|
New to forum, and new home owner!
Hi everyone, I'm Sam. I just bought a house in east central Illinois, and since before I even moved in I already had a million plans to improve the house and property. But my number one priority is getting to a point where I'm able to call up the power company and tell them I'm done with their highway robbery! Fortunately, the seller left what seems to be (to my VERY limited knowledge) a pretty good generator, uninstalled, in the shed out back. The breaker box in the house has an automatic transfer switch next to it, but obviously that isn't hooked up to anything yet. What I'd really like to do is get some solar panels up first, with the generator as a backup, then later on down the road put in geothermal heating/cooling. If anyone has recommendations on where a total newbie can start digging up some good info, I'd love to hear them! And if there are any details I can provide that would help you make recommendations, I'd be happy to give them to you. Thanks in advance!
|
Welcome to the forum and congratulations on your new home! I'm sure the regulars here will chime in with what projects you might consider doing first.
|
Welcome!
First things first, details. What's the square footage? Insulation? Windows? Gas? Electric? The best thing to do is to insulate everything and get the house air tight. Then live there awhile to see what your power bills are going to be. Then you will know about how many panels you will need. Also is the house angled correctly for roof mount? |
Also, how old is your house?
|
Welcome to the site. I'm looking forward to seeing what you do with the house. :)
|
you can get an approximation of your energy bills from the existing electric account and gas supplier (assuming natural gas).
They can't give out any information except billing amounts, units (kWhrs or MCF) and dates. But this can likely give you several year's data. Steve |
Wow, I didn't expect so many replies so soon!
If I recall correctly, the total square footage is 2700 (including the unfinished basement). It's also got a 2 car attached garage, but there's tubing in the concrete that I plan on just hooking up once I get a geothermal system set up. It's all spray foam insulated, has a pretty big living room window, 4 more on the main floor, three skylights and a sliding glass door on the second floor, and a cupola up top with 5 small windows around it. Electric is 200A to the house but for some reason there's only 100A to the breaker box. I do have propane but once that's used up I'd like to switch to natural gas (only as a backup, and possibly for cooking). So far my daily usage has been around 12-18 kWh in the winter, and <10 in the summer. The only time it's gone over that is when my wood pellet stove broke and I had to use space heaters. It's a geodesic dome so the angle of the roof shouldn't be a problem at all. As for the age, it was listed as being built in 2003, but the appraisal said 2005, so I'm just gonna average that and call it 2004. I think those were all the questions, right? |
Sam,
Sounds very nice. Being a dome, the ratio of surface area to volume is a minimum. What you need now is to estimate how many BTU's per hour you need to heat your home. There are several ways to do this. One way is to turn on a known amount of heat, during a cold night and see if the inside temp stays even. For this, you need to circulate air with fans, so there is a uniform temp. For example, if a propane furnace of 36,000 BTU (36 kBTU) on 100% of the time keeps the house at a constant 65 on the coldest of winter nights, then you know the answer (36 kBTU/hr). If the cycle time of the same furnace is 50% (1 unit of time on, 1 unit of time off), then you need 18 kBTU/hr. If your cycle time is 25% (1 time unit on, 3 time units off), then you need 9,000 BTU/hr. You need a COLD night and get up at 4 am to record on and off times of heater when it is coldest. Do this quickly while you still have cold nights! Very hard to do with a pellet stove as the heat output is not a known (but just estimated). Then you know the size of any heating system for your local conditions (geothermal system or whatever). Ask your local electric utility of they do a free energy audit. Get one and let us know. There are, sadly, ALWAYS tiny air leaks that really add up. Hopefully, they will do a blower door test that accurately measures the "tightness" of the envelope. Our first, and collective advice is to button up, insulate up. Sounds like you have foam insulation (how thick?) , but the air infiltration remains an unknown. Monies returned by reducing losses are FAR greater than any energy device be it GSHP, solar, whatever. Welcome to the site. Steve |
Quote:
|
Sam - all you need to know is what is the maximum BTU load your heating system must provide on the coldest night for your specific home. A BTU is a BTU - about the heat output of one lit match.
