Question about Heat Pump Emergency Mode

[600SL]

Hello All

I'm installing a heat pump in my garage. It has a 10KW electric coil. The system is fully installed except for the condensing unit and some ducting which are held up for parts. So I decided to try the electric heaters for the moment using Emergency mode. They seam to work somewhat but not 10KW worth. Shop temperature rose from 53° to 60° in about 45 min. I cannot see the coils turning red when I look down the duct. This is for a 48 x 30 x 10' insulated shop.

So I'm not sure if these coils are working correctly. Is it possible that at 53° the emergency mode doesn't call for full power, possibly because its not really an emergency. Should the coils glow red like a toaster?

 

[mrpizza]

They shouldnt glow red when the blower is running. You do have them on 240v with a 60A breaker? The 10k kit puts out 34k BTU.

 

[600SL]

They shouldnt glow red when the blower is running. You do have them on 240v with a 60A breaker? The 10k kit puts out 34k BTU.

On 240V with 60A. Doesent seam to be performing like my old 35,000 BTU torpedo heater. Maybe its just not as concentrated a heat coming out of an 18 in duct.

 

[Stuff]

Sometimes emergency heat is just that. You got a 7 degree rise which shows that it will keep the place from freezing. Real bad for your electric bill, though.

Think of 10kw heating as equivalent to 7 hair dryers.

 

[matt_i]

My guess on the "emergency mode" is that it doesn't attempt to pump any heat. Just pure electric resistance.

 

[dw1]

do you have an amp probe/ ammeter and a thermometer, turn it on, see what the output air temp is? and see what the current draw is? I just finished up working on a small office/whse that has a furnace/heat pump and they are not installing the heat pump until it gets a tenant, it is running on a 5KW (30 amp) strip, HTG contractor set t stat on 63 on emerg heat, it is keeping the set point.
(This is inside a closed up/insulated set of small offices)

 

[600SL]

Just checked it with a clamp. currently pulling 37 Amps. thats about 89%. Temperature rose from 51° to 56° in 23 min. I think its running correctly. Will get me through until the rest of the parts come in.

Thanks everyone.

 

[bazar01]

put a clamp meter on one leg of the main feed to the heater to make sure you have 10kW.
it should pull about 43amps.

late post, already suggested.

 

[hippie2cams]

you must remember that the heat pump will not cycle as you tested the emergency strip. Later heat pumps cycle all the way down to the 30s without turning on emergency heat. They have come a long way baby.

 

[600SL]

put a clamp meter on one leg of the main feed to the heater to make sure you have 10kW.
it should pull about 43amps.

late post, already suggested.

Should I be getting the full 10KW at all times. Im only reading 37 Amps About 8900 watts.

 

[600SL]

you must remember that the heat pump will not cycle as you tested the emergency strip. Later heat pumps cycle all the way down to the 30s without turning on emergency heat. They have come a long way baby.

Right now only the air handler is installed. Condensing unit is still on a pallet.

 

[600SL]

So in 1 hour temperature is up to 62° from 51°.

 

[PWC Repair]

Sounds to me like it's working properly. Some so called 10kw heaters are actually 9kw.

 

[mrpizza]

Your air handler uses a little of your amperage as well.

 

[600SL]

Your air handler uses a little of your amperage as well.

I believe its 3/4 HP so that should be about 4 Amps. The 10KW heater states it puts out 9.5KW. So really I'm only getting about 8.1KW

 

[sms1974]

it sounds right, what is your actual voltage ( check with a meter ) to the unit? there should be a rating tag that will tell you the required voltage and the amp draw. if your incoming voltage is low your heat out put will be low. also how big of a garage are you tiring to heat? 10kw is not a lot of heat...

 

[600SL]

it sounds right, what is your actual voltage ( check with a meter ) to the unit? there should be a rating tag that will tell you the required voltage and the amp draw. if your incoming voltage is low your heat out put will be low. also how big of a garage are you tiring to heat? 10kw is not a lot of heat...

its not that important at this point I just wanted to know if it was working. 10 Kw will not heat this garage. But it should give the HP the boost it needs when the weather is down to 20°. Garage is 30 x 48. HP is a Goodman 3.5 ton unit. It puts out 25.8 MBh @ 20°. Tomorrows low will be 9°F.

 

[EOC_Jason]

Yeah but when your HP is in heat mode, the unit outside will turn into a popsicle reaaaal quick when the temp drops, then it has to go into defrost mode, etc, etc...

Don't know if your electrical is sized big enough, maybe you can swap out the heat strips for a 15kW without too much work?

 

[pop pop]

it sounds right, what is your actual voltage ( check with a meter ) to the unit? there should be a rating tag that will tell you the required voltage and the amp draw. if your incoming voltage is low your heat out put will be low. also how big of a garage are you tiring to heat? 10kw is not a lot of heat...

This. I'm betting your shop voltage is lower than the rated voltage on the nameplate.

As to whether or not this is enough, don't know, seems low. Some HPs run eheat with the HP and some run either or, not both. Which do you have? If both run together, make sure eheat is after the coil in the air handler.

 

[600SL]

Yeah but when your HP is in heat mode, the unit outside will turn into a popsicle reaaaal quick when the temp drops, then it has to go into defrost mode, etc, etc...

