Aquastat(?) on Forced Hot Water Weil-McClain(about 25 years old)

Users who are viewing this thread

GregoryR

New Member
Messages
21
Reaction score
0
Points
0
Location
Maine, USA
Ah yes, I've seen those in hotels. So how does the inside connect with the outside if there is no duct? That looks like a really cool idea for heating/cooling in general. With a <1000 sq ft year round living space that could probably provide everything.
 

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,770
Reaction score
1,190
Points
113
Location
New England
There are two refrigerant lines and a low-voltage cable. On some, the lines come precharged with quick connects for quicker/easier installation. The compressor is outside, the evaporator and fan are inside on the wall.
 

Dana

In the trades
Messages
7,889
Reaction score
509
Points
113
Location
01609
In tight well insulated homes in southern new england climates it's pretty easy to run the whole thing on a single mini-split even with 2500' houses. The higher the whole-wall R values are, the less temperature difference you'll feel between the rooms with the head vs those without, and there are mini-splits can come as big as 4 tons (48KBTU/hr), which would be ~1.5x oversized for my 2000' + house in MA (3500', if you count the insulated semi-conditioned basement that never drops below 65F.) A 2-ton unit would work for me as an ~80% of design-load solution though, as it very well might for you.

The fact that your burner puts out a gazillion BTU/hr doesn't mean that your actual outside design temperature load is anywhere near that. If you gave us your zip code and the annual gallons numbers for weather data it's pretty easy to come up with a realistic upper bound on what your 97.5th or 99th percentile heat load is based on gallons per heating degree day. The very smallest of oil boilers have ~60KBTU/hour output, which is about 2x oversized for my current heat load, and MANY homes that have had insulation & air-tightness upgrades since the 1978 oil crisis are heated with boilers & furnaces 4x or more oversized for the actual load. Even homes built in the mid 1980s typically have 2.5-3x oversized heating plants for no good reason (who needs to be good down to -75F to -150F?), resulting in a significant hit in as-used efficiency.

If you're on the natural gas grid there's scant economic incentive of going the mini-split route (unless you're adding the air-conditioning, in which case the cost of going with a heat pump as opposed to cooling-only mini-split is negligible) but for those homes heated with oil & propane burners at current fuel pricing (or resistance electric heating in any US market) the economics of mini-splits are pretty compelling. It's only since the development of inverter-drive scroll compressor R410A refrigerant technology that they could work that efficiently at cool Long Island winter temps, but the better ones now still have a COP of 1.5-ish even at -10F. Heat pumps of the 1990s or earlier usually crapped out efficiency-wise at temps as high as +25F, and were pretty useless below +20F. Ductless R410A mini-splits are still delivering OK efficiency at +10F, if not so great at -10F. The 99th percentile design temps for L.I. are typically in the teens- it's not a terrible fit.
 

GregoryR

New Member
Messages
21
Reaction score
0
Points
0
Location
Maine, USA
In tight well insulated homes in southern new england climates it's pretty easy to run the whole thing on a single mini-split even with 2500' houses. The higher the whole-wall R values are, the less temperature difference you'll feel between the rooms with the head vs those without, and there are mini-splits can come as big as 4 tons (48KBTU/hr), which would be ~1.5x oversized for my 2000' + house in MA (3500', if you count the insulated semi-conditioned basement that never drops below 65F.) A 2-ton unit would work for me as an ~80% of design-load solution though, as it very well might for you.

The fact that your burner puts out a gazillion BTU/hr doesn't mean that your actual outside design temperature load is anywhere near that. If you gave us your zip code and the annual gallons numbers for weather data it's pretty easy to come up with a realistic upper bound on what your 97.5th or 99th percentile heat load is based on gallons per heating degree day. The very smallest of oil boilers have ~60KBTU/hour output, which is about 2x oversized for my current heat load, and MANY homes that have had insulation & air-tightness upgrades since the 1978 oil crisis are heated with boilers & furnaces 4x or more oversized for the actual load. Even homes built in the mid 1980s typically have 2.5-3x oversized heating plants for no good reason (who needs to be good down to -75F to -150F?), resulting in a significant hit in as-used efficiency.

If you're on the natural gas grid there's scant economic incentive of going the mini-split route (unless you're adding the air-conditioning, in which case the cost of going with a heat pump as opposed to cooling-only mini-split is negligible) but for those homes heated with oil & propane burners at current fuel pricing (or resistance electric heating in any US market) the economics of mini-splits are pretty compelling. It's only since the development of inverter-drive scroll compressor R410A refrigerant technology that they could work that efficiently at cool Long Island winter temps, but the better ones now still have a COP of 1.5-ish even at -10F. Heat pumps of the 1990s or earlier usually crapped out efficiency-wise at temps as high as +25F, and were pretty useless below +20F. Ductless R410A mini-splits are still delivering OK efficiency at +10F, if not so great at -10F. The 99th percentile design temps for L.I. are typically in the teens- it's not a terrible fit.