The heat source (BTUs) could be resistance heating, propane, oil fired, air source heat pump, or ground source heat pump (GSHP) - or solar hot air collectors. Each of these, when run at 100% has a heat output rated in thousands of BTUs (kBTUs). Sometimes the output is rated in tons where 12 kBTU = 1 ton. The key is to find a cold night, run the heater with the thermostat on 65F, circulate air well and record the cycle time in the early AM when everything has reached a steady state (typically takes 6-8 hours). The resistance to heat flow through your envelope can then be easily figured as kBTU per heating degree day. Then once you know how many kBTUs you need, we can advise what heat source to use that is best for you. Some like to use wood, and that heats you at least three ways (chopping, carrying and then burning) . . . . I have gone with GSHPs and also have a small Vermont Castings wood stove when I want to see flames - or feel the need for direct radiant heat. Record the data . . . . . Steve |
Quick question Stevehull: I like that method of finding the maximum BTU load of your heating system but I have a curveball. What if I have a newer natural gas furnace with throttling gas valves? It's no longer on or off, it can run at a reduced setting for quite some time. How would I go about running this test?
|
Many of those furnaces have a dip switch on the control board that disables the variable gas valve. It then operates in just the off or on mode.
For a +/- approximation, you can look at the plate to find out the BTUs when it runs 100%. A better way is to read the meter, do the test for 12 hours and then read the meter again. Most meters are in ccf with a subdivision to cf. Then you can look up the BTUs per ccf and multiply to get total BTUs and then apply the efficiency number 90-95% or so. Look in the manual or get one on line. Steve |
Well I do have an air source heat pump, but it's neither effective (ductless, so only really warm in rooms with air handlers) nor efficient (runs up my electric bill to near $200 when it gets cold). On top of that, it's currently OOC. I was just planning on running the pellet stove all winter, then ditching the ductless system and installing something better over the summer. But from what you've said, it sounds like I might need to get in fixed so I can calculate the BTU load. Would that probably be better than trying to figure it out using the pellet stove?
Edit: I also have gaps in some of my doors that might be robbing me of heat, so I guess I need to make that more of a priority too. Would hanging heavy curtains on the windows make a significant difference? |
Welcome, Sam!
I have made a number of posts that describe simpler, more effective ways to make the house more efficient and get what you need sustainably so you can fire your utilities. Instead of reiterating, check out my posts and the threads they are in. In particular, AC Hacker's DIY Hydronic Floor Heating, his Homemade Heat Pump Manifesto, and my Passive Annualized Heat Storage threads cover wide ranging topics that all interconnect to make an efficient house and have numerous worthy contributors. Tons of useful info and helpful people in so many threads here! Most important, it is easier to keep your energy in than it is to replace it efficently. Insulate properly and use your interior walls as your infiltration barrier. You can get about as good an envelope this way as you could with exterior house wrap. Electrical boxes and gaps in HVAC equipment/ducts let an amazing amount of air in or out; seal them. $100 of weatherstripping, UL 181B rated duct tape like THIS KIND and fire retardant spray can foam (behind the electrical boxes) could save almost that much per month. Air source heat pumps are great but only worthwhile if they are variable speed inverter drive. Conventional ones only have one compressor speed, making them inefficient and low output when you need their output the most. The inverter drive ones are amazing for their efficiency and output, plus they can modulate to match their output to the need. |
Okay I'll definitely be taking a look at those when I get a chance! Luckily cooling isn't a huge concern due to the shape of the house (cracking open a few windows at ground level and up in the cupola is usually enough to keep me cool), so I should be able to wait until summer when school's out. I'll definitely make sealing up the doors and windows before next fall a priority though.
