Is Noise a Serious Problem with Powered Direct Vent Water Heaters?

[Steve Calif]

I have read several reader comments on this site and others that current Powered Direct Vent water heaters have 1) loud exhaust fans and 2) burner combustion "rumble" (low pitched rumbling noise). Many people are shocked to hear these noises in their very expensive water heaters.

I'm looking at PDV water heaters from Bradford White, HTP Phoenix, Rheem, and GSW.

Which of these are the quietest? Are there others I should consider?

It also seems there are quite a few control problems reported on the HTP Phoenix.

Why am I looking at PDV? Because I need to seal off the existing air inlets to my utility room off the garage. There's an upper air inlet that opens into the ventilated attic overhead and another floor inlet that opens to the ventilated crawl space. The air vent to the attic dumps a huge amount of heat to the attic contributing to snow melt on the roof and ice dams. It's also a good fire path from the utility room straight to the attic. With a sealed combustion water heater, I can permanently close off both the upper and lower combustion air vents. The utility room also has a Bryant condensing furnace with a closed combustion system. So with a sealed, closed combustion burner in both the water heater and the furnace, I won't need the air vents to the crawl space and attic.

 

[Dana]

A heat pump water heater doesn't need any venting, and operating costs are comparable to (and often less than) gas water heaters, depending on your local electricity and gas rates.

At 49 dBa the Rheem Performance Platinum series heat pump water heaters are quieter than many power vented gas units- probably quieter than your condensing furnace. That's about as loud as a typical refrigerator. There are others. Third generation heat pump water heater designs have come a long way toward reducing noise while increasing efficiency.

Minimum room volume for a heat pump water heater is typically between 700-900 cubic feet, though with some of the heat pump water heaters can be ducted for both incoming an exhaust air (including Rheem) could make use of the crawlspace volume if the utility room is too small. (A 12 x 10 room with 8 foot ceilings is plenty for most. Rheem calls out 700 cubic feet, so a 9.5 x 9.5 x 8' room would still work just fine without ducting air to/from some other space.

The down side of a heat pump water heater is slow recovery time when operated in heat pump only mode, though most are "hybrid", with a standard resistance heater element that can be programmed to turn on if/when faster recovery is needed (which comes at the cost of some efficiency.)

The HTP Phoenix is pretty quiet compared to the B-W and others with tank-top blowers, but not completely silent. You can hear how loud it is at high fire at about the 5 minute mark in this combustion test/setup video relative to the technician's voice.

 

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[Steve Calif]

The HTP Phoenix is pretty quiet compared to the B-W and others with tank-top blowers, but not completely silent. You can hear how loud it is at high fire at about the 5 minute mark in this combustion test/setup video relative to the technician's voice.

My utility room is about 8 ft deep x 3.5 ft wide x 10 ft tall, so not enough volume for a heat pump unit. I find the heat pump concept somewhat comical. The heat is coming from the room heat which, in winter, is provided by your house heating system. In the summer, in an air conditioned house, you are extracting heat from the cooled air in the house.

Thanks for the link to the tuning video for the HTP Phoenix. I could barely hear the unit compared to the techs voice. It sounded like a gentle whoosh in the background. I didn't even notice the change in fan pitch going from high fire to low fire.

I talked to the HTP Service Dept. today and was surprised to learn the fan operates at such high RPMs: 5,000 rpm for ignition; 2,150 for low fire; and 6,300 for high fire.

Also thanks for the subjective noise comparison to the BW unit with the induced draft fan sitting on top of the unit.

That video goes a long way toward reducing my fears about noisy units. The HTP service person I spoke to attributed noise complaints to inexperienced home owners trying to set the unit up without a combustion analyzer.

 

[Phog]

Hi Steve, I'm sure Dana will offer a defense of heat pump water heaters as well. But I wanted to add a few comments of my own.

First, regarding extracting heat from conditioned home air. This is true. However a significant portion of the heat pump "captured" energy comes from dehumidification -- the "latent" heat stored in the air (due to phase change of water vapor into liquid). In summer a heat pump works in an additive sense with your existing A/C and will slightly reduce the amount of electricity the A/C draws.

Second, while it is true that in winter the heat pump is just capturing energy that your furnace/boiler puts into the house, and will slightly increase your home heating bills, this round trip is extremely efficient. All told the heat pump water heater is in fact cost competitive, even if this is not intuitive or seems silly.

