Heatpump water heater etc....

[Ai4px]

Just an FYI post in case someone wants or needs to know in the future. We got a 40 gallon AO Smith heat pump water heater. It speaks modbus but I haven't dug in to it yet. I replaced the 4400w water heater elements with 1500watt elements so that even when they run it won't significantly load the inverters. You can put it in electric / heat pump / hybrid mode. In heat pump mode it pulls 360w (measured), pulls 1860w with heat pump and elements running.
We also got a Mitsubishi 3.5 ton ducted mini split. It replaced the ducted conventional 5ton heat pump we had. Most of the time when it runs it pulls 800w. The most I've ever seen was about 1200w. If it was ductless and used a conventional wall mounted indoor unit it would be 26seer... but it's 16 seer as a ducted unit. Although I don't get the efficiency out of it with the duct, my house was already setup for the ducts and I have too many rooms to have a head in each. The value to me is that it soft starts. We got down to 14F (record cold for where I live) and the unit was able to run at a 50% duty cycle. Flipping awesome.
A buddy got pioneer 1 ton (12000 btu) units in his tiny house and each seems to pull 170w most of the time.

Just general info.....

 

[42OhmsPA]

Thanks for this info, very helpful. I've been back and forth on a Rheem HPHW and pioneer splits ... What made you choose AO Smith over Rheem?

 

[zanydroid]

Awesome, I really appreciate the info!

I was actually also considering a swap of 4500 to 2250 on resistive when I get mine (not decided on brand yet), glad to see that you pulled it off.

What were you planning on doing with the serial connection? I believe HPWH sold in the US tend to have a IEEE standard curtailment/demand response control port.

 

[zanydroid]

What is the startup surge, if any, on the 500W compressor?

 

[Ai4px]

Thanks for this info, very helpful. I've been back and forth on a Rheem HPHW and pioneer splits ... What made you choose AO Smith over Rheem?

AO smith was available at my local Lowes.... sorry, not much more thought than that!

 

[Ai4px]

What is the startup surge, if any, on the 500W compressor?

I have not measured it, it's really just like a fridge....

 

[Ai4px]

Awesome, I really appreciate the info!

I was actually also considering a swap of 4500 to 2250 on resistive when I get mine (not decided on brand yet), glad to see that you pulled it off.

What were you planning on doing with the serial connection? I believe HPWH sold in the US tend to have a IEEE standard curtailment/demand response control port.

If you have any info on that port (ie modbus registers), I'd love to know. My understanding is that it has top and bottom tank temp, outlet temp and inlet temp. It would be really nice to roll this up into HomeAssistant and trend water useage or to command the unit on/off... not that I need to do any power management at 360w, but you know ... because I could.

 

[Danke]

We also got a Mitsubishi 3.5 ton ducted mini split. It replaced the ducted conventional 5ton heat pump we had. Most of the time when it runs it pulls 800w. The most I've ever seen was about 1200w. The value to me is that it soft starts. We got down to 14F (record cold for where I live) and the unit was able to run at a 50% duty cycle.

50% duty cycle @ 1200W? So 600Wh?

 

[zanydroid]

Is it duty cycle (on off) or modulated down?

 

[zanydroid]

If you have any info on that port (ie modbus registers),

I’ve had a brain fart on this for the past few days as to what it is called… if I get a chance I will look for it again. It’s referenced in Energy star standards for HPWH.

 

[zanydroid]

I have not measured it, it's really just like a fridge....

OK, cool, if it’s like an inverter fridge in startup power needs (which is sort of what I expected) then it should be easy to start.

 

[Ai4px]

Is it duty cycle (on off) or modulated down?

The compressor is just on/off. The heat elements are also just on/off. I've never timed the compressor but it "seems" to run for about 2 hours after morning shower cycle here.

 

[zanydroid]

The compressor is just on/off. The heat elements are also just on/off. I've never timed the compressor but it "seems" to run for about 2 hours after morning shower cycle here.

Sorry, I was helping to ask for clarification for Danke's question about the mitsubishi mini split.

I don't think it makes sense at all for the HPWH to modulate the compressor. After someone does a shower it just has to go full tilt for a few hours, not much modulation needed.