From what you said about heat pumps, it sounds like mine is the conventional type. As it got colder this winter, it actually started to sound worse and worse when it was running. Then when it got well below zero, it just quit on me. When I called tech support and gave them the error code it was displaying, they said it's a compressor issue and that their units aren't designed to operate below ~15F. Would the inverter drive type be able to keep up when it gets that cold? And would it still draw a lot of power in the cold months (compared to ground source, not to my current system)? |
Yes, the inverter drive units keep up with cold temps. Most are rated to work down to 0F such as THIS Gree U-Match 24kbtu UNIT which replaced my girlfriend's 30 year old gas furnace (with a constant burn pilot light!) and air conditioner. We chose this one since it could be hooked up to ductwork as designed; she didn't want a more efficient unit hacked to mate with the ductwork. That would have worked ok in her case-no return ducts and the supply ducts are short and unrestrictive. ecomfort.com was great to buy from.
It works beautifully! Her 2BR condo is reasonably efficient, and this unit runs less than half the time unless it is extremely cold even though it can throttle down to 8kbtu. To put it through its paces, I set the thermostat to max on "Turbo" mode when it was 20F outside. I burned my hand on the vapor pipe at the indoor unit, the discharge air was toasty warm, and it made the whole place uncomfortably hot in less than half an hour. At sensible settings, it used less than $20 extra electricity during the coldest months. Conventional ones don't pump much heat below 40F which is when you need it most. They rely on resistive heat or gas to make up the difference-expensive. A ground source unit is very efficient because you are pulling heat from a 40F or better heat source, but you need a loop field, which needs to be large because your heating dominated climate will pull its temp lower and lower in a couple years. Good field design becomes evident after the 3rd year. Putting the field on more than one side of the house opens up the area you can draw heat from significantly. Check Energy Star rated units if you want a ready made one instead of rolling your own a la "Manifesto", or to get an idea of efficiency vs airsource. There are few site locations where I think an open loop GSHP makes sense. Their ratings don't include the energy required to "pump and dump" the water, which can be very high. Of course, you could combine ground source and seasonal storage as I describe in my thread for "fire your energy companies" efficiency, but that is a multipart harmonized system. Cheap heat with AC capability in multiple areas? An inverter multi-split (multiple indoor cassettes with one outdoor unit). Get one heavy on the HSPF rating and lowest temp capability. Some are optimized for cooling-dominated climates. My favorite vendors I might buy from are heatandcool.com and highseer.com. Need a ducted system? One of the "concealed duct" models like our Gree. There is some concern about ASHP efficiency in cold wet conditions because of the need to constantly defrost. I have never, ever seen my girlfriends unit have any frost on the fins, ever, even when it was 100% humidity in the low 30's, when in the 20's, or during the one instance we had snow. These observations were made while the unit was actively heating the condo. At low temps, there just isn't that much moisture available in the air to cause frost with. After seeing many systems and installing a few, I would heartily recommend inverter drive heat pumps of any type, and would never recommend a conventional. You will need additional heat sources to keep up if temps are below 0F, but unless you need to rely on them frequently a wood stove or portable heaters would do it. Warm floors are awesome if you feel like doing it. I will never go back to forced air heat if I can help it. |
Sounds like GSHP might end up being the best route for me to go. Where I live, the temp regularly gets into the double-digits below zero. And frost is definitely a concern up here too. It's not uncommon for cars parked outside to be completely covered in a sheet of ice in the morning! My house sits on an acre that's at least half open space, so hopefully that will give me plenty of room for a sufficient loop field.
I was actually talking to a guy I go to school with just a few weeks ago about radiant floor heating (I assume that's what you meant by "warm floors"?). He said he's installed it before and that it's extremely effective. From a quick online search, it looks like it's not unheard of to combine GSHP and radiant heating. What's your opinion on combining the two? |
The air source units frost up the most when temps are in the high 20's and low 30's. It all depends on the dewpoint outdoors. Below about 25, the majority of the moisture is frozen out of the air, so there is not as much available to frost up the outdoor heat exchanger.