Third, regarding the size of the room. You could install a pass through such as commonly are used for air return. And if you have a forced air system you could run a duct to the room to circulate air through.

Finally all this being said I think that the HTP would be a fine choice, and in fact probably what I will choose to install in my own home when my present (gas natural draft/atmospheric vent) tank goes. Just wanted to stick up for the heat pump technology, which really is good in general & in certain applications the best choice.

 

[Dana]

My utility room is about 8 ft deep x 3.5 ft wide x 10 ft tall, so not enough volume for a heat pump unit. I find the heat pump concept somewhat comical. The heat is coming from the room heat which, in winter, is provided by your house heating system. In the summer, in an air conditioned house, you are extracting heat from the cooled air in the house.

You might find this document more insightful than comical. Take the time to fully absorb Figure 2.1. In the fully ducted configuration the water heater's impact on HVAC energy use is less than 1%. In the exhaust-only ducted configuration it was close to 0% in the test house.

Heat pump water heaters still work at reasonable efficiency even with intake air in the high 30s F, and removing the heat in summer reduces the duty cycle of the AC a bit.

The volume of your crawlspace is probably well over 700 cubic feet, and probably never hits anywhere near freezing, suitable for a ducted heat pump water heater. If the floors above the crawlspace are insulated, the bulk of the heat taken from the crawlspace would be sourced from either the earth or the outdoors, but even if it isn't the fraction of heat delivered by the condensing Bryant is at condensing efficiencies. The exhaust air from the heat pump water heater is going to be drier than the crawl space air, reducing the mold potential in the crawl space. If the heating ducts are in the crawl space the water heater would be harvesting a fraction of the duct losses rather than losing them to the ground or outdoors.

It would probably be most efficient for the water heater intake to be drawn from the utility room, exhausting into the crawlspace, with an appropriately sized floor grill (perhaps your existing makeup air grille) to allow the crawlspace air into the utility room equalizing the pressure. If that creates indoor air quality problems in the utility room you could always retrofit-duct it to the crawlspace. Whether or not it makes sense (or is even legal) to use the garage air as part of the loop depends on other particulars.

West of the Rockies the amount of additional latent heat-of-vaporization harvest (latent cooling) is pretty small compared the Gulf Coast states or even New England, but it's still non-zero. In my area people report being able to turn off their basement dehumidifiers after installing heat pump water heaters, but basement dehumidifiers aren't usually necessary on the left coast or the inland portions of the Pacific Northwest, where summertime outdoor dew points average in the 40s F.

So in the worst case 1/2- 2/3 of the heat going into heating the water during the winter is from the condensing furnace, which is pretty efficient (and cheaper than resistance electricity in a plain old electric tank) and during the summer it's lowering the cooling load.

 

[Steve Calif]

You might find this document more insightful than comical. Take the time to fully absorb Figure 2.1. In the fully ducted configuration the water heater's impact on HVAC energy use is less than 1%. In the exhaust-only ducted configuration it was close to 0% in the test house.

Thanks, Dana. That's a good report and insightful. I agree that west of the Rockies latent heat is not going to be a big contributor. We just don't have that much humidity and certainly don't need a dehumidifier in the house. In the cold winter months, RH already drops to very low levels in a warmed house.

Wouldn't the problem with a HP water heater located in a small room be having to install new ductwork to route the air where I want it?

I've got a completely full 200A Cutler Hammer panel that would have to be upgraded to convert to an electric WH. Some of the single breakers have already been twinned. For a heat pump, I'd either have to figure out how to add a new double gang (no space) which probably means a subpanel. So, between the possible ductwork changes and the panel changes, the heat pump solution would become very expensive.

I'm continuing to think the HTP Phoenix condensing water heater makes most sense. Gas supply is adequate. Changing out the exhaust duct for a concentric inlet/outlet PVC piping system is simple. Closing off the ceiling and floor air vents is simple.

The biggest problem is they nearest HTP dealer is 500 miles away. I've started calling local mechanical companies and plumbers to see if they could install it. I need to find somebody who understands combustion, excess air, and tuning O2, CO, and CO2 levels. Few plumbers are equipped to do that; most HVAC guys have the combustion analyzer and manometers, but they typically don't touch water heaters. So installation is a conundrum.

