Heat pump question

[paulmars]

I just replaced 3 ton r22 ac & oil furnace with 2 ton r410 heat pump & matching AHU.

I know they don't produce equally hot air, but is this normal:

45-50F outside between midnight & 5am. Thermostat set to 70F. Cycles on for 15-17 minutes, then off for 2.5 to 3.5 minutes. Repeat. Repeat. Repeat. Next night ditto

1952 cmu house with 9 tight sealing but non insulating plain glass windows & well insulated attic & 2 metal entrance doors. Central west florida. Central air was added by previous owner. I had it replaced in 2002 w\above mentioned 3 ton. Then again a week ago w\heat pump.

800 sq ft house. Yes I now know they installed too large cooling system 22 years ago. It also had 18x12" 8 merv filter (yes I now know 18x12 is way too small)

New unit just installed came with 16x20 fiberglass filter.

Old heater had considerably more off time & less on time. Maybe about 5 on & 10-20 off. Old cooling was the same. Telling me that house is insulated good

I can feel much more air coming from the vents now then the old 3 ton system w\small return. I just looked & old blower fan blades very dirty. I think i remember changing years ago to pleated because sometimes the fiberglass would pull in, resulting in unfiltered air.

Is 16 minutes on, 3 off normal?

Btw burner, oil tank, smoke tester, manometer & other oil furnace equipment for sale. Ill direct you to the online ad if u ask.

Btw can i use a more restrictive merv 5 or 8 16x20 filter? This air handler is speced at 700 cfm.

Thanks,
Paul
.

 

[Ohmthis]

A quick check (not written in stone here as there are more variables) to see if the HP is working properly and refrigerant level is correct is to check the temp of the fat pipe. It should be about 100* higher than the ambient air temp around the HP. If it is too high or too low have the installer come back out.

 

[paulmars]

Will do

 

[paulmars]

139 & 52

 

[paulmars]

Can i get a reference source (websites) so i can sound intelligent when i call him. I dont want to say someone told me

 

[paulmars]

Listen to this. It's not constant. It keeps changing. Is that normal? https://recorder.google.com/6d6284e6-b087-4724-aaf9-1d7db0084243

 

[PopcornSutton]

A r410 unit properly sized and charged, with the ambient temp between 30 and 90, you should get a 20-21 degree differential across the evaporator coil. Below 30 in heat and above 90 in cooling that temp may be lower, but 20 degrees is what you should see. A good temp gauge in the return and supply should tell the tale.

 

[rjacobs]

I bet your settings on your thermo are all jacked up....as it sounds like the system is running properly when its running as far as heat output goes.

Mine for the past 3-4 years have basically caused my emergency heat strips to be our 100% source of heat and the heat pump never had a chance to do anything. The setting for activating the system was also set to 0(or maybe it was 1) so any time the temp moved AT ALL the system came on(this was in AC and heat as there wasnt a separate setting in my thermostat). It was recommended to set it to 2 so the system didnt cycle like yours is doing.

 

[paulmars]

A r410 unit properly sized and charged, with the ambient temp between 30 and 90, you should get a 20-21 degree differential across the evaporator coil. Below 30 in heat and above 90 in cooling that temp may be lower, but 20 degrees is what you should see. A good temp gauge in the return and supply should tell the tale.

In heat mode the outside unit is evaporator, correct? It's 55 degrees outside. There is more then 21 degrees difference.

 

[paulmars]

Sound file https://files.fm/u/sj7vpp4b33?share_email_id=159aebb&share_show_reg_form=true

 

[Yankeefarmer]

I’m thinking there’s something not right with your thermostat. Was it replaced when the new system was installed? Does the house ever get to the 70 degree set point?

 

[paulmars]

House staying at 70, unless i off the hvac. Its from 2018 when old one broke.

Does sound right?

 

[Yankeefarmer]

What size was your old oil furnace? Let’s say your new 2 ton heat pump is delivering 24k BTU/hr. in 16 minutes, that‘s 6400 BTU. If your old furnace delivered that in 5 minutes, it’d be doing 77k BTU/hr, which seems very big for 800 sq ft in Florida. Regardless, the “off” time should be the same, since it is a measure of heat loss without regard to your system’s capacity.

 

[chinboys]

You need a thermostat that has adjustable swing temperature built in.
Is your home well insulated and draft free? You are loosing heat too rapidly.
Your symptoms are indicative of short cycling... on the heating side and probably on the cooling side too.

Per Google AI,
A thermostat's swing value is the number of degrees above or below the set temperature that the HVAC system allows the temperature to fluctuate before it turns the heating or cooling system on or off again.

A smaller swing value means the thermostat will respond more quickly to temperature changes and will switch the heating or cooling output more frequently. A larger swing value can help with short cycling, and is generally considered to be more energy-efficient.

 

[paulmars]

heat pump osculating noise sound can be played here. u wont need to dnld it. https://files.fm/u/sj7vpp4b33?share_email_id=159aebb&share_show_reg_form=true#/view/kydyzdn9wy

 

[PopcornSutton]

You need a thermostat that has adjustable swing temperature built in.
Is your home well insulated and draft free? You are loosing heat too rapidly.
Your symptoms are indicative of short cycling... on the heating side and probably on the cooling side too.

