Water heater wrap

[saichele]

Got the newest gas bill yesterday, and despite not having turned on the furnace, the gas consumption has doubled (to 47 CCF) from the previous month. Only gas consumers inthe house are the furnace, DHW, and range. No changes to the system or our life style, and no gas smell, so I presume no leaks (certainly not of that magnitude) and no dramatic change inthe amount of cooking.

So I'm suspecting the DHW, which is now sitting in a 40F basement instead of a 65F basement. It's a newer, fairly generic gas unit. I've gotten mixed opinions from coworkers, so I thought I'd see if I could get some mixed opinions here.

One school says wrap that sucker in a fiberglass blanket. intuitively straight forward.

The other school says never to wrap a gas water heater, because it causes back drafting. Interesting, but I'm not sure of the physics (and neither are they).

Any thoughts?

Thanks
Steve

 

[Eric Johnson]

This won't answer your question and might generate some conspiracy theories, but here goes:

About 10 years ago my local gas/electric utility started handing out fiberglass insulation shrouds for their customers' water heaters. They said it was to help conserve energy, but they are in the business of selling energy, so one has to wonder.

But it just makes sense to me that the same water heater is going to use more fuel if it's in a 45-degree environment compared to a 65-degree one. I guess if you shroud it up and it doesn't operate properly, that would answer the backdrafting question. You'll only be out $10 or so if that's the case.

 

[begreen]

It is ok to wrap it I believe, but be real careful not to cover any portion of the air intake or pilot area. Have the blanket stop about 2-3" above this.

 

[saichele]

I guess the good news is that the rate is still relatively low - $1.03/ccf + 7.50 (fixed) deliver charge.

 

[Corey]

I am in a similar boat - gas water heater and furnace. I always notice a good spike in the gas usage even though the furnace does not even have the pilot light lit yet. Some of the extra usage is likely due to the cooler basement, but some is also likely due to cooler inlet water. 1 BTU per pound per degree F so a 50 gallon water heater w/ 80F inlet water would need about 24,000 BTU to get it to 140F. If the inlet water is 40F, you'd need 40,000 BTU or about 2/3 more gas. The efficiency should nearly cancel out, being roughly the same in each instance. (check all that math!)

Corey

 

[Eric Johnson]

In central New York National Grid is getting $1.32 per therm, plus delivery, according to my last bill. That compares to 76 cents per in August. It took awhile to dope out the price, given the way they break it down these days in a dubious attempt to make things clearer and to minimize paperwork. Methinks it's to confuse the customer.

 

[Corey]

Eric -

As for the conspiracy theories - it does seem a little strange that utilities give out information on energy savings or even devices (like the water heater blanket) to help customers save, thus using less of what the company sells.

My take on that has always been that the "customer charge" part of the bill seems to be a pretty big proportion of the whole bill. My feeling is that when all the costs of the commodity and delivery are figured in, the utility may make a dollar or two per month off of selling the gas/electricity or what ever, but they make $10-$15/mo or more off of you as a customer. Then add late fees, deposits, hook-up fees, etc and it becomes very profitable to have new customers.

The net effect is that it is better to have a bunch of customers using a little commodity than have a few customes using a lot of commodity. If everyone conserves they can add more customers and sell less commodity.

Of course, the net effect is that if you want to "stick it to the utility", burn more of their commodity!

Corey

 

[Eric Johnson]

I agree about the service & delivery charges. I only used 16 therms of nat. gas. last billing period, but still got stuck with more than $20 in charges not related to the actual price of the gas. 12 months out of the year.

I was only kidding about the conspiracy part. Actually, it was an electric water heater and what the utility (Niagara-Mohawk at the time) was trying to do was avoid having to build more power plants to satisify rising demand. As you point out so well, they would rather have lots of lower-use customers than a couple of big ones.

 

[Metal]

Newer hot water heaters have internal insulation that is pretty good, but if it is in an unconditioned area, i.e. basement, garage, etc. it would be a good idea to cover it. Even though the outside of the water heater may not feel like it is losing heat, it is. If you want proof, put the cover on, then after a few hours put your hand between the waterheater and the cover, you will feel how much heat you were losing. Be careful not to cover up the air inlets or any safety stickers (some manufacturer's void the warranty if their stickers are covered.