 

[Dana]

The ductwork for a heat pump water heater isn't very big. You already have one hole in the floor that's probably more than adequate for one end of the heat pump water heater. Without the full layout it's hard to guess how messy it's going to be, but even un-insulated flex duct is fine for these applications.

The breakers for a heat pump water heater aren't any greater than for a standard electric. The HTP Phoenix Light still needs a breaker too (though only 120VAC)

The Westinghouse WBGRxxxNG076 versions of the Phoenix Light Duty are sold through the orange box store, which would have to be closer than 500 miles away. (Insert 050, 060, or 080 for the xxx in the model number for the tank size.) It's exactly the same unit under the label, and calling Westinghouse tech support on them rings a phone at HTP headquarters. Warranty stuff would go through the Westinghouse (and or box store) channel, but the units themselves are identical.

Any competent installer of modulating condensing heating boiler equipment should be able to set up a Phoenix /WBGR water heater. If you tell the HVAC folks that it's a modulating commercial water heater (which it is) and that everything about it is more akin to a mod-con boiler than a water heater, maybe that will pique more interest in taking on the job. Most should work pretty much OK right out of the box, but it's good to fully commission the thing rather than cross your fingers and hope that it's about right (and it probably is.)

 

[Steve Calif]

The ductwork for a heat pump water heater isn't very big. You already have one hole in the floor that's probably more than adequate for one end of the heat pump water heater. Without the full layout it's hard to guess how messy it's going to be, but even un-insulated flex duct is fine for these applications.

The breakers for a heat pump water heater aren't any greater than for a standard electric. The HTP Phoenix Light still needs a breaker too (though only 120VAC)

The Westinghouse WBGRxxxNG076 versions of the Phoenix Light Duty are sold through the orange box store, which would have to be closer than 500 miles away. (Insert 050, 060, or 080 for the xxx in the model number for the tank size.) It's exactly the same unit under the label, and calling Westinghouse tech support on them rings a phone at HTP headquarters. Warranty stuff would go through the Westinghouse (and or box store) channel, but the units themselves are identical.

Any competent installer of modulating condensing heating boiler equipment should be able to set up a Phoenix /WBGR water heater. If you tell the HVAC folks that it's a modulating commercial water heater (which it is) and that everything about it is more akin to a mod-con boiler than a water heater, maybe that will pique more interest in taking on the job. Most should work pretty much OK right out of the box, but it's good to fully commission the thing rather than cross your fingers and hope that it's about right (and it probably is.)

Thanks. You raised a good question -- does the HTP Phoenix require a dedicated breaker? Or can I plug it into the 110 VAC outlet that the furnace uses?
I talked to two local mechanical companies today. Both are willing to do the install on a T&M basis. They are familiar with other PDV water heaters and PDV furnaces. One thought the total installation price would be about $1,000. The gas, cold water and hot water connections are simple. I'm guessing the most time consuming thing will be replacing the current exhaust duct with the Concentric Vent kit and properly flashing / roof jack / boot on the roof. They have the necessary combustion analyzer and manometers.

Both companies said they really don't like doing service work like this because the margins on labor are not very good. The prefer a bundled product + labor package to earn higher margins (I spend 15 years in Sales Operations for large high-tech sales and we had the exact same problem). One company is already booked out through June!

The closest Home Depot is only 4 miles away. The dealer I mentioned was in Bozeman, Montana, 500 miles away. I originally thought I would have to buy from him, but that was before I realized HD sells the exact same HTP water heater with the Westinghouse brand. The tech support guy I spoke with at HTP confirmed exactly what you said - the Westinghouse unit sold at HD is the exact same water heater and a call to Westinghouse tech support goes directly to the HTP service department.

 

[Dana]

Without knowing how much current the furnace draws it is not possible say whether the water heater can share the circuit used by the furnace. Look up the electrical specs on both the furnace and the water heater. Some furnace air handlers are serious power hogs- most air handlers run on 240VAC, not 120VAC and hard-wired, but maybe it's just the furnace controls that are plugged into the outlet (?).

 

[cub123]

The easiest, quickest, cheapest way to silence a direct vent on a water heater. Shows how to make a resonator/muffler.
https://www.youtube.com/watch?v=dB1sxsmz3Vk