Nyle's numbers (HPWH)

[Ashful]

I've missed yet another summer of installing a air-source HPWH in my basement boiler room, and now that we've finished most of the basement, there is yet another reason why I should be taking advantage of this technology. Our current setup uses the boiler to heat our water, via an Amtrol Boilermate, and burns about 1 gallon per day for DHW. The efficiency of just heating the water isn't terribly bad, but it dumps enormous excess heat into the house, which I must then battle down with my air conditioning. Horribly wasteful.

So, I'm on the Nyle site, checking out their offerings, when I see some graphs that just don't seem to jive. First, there this:



That oil usage seems awful low, even at today's $1.86/gal rate. Most folks report burning at least 0.6 gallons per day per household for DHW, so it's really more like $410 by today's pricing ($800 two or three years ago). Does that mean I should scale the HPWH costs by 160%?

Then there's this:



Okay... so what "household" was $172 in the first graph, when Two People = $270 in the second?

Given my situation, I don't expect as quick an ROI as the folks running electric resistive water heaters, but it would be good to get some sense of the relative costs. These numbers really cast some doubt on Nyle's marketing, as they have both apparently-disagreeing graphs side-by-side on the same page:

(broken link removed to http://www.nyle.com/water-heating-systems/air-source/)

 

[Ashful]

Oh, and this has nothing to do with Nyle, but something I found pretty cool: http://www.statewaterheaters.com/product_selector_one_page.aspx

It's the nicest sizing guide I've seen, in that it accounts for number of concurrent AND consecutive showers, along with maximum tub size.

 

[WoodyIsGoody]

I think a bigger discrepancy exists in the second chart.

The relative costs between resistive and heat pump remain the same whether there's two people or six people while it's well understood that a heat pump water heaters efficiency will drop with six people using it unless all the showers are spaced exactly 4 hours apart. Because it takes 4 hours for a heat pump water heater to recover without using resistive heat.

Regardless, in your case, it's obviously cost effective to go with a heat pump water heater in the warm season so why are you worried about the details? And if you are really interested in them, it's a simple matter to calculate them yourself by knowing the flow rate of your showerheads and faucets and average time used per day (coupled with the cost/btu of different solutions and the water supply temperature). It's always more accurate to run the numbers yourself than rely on gross generalizations.

But, yeah, the two charts are probably from two different sources who calculated the cost at different times based on different water supply temperature assumptions, different energy prices and different usage patterns. I doubt there is a hidden agenda but this is a good illustration how facts and figures COULD be used to deceive. Always do your own analysis if you want to know what it means.

 

[woodgeek]

To start you need to assess your HW usage. This will be a timing the flow from showerheads in gallons per minute. If you have 2-2.5 gpm and 2 adults (like 20-30 shower minutes per day), no frequent use of giant jacuzzi tubs, etc, you have 'normal' HW usage. Add in a child and appliances, and you are probably in the $400/yr range for conventional electric, and a third of that for HPWH.

Be advised that the package HPWHs have improved over the last few years to EFs up to 3 and higher, while the first gen ones were more like 2. I have not seen any non-package system specs lately....are they at EF = 2 or have they improved too?

I had the same problem with AC with my old boiler....in my shady/smaller house my AC bill dropped 50% when I tore out the boiler. It sucked to run the AC when it was 65°F outside on a beautiful September day (I could open doors and windows....and the house would still be too hot).

While I am happier now (I was burning 1.2 gal oil/day in the summer), afterwards I sometimes had a humidity control problem in the fall, when the dewpoint outside is >70° for a week in a row, but it was not warm enough inside to run my AC for very long. I had to tweak my system to deal with that.

 

[begreen]

Is clothes washing too small of a HW hit?

 

[Ashful]

Is clothes washing too small of a HW hit?

Clothes washing = 15 - 30 gallons per load. My average shower = 5 minutes at 2 GPM.

 

[sloeffle]

Our 50 gallon Marathon electric water heater was costing me roughly $50 - $60 a month to run. I bought a 50 gallon A.O Smith that I tied inline with the Marathon a couple years ago. We have a GSHP, so I hooked the Marathon up to the GSHP. It costs me roughly $6 - $10 a month now to make hot water with the HPHW and I no longer have to run a dehumidifier in the basement. I'd say my ROI is roughly 18 months or so. Their are three people in our household.

I bought a Nyle and could not get it work with my Marathon correctly so that is why I went the stand alone HPHW route.

 

[begreen]

Clothes washing = 15 - 30 gallons per load. My average shower = 5 minutes at 2 GPM.

So that should be included in the normal HW usage too.

 

[woodgeek]

So that should be included in the normal HW usage too.

In our house few loads are 'HOT', most are cold or maybe warm. And our HE washer only uses a few gallons per load.

 

[WoodyIsGoody]

Clothes washing = 15 - 30 gallons per load. My average shower = 5 minutes at 2 GPM.

My full sized Bosch washer uses as little as 13 gallons/load, all of it cold except for the initial wash fill. Since it fills three times, the hot water usage (when selecting a hot cycle) is under 5 gallons. A warm cycle will be well under 3 gallons of hot water. I've been using them for about 4 years and my clothes have never felt or looked better. My clothes are staying new looking about twice as long. I've used the "Comforter" cycle for washing large comforters and 4 season winter mountaineering down sleeping bags with excellent results. The comforter cycle will use more water but less hot water since it uses cool-warm water.

My showerheads are 1.5 GPM Sierra brand that feel powerful, very wet and rinse shampoo and soap off quickly.

I don't feel I'm giving up any luxury with these water saving appliances, in fact, I wouldn't go back to old top-loader washers or 2.5 GPM showerheads even if they were just as efficient. The new stuff actually works better. Everything is so efficient I can run a three bedroom, three shower house with a electric on-demand water heater even though the year-round water supply temperature is a ball busting 41-43 degrees! The shower flow rate s good for two simultaneous showers but, there has never been an occasion when people wanted to use three showers at the same time. I've had 6-8 guests a few times without any issues. If there was too much simultaneous demand, the showers would not go cold, the WH just reduces the flowrate while maintaining the output temperature. Running out of hot water iss a thing of the past. I've even filled my 385 gallon hot tub with 104F water. No wait for the spa heater to bring it up to temperature. That takes about $4-$5 worth of electricity but only because my supply water is so frigid.

 

[begreen]

Everyone doesn't have miserly washers. The point being that the average home is going to use about 10-20 gallons of hot water per washer load. That should be included in the accounting for HW usage.

 

[WoodyIsGoody]

Everyone doesn't have miserly washers. The point being that the average home is going to use about 10-20 gallons of hot water per washer load. That should be included in the accounting for HW usage.

I think the original estimate I saw in this thread of 15-30 gals. hot water/washer load is unrealistically high because not many loads are done on "hot" cycles and, with most machines, even those loads done on "hot" don't use hot water for the rinse cycles. Most machines people have purchased over the last few years are Energy Star rated and so the average water needed for each load is dropping every year.

Showers need to be calculated with a blend of hot and cold water too.

 

[maple1]

I've missed yet another summer of installing a air-source HPWH in my basement boiler room, and now that we've finished most of the basement, there is yet another reason why I should be taking advantage of this technology. Our current setup uses the boiler to heat our water, via an Amtrol Boilermate, and burns about 1 gallon per day for DHW. The efficiency of just heating the water isn't terribly bad, but it dumps enormous excess heat into the house, which I must then battle down with my air conditioning. Horribly wasteful.

So, I'm on the Nyle site, checking out their offerings, when I see some graphs that just don't seem to jive. First, there this:

View attachment 200701

That oil usage seems awful low, even at today's $1.86/gal rate. Most folks report burning at least 0.6 gallons per day per household for DHW, so it's really more like $410 by today's pricing ($800 two or three years ago). Does that mean I should scale the HPWH costs by 160%?

Then there's this:

View attachment 200702

Okay... so what "household" was $172 in the first graph, when Two People = $270 in the second?