According to NOAA's heating degree day chart by month(for my town):

Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Annual
27 62 231 555 882 1339 1504 1280 1091 696 352 90 8109

A high pressure natural gas line does run under the town, but town officials have been using that as an excuse and refuse to do something to build a substation. So we have no natural gas in sight. Hope this and my chart of oil usage on the page before helps.
 
Last edited:

Dana

In the trades
Messages
7,889
Reaction score
509
Points
113
Location
01609
Gregory- somehow I'd gotten you confused with the original poster from Long Island (as sometimes happens when you take over a thread. ;-) )

It looks like you used ~650 gallons of oil in all of 2010. With a zip code we can look up something more accurate better than the 25 year HDD averages from the NOAA, but for the time being we'll use that. A zip code would also be necessary determining the outside heating design temperature (which is not function of HDD) , but for the time being we'll use -10F (about the 97.5th percentile design temp for Millinocket.)

Assuming your boiler isn't a new-school lower-mass smart-controls system, with 3x oversizing and and an as-used AFUE of 75%, you're delivering:

(.75x 138,000= )103.5KBTU/gallon.

Over 8109HDD (base 65) that means the house needed (650 x 103.5K=) 67275 KBTU

or (67275K/8109=) 8.3KBTU per heating degree-day.

That's (8.3K/24 hours=) 0.346 KBTU per heating degree-hour, which is the same as 346 BTU/degree-hour.

With a design temp of -10F, you're looking at 65-(-10)= 75 heating degrees, so the heat load at design temp will be (at most) about

75 x 346= 25,950 (which would indicate a fairly small &/or a very tight house.) If rather than 3x oversized, yours is a perfectly right-sized 85% boiler you'd be looking at a -10F heat load of 29,500BTU/hr- call it 30K.

At -10F the Mitsubishi Hyper Heating (aka "Mr. Slim") units put out about 73% of their fully rated heating load, with a COP of ~1.5, so to do the whole thing with a mini-split would take a 3+ ton unit, but a 2-ton would handle your average load just fine. (Other vendors have somewhat different very-low temp performance, but both Daikin & Fujitsu make units that work fine at -10F as well.) The mean January temp in Millinocket is ~15F, a temp at which most mini-splits are running COPs of ~2.5, and electricity costs in most of Maine is about half of what it is on Long Island, so the dollar savings for YOU may be quite significant compared to those of a L.I. resident. During warmer months the average COP will rise, making it an even better deal, with an even larger share of the total load handled by the mini-split, but your seasonal average will still likely be about 2.5-ish since most of the heating energy will be used when it's under 20F, at COPs under 3.

Assuming you're paying 10cents/kwh and averaging a COP of 2.5, you're getting 8530BTU of space heating for every kwh, so using the 75% oil-boiler example that's a gallons-to-kwy equivalance to 103,500/8530= 12kwh, which costs you a $1.20, which is a third the price of your last 100 gallons, half your 2009 average. Have you seen $1.20 oil anytime in the past 20 years?
 

GregoryR

New Member
Messages
21
Reaction score
0
Points
0
Location
Maine, USA
Gregory- somehow I'd gotten you confused with the original poster from Long Island (as sometimes happens when you take over a thread. ;-) )

It looks like you used ~650 gallons of oil in all of 2010. With a zip code we can look up something more accurate better than the 25 year HDD averages from the NOAA, but for the time being we'll use that. A zip code would also be necessary determining the outside heating design temperature (which is not function of HDD) , but for the time being we'll use -10F (about the 97.5th percentile design temp for Millinocket.)

Assuming your boiler isn't a new-school lower-mass smart-controls system, with 3x oversizing and and an as-used AFUE of 75%, you're delivering:

(.75x 138,000= )103.5KBTU/gallon.

Over 8109HDD (base 65) that means the house needed (650 x 103.5K=) 67275 KBTU

or (67275K/8109=) 8.3KBTU per heating degree-day.

That's (8.3K/24 hours=) 0.346 KBTU per heating degree-hour, which is the same as 346 BTU/degree-hour.

With a design temp of -10F, you're looking at 65-(-10)= 75 heating degrees, so the heat load at design temp will be (at most) about

75 x 346= 25,950 (which would indicate a fairly small &/or a very tight house.) If rather than 3x oversized, yours is a perfectly right-sized 85% boiler you'd be looking at a -10F heat load of 29,500BTU/hr- call it 30K.

At -10F the Mitsubishi Hyper Heating (aka "Mr. Slim") units put out about 73% of their fully rated heating load, with a COP of ~1.5, so to do the whole thing with a mini-split would take a 3+ ton unit, but a 2-ton would handle your average load just fine. (Other vendors have somewhat different very-low temp performance, but both Daikin & Fujitsu make units that work fine at -10F as well.) The mean January temp in Millinocket is ~15F, a temp at which most mini-splits are running COPs of ~2.5, and electricity costs in most of Maine is about half of what it is on Long Island, so the dollar savings for YOU may be quite significant compared to those of a L.I. resident. During warmer months the average COP will rise, making it an even better deal, with an even larger share of the total load handled by the mini-split, but your seasonal average will still likely be about 2.5-ish since most of the heating energy will be used when it's under 20F, at COPs under 3.