The old school units defrost on a time vs temperature scheme: when it's below about 40, they defrost every 30, 60, 90,or 120 minutes and don't switch back to heating until the heat exchanger warms to above 50 or so. If there's not much frost on the coil, they might only defrost a minute or two. The colder it gets, the longer it takes for the coil to warm up, and the more heating capacity you lose every defrost cycle. The newer units use more sensors, both on the coil(s) and in the open air. They can sense if the outdoor unit needs defrosting and when. They vary so much more stuff (fan speeds, compressor speed, flow rate of refrigerant, etc.) to do their job than the old school units that it is difficult to compare them with each other in side by side tests. The ground source systems take energy efficiency to a whole new level. When it is -10 outside, they straight up whoop an air source unit if the ground loop is designed correctly. Having a 40 degree heat source to pull from, they don't take a penalty in power or capacity. If the wind starts howling, they don't mind at all. The unit might run a little longer, but that's because the wind is robbing more heat from the house. Combining a GSHP with a low-temperature radiant source can save you a whole lot of KWH to get the same BTU of heating capacity if the system is designed correctly. When combined with domestic hot water heating, the savings can be very substantial. A straight electric water heater has a performance level of 1. This translates to about 4 EER. An old school air source unit might have an EER of 10 or 12, a newer one maybe 20. An old school GSHP might start out at 20 EER, and the newer variable-speed "water furnaces" are pushing 40 EER. There have been measurements made by members of this forum where their GSHP systems averaged between 25 and 30 EER all season long (COP values of 4 to 5) and saved them the cost of their systems in electric bills in just a few years. Of course, a lot of them did a large portion of the labor involved on their own. |
Sam,
Yes you can provide hot water for a radiant flooring with a geothermal heat pump. You can buy a unit that is a "water to water" type that uses ground heat/water to then heat water that is stored in an insulated tank. That stored hot water is then used in the radiant floor system for heat. Here is one such water to water unit (I have no financial link to this or any GTHP retailer). Buy Goodman Heat Pump | Geothermal Heat Pumps | Goodman Air Conditioner The above is a 4 ton unit that will provide 48,000 BTU (40 kBTU) per hour. I don't know your total envelope insulation values, so I can't tell you if this will provide you enough heat when it is -15 F and windy. Even though you can "reverse" the GTHP cycle and provide cold water to the floors, as in summer for cooling, your humid summer environment does not allow this. You regularly have dew points in the high 60 to mid 70s F. The reason is that you will literally have wet floors when the cold floor is below the dewpoint. To get much cooling, you need the floor about 45-50 F and that is WAY below the summer dewpoint. Example. Put a glass of cold water on your kitchen table in the summer. That water is about 40 F or so. Note the condensation on the outside of the water glass? That is what your floors will be like. So radiant "cold" does not work for your location. A small (compared to heating need) tonnage ac unit is called for. It could also be a GTHP. WaterFurnace, a physically close to you manufacturer of GTHPs, makes a unit that not only provides chilled or hot air, but also radiant water for a loop. Problem: $$$$$ about $10k+ WaterFurnace Residential Product Line : Synergy3D Personally, I would start with a water to air GTHP from Ingrams such as this: 4 Ton 2 Stage GeoCool Geothermal Heat Pump The above is a 4 ton (48kBTU) unit that will certainly provide enough cool in summer and likely 60-80% (?) of your winter heating need. Many people in your area use open loop systems where water from their domestic water well is used. The output water from the GTHP goes into a pond or such. Least expensive, and where lots of ground water is available and a high water table (such as you have), it is a very rational solution. But again, we are just guessing at the tonnage size needed. You need a assessment (manual J or utility) or a load test for your home such as I described above. I can tell you with winters like you have at least 3 tons for heating and perhaps as much as double (triple?) that, depending on the above results. Your summer cooling load is low, so any system that provides sufficient heat at -15F winter will cool off a house when it is 95F summer. No point is spending more for a heating/cooling system that you need. Or read the manifesto and build your own . . . . Steve |
New home owner wanting to fire utilities
Samerikson
It sounds like your ready to embark on a great journey to net zero. If I'm understanding you want to tell the utilities to take a hike and still stay warm and in the light. Of course we will need more details but it sounds like your new digs are well insulated and just need the investment to take your new home to the next level. My experience is I built a countryside contemporary home in Canada with solar hot water heated floors backed up with geo-thermal. The solar PV is my next step. I believe your heading in the right direction. We fired the furnace oil delivery guy and are grinning ear to ear. I would like to wet your appetite. For your homework have a look at what this smart guy Jerry accomplished DIY Geothermal Heat Pump + PV System - No Heat Bills! After you have a look at that drop back by Randen |
Sam, +1 on Jeff & Steve's comments. I will add that the efficiency of an open source heat pump depends heavily on the energy needed for pumping. Your ground & groundwater temp is probably around 47F where you are (confirm on a map), and you will surely drag the temp down below 40F in your heating dominated climate. You will need to plan for at least 2gpm per ton of capacity.