Given my situation, I don't expect as quick an ROI as the folks running electric resistive water heaters, but it would be good to get some sense of the relative costs. These numbers really cast some doubt on Nyle's marketing, as they have both apparently-disagreeing graphs side-by-side on the same page:

(broken link removed to http://www.nyle.com/water-heating-systems/air-source/)

Yes, those graphs are rather messed up.

With my experience, you will see a much shorter payback time than those who would switch from resistance electric, no question. I was burning around 0.6-0.8 gallons of oil per day with our tankless coil oil boiler DHW. We now do it with $30/mo (actually more like $25 I think but let's compare conservatively) of $0.18/kwh electricty, using an ordinary 80 US gallon resistance tank heater. (Not a fancy one - garden variety). I did add heat traps and put a layer of FG insulation around it - so it's not quite stock. But I have no doubt you will be way ahead in switching to something heat pump based. I am not sure if I would go the add-on route, or the tank type. That might depend on how you would adapt the add-on to what you have now. If I was going add-on I think I would marry it to a new electric resistance tank heater so it would be there for backup & I wouldn't need to fire oil at all in the summer. Maybe?

Do you plan on keeping your oil boiler in place - can you let it go cold for the summer if so? That would also pay a large part in payback numbers.

 

[Ashful]

Do you plan on keeping your oil boiler in place - can you let it go cold for the summer if so? That would also pay a large part in payback numbers.

Yes, shutting down that boiler is the primary goal, but not really for the cost benefit. The consideration of cost and ROI are always interesting, which is why I called out these graphs, but frankly too small to be a deciding factor or make any difference in my budget.

The goal is eliminating the waste heat that boiler is pumping into my basement all summer, so we can have a cool and comfortable basement rec room in the summer. Our central AC is on the fourth floor, and not piped down to the basement, and I see this as an easy way to achieve that goal. I have noticed that when I shut off the boiler, even in the hottest weeks of the summer (eg. when we're away from the house on vacation), that basement stays very cool and comfortable. However, it gets very warm and less comfortable with that boiler running all summer, not to mention the noisy (and also heat-producing) dehumidifiers we run down there all summer.

 

[maple1]

Yes, shutting down that boiler is the primary goal, but not really for the cost benefit. The consideration of cost and ROI are always interesting, which is why I called out these graphs, but frankly too small to be a deciding factor or make any difference in my budget.

The goal is eliminating the waste heat that boiler is pumping into my basement all summer, so we can have a cool and comfortable basement rec room in the summer. Our central AC is on the fourth floor, and not piped down to the basement, and I see this as an easy way to achieve that goal. I have noticed that when I shut off the boiler, even in the hottest weeks of the summer (eg. when we're away from the house on vacation), that basement stays very cool and comfortable. However, it gets very warm and less comfortable with that boiler running all summer, not to mention the noisy (and also heat-producing) dehumidifiers we run down there all summer.

Add in the fact that the HP will also dehumidify and AC to some extent - this is starting to look like a no-brainer.

It will contribute a bit to noise, but personally that wouldn't factor in to my decision.

 

[Ashful]

Add in the fact that the HP will also dehumidify and AC to some extent - this is starting to look like a no-brainer.

It will contribute a bit to noise, but personally that wouldn't factor in to my decision.

You got it! The noise shouldn't be much of a problem, as it's buried back in the boiler room, two rooms removed from the rec room. I can close a door when we're down there, to isolate the noise, but leave it open for dehumidication when we're not.

I'm still not finding what I would consider a good indirect option (the Nyle's footprint is unacceptable), but I'll post another thread on that. These hybrid units, with the HPWH mounted atop the tank, are so ubiquitous and inexpensive that I guess it's the way I'll end up going. But that creates a few questions and options, when it comes to integrating that into my existing indirect system. I can't just put it upstream of my boilermate, if I intend to shut the boiler off for the summer, unless I valve around it and drain down the boiler storage tank (read: PITA).