Assuming you're paying 10cents/kwh and averaging a COP of 2.5, you're getting 8530BTU of space heating for every kwh, so using the 75% oil-boiler example that's a gallons-to-kwy equivalance to 103,500/8530= 12kwh, which costs you a $1.20, which is a third the price of your last 100 gallons, half your 2009 average. Have you seen $1.20 oil anytime in the past 20 years?

My zipcode is 04276. With delivery(CMP, Central Maine Power, is not allowed to generate and directly deliver, so there is one company to generate and one to deliver) I figure we pay $0.18/kwH. I did pay about 99 cents/gal for my deliveries between 1997-1999. Nothing less than $2.30 since 2004 I don't think.


Having established a cost savings, how much might an install of a minisplit be? I'm still waiting on the oil companies quote on an indirect. I'm guessing the indirect is going to cost wayy too much to make it worth it.
 

Dana

In the trades
Messages
7,889
Reaction score
509
Points
113
Location
01609
Just eyeballing it (http://weatherspark.com/#!dashboard;a=USA/ME/Rumford ) mean January temp in Rumford is also ~15F, so using the numbers for Millinocket aren't very far off. The statewide average residential retail electricity price (delivered) is still under 16 cents/kwh, but it varies widely. (seeL: http://www.eia.gov/cneaf/electricity/epm/table5_6_b.html ) According to 2009-2010 data the standard residential rate through CMP was 14.4 cents: http://www.maine.gov/meopa/electric/current_rates.html, but you might be one of the "lucky" ones to have it 18cents recently.

A 2-ton mini-split (single head) is usually somewhere around $4500. (you can basically double the online "street price" as an estimate of the installed price much of the time, eg: http://www.e-comfortusa.com/products/mszge24namuzge24na-mr-slim-wall-mounted-ductless-heat-pump-22500btu/4377 ). With multi-splits the compressor alone costs about as much as a single-head mini-split, then you add ~$1200-1500 (installed)/per for additional heads:

http://www.e-comfortusa.com/products/daikin-3mxs24jvju-dualtri-zone-outdoor-condenser--24000-btu/6519

and

http://www.e-comfortusa.com/products/daikin-3mxs24jvjuctxs09hvjuctxs12hvju-dual-zone-heat-pump-system--21000-btu/6530

or:

http://www.e-comfortusa.com/products/mitsubishi-mxz3b24na-mr-slim-dualtri-zone-outdoor-condenser--24000-btu/5595


and

http://www.e-comfortusa.com/products/mitsubishi-mxz3b24namszge06nax2mszge09na-mr-slim-wall-mounted-tri-zone-mini-split-heat-pump-system--21000-btu/5657

The specs count- you want something with a heating season performance factor (HSPF) of 8.5 minimum, 10 or better is preferred. The real efficiency/performance isn't always reflected in the HSPF test number, but it's better than nothing at all to go by. Finding a model eligible for a federal tax credit or other subsidy can also take the sting out of it.

The manufacturer is less important than the local distribution & support (if the nearest distributor for brand X is in New Jersey you probably don't want it no matter HOW great the specs look.) Finding a factory certified installer is also important. As idiot-proof as they've made the installation of some of these, there's always a cleverer idiot to be found, and you don't want somebody who can't adequately test or debug the thing on-site as part of the intial commissioning of the system. Many come with the refrigerant pre-charged at the factory, but factories aren't perfect, and leaks can happen during shipment/storage/installation, and getting the charge right for the as-installed system is critical to getting the performance out of it.

The indirect will cut your water heating costs by at least 30%, maybe even 50% in water-heating-only mode, but there are additional savings to be had by not needing to keep the boiler so hot even during the heating season. With an embedded coil the hot water craps out pretty fast if you idle the boiler at 130-140F between calls for heat, and keeping it at 150-160F increases the standby losses by quite a bit. With an indirect and an Intellicon HW+ control you'll almost certainly see 10-15% annual fuel savings (sometimes more) due to the lowered standby loss. At $3+/gallon saving 65-100 gallons/year adds up (especially since it's after-tax savings.) If you plan to live there more than three years there's usually some payback to be had.
 

chapchap70

New Member
Messages
3
Reaction score
0
Points
0
Location
Long Island, NY
Gregory- somehow I'd gotten you confused with the original poster from Long Island (as sometimes happens when you take over a thread. ;-) )

If you were referring to me, this is not my thread; though I happened to be the initial poster of Page 2. It is actually GregoryR's thread.
 

Dana

In the trades
Messages
7,889
Reaction score
509
Points
113
Location
01609
I'm easily confused, eh? (Why anybody would take MY advice is beyond me! ;-) )
 

GregoryR

New Member
Messages
21
Reaction score
0
Points
0
Location
Maine, USA
The quote for the Indirect came in - 41 gallon Pure Pro installed for $3,380! Eek!

I guess that isn't going to happen. I really need to find somebody to quote me on something electric. Looking at the data pdf somebody had posted, my tankless coil is about 24.5% efficient in the summer season.
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks