Lennox Heat Pumps & Philadelphia Winter

josh28

We are having two Lennox heat pumps installed in the next few weeks. Upstairs we'll have a ML14XP1 (HSPF maximum of 9) using existing ductwork. Downstairs, we'll have a MPB030S4M (HSPF maximum of 10.3) with three mini-splits. House is ~2500 square feet.

Does anyone have real world experience with how effective these are at heating when the temperature drops below 30 degrees?

We are keeping our gas boiler for the very cold days.

Steamhead

I've never seen a heat pump that worked well below freezing. Every so often some manufacturer comes out with something that is supposed to (remember the Acadia?) but they never live up to the hype. Don't let anyone talk you into trashing your boiler system.

Hot_water_fan

Heat pumps work well below freezing, don’t stress. I’m not familiar with Lennox though, worth looking around to find its capacity chart. 

STEVEusaPA

I’d probably drop them out at 40 degrees, and use the boiler.
Nothing is more comfortable than hydronic (radiant) heat.

Steamhead

Several winters ago, one of our customers' boiler died and we had to replace it in a particularly cold stretch of winter. We were lucky if the daytime high reached 20 degrees. The owners had recently had these super-duper heat pumps installed which were supposed to handle weather this cold.

Well, they managed to keep the house up to 54 degrees or so. They didn't live up to the hype.

I used to say heat pumps didn't belong anywhere but the Deep South, but then we had the polar vortex that nailed Texas.

Hot_water_fan

They work well under freezing, can't stop an installer from putting in something undersized. They're used successfully in locations much colder than Philly.

Steamhead

Well, on this job, the owners were told the heat pumps would heat the house satisfactorily down to zero. The fact remains they did not. They did keep the pipes from freezing..............

Ctoilman

Heat pump at zero???!!....omg

Hot_water_fan

The right heat pump can easily below zero, but will the installer do the right heat loss and right equipment selection is the challenge.

pecmsg

Heat pumps have there place, shoulder seasons 20 - 30°fine after that use your back up source.

Hot_water_fan

@pecmsg Philly's pretty mild: over the last 36 months 95% of heating degree days were less than 36, so warmer than an average temp of 30. 99.6% were less than 46, so warmer than an average of 20 degrees. It's basically always shoulder season.

Jamie Hall

Hot_water_fan said:

The right heat pump can easily below zero, but will the installer do the right heat loss and right equipment selection is the challenge.

Tell you what, @Hot_water_fan . A hypothetical project for you (that is to say, no way is it going to be done, but it might be interesting for the Wall to see, from your point of view, what would be required -- and you can PM me with a cost estimate).

Design day: -10F
Actual measured heating load at -10F: 3,300,000 BTUh
Existing system: vapour steam
Proposed system: air to circulating hot water heat pump (probably 4 zones)

Cost to include demo. and removal of entire steam system, installation and commissioning of heat pump, installation and all piping and auxiliary equipment and controls for hot water heat (true radiant is not an option) (assume four zones). 200 amp 120/240 volt single phase electrical service is available, no upgrade possible at this time.

I'd add that the property is a registered National Historic Landmark, so National Park Service guidelines for restoration must be followed -- but that is perhaps an unnecessary complication!

Have fun!

Hot_water_fan

@Jamie Hall ha! That's good. Luckily (unluckily?) most Americans don't live in houses that big and old. Does the museum have a website? Seems cool

Jamie Hall

No, we've never created a web site. Nor are we generally open (have you priced liability insurance for a museum?!) -- but anyone from the Wall is welcome to visit almost any time. Send me a PM...

STEVEusaPA

@Jamie Hall where ya at again? I may take you up on that one day. Would love to see the place.
Looks awesome.

Jamie Hall

northwestern Connecticut, @STEVEusaPA . Two and a half hours from either New York or Boston.

Steamhead

Jamie Hall said:

Hot_water_fan said:

The right heat pump can easily below zero, but will the installer do the right heat loss and right equipment selection is the challenge.

Tell you what, @Hot_water_fan . A hypothetical project for you (that is to say, no way is it going to be done, but it might be interesting for the Wall to see, from your point of view, what would be required -- and you can PM me with a cost estimate).