I was hoping to have something like the Nyle, which could just piggyback onto the existing storage, but in a vertically-oriented package that eats up less square footage. My boiler room is getting tight, used for storing things like window and door screens and storms, since we finished most of be basement.

 

[maple1]

I would be tempted to just yank the boilermate and replace it with a HPWH.

 

[woodgeek]

I would be tempted to just yank the boilermate and replace it with a HPWH.

Me too. The whole indirect tank concept is obsolete IMHO...get's you better HW quality than a coil, but at the cost of even more parasitic losses than the boiler alone, and more space occupied and more things to break. Sitting in a warm boiler room, the HPWH would be happy and efficient all year round. In the winter it will be stealing heat that otherwise you would be sending to the Morlocks.

I think the piggy-back HPWHs are scarce b/c the high EFs and the low costs (from mass production) of the all-in-ones are killing them in the market.

The question is whether you can get an 80-gallon unit in there...a big house will want a big heater. My slowest recovery is in January with the heater sitting at 48°F in my garage. You will not have that problem.

 

[maple1]

The question is whether you can get an 80-gallon unit in there...a big house will want a big heater. My slowest recovery is in January with the heater sitting at 48°F in my garage. You will not have that problem.

That could be (fairly) easily remedied by also at the same getting a new conventional electric tank heater (sized to fit the space you have) and plumbing to the HPWH, in series, just downstream. Put a small recirc pump in a loop between them - you would have all kinds of reserve then, and also added redundancy if concerned about the HPWH heater ever going kaput for weird reasons. Electric tank heaters are cheap - can get one sized to fit whatever space you have. Add in a B&G Ecocirc and Johnson A419 to control it & Bobs your uncle.

 

[STIHLY DAN]

That could be (fairly) easily remedied by also at the same getting a new conventional electric tank heater (sized to fit the space you have) and plumbing to the HPWH, in series, just downstream. Put a small recirc pump in a loop between them - you would have all kinds of reserve then, and also added redundancy if concerned about the HPWH heater ever going kaput for weird reasons. Electric tank heaters are cheap - can get one sized to fit whatever space you have. Add in a B&G Ecocirc and Johnson A419 to control it & Bobs your uncle.

HPWH is also an electric tank. If the HP goes kaput, push the button to resistance heat element only.

 

[maple1]

HPWH is also an electric tank. If the HP goes kaput, push the button to resistance heat element only.

Roger dodger.

Some people REALLY like redundancy though, and maybe are doubting the durablity - so would be a way to increase that along with increasing reserve capacity if that was an issue.

 

[STIHLY DAN]

Is there a doubt in durability on resistive heat? Its been out for 100 years.

 

[maple1]

I meant durability of hpwh's as a whole. I think some are still suspicious of them even though they have a separate resistance side.

 

[peakbagger]

I have a Solar Hot Water tank with a backup electric coil (that wasnt hooked up for 15 years) I also have a remote (hot watermaker) tank that is fed from oil/wood boiler. For about 8 months a year I run strictly off the SHW tank. When the wood boiler is in operation, I switch over and use the SHW tank as preheater to makeup on the hot water remote tank which has the thermostat set at 180 deg F. When I am running the wood boiler and max out my storage, I flip the wood boiler zone on and heat up the remote tank .

As I am feeding the remote system tank from the SHW tank the water is already warm so it doesnt take much hot water from the remote tank to produce 130 deg F household water. The issue I ran into is that I use a mini split to heat the house in the shoulder season and there is gap when the SHW temp doesnt get high enough yet the wood boiler isnt running. I finally hooked up the backup coil this spring and manually switch it on when I run short of hot water. I have surplus PV generation so it doesnt cost anything to use on occasion.

Given the capital cost of the SHW system, I wouldnt install another one. I would instead install a couple of extra PV panels and an external HPHWH hooked to a well insulated electric hot water heater with heat traps on the outlet lines. I would consider installing a heat exchanger on the HPHWH loop and using the wood boiler to charge up the tank when the boiler is running. Note this will heat the tank well over standard settings but I have a mixing valve that has a combined high temp protection valve.