If your water table is consistently less than 25ft down from your pump location, you can use a shallow well pump and the lift isn't too bad. If not, the energy required to pump 8 or more GPM from lower depths really adds up. You only need 2 boreholes, saving installation cost, but the average efficiency gets dragged way down by a pump powerful enough to meet peak flow requirements. If you were going to pump that much water anyway to fill a lake or somesuch then it doesn't matter much. The beauty of a closed loop system is because it works like an elevator with a counterweight. The energy required to pump your fluid up the pipes is returned to you as it flows back down. The only "wasted" energy is the amount required to overcome flow resistance. If designed properly, that amount can be very low. Concerning frost on ASHP coils: I really think it's mostly a nonissue now. The worst possible conditions would be near freezing when it's misty and 100% humidity outside. During these conditions I've never seen frost on the coils or moisture draining from the unit indicating there had been. Air can hold only 1/10th the moisture at 32F as it can at 95F. I and others have talked a lot about raising the efficiency of heat pumps. Check my posts, especially starting HERE. The important thing is the amount of temperature "lift". If you don't have a high water table so water doesn't steal your heat away, you can have a perimeter of shallower boreholes around your home, using solar thermal collectors (dedicated or behind PV panels) to raise the soil temp under your home to 73F or so during the off season. 135F output from a water/water heat pump using a 73F source is more efficient than getting 105F water from a 40F source. You are now passively heating the home from below in winter but not continuing to heat when the house is above 73. 135F water is hot enough for retrofit hydronic heat with transfer plates (the warm floors I mentioned) as well as the ideal (and safe from Legionella) temps for DHW. Combining systems and using a buffer tank so you can size for average load instead of peak load could get you free of your energy companies. I will never see -15F in Atlanta. Does anyone have experience with a modern inverter drive heat pump in those temps? Does it shut off below a certain temp as Sam's did, or does the output just dwindle down? At least the COP would always be greater than 1 and therefore better than resistive heating, since you get the energy consumption of the compressor and the indoor fan back, unlike cooling mode where you are trying to get rid of heat. |
Jeff, those EER numbers are off a bit. 1:1 COP=3.41 EER, since 1 Kw=3412 btu. A COP of 4-5 would be to 13.6-17 EER. An EER of 30 would be a COP of 8.8. Doable, but very lofty. Were they getting SEERs of 25-30 instead?
Sam, if you are unfamiliar with any of the terms we are describing, shout out if you can't find your answer after searching. |
In general, all of the manufacturers inflate their EER / SEER / HSPF ratings on banner ads, posters, line art, etc. Most likely, the advertised values are peak values, not hard ASHRAE or ARI test numbers over the range of operation. The easy-to-see numbers are inflated like wattage ratings of knockoff audio amplifiers and speakers! The main number-inflating factor in the geo heat pump testing is that the numbers are calculated without water pumping power in the equation. This is one big reason why the larger-capacity units nearly always beat the smaller units in the standardized tests, and why the numbers are better in heating mode vs cooling mode.
