Hi,

Is is possible and/or advisable to put Geo in this kind of house?  1922, 6700 sq. ft, oil boilers with hot-water radiators in rooms, no ducting in house, plaster walls, 3 floors of living space.  How many systems? Cost?  Payback time?  Don't know heating costs (haven't bought the house yet!), but expect substantial, and would only buy if can install AC - ideally and get rid of oil heat.  Had one HVAC contractor give bid of $115k for AC/ducting only (conventional, not Geo); that's for 3 5-ton systems, plus 3 2-ton systems.

Thanks for any advice; really would rather have Geo if would work!  (with ducting of course - I do understand that Geo would not heat water hot enough to use radiators...).

Its possible, actually very interesting project. If I were designing system , this is without looking at the house, I would lean toward using Spacepak with a water to water gshp and you could incorporate the existing radiators into the design.Its possible to install hvac without removing plaster and creating a bunch of soffits and chases if designed carefully. 1st step in any hvac system design is a manual J load calc. No matter if its a boiler replacement, AC system, or geothermal system. Stay away from contractors that dont do this as they are shooting from the hip. A lot of them do. This house could have a heating load of 120,000 to 500,000 or more. In this situation I would probably design for 80 to 85% seasonal heating load and pickup the rest with a condensing boiler which would also provide emergency heat. Where are you located and how well is the house insulated. Eric

Yep, as Eric asked, where are you located?
Lots of ways to skin this cat, but heat load is absolutely the first step.
Floor plan also has big impact on design. Old Farm house we looked at had very open 3rd floor which could be solved with existing radiators and in floor radiant (3/8" tube embedded in OSB under carpet). 1 console (hotel type unit) handles cooling.
Ground floor easy (as it is over basement).
Middle floor toughest. Still deciding on consoles or.......?
10 ton WTW. Electric back-up.
Far less than $100K.
Savings over fuel oil ~$6K/yr.
Good Luck,
Joe

Does console handle cooling via chilled water from WTW geo?

My builder partner and I are trying to wrap our minds around the possibilities of chilled water systems on larger (5k SF and up) houses. Chilled water would seem to allow zones of any size w/o minimum airflow worries, and ductwork could be greatly simplified.

Thanks to all for replies; not familiar with Spacepak...

The house is in a suburb of Philadelphia, so hot summers, fairly cold winters.  would want to minimize soffets as much as possible to preserve interior looks; the HVAC contractors we had come so far said would be minimal, and work through ceilings...   Geo contractor to come today...

Thanks!

Dave

Dave,
Spacepak is a mfg of hi velocity air conditioning systems. Unico is another, as is ESP's "Hi Velocity" brand. I have installed all 3 and prefer Spacepak overall.Try this link not a lot there but go back to home and browse around. http://www.spacepak.com/water-cooled-central-air-mini-duct.asp ... some of the pertinent features are great humidity control and the ability to be used in a retrofit application. IT MUST be installed properly and that starts with a manual J load calculation. I can't stress this enough as it is the cornerstone of an installation. If a contractor shoots from the hip take it as a bad omen..There is no way a project of your magnitude can be done properly with out a lot of preliminary engineering and design.
The 1st step in the process is the manual J it will tell you room by room what the heating and cooling load is in the house, it should take about 6 to 8 hrs to do a house this size. Then you design the air handlers, duct work, radiators etc to meet the load in each room. Then the piping system to handle chilled, hot, and condensate water. Then you design the geothermal system to provide the appropriate amount of heating and cooling needed. This would take several days to put together and provide an accurate cost estimate. You could get budget numbers on the 1st visit but no way could you get an accurate estimate in less than 2 to 3 days....I could not and I have been in HVAC for 23years with 15 years doing estimating and design...Eric

Eric,

Thanks for the help; where are you located?  We've had 2 HVAC contractors look at house (again, we don't yet own it - trying to approximate costs to upgrade to AC prior to buying).  The first one recommended conventional AC system, with three 5-ton units, plus three 2-ton units, plus air handlers, etc.  He did measure each room, and noted the 1922-era windows, french doors with single panes, etc.  Price - 115k.  Second one - who specializes in Geothermal and has been doing it for 30 yrs - walked around (for about 1 1/2 hrs) with assistant, and looked in every room, closet, etc, and seemed very knowledgable.  Recommended self-contained units, with methanol lines from basement units to attick units, and will give us an estimate in a few days.  He didn't measure - but said he would do an exact measurement if we decide to move ahead.  I asked him about the Spacepak and Unico - he's used them before and said not great, very expensive, and would recommend conventional ducting - especially since using ceilings and floors only in this house.  He did go over the other guy's estimate, and said with the 30% tax credit it should be equivalent - and then will save on heating oil costs long term.  Seems to make sense..

Your thoughts?  Want to come and take over?!

David

I would recommend a geothermal Liquid-to-Water or DX-to-Water system that would use your existing (probably large cast iron) radiators and make up the difference in reduced Btu due to lower water temperature with something like ‘Multiaqua’ fan coil units placed strategically on each floor. This would take care of heating.

During the summer, circulation is cut off to the cast iron rads and chilled water delivered only to the fan coil units. This way you would have central heating AND A/C – without ever having to install ducts! Each fan coil unit would be a separate zone.

This solution may be the best for energy efficiency AND preserving the architectural and heritage value of your house.

