heat pump musings

[vavet]

House was built in 1994. We bought it in 2006. Heat pump was replaced in Jan 2009 while we lived there with a new Bryant 2 ton unit, 15 SEER.
Work was done by a reputable local HVAC company. It wasn't the top of the line unit, but it wasn't the cheapest thing - a nice solid middle of the road unit.
We had a contract with the company that installed it for a few years where they'd come out and inspect it twice a year, but we let that lapse because I wasn't seeing much value in it. It was last done in 2016 I think.
The house was converted to a rental in 2015. The tenants recently moved out so we're updating things and catching up on some maintenance. Included in that is the HVAC maintenance. I asked a coworker who has a HVAC hobby to take care of it for me. He's super meticulous with this stuff. First he cleaned the outdoor unit. It was nasty with a layer of dust, dirt, and **** all over. It appears to be thick enough that he peeled it away. Shame on me for not keeping up with this unit more proactively. I can't believe the tenants didn't complain about high power bills.
He checked pressures and temps last weekend. He told me it had 0 supercool. He's added two lbs of refrigerant (R-410A) and says he has it down to 7 supercool. The system holds 10 lbs refrigerant total. Supercool is supposed to be 11 so he intends to go back and tweak that with a few more ounces of refrigerant. It seems everything is tight - no leaks. Being 14 years old, I would not have been surprised if he'd have reported back that it was on it's last legs and we should replace or budget for imminent replacement. I'm pretty happy with that.

 

[danski0224]

IF it was installed properly, and needs 2+ pounds of refrigerant, everything is NOT "tight".

This is the benefit of annual maintenance that is performed properly- stuff like subcooling can be checked, and if it is changing, that indicates a problem. If there is a component failure, like evaporator coil, it might be found while still under warranty.

Of course, the maintenance has to be performed properly, not by "add a pound" guy.

 

[vwtrey]

Buying a house with heat pump/ac for the first time. What's a round about price for annual maintenance on these?

 

[bonneyman]

I recommended a spring and fall service schedule for my customers. Back then it was $70/hr for a service (today I'd be charging $100 or so per for established customers). First time out would take a little longer as thoroughly cleaning coils and drain lines, oiling motors, tightening all applicable electrical connections, and finely checking charge takes time. Say 2 hour initial svc per unit, 1 hour thereafter. So that's $200 X two the first year, $100 X two after that. Cleaners and lubricants I included, freon was charged for. Factor in a dozen filters (changing them once a month) at about $5 a piece, you're looking at annual maintenance of about $260 or so for established customers. If folks bought filters by the box of 12 I would pay the tax on them and deliver them for free.

After 14 years in business I had very few call blacks and emergency calls. Sure the occasional relay fries or birds nest clogs up the furnace flue. But good maintenance pays for itself.

 

[vwtrey]

I recommended a spring and fall service schedule for my customers. Back then it was $70/hr for a service (today I'd be charging $100 or so per for established customers). First time out would take a little longer as thoroughly cleaning coils and drain lines, oiling motors, tightening all applicable electrical connections, and finely checking charge takes time. Say 2 hour initial svc per unit, 1 hour thereafter. So that's $200 X two the first year, $100 X two after that. Cleaners and lubricants I included, freon was charged for. Factor in a dozen filters (changing them once a month) at about $5 a piece, you're looking at annual maintenance of about $260 or so for established customers. If folks bought filters by the box of 12 I would pay the tax on them and deliver them for free.

After 14 years in business I had very few call blacks and emergency calls. Sure the occasional relay fries or birds nest clogs up the furnace flue. But good maintenance pays for itself.

Awesome, thanks for the detailed info. I'll definitely find someone to do spring and fall.

 

[vavet]

IF it was installed properly, and needs 2+ pounds of refrigerant, everything is NOT "tight".

This is the benefit of annual maintenance that is performed properly- stuff like subcooling can be checked, and if it is changing, that indicates a problem. If there is a component failure, like evaporator coil, it might be found while still under warranty.

Of course, the maintenance has to be performed properly, not by "add a pound" guy.

Losing 20% of the charge over 14 years? I thought that was pretty good.

 

[danski0224]

Ah, but do you know that it happened over 14 years, or not?

 

[vavet]

Ah, but do you know that it happened over 14 years, or not?

