TREC rules don’t allow us to run the heat pump in normal mode if the ambient temperature is above 70 degrees, so I’ve been running the emergency heat setting when evaluating a zoned system. In the last 2 weeks I’ve operated several and all were on new homes or 1 year old homes. I had one get to 91 degrees and all of the rest have been around 85 degrees, which is equal to or lower than the ambient temperature. I’ve been running emergency heat for years and in the past, I’ve gotten supply air temps at or above 100 degrees in less than 10 minutes, so I’ve been calling these all out as deficient.
I’D like to see if anyone has a source for what’s acceptable on emergency heating, or what you generally see. Also, on these newer systems, is there some kind of control that won’t let the heat strips fully engage if ambient air temp is high. BTW, it’s hot in Central Texas right now.
Normally they (electric heat strips) go above 100…. umm edit. Normally they don’t operate as intended in my area. When they work correctly they go typically go above 100 in a matter of minutes. About 10 years ago I called this out (heat temp 80-90ish) at a new build and while doing the neighbors the homeowner from a couple weeks before told me his HVAC pro explained to him they had wired the heater wrong.
Bert, Of course I run it in cooling mode, that’s what the system is designed to be used for. I’ve also always tested the emergency heat function, it’s just that lately, all of the numbers have been poor.
Thanks Dave. If I hadn’t seen these types of numbers in 6 straight inspections I wouldn’t have questioned myself. I think I’ve just run into a bunch of duds.
There is absolutely no way with a thermometer and your knowledge to determine a deficiency based on what you have stated above.
, is there some kind of control that won’t let the heat strips fully engage if ambient air temp is high.
Yes, there are several potential things that affects the output temperature from the resistance heaters. Heaters have time delay relays that prevent all the heat strips from coming on at one time if not required such as high ambient temperatures. There are thermostats that only allow second third or fourth stage heaters from coming on when weather conditions prevent the unit from reaching set point temperatures. There are other factors that affect temperature such as the length of the duct, the air flow of velocity through the duct, turbulent versus laminar air flow, bypass Factor of the air passing through the elements Etc.
You are testing resistance heat which produces 3.421Btu per Watt. No more and no less. So your measurements have nothing to do with the heater, rather the system design for a particular building design.
David, Thank you sir and that may be the answer here. It is just too coincidental that this has been happening on all of the heat pump systems. I initially reached out to my HVAC installer and he told me 110-130 degrees but we just exchanged texts and didn’t talk it out. I’ll ask the builder to put me in touch with their installer to cover this and I’ll follow up here.
I did not dig into your observations much, just concerned with the test procedure.
Which ambient are you talking about? IA or OA?
I can’t see that it would be lower unless you’re running in cooling first.
You could have a heat breaker off. You may not have any heat installed. They come without you know? Did you look inside the unit?
If you’re going to go beyond the, “Turn it on and see if something runs” standard, you need more tools and training. The Delta-T crap TREC requires is total BS. The cheapest way to test electric heat is with the Amperage you can test at the panel of the unit or disconnects along the way. I would just turn on the heat and go to the meter and watch it kick up 45 amps or such (depending on the heaters installed). No Amp Meter needed.
Back in the day when this supply/return Delta-T hit the service industry, I was hired by an HVAC company to fix what could not be fixed during service calls or equipment no one dared to even look at. The Service Manager told everyone that he wanted a Delta-T taken at the end of every service call, even if it was just a tripped breaker reset. He called me into his office, where the Big Boss was hanging out and asked me why I didn’t put a Delta-T in my report one day. I told him if he would tell me what he was using a sensible heat measurement from just a thermometer, I would include it in my report when applicable. Silence.
Electric heat only adds Sensible Heat, so a thermometer can be used in the temperature rise method, so long as you measure voltage/amperage in the process. As I previously noted, if you’re not getting the temperature rise you expect, you need to dig in further if you’re going to put it in your report. Again, this is a heat/no heat test. A (+/-) 20 degree difference means nothing. If you don’t have the tools to move further. It’s a WAG (Non-Sientific guess) and it should not be addressed. You are a HI not a TAB.
David, Thanks for your thoughtful response. My testing methodology goes beyond turn it on and see if it works, but not to the point where I’m using a voltmeter to diagnose a problem. For instance, I did check for the on-unit breaker but I didn’t check for the presence of internal heat strips. When it comes to operating and evaluating emergency heating on a heat pump, I simply turn the emergency heating on at the thermostat and I check the supply air temperature. Basically I’m operating the systems using normal controls. If the supply air temperature is inadequate, then I’ll mark it as deficient and move on. IMO, this method aligns with my SOP’s.
With that said, I don’t want to call out as deficient a system that is performing as intended. So if the reason I’m not getting an acceptable air temperature is due to a built in control (like a temp sensor) or sequencing heat strips, that wouldn’t be deficient. But it would make it difficult or impossible to evaluate the performance of heat strips when it’s 95-100 degrees outside.
Looking back, I didn’t do a great job with my OP last night and I should have simply asked what’s a good target temp for a heat pump using heat strips and is there anything built into the system that wouldn’t allow the heat strips to perform as they should when it’s 100 degrees outside. I shouldn’t have even mentioned anything about using the heat pump in normal mode because that has no bearing at all with my question.
In this case my client manages 20 units and they have hired me for an 11 month warranty inspection and I’m spending 90-100 minutes inspecting each unit. I spoke with my client today and they have put me in contact with the builder. Hopefully the builder will put me in contact with the installer so that we can discuss this.
Thanks again and I’ll let you know more when I know more.