Are powered direct-vent water heaters unbearably noisy?
After a lot of research and input on another post (see “Water heater: Makeup combustion air source”), I’ve concluded I should change to a Powered Direct Vent (PDV) hot water heater. I’m looking at Bradford White; HTP Phoenix (sold under the Westinghouse name at Home Depot); Rheem; GSW; and A.O. Smith.
I see some reports on the web from unhappy buyers complaining about PDV water heater noise from 1) the exhaust fan and 2) the natural gas burner rumble. I also see a number of complaints about the controls causing problems.
It’s hard to tell if these are serious problems with PDV water heaters. Our water heater is in a utility room with a Bryant condensing furnace that has a powered exhaust fan and the furnace noise is hardly noticeable. The high efficiency Bryant furnace burner does not rumble at all.
Does anybody have first-hand knowledge about these noise sources on PDV water heaters? Are they especially objectionable?
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Poor installations can create a lot of vibration also which you will feel and hear throughout the house. I saw nothing wrong with the set up you have now other than the combustion MU air vent going into the attic which should be brought down to the floor level where the combustion is happening.
Thanks. I think the purpose of the upper fresh air vent is to make sure the upper portion of the room is ventilated and free of any gases that might accumulate there. Wouldn't bringing the top vent down to floor level defeat that purpose? The building inspector I spoke with said that an upper vent and a lower vent are required. Figure 7 (attached) at http://www.americanwaterheater.com/media/42218/flameguard.pdf (page 9) shows attic air being delivered to floor level, but that is in addition to ceiling vent communicating to the attic. See attachment.
Well if that is what they require then leave it. But obviously, your floor vent does not correspond to the venting they show in the drawing which is causing the hot air drafting into the attic. Normally, intake and exhaust vents have to be a certain distance apart to prevent intake from pulling in exhaust. Do you have other venting in the attic as described in the drawing, eg. the gable vent? If you go by the rule of thumb in the drawing, a 120000 btu tank only requires 30 sq in. which would translate to a 6 in. diameter hole for both.
My venting configuration follows Figure 6 below. MU air from the crawl space AND from the attic. I was just showing Figure 7 because it illustrates what you were suggesting. Our attic ventilation is a combination of eave/soffit vents, ridge vent, and a few turtle vents in areas without ridge vent.
The figure shows the same 1 sq inch per 4,000 BTU. For a 76,000 BTU/h burner, that equates to a 5 inch diameter fresh air inlet in the ceiling and the floor. The ceiling pipe extending into the attic appears to be 5 or 6 inch in diameter.
I was thinking early today about switching my plan to an electric water heater, but I'm concerned how hard our utility (Avista) is pushing customers to change to gas. That suggests they are going to be jacking up electric rates and are concerned about electricity supply. So I'm leaning back toward gas tonight, probably the HTP Phoenix 80 gallon. Home Depot sells it under the Westinghouse brand name, Model #WGR080NG076.
Yeah, those sly power companies. With AC season coming up, so do rates. Main thing obviously is the location of the MU air coming in near the combustion which you already have with the floor vent. With the warmer weather coming in, you shouldn't have the problem with the warm air causing problems in the attic so you can buy yourself some time. Perhaps if you run / extend the vent through the ceiling along the attic floor over near to the soffit vent and insulate over it, it may help prevent the build up of hot air in the attic in the winter.
Gas is generally much cheaper per BTU than electricity for heating. That is for resistance heating, heat pumps are different.
A lot of the utilities have been pushing efficiency improvements to be able to delay capital outlays for construction of new generation. That doesn’t necessarily mean they are planning on jacking up rates. Utilities work by extrapolating out load increases to plan when new generation will need to come online. Encouraging customers to be more efficient (use LEDs, heat with gas, etc), tends to flatten that line out a little so that new generation isn’t needed as soon.
If it was my house, I’d go with either a power vent gas heater or a heat pump.