Design day: -10F
Actual measured heating load at -10F: 3,300,000 BTUh
Existing system: vapour steam
Proposed system: air to circulating hot water heat pump (probably 4 zones)

Cost to include demo. and removal of entire steam system, installation and commissioning of heat pump, installation and all piping and auxiliary equipment and controls for hot water heat (true radiant is not an option) (assume four zones). 200 amp 120/240 volt single phase electrical service is available, no upgrade possible at this time.

I'd add that the property is a registered National Historic Landmark, so National Park Service guidelines for restoration must be followed -- but that is perhaps an unnecessary complication!

Have fun!

Oh, don't forget- system shall heat all rooms to 70° F when the outside temperature is -20°F or the contractor doesn't get paid. That's how they did it in the old days..................

Jamie Hall

Which, I might point out, the steam system does very nicely now, thank you!

Steamhead

Thank @Charlie from wmass .

Jamie Hall

I do, frequently

pecmsg

Jamie Hall said:

northwestern Connecticut, @STEVEusaPA . Two and a half hours from either New York or Boston.

Next trip on the Cross Sound Ferry I may take you up on that!

Jamie Hall

A bit over an hour up Rt. 8 from the ferry terminal in Bridgeport, @pecmsg . I'd be delighted! Or an hour and a half or so from New London.

josh28

Finally got the heat pumps installed. Now using them to keep home warm.  I'm wondering if their performance so far is typical. 

Weather here (Philly suburbs) this November: lows around freezing and highs around 55F (13C).  Heat pumps are doing an adequate job keeping the house comfortable.  I have always expected we may need to use the boiler when it drops well below freezing but it's not 'winter' cold yet.

Our electricity usage increased by more than I expected.  Daily usage before using heat pumps was about 18kWh/day.  Usage since using the heat pumps is 45kWh/day (so w/ heat pumps we're +27kWh/day).

We have a Lennox MPB030S4M downstairs with 3 wall units and a Lennox ML14XP1-030-230 upstairs (using existing ductwork)

I would have a little more confidence that they're working correctly if the wall units didn't have multiple error codes when they were first installed (since resolved) but has affected my confidence a bit.

Is there best practice recommendations for adjusting the temperature with the wall units?  Leave on desired temp?  Adjust up and down during sleep/daytime?

Thanks.

pecmsg

Heat pumps you set and forget.

EBEBRATT-Ed

@josh28

keep the updates coming i would like to see how this turns out

jumper

>>Oh, don't forget- system shall heat all rooms to 70° F when the outside temperature is -20°F or the contractor doesn't get paid. That's how they did it in the old days..................<<

Was that when furnace coal was a buck a sack delivered? For most places 70° @ -20° is oversized unless house is Canada2000 or better.

Hot_water_fan

Pretty similar climate to yours: this is all of my electricity usage, not just heating. I have a ducted unit and a ductless unit, both Mitsubishi’s. 32kBtu total. 21 kwh/day for everything including 24/7 blower fan. .4 therms for water heating. 

 The below gas usage is from 11/2/2020, same average temperature. Used 2.7 therms (18kwh of electricity, including the ductless that day). 

COP somewhere between 2.6 (all 21 kwh for heating) and 4.5+ (Say 21-9 for other uses). About 35- 60% cheaper than gas.

josh28

I'm wondering if we have a faulty system or a bad install or something else. Our mini-split is unable warm our living room beyond 68 degrees. Even today when it was 52 degrees outside, we peaked at 68 in the living room. The wall unit is set at 76.

It's mid-December and we haven't had to use our boiler yet which is nice. But it's been a very mild fall so far. And we're often using a space heater to make ourselves comfortable.

Our installer was last here about a month ago. He recommended not using the 'auto' setting on the fan and turning it up all of the way. This has had a negligible effect.

System size is 28,000 BTU. We have three wall units.

Any comments, suggestions, recommendations?

EBEBRATT-Ed

None, except call the installer and tell him your not thrilled

Steamhead

We'd need to know what the heating and cooling loads are for your house. If I had to guess based on what you've posted so far, I'd say the heat pumps are sized for the cooling load, which is significantly smaller than the heating load.

Long story short- time to turn on the boiler.