 

[zanydroid]

If you have any info on that port (ie modbus registers)

I’ve had a brain fart on this for the past few days as to what it is called… if I get a chance I will look for it again. It’s referenced in Energy star standards for HPWH.

My Google-fu is better today than last night when I had my brain fart. The standard is called CTA-2045. I believe it's a serial port you plug some wireless or whatever communications thing into, that is supplied by your energy management system or utility. I haven't looked into it in detail so I could be wrong except for the name of the standard :laugh:

 

[Ai4px]

50% duty cycle @ 1200W? So 600Wh?

No, it ran at 1200w for about 2 hours at a time. Then shut off. Two hours later pulling 1200w again.

 

[ChrisG]

Just an FYI post in case someone wants or needs to know in the future. We got a 40 gallon AO Smith heat pump water heater. It speaks modbus but I haven't dug in to it yet. I replaced the 4400w water heater elements with 1500watt elements so that even when they run it won't significantly load the inverters. You can put it in electric / heat pump / hybrid mode. In heat pump mode it pulls 360w (measured), pulls 1860w with heat pump and elements running.
We also got a Mitsubishi 3.5 ton ducted mini split. It replaced the ducted conventional 5ton heat pump we had. Most of the time when it runs it pulls 800w. The most I've ever seen was about 1200w. If it was ductless and used a conventional wall mounted indoor unit it would be 26seer... but it's 16 seer as a ducted unit. Although I don't get the efficiency out of it with the duct, my house was already setup for the ducts and I have too many rooms to have a head in each. The value to me is that it soft starts. We got down to 14F (record cold for where I live) and the unit was able to run at a 50% duty cycle. Flipping awesome.
A buddy got pioneer 1 ton (12000 btu) units in his tiny house and each seems to pull 170w most of the time.

Just general info.....

@Ai4px
Can your provide more info on the ducted mini split. I have a Trane 5 ton that is 20 years old and on its last legs. Between the air handler and heat pump it uses 6.5kw after starting.

 

[Danke]

No, it ran at 1200w for about 2 hours at a time. Then shut off. Two hours later pulling 1200w again.

For your HP furnace? Isn’t that an average of 600Wh?

 

[Ai4px]

My Google-fu is better today than last night when I had my brain fart. The standard is called CTA-2045. I believe it's a serial port you plug some wireless or whatever communications thing into, that is supplied by your energy management system or utility. I haven't looked into it in detail so I could be wrong except for the name of the standard :laugh:

I found this document. In truth everything I found using google-fu and duck duck centric powers leads me to documents describing how commands would be sent from/to a utility provider. While I think there is a sub set of commands the water heater will take to play well with these supervisory devices, I can't find a thing about which modbus registers are which inside that unit. For example, the utility provider doesn't care about the tank temp... they just want to command the unit to lower the setpoint or shut off for an hour.

 

[zanydroid]

Can your provide more info on the ducted mini split. I have a Trane 5 ton that is 20 years old and on its last legs. Between the air handler and heat pump it uses 6.5kw after starting.

Not OP but I dug out some info on ducted mini split project for some DMs so I have it ready to share

For a project last year, I was interested in the Fujitsu medium-static models. This is designed for concealed duct, I think custom designed for mini-split. Medium static means it can handle more ductwork than a low static model (albeit at a potential efficiency deficit, though efficiency needs to be considered holistically vs how much insulation is surrounding the ducts, sometimes you want high static to push it faster)

ARU12RGLX = 3100 - 19400 (BTU range heating)

Oops, this one is retired. Here is the product line.

Medium Static Pressure Duct - AIRSTAGE SINGLE-ROOM MINI-SPLIT SYSTEMS - Residential - FUJITSU GENERAL United States & Canada

Medium Static Pressure Duct - AIRSTAGE SINGLE-ROOM MINI-SPLIT SYSTEMS - Residential - FUJITSU GENERAL United States & Canada

www.fujitsu-general.com

Next week I'm getting a Mitsubishi multi-position air handler installed
SVZ-KP36NA_SUZ-KA36NA2

IIRC this is a mid and high static unit. It is designed to drop into air handler or furnace for a whole house.

 

[Ai4px]

For your HP furnace? Isn’t that an average of 600Wh?

Indeed..... I have an ICF house.... very efficient.