R8 at best.

If your not comfortable debugging this it would be a simple task for a tech that knows the equipment you have.
 
Last edited:
Solar Guppy said:
That would seem to point to running in recirculation mode as its suppose to help even out the temperatures within the structure.

Has anyone changed the setting ( or the thermostat ) recently?

It could be a failure of the control board in the air-handler, One could temporally disconnect the fan wire ( usually green in the common heat pump ready thermostats ) and see what happens and yes, running that will create large heat loss as the duct work usually is something like R8 at best.

If your not comfortable debugging this it would be a simple task for a tech that knows the equipment you have.
Click to expand...

As far as changing settings, nobody should have touched anything. We do bump the temperature on the thermostat up and down every so often, and turn the whole system off and on every night. System's been in place for a few years now and we've always done this, and only recently has our power usage spiked.

I think I could learn the ins and outs and figure it out eventually, but no clue how long that would take me. Going to call a tech out and quit burning power.

Thanks everyone, appreciate the input.
 
I would replace the capacitor in the compressor just to be sure. Since there was a rapid power jump, it is not likely that coils are dirty etc. The cap is cheap and easy to change, so if it does not fix - no harm. Normally a compressor will not start if the cap is bad, but I had a soft start on mine and it would crank up the compressor even when the cap was bad. If you have a current meter is it a good idea to check the amp draw. I have a sense.com power monitor in my main panel and that gives me a good idea how much power is used and how long the compressor is running. Changes are easy to see on a graph. The key thing only you would know is whether the "on time" is normal for your system. If it is running a lot longer, it probably some other issue hurting efficiency.
 
RDuke said:
I would replace the capacitor in the compressor just to be sure. Since there was a rapid power jump, it is not likely that coils are dirty etc. The cap is cheap and easy to change, so if it does not fix - no harm. Normally a compressor will not start if the cap is bad, but I had a soft start on mine and it would crank up the compressor even when the cap was bad. If you have a current meter is it a good idea to check the amp draw. I have a sense.com power monitor in my main panel and that gives me a good idea how much power is used and how long the compressor is running. Changes are easy to see on a graph. The key thing only you would know is whether the "on time" is normal for your system. If it is running a lot longer, it probably some other issue hurting efficiency.
Click to expand...

Thanks for the idea. It's an inverter drive compressor, I can watch my Emporia Vue and see the compressor start at ~200w and ramp up all the way to nearly 3kw as needed. Not sure there are even start caps on an inverter drive system.

Wish I'd installed the Emporia Vue years ago. Highly recommended.
 
I don't have a heat pump, but my furnace will do the same exact thing you're describing if the fan switch is in the ON position. It will shut off briefly when the thermostat calls for heat and continue running when heat is no longer needed. On AUTO, it shuts off after a couple minutes when heat is no longer needed.

As everyone has said, check your thermostat. You should just be able to disconnect it from its cradle and the fan should stop.
 
Fan is definitely set to auto, it does turn off in between heating cycles. When set to "on" the fan never turns off.

I'll try disconnecting the thermostat from it's cradle and see what that does. We have a tech scheduled to come take a look at it tomorrow.
 
OM617YOTA said:
Not sure there are even start caps on an inverter drive system.
Click to expand...
There are not start capacitors in these like a regular system.
The continuous running fan is 100% running up your bill, these lower but long term loads really add up.
Pull the thermostat and see what happens, perhaps the relay/switch in the stat is knackered.
 
Quattrohead said:
There are not start capacitors in these like a regular system.
The continuous running fan is 100% running up your bill, these lower but long term loads really add up.
Pull the thermostat and see what happens, perhaps the relay/switch in the stat is knackered.
Click to expand...

Will definitely pull the thermostat and see what happens, but the fan isn't running continuously, just a LOT.
 
Alrighty, tech came out and took a look. Tested a bunch of temperatures(cold air return, hot air out, outside temp), measured power consumption, did some calcs and said the system is heating more efficiently than it should be and he couldn't find anything wrong at all. Dammit.

Wondering if he reset something or restarted something though, because now it seems to be running the way it used to be. Heating cycle starts, air handler fan turns on, heat pump ramps up and gets warm fast, temp achieved heat pump shuts off, air handler fan only runs barely longer than the heat pump runs, shuts off. Better part of an hour before the cycle starts over again, instead of only a few minutes between cycles.

Will monitor over the next few days or weeks.
 
Thought of something else. HVAC heat pump costs spiked before I installed my heat pump water heater, so this is unlikely and me grasping at straws.

My heat pump water heater is in my unconditioned garage, but to keep it from cooling the garage unnecessarily during the winter I have it ducted up into the garage attic. The garage attic connects to the house attic where the indoor air handler is located. That attic is very well ventilated, can see daylight through the ridge cap the entire length of the house, plus large vents on either end of the house and a large exhaust fan for summer time. When there's any breeze outside you feel it in the attic. I'm not expecting there to be any buildup of cool air that would impact the air handler to any significant degree, but it's possible.

Going to pay attention to how the HVAC heat pump behaves while the water heater is running and see if there's a correlation in behaviors. Might switch the water heater to pure resistance mode for a bit and see if HVAC heat pump load goes down. Might need to vent at least the cold air output duct outside the structure entirely.
 
You must log in or register to reply here.

Similar threads

R
Looking for advice - Off Grid cabin in Utah - winter heat
2 3
Replies
58
Views
2K
Daddy Tanuki
Daddy Tanuki
M
Full Electric Home - Can I power a 5 ton heat pump w/ 20kW heat strip?
Replies
20
Views
960
OzSolar
O
onokai
Heat Pump water Heaters
8 9 10
Replies
231
Views
13K
Supervstech
Supervstech
G
Help needed Inverter power issue
Replies
2
Views
461
gold64bond
G
O
Midnite All-in-One with 150+ kWh storage (from EVs)
2
Replies
31
Views
1K
Steve777
S

diy solar

diy solar
Back
Top