We are considering a geothermal retrofit for a complex house. We've been very impressed with several of the geothermal contractors we've had on site, and are considering moving forward on this project. Here are the details: 4000 sq ft house, complex layout requiring three separate heat pumps (we concur), roughly 122 million BTU / year heating load, and currently on oil baseboard heat. We'll have to add considerable ductwork. We'll pair the geothermal install with a large PV array which makes for a cost-effective solution over the short- and long-term (since this is our 30-year house and we'll roll the capital cost of the system into a mortgage). A few questions, I'd welcome feedback on... First, the strongest proposal we've got is for three Water Furnace units (2-, 2-, and 4-tons) - Series 5. I searched for Water Furnace and reliability issues, and the numerous stories on the web raised my concerns. Despite the claims of the company and the dealer (negligible maintenance; near-perfect reliability), it seems a lot of people have had poor experiences with their products over the years. My concerns are heightened by the fact that we'd have 3 units! The other contractor installs Hydron; is the story any different there? Second, how noisy are these units? To service the various parts of our home, we need to locate the GSHPs in attic or other spaces that are adjacent to living or sleeping areas. I was envisioning whisper quiet operation, but I gather that isn't necessarily the case. How concerned should we be about noise and vibration? Third, as I understand it, there isn't a viable geo-based replacement for our oil-fired boiler. The WaterFurnace Series 5 produces "up to" 15oF water. I've wondered if we could use that to drive our existing baseboard system, and then use the oil-fired boiler to supplement (it is a 180F system currently). We realize a downside here would be the lack of geo-based A/C. Is this an option worth exploring? It could get potentially be a simpler system, with only 1 GSHP. As you might guess, this is a costly project ($80k-$100k total). I should mention that we are also taking steps to tighten up the envelope and improve insulation as part of this project. While I am very much interested in the advantages of geo and reducing our oil consumption, I'm concerned we may spend a lot of money with the expectation of a quiet, very reliable, and long-lasting system and instead find ourselves with a noisy and not-so-reliable system (in part because we've got 3 heat pumps!). I'd welcome feedback and thoughts from people who have own geo systems and experience with Water Furnace or Hydron. Thanks. Mort
I've done WF and Hydron. Both decent units. You likely hear issues about WF more because they are one of the most popular brands out there. So you will get issues purely based on numbers. But I quite like their product. They are noisy enough that if you are asking that now, you will notice them. I'm being honest on this. Though I find them quite quiet. You put a bed beside your fridge, and suddenly your fridge is noisy. You live in the country, and suddenly your clock is noisy. But I'm sitting here listening to my noisy gas furnace right now as it hammers scorched air through its tight ducting (new house for us, so haven't switch over yet). Maybe look at hydronic fan convectors (Myson) as a potential replacement for some of your baseboards. You can zone some cooling that way. Not sure why you need 3 separate units on an existing boiler system, but I'm assuming boots on the ground has considered options.
It is possible to feed your radiation with a water to water geo unit, and then as you mention use your supplement the geo with your boiler. I have designed and built such a system in Valley City, OH. We have 2 5-ton W2W units feeding a buffering tank. When they can not keep up with the load we then fire the boiler. You can also do some of the cooling load with your radiation. The temperature in cooling must be above the dew point. The rest of the cooling can be done with small foot print, very quiet, high velocity air handler and duct work. You need two things to make what I described work. First you need a detailed heat loss calculation on a room by room basis. Second you need to measure the heating capacity of your radiation. With those two numbers it could be possible to halve your equipment and there for your costs. Mark
Third, as I understand it, there isn't a viable geo-based replacement for our oil-fired boiler. The WaterFurnace Series 5 produces "up to" 15oF water. I've wondered if we could use that to drive our existing baseboard system, and then use the oil-fired boiler to supplement (it is a 180F system currently). We realize a downside here would be the lack of geo-based A/C. Is this an option worth exploring? It could get potentially be a simpler system, with only 1 GSHP. I'm not sure how relevant this is, but I just had a 7 ton WF 5 installed. We have a drafty old Victorian, and 16 cast iron radiators. I was told at one point by an engineer that these radiators needed 160-180* water, but I am sitting here now in my living room, the temp outside is 40 (a heat wave for MN), and the WF just cycled off but was putting out 113* water and heating our house to 70 degrees. On the coldest day/nights of the year a few weeks ago, with actual temps of -7 and windchill of -25 to -30, the HP put out 150 degrees and the gas boiler had to kick in an extra 4-5 degrees sporadically. As far as reliability, I have no concerns about WaterFurnace. As Urthbuoy mentioned they sell a lot of units...and you're much more likely to read about someone with an issue than 100s of people who don't have an issue.