IMPO

SR

Posted By ilgeo on 16 Jun 2010 09:19 PM
The 1st step in the process is the manual J it will tell you room by room what the heating and cooling load is in the house, it should take about 6 to 8 hrs to do a house this size.

Typo?
This house would take me (maybe) an hour to measure and 1 hour to do data entry in load software- tops.
I don't think we want to give the impression that someone must spend 6-8 hours to do a good heat load calc.
J

Joe,
yes your right 2-3 hrs for M-J, to many hours in the sun yesterday...Was thinking thru entire design...Eric

Posted By engineer on 16 Jun 2010 03:15 AM
Does console handle cooling via chilled water from WTW geo?

My builder partner and I are trying to wrap our minds around the possibilities of chilled water systems on larger (5k SF and up) houses. Chilled water would seem to allow zones of any size w/o minimum airflow worries, and ductwork could be greatly simplified.

Some time ago one of the smart folks around here (perhaps dewayne) referred me to a link that had consoles with hydronic fan coils and electric auxiliary strips. These would handle chilled or heated water.
Geo consoles (I'm sure you have seen) are WTA and not much more expensive.
j

David,
I'm located in N IL 60 mi W of Chicago, and I sure could go for a good steak sandwich. I'm sending you a PM later today.
Yes Hi V systems are expensive, but they have a niche and it happens to be retrofit.. while the equipment is more expensive the installation may not. The amount of repair work and time to install are substantially less. Humidity control is better and air balancing is easier. It must be properly designed and installed. Eric

I'm shocked that you guys can do a Manual J energy model in a couple hours, especially on a home this size.

I, and many home energy raters with whom I've discussed this very issue with, bemoan the fact that an accurate energy model of a typical, 3000SF home, is a day-long process to do it right. In order to accurately model a home, you need every room measured, with every door, window, wall carefully sized and U or R value determined. You need to accurately determine insulation levels of walls, attic, etc. In order to get any sort of accuracy, you can't just go on program defaults, you have to determine actual air leakage rates and more, since those, by themselves, can and do vary tremendously from home to home.

Energy modeling is truly a case of Garbage In, Garbage Out. I've seen models vary by as much as 100% and a recent research report analyzing numerous models supports the assertion that there's great variability in predicted vs. true loads in all software measured.

This can be greatly improved through "sanity checking" - tweaking the models based on actual fuel usage and known usage patterns. However, this turns into a research report, not just a couple hour Manual-J exercise.

I'm not arguing against Manual-J, on the contrary, it's absolutely required. Just bear in mind that the calculation is only as good as the numbers put in.

Tinoue,
I agree with you and it would be ideal to have a design done independently of the contracted work. Eric

I agree with tinoue.

Furthermore, Manual J is not the god you may think it is - but often a false idol.

Do you believe everything you read?

Garbage in – Garbage out!

SR

Fsq4cw,
I do not worship the Man J but it is the best that we have. Like anything else it can be a force for good or evil....anything in the hands of the inexperienced, ignorant or misguided has the potential for disaster. The man J is a very good starting point. Contractors who are too lazy or arrogant to do one are a disservice. Eric

Determining whether the correct load on a house is either of 4.5 or 4.516 tons is immaterial if you are gonna install a 5 ton unit either way.

A Man J and Man D done to within 10-20% accuracy and pointing at a 3 ton unit makes me look better to a client when I use the program result to refute a nitwit hack competitor who wants to overcome crappy ductwork and spot comfort complaints with a 4 ton replacement of a 3 ton unit.

Curt, you know that that's not the type of difference I'm talking about. The errors are not trivial, second decimal type of things.
I'll give you a concrete example. When I had my house done five years ago, I had a couple very experienced pros come in and do manual J's. One came in with a heat load of 80k+ BTUh. The other was 60k. I did my own and got about 50k. You're talking nearly 60% oversizing between the high number an my number, (which turned out to be dead-on when later confirmed through actual analysis).

Why did the numbers vary so much? GiGo. The high number guy was disobeying Man J rules and building in a buffer by using a design temperature that was worst case. He also used worst case numbers for anything he had to estimate. If I had been a typical homeowner, I would have just trusted his numbers and ended up with a massively oversized system.

This isn't just an isolated case. I've analyzed a number of quotes for my clients where the installers have grossly padded the system sizes. Again, if they were following Man J rules to the letter, they wouldn't pad the size, but they often do as a CYA move.

It's problems like this that are part of why consumers mistrust the industry and (to answer another thread) what slows adoption of the technology. Mistakes like this drive GSHP system costs from $20k to $30k.

ok, reality check I have a choice of 5 sizes if we're talkin' 2 stage (2-6 tons) for a single zone, I can easily come within 12kbtu (20%) without hours of measurement.
Tinoue, the shortcomings of manual J you seem to emphasize cite padding by the person doing the calculations. How does that condemn the process by those that do it right?
j

Joe,
That's a single example. As noted in my original posting, I fully support doing an accurate Manual J calc as long as the time is taken to use reasonable figures.
The more insidious shortcomings relate to using default values instead of the actual construction involved.

As I said, you're a better man than I if you can take measurements for a room-by-room floor plan and put it into the software, with takeoffs for every pertinent construction detail, of a 6500 SF home in an hour or two.

Furthermore, for the house in question, you're looking multiple zones and a heat load of what, 200+ kbtuh, so if you're shooting for 20%, and you're rounding up, you could be quoting the homeowner 3-4 tons of extra capacity. In this area, that's an entire system. No problem, that's just an extra $20k of equipment and wells.