The big question "what to do"

[YKdave]

Hello from the great white north! Yellowknife NT to be exact!

not sure if this is the correct section i should post this or not, but ya never know till you take a stab at it!

Brace yourself, this is going to be long winded...

Just bought my first 'home' last fall (first time homeowner, long time renter), its an 1984 "alma" manufactured home. Its had some renovations over the years which includes the roof being re-done as well as the roof in the living room (center of the trailer) has been raised, but neither me or the previous owner know whats been done for insulation. the windows have all been replaced with triple pane lowE w/pvc frames as well as the exterior doors have been replaced with insulated metal and new screen doors. Overall a pretty tight and efficient setup for a 30 year old trailer.

Ive also got a wood fireplace in the living room, which is great because wood comes cheap, but its use is limited to outside temps in the low negative teens. even running the furnace circulating fan and living room temps over 30c, the end rooms struggle to make it to 20c and with any lower outside temps the bellybag starts to cool drastically (floors are f'n cold!), as does the crawlspace (uninsulated skirting). unfortunately, the sewer line from the bathroom runs outside of the bellybag, the full length of the trailer almost, till it hits the main. This line is insulated, but without the furnace being used, it cools off too much under there and the line will freeze eventually. (it needs some better support as it looks to be sagging in places and likely holds water or other goodies )

The current furnace is a 1992 nordyne M1GH090, and typical as always to a MH the furnace is a noisy SOB!

As per the usual, the 'normal' operating noise(air movement) of the furnace is a major nuisance as the furnace is located in the hall beside the living room.

I would like to do something about this noise pollution as well as move towards something more efficient.

J load calculation put me right around 26k/btu/hr (using a 60c temp rise) using guesstimate (worst case) values for the roof/wall insulation. using known values, my heat load is actually more like 17k/btu/hr ( average for a month of -20c to -25c outside temp).

ive also come to realize that the current furnace is a bit oversized. Currently its -35c (9km/h wind, -44c windchill) and with the t-stat set to 20c im seeing very consistent 10min/20min (50%)cycle times. even with outside temps dipping down to -40c (almost -60c with the windchill) i still wasnt seeing much more than 55-60% burner time and as much as the weather bites around here, we dont usually get more than a couple days a year where ambient temps are much lower than -40c (without the wind).

This average winter weather puts me around 800-1000L of propane per month (though only 600-800L is used for heating, i have other propane appliances) and at my current contract price of .65/L thats a bit over $400/month in heating

So...

I would like to do some upgrades over the following summer and im starting to put together a plan for this.

I would like to make the switch to a high eff furnace and keep it gas (propane, as to simplify the install and costs). ive been looking at the nordyne (miller/intertherm or whatever the heck else they want to call themselves these days) M7 series as they are as close to a "drop-in" replacement as a guy is going to get.

What im thinking, is an M7TL060A (possibly buy with a coil cabinet for future a/c because i hate the heat although it doesnt get overly hot here ). first stage should be more than sufficient to maintain a 20c inside temp during our coldest weather which should make it as efficient as its going to be while running the first stage, and the second stage should have no problem recovering heat loss from open doors/setback temps

My next an biggest concern of the project is the noise!

Ill make the assumption that the M7T is going to be a bit quieter than my current M1G (especially on first stage) but i would like to take it a step farther if at all possible. The biggest issue as usual is the noise at the return air (front panel). would their be much benefit in using a M7 with a top return air and ducting it through the adjacent bedroom closet and have it draw the return air from farther down the hall? (and installing a solid door infront of the furnace which is currently open, and better sound insulate the cavity it sits in). or would this make it slightly quieter in the living room, yet resonate and make it even worse for anyone in the bedrooms down that hallway?

Other plans for the summer would include insulating the skirting (R12 fiberglass w/vapor barrier) as well as inspecting the roofs insulation situation and maybe doing something there. Within the next few years the siding will have to be done, its got pretty old wood plank siding, i would like to do some R5 poly on the outside wall for a little extra wall insulation and likely do vinyl siding.

Crunching some numbers, making the switch to the M7T furnace alone should save me at least $70/mo in heating costs as well as some headaches from the noise! then the insulation is only going to compound the savings and hopefully with the crawlspace better insulated i will be able to set back the temps below 20c while i am away and save some heating costs there without having to worry about things freezing up.