Bill
Avista announced plans a couple weeks ago to go 100% renewable power within 20 years. That tells me high electricity prices and unreliable power are coming (I was in the power business for 30 years). So I'm going to stick with gas. In the Northwest, "renewable" means a lot of hydro generation with existing dams, but it also means big expansion of windmills and solar panels.
I got rid of ours after replacing the blower once. The noise in the house wasn't too bad. It was located in a basement directly underneath the kitchen. I did know when the water heater kicked on, when I was in the kitchen. The problem I had was the noise outside and the occasional whiff of combustion. It exited near a patio area and there wan't another convenient location for the exhaust.
I’ve never noticed much noise, but ours is in the basement. A key thing to do to minimize noise transmission is to not rigidly mount the exhaust vent pipe to floor joists or wall studs. My installation is such that the exhaust pipe goes directly from the water heater to the block foundation wall and out with no need for any pipe hangers.
If you have to run a length of vent pipe and it needs to be supported, don’t use rigid hangers. Steel strap suspended between joists with the pipe hanging from the middle is much better than strapping the pipe tightly to a joist. The springiness of the hanger helps to isolate the vent pipe from the joists a bit to limit sound transmission. I’d guess that most people that don’t like the noise from these things are hearing resonances in their floor that have been transmitted from the vent pipe. Avoid that sound transmission and you’ll have less noise. Another thing to do is to line the mechanical room with mineral wool insulation and leave it exposed. The soft mineral wool will absorb sound and keep the room quieter. This is a lot cheaper than a full soundproofing job.
Bill
Thanks, Bill. Agree with you on all counts. We have an existing hot water recirc system and it is hard-plumbed with rigid copper tubing. It transmits low frequency resonances to the piping and I can hear the low rumble in the kitchen. The pump is not mounted to the house structure - it is just suspended from the rigid tubing at the water heater.
We have an almost straight vertical shot from the HW heater through the attic sheetrock and straight to the exhaust vent in the roof, so no horizontal inlet/exhaust pipe runs are required. I'll have to think about how to suspend the vertical concentric pipe from the wood structure. Thoughts on how to mount a vertical concentric pipe?
I've used 2" or 3" thick Roxul to line built-in speaker cavities with great success. I was already thinking about lining the wall that the utility room shares with the kitchen with Roxul (now called just ROCKWOOL). I was also thinking about adding a sheet of Mass Loaded Vinyl to that wall followed by another layer of 5/8 fire rated sheetrock over the vinyl mat. I would be able to modify about half of the long 8 ft dimension because the furnace restricts access.
If you want to soundproof the room, skip the MLV sheet. Use resilient channel to hang the drywall, then two layers of 5/8” type X (not ultralight, you want the mass here) with green glue between the layers. I’d try the exposed mineral wool first, then add a layer of 5/8” drywall on resilient channel next. If you still want more sound isolation, add the second layer of 5/8” drywall and green glue.
For that vertical pipe, there are purpose-made hangers for that. They are a clamp with arms on the sides. Mount the arms on vibration isolators (rubber mounts, you can get them from McMaster Carr). That will probably be enough to keep it quiet. Make sure the pipe doesn’t contact anything else that is rigid.
To isolated your recirc pump, I can think of two options:
1- rigidly mount the pipe above and below the pipe to concrete. This will tend to damp the vibrations and quiet things down. You can use pieces of 2x4 as spacers. You want a SOLID mounting though so that it ramps vibration. That means short pieces of wood that are straight to concrete. If that doesn’t or can’t work, then put short flexible jumpers (usually braided stainless steel like water heater connectors) above and below the pump. Arrange things so that the flex jumpers make a single loop above and below the pump, then rigidly mount the pump to separate structure from the piping. This will help to limit sound transmission between the pump and the rigid copper piping.
Bill
Yes, they are unbearably noisy.
My experience was miserable despite Roxul into the ceiling above the water heater (which did help somewhat), suspending the pipes on hangers for isolation from the joists, etc. The joists transmit the rumble to the floor above.