Hmm, if 120 Million BTU/yr is accurate (which sounds about in the ballpark of a reasonable 4000 sq ft house in MA), then I'm suspicious that your bids are oversized (and therefore more expensive than they have to be). What do they say the Manual J design heating and cooling loads are (in BTU/hr)? You didn't say where you are in MA, but here's the math I would use to get a good ballpark: Suppose you're in a mild area of the state like Boston. Average yearly heating degree days (HDD) is 5630, and design temp is 12F. (120 MMBTU) / (5650HDD * 24 hr/day) = 885 BTU/hr/°F. For a interior temperature of 70°F and design heating temperature of of 12F, the load would be (885*(70-12)) = 51330 MBTU/hr. Given the wide error bars of this rough ballpark calculation, I could see anywhere from 3-5 ton fitting whatever your actual calculated load is. This is way different from the 8 ton estimate, so would be enough for me to raise an eyebrow and ask for more details about their estimate. If you were in a colder area of MA like Pittsfield, HDD is about 7500, and design temp is -3, the same math ends up at about 48667 MBTU/hr. ~50000 MBTU/hr feels plausible to me for a decently insulated house of about that size with fairly normal fenestration ratios (i.e. not all glass). 8 tons would suit a house with 100k+ MBTU/hr heating load at design conditions, which would be plausible if your house were a leaky Victorian with minimal insulation. If you were in that boat, your annual consumption would be on the order of 230 MMBTU/yr, nearly double what your rough estimate is. Hydron is great - they moved to an aluminum microchannel coil, which should be immune to formicary corrosion. Comparable to WF 5 series, but with a better warranty. They do not offer anything like the variable-speed WF 7 series, however, which is the current state of the art (along with Climate master trilogy) in comfort and efficiency.
I should mention that the 7 ton WF5 has two 3.5 ton compressors....only one of which is cycling on and off today. Sorry, that's an important detail!
The 122MBTUs/year, is that your actual total heating load without your internal and external gains? Or a calculation based on your current consumption, where you use your equivalent gallons of oil used last year? Keep in mind, w-w has no strip heat for bail out, and usually needs to cover 100% of the load. 1) All the manufacturers have small issues here and there, and usually they are installation issues. WF sometimes creates the perception that with their dealer direct model, that the dealers are especially well qualified. Most of the time they are experienced, and WF is usually pretty picky who they ask to join their dealer network. Overall they are one of the best out there, together with Enertech (Hydron) and Climatemaster. The contractor needs to be good, the heat pumps are interchangeable, with WF having the technological edge (my biased opinion). We sell all 3 of them. 2) The quietest ones are the variable speed HPs, but I usually resent the notion to place compressor units all over a house, unless they are in the basement. The quietest is radiant, followed by variable speed air handlers. The 7 series is very quiet, but how quiet is quiet. Try to see an install of your contractors and see for yourself. A dual stage is the loudest, where the WFs are the quietest of the gang (dual stages). 3) The 5 series can do the job up to 150F, it totally depends on how much heat capacity your baseboards have at 150F. You cannot supplement to 180F with your boiler, the return temps would still be too high entering the WF high temp unit. You can shut the HP off and solely run your boiler above 150F , but I would abandon the idea to keep and maintain your oil system. I would rather entertain adding a radiator or two, or some staple up under the floor to increase your radiator capacity at 150F. Keep in mind that due to high needed supply temps the efficiency of the geosystem will be much higher with forced air than with radiant in your application. But nothing beats radiant for comfort....