Don't know if your electrical is sized big enough, maybe you can swap out the heat strips for a 15kW without too much work?

Are you saying I'm not going to get my 25.8 MBh @ 20°. That and the 30MBh from the coils should be fine.

 

[600SL]

This. I'm betting your shop voltage is lower than the rated voltage on the nameplate.

As to whether or not this is enough, don't know, seems low. Some HPs run eheat with the HP and some run either or, not both. Which do you have? If both run together, make sure eheat is after the coil in the air handler.

These run together. Heater is after the coil.

 

[sms1974]

Heat Pumps are 65-70% of my business.

Typical operation for our systems is as follows:
The first 2 degrees of thermostat we are running the heat pump only, however some thermostats can be setup to turn on the auxiliary heat after a long run time.

example: The thermostat is set at 70 and the house temp drops to 69, only the heat pump is going to be turned on and run until the thermostat is satisfied, or... if the temperature drops to 68 degrees the auxiliary heat is also turned on to supplement, depending on setup it might run just to bring the house temp to 69 or it may keep the auxiliary on until the thermostat is satisfied, i always setup to run till satisfied.

By switching your thermostat to emergency heat all your really doing is shutting off the heat pump and giving the call for heat straight to the auxiliary heater. emergency heat and auxiliary heat are the same.

like i said before i think your system suffers from one of the following low voltage or it's undersized...

Amps X Volts = Watts

 

[600SL]

Heat Pumps are 65-70% of my business.

Typical operation for our systems is as follows:
The first 2 degrees of thermostat we are running the heat pump only, however some thermostats can be setup to turn on the auxiliary heat after a long run time.

example: The thermostat is set at 70 and the house temp drops to 69, only the heat pump is going to be turned on and run until the thermostat is satisfied, or... if the temperature drops to 68 degrees the auxiliary heat is also turned on to supplement, depending on setup it might run just to bring the house temp to 69 or it may keep the auxiliary on until the thermostat is satisfied, i always setup to run till satisfied.

By switching your thermostat to emergency heat all your really doing is shutting off the heat pump and giving the call for heat straight to the auxiliary heater. emergency heat and auxiliary heat are the same.

like i said before i think your system suffers from one of the following low voltage or it's undersized...

Amps X Volts = Watts

I understand that I am probably low on the aux heat right now. But that is the only part that is connected. The condensing unit will be connected hopefully next week.

Right now the temp here is 27° F and my garage is now up to 58° in 2.5 hr running only the aux heater. I'm sure it will get up to 65 in another hour. But I am hoping to get a 25,000 BTU boost from the HP once installed. Garage temp started at 44° F when I turned it on with an outside temp of 24° F. Very rarely gets colder than 20° F except Sunday night we are calling for a low of 5° F. But I'm never in here at night. At least not on real cold nights. I could go to a 15K unit but that would mean I cant weld when its on.

Am I not reading the specs right about the HP performance at 20° F?

 

[LS6 Tommy]

I think the toaster is doing what it's supposed to. Emergency or auxilliary heat is not supposed to handle the entire load. It's basically freeze protection.

Something no one else has mentioned is that you said your ductwork is not complete. If you are not developing any static pressure you're moving more air across the toaster than it normally gets and that will decrease the delta T.

Tommy

 

[600SL]

Yes its currently an open 18" duct. But I blocked it of ~ 50%

 

[600SL]

Right now temp is about 62° after running 5 hr with 24° outside temp. I think that's all these coils have on there own. Which is fine providing the HP will make up the rest.

 

[EOC_Jason]

Well, outside temp is only one factor... How well insulated is your garage? How many cubic feet is there of conditioned area? That's how you calculate your heat load and size the unit accordingly.

 

[600SL]

Well, outside temp is only one factor... How well insulated is your garage? How many cubic feet is there of conditioned area? That's how you calculate your heat load and size the unit accordingly.

They never stated an R value but its 4" for the walls and 6" for the roof. It has 2 10' by 8 ft R6 insulated doors and 2 steel man doors. It also sits on and un insulated slab.

30' x 48' with 12.5' average height. That's 1440 sq ft. With 18,000 cu ft volume.

It has steel on both inside and outside. I never found a calculator that handles this type of building. Pictures of the construction with insulation are on my signature link below.

 

[600SL]

Picture of the duct blocked off with duct tape and the air handler installation.

 

[LS6 Tommy]

You are running the unit with the cover on, right? also all your heated air is up at the ceiling. I'f put an elbow on the trunk line to aim it down towards the floor until the duct work is finished.

Tommy

 

[600SL]

You are running the unit with the cover on, right? also all your heated air is up at the ceiling. I'f put an elbow on the trunk line to aim it down towards the floor until the duct work is finished.

Tommy

I have been running it with the covers off but only on the electric aux heaters. Ducting will continue across the shop staging down from 18" to 16", 14" and 12" with a downward pointing register at each stage. The 18" duct you see in place will be shortened and a 16" insulated duct will do in its place.

Cant install ducts yet until my duct insulation sleeves come in, which I'm now hearing will be the end of the month.

See duct layout in attached pic