Per Google AI,
A thermostat's swing value is the number of degrees above or below the set temperature that the HVAC system allows the temperature to fluctuate before it turns the heating or cooling system on or off again.

A smaller swing value means the thermostat will respond more quickly to temperature changes and will switch the heating or cooling output more frequently. A larger swing value can help with short cycling, and is generally considered to be more energy-efficient.

Most of the heat pump controls I've seen, in heat mode, if the stat senses more than 1 degree lower than set point, it kicks in the backups to recover faster. Maybe an adjustable dead band stat like you are talking about will adjust that as well.

 

[fitter30]

Thermostat brand and complete model number. Usually its on the main part of the stat that comes off the sub base.

 

[paulmars]

Honeywell pro th4110b

 

[SwissMetric]

Cycles on for 15-17 minutes, then off for 2.5 to 3.5 minutes. Repeat. Repeat. Repeat. Next night ditto

How many starts per 24 h are considered as a general upper limit for the compressor?

I was surprised to see heat pumps starting maybe 100 times per day. Shouldn't the number of starts be lower to increase the lifetime of the compressor or are such short cycles considered as normal?

As I wrote the program for a controller I set some minimum running time as well as a minimum delay before the next start at much higher values and it didn't cause any problem though it was a water/water heat pump. I hesitated to install a VSD but it wasn't worth the effort.
Usually I try to not get involved in anything HVAC nor building automation, excepted large stationary gensets.

 

[rjacobs]

Honeywell pro th4110b

Im not telling you what to do with this manual or the settings contained wherein, but here you go... It doesnt have nearly as much as the newer T6 like I have, but its got a few things you can check.

HONEYWELL PRO TH4110B INSTALLATION MANUAL Pdf Download

View and Download Honeywell PRO TH4110B installation manual online. PRO TH4110B thermostat pdf manual download.

www.manualslib.com

 

[paulmars]

Thermostat manual:
Looking at page 4 & 5 I dont know if all those wires are correct. See my pics.
He told me he installed that w-y jumper.
He told me he set that switch on page 6 to heat pump.
Page 8:
Setup function 1 was set to zero. I chng to one.
No setup function 5, it skips to 9.
Mistakenly I may have chnged setup functions 9, 13, & 15.
I reset them to:
Setup function 9 to three.
Setup function 13 to zero.
Setup function 15 to five.

 

[paulmars]

I attached pics twice and it looked like it doing it, but it didnt. Ill try again.

 

[paulmars]

4th try with different image app

 

[danski0224]

No setup function 5, it skips to 9.

You won't have #5 because it's a heat pump.

I'd set #9 to one (1).

There doesn't seem to be a deadband adjustment.

If it's only 1 degree, that will make it turn on quickly after the thermostat is satisfied.

I'd also plug the hole in the wall where the wires come out with electrical duct sealer (a non hardening putty like Play Doh).

 

[paulmars]

9 to one why?

 

[danski0224]

That's what I've been told to set cycles per hour for a heat pump at a manufacturer training class.

 

[paulmars]

Ok.

Id like somebody to comment on sound link I sent.

 

[Wiz02]

That's what I've been told to set cycles per hour for a heat pump at a manufacturer training class.

My HP is short cycling too, but it's been consistently below 40F here so I am running the gas furnace all the time, so I can't test out changing cycle per hour to 1 and see if it changes the short hp on time.

 

[paulmars]

When it cycles on the air out vent is 5 degrees higher then ambient. It slowly gets hotter usually toppings out at 22 to 24 degress hotter, but occasionally as much as 30. That takes 7 to 10 minutes. Then i hear thermostat clicking off and temp begins to drop until AHU fan stops. It's not as cold now so it's on less. Is it normal for temp out vent to keep increasing until thermostat cycles off?

 

[rjacobs]

When it cycles on the air out vent is 5 degrees higher then ambient. It slowly gets hotter usually toppings out at 22 to 24 degress hotter, but occasionally as much as 30. That takes 7 to 10 minutes. Then i hear thermostat clicking off and temp begins to drop until AHU fan stops. It's not as cold now so it's on less. Is it normal for temp out vent to keep increasing until thermostat cycles off?

A heat pump is able to put out like 85-90 degree air at the most. Thats why most people who dont understand how heat pump heat works complain that the air coming out of the ducts is "cold"... No its just not 120 degree air from a real heat source(like a gas furnace, heat strips, etc...). So at a 70 set point seeing 30 degree's hotter air to me says your backup heat strips(or whatever your backup source is) is coming on to attain that.

I would honestly buy a newer thermostat that can control your setup better.

Get something thats "smart" and has a lot more control over what you are running. Ive got Honeywell T6's in my house and they can control a ton more stuff than yours. There are even more advanced thermostats than the T6.