So, my biggest concern is the noise, what are my best options for reducing the noise from the furnace and hopefully not just move the noise down the hallway. The ol lady wants to have kids in the near future and neither of us need a screamin banshee every time the furnace kicks in

[DaleM]

Not really sure if you're going to much to reduce the noise no matter what plan of action you take. I see some new homes that have return air systems built in that utilize a solid door on the furnace alcove. These starve for air and we ultimaley have to cut a grate into the door. There went any noise reduction. Another concern is the drain tube from the furnace. The M7 will have a condensate tube that will have to be plumbed into your sewer. If you go ahead with all the insulating you are talking about as for the skirting I think you will have it covered. I'm near Chicago and when our temps drop I see frozen sewers from these furnaces being plumbed into the sewers. There's just not enough water flow on the longer sewers and they eventually form a giant icicle inside the pipe.

[YKdave]

Yes, I can foresee that being a possible issue as the only sewer on that end of the trailer is the 3" line that runs below the bellybag that runs to the main bathroom.


Not that myself or any contractor in town would be up for the task, but would their be much (noise) benefit from enlarging the trunk? (Worth the cost/hassle)

Until the skirting is sealed and insulated properly I don't want to start tearing into the bellybag, but once that's done, I could care less if I drop the bag if I had to run a decent sized trunk as long as it means I can watch tv without having to turn on the surround sound just to hear it!

[DaleM]

No there would be no benefit to enlarging the ductwork. Keep in mind your furnace is 20 years old, they get noisey with time. The new one may surprise you.

[YKdave]

the biggest concern is that its just an air movement noise. Otherwise, it runs like a champ, not a rattle or squeak in the whole thing. I pulled everything apart this summer, and cleaned up the wheel and oiled the fan motor. with no effect at all, other than a little peace of mind knowing that its been done as well as a quick visual at everything else.

i know MH's are typically noisy (hey, 3/4 of this city is MH's! LOL), but this thing is beyond the normal as far as the noise from the return air, and their is nothing seemingly out of the ordinary.

Though i'd have to say that personally comparing a nordyne/miller/intertherm to anything else ive seen in a MH, they are the noisiest as far as return air noise goes. though i cant say whats been done as far as the install, they were all alcove installs with grill returns, no fancy return systems. One of my buddys has an older coleman and you can barely tell is running when your in his living room (although the furnace is on the opposite end of the kitchen), and you can actually carry on a conversation if your standing in his kitchen right beside it. When mine kicks in, being at the hallway directly beside the living room, i have to crank the hell out of the volume on the TV just to barely hear it (need the surround sound to be able to hear good!) and its even annoying trying to talk to anyone in the room LOL

i would actually personally like to go with a coleman, as ive found them to be the quietest. but of course that would also mean alot more work at its nowhere near a direct replacement as well as the alcove is too narrow (width and depth)

[DaleM]

The Colemans and Nordynes are sized about the same. Both at about 20" wide and height may vary just a bit. The only "thin" unit out there is the CMF series, those are 18" wide. Is your blower on the right speed for heat? Usually they run a speed or 2 slower for heat than they do for cooling. Of course that won't do anything for noise when running A/C in the summer.

[YKdave]

yes, the low eff furnaces are all relatively the same dimensions. but the high eff is where they begin to vary (where it begins to be a problem for me)

And the high eff coleman is about 2" too 'deep' to fit in the alcove. thats alot of work just to make it fit. Looking at the drawings, it would fit in place for all intents and purposes, but it would stick out into the hallway about 1", which would kill any plans of putting a solid door in there to keep the noise out of the living room.

And, by law, i have to use a high eff furnace if im going to go through with this, as we are legally only allowed to directly replace a low eff furnace with another. Since i plan on doing some duct work along with this, its in that grey area of what is allowed. Also, their are tax benefits for going high eff, so why not enjoy that along with the fuel savings.

Unfortunately my furnace is an "older" M1GH, which only has a single speed fan, that funs flat out or nothing. And no worries about A/C, thats a very rare sight around here and i sure as heck dont have it (but it would be nice for a few weeks in the summer!)