Suggestions please

Jerry Scharf_4

Steve,

I'd still start with getting the load down. Just because the remodel was done doesn't mean it was done right. I think it's time for a blower door test. It will get you the real infiltration numbers and may be able to spot some serious issues. If there are any local services that do the infrared camera evaluation, I would jump on that as well.

Having never lived in a 8K+ sqft house, it's hard for me to imagine using all that space all the time. Would there be ways to control where the heat was at what times of day? I've never controlled a high velocity system, and standard dampers/actuators don't seem like they would just drop in.

Definitely the high temp fan coils make life harder...

jerry

Steve Ebels_3

Looking for ideas to help this guy out

I did a service/maintenance call for this guy during the winter and now he's asking for ideas to cut his $2,000/month LP gas bill. The system presently in place had been serviced and maintained by the local heating dork. (I found water heater relief valves in both boilers and the HO was wondering why there was always water on the floor........no joke, water heater T&P valves!!)

What he has presently is two Dunkirk induced draft cast iron boilers run by a Tekmar which provide heat for two 3T Unico Hi-Velocity air handlers. There is no possible way to retrofit the duct work so we're pretty much stuck with the Unico system. There is a full basement under the main part of the house so panel rads could be installed or even some staple up.

He asked me about the feasibility of using a heat pump but I doubt if that's possible due to the high temps needed by the AHU's. Short of installing 1 or 2 condensing boilers, is there anything you can think of that would help him out more than that?

The house was remodeled completely in 1998 and has all new windows and insulation. It's about 8,200 sq ft with a LOT of glass on the north and the south sides. The master suite is over the garage and is always colder than the rest of the house. It's approx 1,300 sq ft alone.

Looking for some "off the Wall" ideas.

George Peteya_4

Learned something last week ...

... that you may find helpful. Oil-fired boiler, combustion air from outside through a Field boot, induced draft via Tjernlund SS2. The post purge had been set to 2 minutes. So, when the boiler shut down on limit, the Sideshot continued to pull cold(45°F that day ... imagine when it's zero or below) outside air through the boiler, chilling it down through the aquastat's differential in, oh, a minute 15 seconds or so. Aquastat called the boiler again, even before the post purge was over. Repeat.

Bottom line is that a lot of outside air was getting pulled through the boiler, heated, and thrown away. Reducing the post purge to 1 minute helped a lot.

ALH_4

The Usual Suspects

It's probably least expensive to cut the heat loss. How about window quilts? Maybe an inch of Thermax on the garage ceiling? How about programmable thermostat(s)? How much hot water do they use? Do they have an indirect or a gas fired water heater? Is the piping correct? Running the flow through the boiler backwards could sure affect things. A 15/60 probably wouldn't hurt.

Steve Ebels_3

The basics are pretty well covered

The boilers are piped parallel, reverse returned. There are 2-40 gallon superstores, one for the master bath, one for the rest of the house. The house was insulated pretty well from what I can tell when it was remodeled/added on a few years ago and the Windows are Andersons installed at that time so it's wrapped pretty well. The joists in the garage ceiling are blown full, approx 12" so I think the "cold issue there is more to do with balancing with the rest of the house.

I was working there on a 5* day and both AHU's were running continuously with one boiler constantly firing and the second one cycling on/off every 15 minutes. Looks like a pretty serious heat load as both the boilers are 125K input.

Thinking about it this AM, the part of the house with the basement under it could be retrofitted with regular duct, allowing the use of a GSHP for that half at least. I'll have to do a heat loss and see if it's feasible for a retro. That and a condensing boier for the other side is what I'm pondering right now.

jp_2

do a basement heatloss

the house may have been insulated well but what about insulation below the joist line?

the heatloss on my basment equals the poorly insulated house. if I insulate well i should end up with 16,000 btu loss but basement is still at 29,000 btu's(old stone basement).

I'm playing with ideas to cover outside foundation walls with 2" blue foam then stucco of some sorts, I think even digging down 2 ft below ground could make a big difference.

i like the idea of motorized insulated window blinds that will lower at night and open in morning, then somewhat reversed in the summer(programmable).

Steamhead (in transit)

Steve, I'd go full hydronic

and leave the Unico just for A/C. Not sure what design temp is for cooling in your area but I'm sure it can't be more than 25-30 degrees above indoor temp, whereas for heating you probably have something like -20 for your design temp- that's 90 degrees below indoor temp. That's quite a difference. Unico ductwork might just not be big enough, and if it's marginal you'd need to run high water temps to make it work.

Installing a separate hydronic system with panel rads, radiant or even baseboard would allow you to design for lower water temps and take full advantage of condensing boilers. But you know that ;-)

Also look at the cost per BTU of propane vs. oil in your area. I'll bet that's part of it. Consult Ken Secor for his experience with the Monitor oil-fired condensing boiler.

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hot_rod

8200 square feet at

25 btu/ sq ft is a 205,000 BTU/hr load. Calculate the lp use at close to 3 gallons per hour at design. Plus the DHW load at 82% boiler efficiency

Not sure how high your lp prices are but I doubt you could half that fuel cost for him. Maybe find 10% savings or so by upgrading? Then again if LP, oil, and other fuels rise like predicted???

Better quote it as the amount of fuel you might save him not monthly fuel cost savings

Sounds like he needs a smaller home.

hot rod

Glenn Sossin_2

Along similar lines

What about combustion air? Where is that coming from. Is he sucking it from inside the house. That would increase his infiltration/air changes. Perhaps using a Fields CAS 3 would help.

Radiant Wizard

Air Handlers Are too small

Stop and go back to the basics. Two 3T A/H are about 160,000 btus. Do you thing that's enough to satify the load of the house? Do a heat loss, start there before introducing a solution...I'm taking it you are using Dunkirk XEB's...