I suppose I don't. The last service was ~7 years ago. I suppose they could've topped it up then, but even so...losing 2lbs over 7 years seems small enough that you would not be able to find a leak without the most sensitive of equipment. Am I wrong? Tell me if I'm wrong. What's an acceptable loss rate before you have to do something?
Residential HVAC is not in my wheelhouse so I might be talking out of my ****. I've done some automotive HVAC. You know it's possible to lose some that standard commercial grade equipment won't be able to detect. Maybe with laboratory grade equipment at 10x the price.

 

[danski0224]

I suppose I don't. The last service was ~7 years ago. I suppose they could've topped it up then, but even so...losing 2lbs over 7 years seems small enough that you would not be able to find a leak without the most sensitive of equipment. Am I wrong? Tell me if I'm wrong. What's an acceptable loss rate before you have to do something?
Residential HVAC is not in my wheelhouse so I might be talking out of my ****. I've done some automotive HVAC. You know it's possible to lose some that standard commercial grade equipment won't be able to detect. Maybe with laboratory grade equipment at 10x the price.

FINDING the leak(s) is a PITA. No doubt about that.

What is EASY to find is a change in subcooling when the proper gauges are used. This is evidence of the leak. Adding any or more refrigerant on recurring visits shows that the leak is real and/or getting worse.

Once the loss of refrigerant through the changing subcooling value is established, then one can decide whether or not to find the leak. Or, at least try to.

 

[American Locomotive]

I suppose I don't. The last service was ~7 years ago. I suppose they could've topped it up then, but even so...losing 2lbs over 7 years seems small enough that you would not be able to find a leak without the most sensitive of equipment. Am I wrong? Tell me if I'm wrong. What's an acceptable loss rate before you have to do something?
Residential HVAC is not in my wheelhouse so I might be talking out of my ****. I've done some automotive HVAC. You know it's possible to lose some that standard commercial grade equipment won't be able to detect. Maybe with laboratory grade equipment at 10x the price.

A residential system should never lose any refrigerant. There are systems that are 30+ years old and still have every ounce of their original charge.

Generally very slow and gradual leaks can be found by looking for oil/dirty spots on piping or coils.

 

[juddspaintballs]

I suppose I don't. The last service was ~7 years ago. I suppose they could've topped it up then, but even so...losing 2lbs over 7 years seems small enough that you would not be able to find a leak without the most sensitive of equipment. Am I wrong? Tell me if I'm wrong. What's an acceptable loss rate before you have to do something?
Residential HVAC is not in my wheelhouse so I might be talking out of my ****. I've done some automotive HVAC. You know it's possible to lose some that standard commercial grade equipment won't be able to detect. Maybe with laboratory grade equipment at 10x the price.

I think the point he was making is that it could have been perfectly sealed up and not leaking for the past 13 years (or pick an arbitrary timeframe exceeding the date of your last service) and then it suddenly started losing 2+ pounds of refrigerant over the last year or so. You have no idea if it slowly lost 2+ pounds over 7 years or quickly over 7 days.

 

[PoorUB]

Losing 20% of the charge over 14 years? I thought that was pretty good.

Ah, but do you know that it happened over 14 years, or not?

Who knows if it was ever charged correctly.

I suppose I don't. The last service was ~7 years ago. I suppose they could've topped it up then, but even so...losing 2lbs over 7 years seems small enough that you would not be able to find a leak without the most sensitive of equipment. Am I wrong? Tell me if I'm wrong. What's an acceptable loss rate before you have to do something?
Residential HVAC is not in my wheelhouse so I might be talking out of my ****. I've done some automotive HVAC. You know it's possible to lose some that standard commercial grade equipment won't be able to detect. Maybe with laboratory grade equipment at 10x the price.

I wouldn't get concerned about a couple pounds, but have him check it again next spring. If it is low again, you have a leak.

As for being 14 years old, I would just keep on running it until it doesn't run any longer, or at least take a good look at every thing. Visual on an older unit means a lot, at least IMO. If the unit is clean, no rust, furnace or air handler is clean and looks good, run it.

 

[danski0224]

Who knows if it was ever charged correctly.

You don't.

And it probably wasn't.

 

[danski0224]

Buying a house with heat pump/ac for the first time. What's a round about price for annual maintenance on these?

A price that covers the trip charge and at least 1 hour of labor for the initial evaluation.

Refrigerant charge can only be checked on a split system heat pump in cooling mode. There are exceptions, limited to high end models with self diagnostic capabilities.

The "$29.95, $49.95, etc" "service" companies with their "AC Checks" are not who you want to call. Good luck on that.