Design Help for a New Guy

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  • Fishermedic
    Fishermedic Registered Users Posts: 9 ✭
    #32
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    Re: Design Help for a New Guy

    Lee,

    Do you have anything for pre-warming the fresh air into the HRV? I noticed the outdoor air temp at -15.7 and a fresh air to HRV temp of -10.9. What's warming the air before the HRV? I've seen mention of a ground loop in the intake duct for this purpose, is that what you're using?

    Bryan
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  • Lee Dodge
    Lee Dodge Solar Expert Posts: 112 ✭✭
    #33
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    Re: Design Help for a New Guy
    Fishermedic wrote: »
    Lee,

    Do you have anything for pre-warming the fresh air into the HRV? I noticed the outdoor air temp at -15.7 and a fresh air to HRV temp of -10.9. What's warming the air before the HRV? I've seen mention of a ground loop in the intake duct for this purpose, is that what you're using?

    Bryan

    Bryan,

    Good eye for catching the pre-heating effect. The pre-warming of the fresh air coming into the HRV is mostly due to the rather long ~25' entrance air duct that runs through the conditioned crawl space. Although the air duct is insulated, it still picks up some heat from the conditioned crawl space, especially at the low fan speeds where there is a lot of time for heat exchange. During the daytime and very early evening, it also picks up some heat relative to the average outdoor temperature since the long duct run is to get the entrance air from the south side of the house to take advantage of the solar heating at that end. (The exhaust goes out the east side toward the driveway, the "low-pressure" side of the house with prevailing west winds.) Cooling the crawl space air by pre-heating the fresh air is not as bad as cooling the air on the main floor, but it is not "free" from an overall energy standpoint. The stale air inlets for the HRV are in the crawl space, and this provides the circulation of air from the main floor to the crawl space. It also means the cooled air in the crawl space is more likely to be exhausted from the house.

    The idea of earth tubes to preheat the air is always popular, but usually not practical due to the expense for a small gain, and the growth of mold, etc. due to condensation, rain, or leakage in the earth tubes.
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  • Tradiscantia
    Tradiscantia Solar Expert Posts: 35 ✭✭
    #34
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    I just read this whole thread and didn't see anyone address this issue:
    "We are doing new house design/construction in a very hot dry climate and want to take advantage of the sun for thermal solar, even if only for preheating the water. We were thinking that with water preheated to say, 70, in winter, a hot water on demand system would be more efficient. The big issue is whether electric water heating has sufficient recovery to allow two or more showers and dishwashing in the evening when there is no sun. How large would the tank have to be? And what kind of system will fuel "the regular tank"?

    The bigger question is how do we heat our water in the most efficient way? What about preheating with solar and then using an electric water heater? Maybe a few extra PV panels to heat a largish storage tank which would feed into a smaller tank to bump it up to final temp for use. If the solar heated tank gets a little cool in the dark winter we still have the regular tank to keep us having warm showers and for most of the year that solar storage tank would provide the bulk of our hot water."
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,440 admin
    #35
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    In general, any heating by direct resistance electric heaters is pretty difficult to justify. For places with above freezing temperatures (or above ~55F), there are various air sourced heat pump systems for space/water heating. These are getting efficient enough for even off grid folks to use without spending huge amounts of money on a large solar array+battery bank.

    However, for folks in freezing climates/little winter sun--It is a much more difficult task. Besides needing to use anti-freeze (cost, maintenance, secondary heat exchangers), if there is little sun, there is little "free energy" for heat.

    However, if you have cold/clear winters and "enough sun", there have been some pretty interesting solar powered solutions for heating (air and water).

    http://forum.solar-electric.com/forum/solar-news-reviews-product-announcements/solar-information-links-sources-event-announcements/4426-working-thread-for-solar-beginner-post-faq?5556-Working-Thread-for-Solar-Beginner-Post-FAQ=
    This is an interesting project for a solar heated shed and a control the guy now sells to support a pure DC off-grid solar heating system.

    And this one is a bit more low tech home made heating system. Also very interesting and informative.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Tradiscantia
    Tradiscantia Solar Expert Posts: 35 ✭✭
    #36
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    mike95490 wrote: »
    Re: Design Help for a New Guy
    We were thwarted by the requirement for Low-E windows registered by California. So we have minimal solar heat gain unless we open a window! Governmental idiots.

    I am also in CA. Are we wasting our time trying to design for south-facing windows and overhangs?
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  • mryimmers
    mryimmers Solar Expert Posts: 117 ✭✭✭
    #37
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    Fishermedic wrote: »
    My first choice at the moment is a fireplace


    Hi, I am near Thunder Bay, so our weather is about the same. We have a 2000 sq ft bungalow with a full basement, everything electric. 5 years ago I put in an RSF Energy fireplace (Onyx 2 model), our electric furnace has not run once since we started burning it. I have an 8 inch in-line blower plumbed into it and circulate air all thru the house with it. Our Ontario Hydro bills are now $150-$180 year round, being that you are from here, I'm sure you know that is not too bad. That unit probably paid for itself in the first 2-3 years. Not sure exactly but I think I burn about 5-6 real cords per year. Sitting in front of the fireplace is a real nice place to have a beer too.
    510 watt pv, TS-MPPT 60, Exeltech XP1100, XP600 & XP250 @ 24V, 4x Trojan 105RE, Trimetric 2030, Yamaha EF2400i gen.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #38
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    Tradiscantia wrote: »

    I am also in CA. Are we wasting our time trying to design for south-facing windows and overhangs?

    We found it a complete waste. The idiots making the rules live in beach cities and are dictating how mountain houses should be built so that owners will spend $$ and be frustrated. 3 years later I am still steaming mad about them. Don't get me started about installing fire sprinklers in a unheated, detached garage, in a freezing climate. (and you can't leave the car running for heat, because that sets off the CO alarms (that only have a 5 year lifetime sensor))......

    But seriously, find out what windows are certified, and see if you can get any heat gain from the low E glass. Other states you can order the panes reversed so they keep heat in, but in kalifornia, everyone needs air conditioning, so heat must be kept out at all times.

    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
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