Thanks for all this helpful input. I’ve learned a lot from these comments — some good ideas and questions to ask. We haven’t had a Manual J completed yet; none of the contractors want to undertake that work unless we have committed to doing the project with them. So, the annual BTU load is based on historic oil consumption and I don't have a sense for how well the existing baseboards match up the heating load in each room. The house is a reasonably well insulated, although it is leaky (based on a blower door test). We are undertaking improvements to the building envelope in conjunction with this geothermal retrofit. It seems like the big driver in our project cost is the need for multiple heat pumps and associated ductwork. Since we have a finished basement, running ductwork from a central pump is difficult/impossible. (And there are several strategically located attic or dead spaces where heat pumps could be located). But the total project cost, even if it yields a reasonable return is obviously high. The possibility of using geothermal to drive the baseboards up to 150F is interesting. Glad to hear that has worked for others. It makes sense we’d need to switch to boiler over 150F (due to return temps); but the loss of efficiency is a concern (since we can only generate so many kWh off a PV array on the roof) and we are striving to get as close to net zero as possible. Any rough sense for how much less efficient it is? Also good to hear that the complaints we are seeing regarding WF may be a product of volume, rather than an underlying quality issue. Thanks for the input - comments are much appreciated.
Can you turn down your oil fired boiler as a test? Last year we survived the polar vortex in MN with a boiler turned town to 156 degrees top temperature. That gave me confidence that the WF Series 5 could do the bulk of the job for us with its 150 degree max temp. COP drops to about 2 when it is putting out that temp water, but the amount of time it has to produce that temp of water MIGHT be 40 hours or so a year. It isn't constant even when it's needed.
Mort: No one knows your home better than you do. I would look at the DIY heat loss one time license at about $50.00. Joe Harden mentioned the site. If you chose to go that route I will get you a link to how to measure every hydronic radiator ever. It is a book by Dan Hollahan. He can be found at Heatinghelp.com. I would have you look at Unicosystems.com to solve your ducting issues. You are in range for me to look over your shoulder. Mark lake-erie-indoor-air-services.net
You could fish water load lines to the parts of the house which are hard to reach, and supplement your baseboard heat with some fan coils. That way you would never need the full 150F, and you could down regulate your supply temps for higher efficiency. Where are you located? How many gallons of oil did you use over a 12 months period? Where did you keep your thermostat, what was the coldest night you had last year in terms of outside temp? Then we can calculate your heat load. What about A/C?
Thanks for that suggestion, Tamar. Great idea. We've got a Burnham oil-fired burner (V8 Series - V86). Does anyone know if there are downsides to reducing the temperature range as an experiment (right now it seems to be set for 160 low and 180 high)? I assume the pumps serving the zones would run more frequently to try to satisfy the thermostat? Mark, what is that website for the DIY heat-loss analysis? I didn't see anything posted by Joe Harden. I'd like to look into that. We are outside of Boston. The house used 2000 gallons to provide space heating and domestic hot water last winter. We are new to the house this winter, and seem to be tracking for about 75% the oil consumption of previous residents -- I think we set the thermostat lower and the winter has been milder. We keep the thermostat around 66. Coldest night last winter? Well, we are forecast for -2 tonight! As for A/C, there is an existing A/C system. Unfortunately the duct work can't be easily retrofitted to provide heating. If we go with a geo-to-air system, we'll replace the A/C system. If we pursue a geo-to-water system, I expect we'd keep the A/C system. Thanks for the help.
I will drop Joe a note and find out. I have not used it, but it gets rave reviews here. Anybody that has the site chime in, please. The control you looked at to tell me the boiler runs between 160* and 180* should let you turn down the boiler. If you are in doubt, post a picture. If you lower the temps do not go lower than 135* or so as the cut in temp. With the 20* differential that should give you 155* cut out, higher than what a water to water geo with cooling can do but it will give you a feel for comfort. The control may have an adjustable differential so we can look at that change too. Do not dally on this test as we are running out of cold weather. You need a comfort fix now. We can do the math later. I am about comfort first. The rest is easy when the goals of a project are known. Mark
Hvaccalc offers a DIY 90 license for about $50.00 worked pretty good for me. If you have a fairly good understanding of what's in your home (insulation, windows, ) and can read a tape measure you should be able to use this software. Also if you have them you can use actual fuel/electrical uses from prior years as a reality check.
HVAC-Calc, the easy to use Heat Loss and Heat Gain Calculator, residential and commercial. http://www.hvaccalc.com/