Let's say we are using a super duper waterfurnace 7 series, with a pump-and-dump borehole with 65 degF source water temperature (not totally unrealistic). At the high end of its capacity range, the COP is going to be around 5, and the unit is going to greatly exceed its BTU rating, maybe moving 140% of its rated heating capacity. As we slow down the compressor to reach rated capacity, the COP might soar to above 7 at its rated capacity, maybe even reaching 8 at normal water pump speeds. If we then run the water pumps at full throttle, the instantaneous peak COP will rise even higher (near 10-11), then fall off as the balance point is reached. Believe me, the marketing teams will encourage the engineers to push the envelope as far as they can to inflate performance numbers. Of course, those with a good grasp at the factors at play inside the box and elsewhere in the system are going to voice skepticism when presented these numbers. For those potential customers, most sales pros have no problem producing spreadsheets common to the HVAC industry which present a more realistic picture of actual field performance. But there is a major tendency in the entire residential realm for the manufacturers to quote inflated values on big ads. Some of the less reputable companies don't provide enough test data to establish a level comparison, making it incredibly difficult or impossible to do so objectively. My main point here is there are so many configurations and factors to consider, that you really have to ask the right questions and look at a number of measurements to get an apples-to-apples comparison between units. Many GSHP units don't even have water pumps or fans inside the box, so presenting the total system performance questions has to be narrowed down from the getgo. The governing bodies have decided not to do this narrowing down, giving the manufacturers extra leeway during the certification process. |
Even if there are pumps in the box, their energy draw is not subtracted from the COP, making those advertised numbers bigger.
From Wikipedia: "ASHRAE transitioned to ISO 13256-1 in 2001, which replaces ARI 320, 325 and 330. The new ISO standard produces slightly higher ratings because it no longer budgets any electricity for water pumps." Rough example: At 600w per ton of capacity for the compressor power alone (should be this or less), 4 tons is 2400w. If we lose maybe 40 feet of head pumping 10gpm through the heat exchanger, 50' each way of 1" piping to the loop field, and the loop piping, plus lift the water 100ft (open system) the pump will take about 350w, assuming 90% motor efficiency and 78% pump efficiency. That drops our "rated" efficiency almost 15%. Since the heat pump efficiency will go up and the water pump efficiency will go down at lower loadings, the actual efficiency will be affected by the pump draw by a much larger percentage at lower loadings. |
Quote:
Most likely, you will have to wait awhile for a report to be filed or an analysis to be prepared. Since your heat pump system is on the fritz, you may be able to get a few HVAC contractors to come out and do some bids on a replacement or complete overhaul. Again, stating that you might DIY some or all of the work is a bad idea for an accurate assessment. These firms are interested in doing everything for you. Let them do their preliminary work, and be there if you can. Once the reports, analyses, bids, proposals, and the like are delivered to you, it will be much easier to determine where the home stands in multiple areas of interest. Since you are considering multiple strategies in both reducing your energy usage and generating your own heat and electricity, these papers will provide different points of view taking aim at the same (or similar) goal. You can then use your own judgement to weigh these options against each other. Being better informed before you do anything major will help prevent costly mistakes. I would take the info you got from phone support with a couple grains of salt concerning your ductless system. Many of these units fault out with the same types of error codes when things go wrong. Just as calling the computer help desk most always ends up with your system needing a new motherboard or hard drive, the mini-split manufacturers blame the compressor or control board in nearly all cases where the system doesn't have a leak. Read through some past topics, as many fellow ecorenovators have been the same place you stand now. This forum has become a huge resource because of people in all walks of life helping each other out. It is not that difficult to save a few thousand dollars a month in labor during the planning and construction phases if you have the time, determination and skills to DIY. Having willing friends or kids who will work for ice cream, pizza and beer doesn't hurt either! |
"...fire retardant spray can foam (behind the electrical boxes) could save almost that much per month."
I've looked into this, spray foams such as Great Stuff Fireblock are not UL rated for this use. With enough heat or direct flame, they do burn. I tried this with a lighter, I have lit this stuff and it does not immediately extinguish when the lighter(not blow torch) was removed. Fire blocking spray foams are fire blocking in the sense that they prevent a cavity from having access to air, which will suffocate most fires. Electrical fires are different than this, they continue to produce heat in the absence of a fuel, this makes such a product as "Fireblock foam" unsuitable for this application and the product is likely to burn. UL1479 fire rated sealant exists for this purpose as specifically labelled caulking products. Here is an example of such a product: 3M 10.1 fl. oz. Fire-Barrier Sealant Caulk-CP-25WB+ - The Home Depot |
| All times are GMT -5. The time now is 05:37 PM. |
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Ad Management by RedTyger