To me it sounds like you have no temp offset ability so if your temp drops 1 degree the system kicks on. Then you dont have an ability to call for only heat pump for say 10 minutes or 3 degrees and let the heat pump work and your backup heat option is kicking on very early(I had this problem with mine with how the original installer programmed my thermostat). Then the newer stuff has the ability to learn how long it takes to bring your house up to temp to tailor run times a bit better. They can also continue to run the fan after your heat/ac kicks off to harvest the rest of the hot/cool air out of the unit. IMO the thermostat is just as important as all the new fancy high efficiency air handlers, heat pumps, etc... in how it all gets controlled.

 

[danski0224]

A heat pump is able to put out like 85-90 degree air at the most.

This is NOT true any longer.

 

[danski0224]

When it cycles on the air out vent is 5 degrees higher then ambient. It slowly gets hotter usually toppings out at 22 to 24 degress hotter, but occasionally as much as 30. That takes 7 to 10 minutes. Then i hear thermostat clicking off and temp begins to drop until AHU fan stops. It's not as cold now so it's on less. Is it normal for temp out vent to keep increasing until thermostat cycles off?

So, what kind of equipment is it?

An inverter condenser unit will do this as the system (compressor) adjusts to the airflow. It takes time for the inverter to find the best frequency.

I saw this phenomenon while doing a startup of a Unico heat pump AHU (6 row evap coil). It took several minutes for the air temperature at the diffusers to rise and meet their discharge temperature claims. I'm sure that some of this had to do with heat loss to the cold HVAC ducting in the attic.

The fancy Bosch matched air handlers (not furnaces) have a delay timer for the fan, until the coil reaches a set temperature, to avoid "cold blow" in heating mode. The Bosch furnaces lack this technology. Many mini splits have a similar feature that may need to be enabled.

A delay timer can be fabricated and installed to keep the blower fan off until a set refrigerant line temperature is reached at the indoor unit.

As has been mentioned before, a better thermostat will allow more opportunities for fiddling and control.

 

[paulmars]

This is florida. No backup heat strips. Im not against getting a new thermostat if needed but 1ll need to understand better as to why.

In 2018 when the 3 ton simple thermostat broke i had a hard time finding one w\o extra fancy functions. That is why i finally chose the th4110b. With just one button i can off the added functions. Batteries too. I dont want one that needs batteries!

I dont even like power windows & mirrors. I will not even consider a car witha fob. Kiss.

This thermostat is designed to operate a heat pump. The house stays at the set temperature.

If heat pumps gradually increase delivered temperature over 7 to 10 minutes, then mine is ok. If not, is it because of the thermostat? I havent yet changed the software settings from what i posted above.

 

[paulmars]

Not inverter.

 

[danski0224]

Im not against getting a new thermostat if needed but 1ll need to understand better as to why.

It's already been explained.

You need a "deadband" adjustment.

Something else that may work is a "droop" adjustment.

Technically, they are not the same, but without backup heating, "droop" may limit your cycling.

 

[danski0224]

Not inverter.

Temperature rise at the register might be normal if the ductwork is cold.

A temperature reading would have to be taken much closer to the indoor coil.

 

[bonneyman]

I just installed a new Honeywell stat in my house, and the set-up menu had like 60 parameters. Geez!

Too bad I couldn't program it to cook dinner and wash the laundry!

 

[akasrick]

I just installed a new Honeywell stat in my house, and the set-up menu had like 60 parameters. Geez!

Too bad I couldn't program it to cook dinner and wash the laundry!

Not so smart but can an old style table lamp and bulb be placed under the thermostat.
Would that bring up the surrounding temps?

akasrick

 

[danski0224]

Not so smart but can an old style table lamp and bulb be placed under the thermostat.
Would that bring up the surrounding temps?

Won't work so well in heating season...

 

[American Locomotive]

You're all chasing a red-herring here with this hysteresis/dead-band adjustment. Thermostats like this have automatic hysteresis adjustments based on the type of heat selected and how long it takes to bring the house to temperature. The Honeywell marketing blurb for this thermostat backs that up as well.

We have to look at the duty cycle. With ~9 minutes of off time and 51 minutes of on time per hour, the system is operating at an 85% duty cycle -it's giving just about all it has to keep the house at 70°F with a 45-50°F. The thermostat sees how long it takes to satisfy, and drops the hysteresis. If it ran a typical 1.5-2 degree hysteresis the system would need to run for hours to hit set point.

Your oil furnace was conservatively around ~7 tons in capacity, likely more. It could heat the house up fast, so the thermostat set a larger hysteresis. It would allow the furnace to stay off for 15-20 minutes because it could make up a 2 degree difference very quickly.

The unfortunately reality of the situation @paulmars is that your home's insulation is almost certainly much, much worse than you think.
- CMUs are only about R1 , the drywall or plaster ontop of that is about is about R0.5. That is very, very little insulation
- Single pane windows at R1 at best.
- What exactly is a "well insulated attic" to you? Current standards for your area are R49 - that's a solid ~15" thickness worth of fiberglass batts or blown cellulose.
- Metal doors - are they insulated foam core, or old uninsulated doors? If uninsulated, their R-Value is 0.

My buddy has 18,000 BTU worth of heatpump minisplits in his 1000 sq.ft mobile home. At a 45-50°F ambient, they're hardly running at all. His house is objectively very poorly insulated for this area, with very minimal wall insulation and poor spotty attic insulation.