 

[drizler]

All those fees ect are why I buy and haul my own propane myself for my dryer. I save about 40% by tossing the 100 cf cyl in my truck myself. Ask the gas co about that they start to stammer and dance................

 

[Mo Heat]

Steve, Sometimes those quantities are 'estimated'. If yours is, the gas company may be front-loading a bit of (soon to be) usage so as not to give you a heart attack when your REALLY big bills start coming in during the coldest months. Like they do with their quarterly financials (probably) to make things look a bit smoother.

Driz, I hope you strap that dude in.

 

[Rhone]

One thing I've noticed is my boiler is kicking on a lot for standby since I got my fireplace insert. I wrapped all my pipes within 10 feet of it, insulated above it, and sort of closed off the area it's in. Still, almost every hour it seems to kick in for 5 minutes or so for standby (it's tankless) and so far surprised at the amount of oil I've used in a month when I've been burning wood.

I think I know the reason. My insert and boiler share the same chimney (not same flue) and what I think is happening is that my insert is warming up my entire chimney including the flue my boiler is attached to. The air inside my boiler flue is getting warmed, rising, and being replaced with cold air that has to go through my boiler to replace it, and hence the hotter I make my insert the more cool air is going through my boiler increasing its standby run time. You happen to have a tank and insulate it, it's one of the things that will pay for itself in savings the first year. I have a tankless right now, but I'm really thinking about going for a tank. One of those things you don't realize.

 

[begreen]

Do you have hot water heating? Just a guess, but is the boiler's room thermostat near the space being heated by the insert? Try dropping the room thermostat down a few degree's and see if that stops the short cycling. If not, it is cycling to heat domestic hot water. This might be because the delta (on/off range of temp) is set a bit too narrow on the aquastat?

 

[Rhone]

I have forced hot water baseboards so in winter I keep the delta set 180 & 200, 120 & 140 in summer as being tankless it needs a little higher setting. I piped in a Watts 70A mixing valve set to 120 degrees so no surprises when I change over the boiler settings for winter/summer use (it's a code thing also). Boiler for the most part rarely kicks in for heat with my insert, it's set to 60 degrees and my insert keeps my house at 68 in the hallway where the thermostat is. My wife is the only one that uses hot water but on those cold nights on the hour, practically every hour the boiler kicks in to warm the 3 gallons stored in my tankless back to 200 degrees when my insert is going. It doesn't do it near as much when my insert isn't running, the only thing I can think is that as my other post stated my insert is warming my boiler flue and the air is rising out and it's pulling cold air through my boiler to replace it and cooling off my 3 gallons of water. My boiler is in my basement which is usually around 45-50 right now.

 

[Rhone]

I do bathe but in in cool-warm showers with the water set for less than 1 gpm (a twinkle). My tankless has a 3 gallon reservior and usually I can take a shower without it kicking in. I rinse my dishes off in cold water, laundry, wash my hands, brush my teeth. Besides my cool-warm twinkle showers if the heater wasn't working I'd probably never know. My wife I could shut off all the cold water and she'd never realize it.

 

[saichele]

Uh, nevermind the showers part...

I was curious, along a similar line, regarding the airspace at the top of my NG water heater. every other flue I've ever talked about had to be tight. This one they engineer an air space into it. Shares a flue with my furnace, so it seems like all winter it must be sucking warmish air from my basement, more so when the furnace is firing. Any thoughts as to the purpose of that little air space?

Steve

 

[Metal]

The little airspace is the Draft Hood. Here is a definition:

Draft Hood - a device placed in and made a part of the vent connector (chimney connector or smoke pipe) from an appliance, or in the appliance itself, that is designed to (a) ensure the ready escape of the products of combustion in the event of no draft, back-draft, or stoppage beyond the draft hood; (b) prevent backdraft from entering the appliance; (c) neutralize the effect of stack action of the chimney flue upon appliance operation.

In other words, it keeps the stack action from pulling too much air through the appliance and blowing the pilot light out and it keeps back-drafts from doing the same.

 

[bruce]

it really does work, i wrapped my heater and the next day i stuck my hand threw the insulation to the metal and guess what? it was hot!,, that was heat just going to waste! and my heater was 4 inches from a block wall, but all fixed now!