We replaced entire water heater/hydronic system with an indirect hot water heater off a direct-vent boiler and life has been much, much quieter. It was worth it for the (pretty big) hit to the wallet.
I don't have major noise issues with mine. It is in the basement, directly below the sink. 2" PVC vent 3ft long going up out the rim joist. It is louder than I like with the window above the sink open. With the window closed, it is no louder than my fridge.
My only complaint is the thermostat is touchy.
https://www.lowes.com/pd/A-O-Smith-Signature-Premier-40-Gallon-Tall-6-year-Limited-50000-BTU-Natural-Gas-Water-Heater/1000213627
The HTP/Westinginghouse condensing units are pretty quiet compared to the rest of the pack. Take a listen starting at about the 5 minute mark in this combustion testing instructional video when they ramp it up to max fire:
https://www.youtube.com/watch?v=eX0FfYyQ5Lg
Didja hear it? It's definitely there over the background white noise, but the technician doesn't have to raise his voice to be heard.
Steve, the noise is akin to a vacuum noise if you listen to it from the outside. Inside the home theres a medium hum from the fan motor.
The more hot water you use the more it runs and the more annoying it may get. In typical low use homes the heater only fires a few times a day for a short while.
While on the subject of direct vent water heaters, I am NOT a fan of them for the shear reason of the PVC venting. PVC pipe fittings and glue are not rated for the temps the water heater exhaust sees on a cycle. Worse is when the heater scales and the heat from the fire is not being absorbed into the water and the stack temp is raised significantly. When required to install one of these heaters we spec Centrotherm or Duravent Polypropylene vent approved pipe. Feel free to reach out with any questions.
Moe from TurnUpTheComfort.com
Thank you, Moe. I found a couple of articles last night pointing out the same thing -- that PVC is not really rated for exhaust stack duty. One article pointed out that PVC use as a condensing unit exhaust stack has already been banned in Europe and the author expects a similar ban in the U.S. I was looking at Duravent last night, too. I had not heard of Centrotherm and will check that out.
Interesting point about the stack temperature increasing as the heater scales up and heat transfer is reduced.
I installed a thermocouple in my condensing furnace stack and it rarely goes above 105F. I use that to monitor the furnace when we are out of town in the winter. It gives me an early indication that the furnace didn't ignite after a call for heat rather than waiting for the house to cool down below 55. I monitor the temps remotely using Wireless Sensor Tags (wirelesstag.net) -- very reliable and affordable remote temperature monitoring.
Your very welcome Steve!
Centrotherm is the same as Duravent, just a competitor. I personally use Centrotherm as its what the suppliers I use stock.
I found glue joints unglued on PVC on installed systems. If you do use PVC, make sure to pin the fitting to the pipe with a stainless steel screw.
Feel free to ask any questions.
Our neighboring (100-yds or so) laundromat installed a direct vent, probably high capacity, appliance with the pipes terminating a few feet above grade facing the front of our house. The TONE produced when the appliance is operating is heard whether outdoors or indoors throughout with every window shut tight. Just a miserable effect.
Sound can be modified. I have this problem when designing generator rooms at work. There are sound baffle devices (they look like airfoils made of perforated sheet metal with mineral wool inside) that are amazingly effective. For round exhaust-pipe systems, sometimes a resonator will work, which is basically a section of larger or smaller pipe cut to a length to act as a trap for a particular frequency. There are some articles written about tuning mufflers on high-end cars to accomplish things like this.
You'll need to work with the laundromat operator to try to find a solution. Commercial mechanical contractors may help, but I'd call a generator dealer (a commercial generator dealer, look for Kohler Power, Cummins/Onan, or Caterpillar), ask if they can refer you to someone who makes sound attenuated generator enclosures. The same fabricators that make the sound enclosures for generators will likely be able to help with a noisy exhaust from a direct vent appliance.
Bill
The easiest, quickest, cheapest way to silence a direct vent on a water heater.
https://www.youtube.com/watch?v=dB1sxsmz3Vk