My geothermal compressor just died.

[LD1]

Sounds like you guys have units oversized according to every pro I talk to that wants to size me a unit. If you aren't on backup heat by 25-30 degrees they think it's too big.

The thing about a manual j...it can be deceiving. You calculate it around a design temp. IE, what temp do you want to maintain and at what ambient outside temp.

So if whoever does the manual j calculates based on 68* inside and 25* outside...and you want to keep the house 72* and it frequently gets to teens or single digits, your system will be too small and need backup very frequently

 

[midwesternhayfarmer]

I am afraid they have me by the b**s. There are not that many choices between installers. I would switch brands if I know which to select. There are complaints on internet about all of them.

Clarke electric the original installer?

 

[buckeyefarmer]

I ran my own manual j, and designed my systems, and installed my systems. Used to be IGSHPA accredited but i let it expire. I prefer to minimize backup electric. My breaker is off on mine, has called for it for 5 hrs so far this month.

 

[TheGoose]

I think a big problem is HVAC installers like to size based on cooling load. It isnt as hard to keep a home 20 degrees (F) cooler than ambient than it is to keep it 80 degrees warmer.

Doing a manual J load calculation, heating load is usually around double the BTUs than cooling load. (I am getting ready to do a geo when the weather breaks and did a manual J) my cooling load is ~26k BTU and heating load right at 48k BTU. This is based on outdoor temps of 0F for heating and 95F for cooling.

So if sized according to a HVAC guy, I would get a unit that runs almost all of the time when temps are 95+ trying to keep the house cool (which is what they want for humidification). But anytime the ambient temps drop much below 30F (which is alot), the system cannot keep up and needs a backup source like heat strips. Sure dont sound efficient to me. I'd rather have a larger unit that dont run as often but is able to keep my house warm in the winter.

I am likely going to be installing a 4-ton based on my 48k heat load.

How exactly do you do a manual j load calculation?

 

[buckeyefarmer]

Manual j is a book put out by ACCA that tells you. Most buy the software. I have both but software license is now expired.

 

[buckeyefarmer]

You can do manual j by hand, but is a pain. Calc for each room, each surface area the thermal conductivity to determine amount of heating,cooling, airflow required to maintain an indoor temp versus outdoor temps.

 

[Redneck in training]

Clarke electric the original installer?

It was not Clarke Electric. It was LessMess out of Truro. Clarke Electric is out of geothermal business.

 

[fordmantpw]

Sounds like you guys have units oversized according to every pro I talk to that wants to size me a unit. If you aren't on backup heat by 25-30 degrees they think it's too big.

If you are talking about the resistance heat as backup, for a ground-source unit, you only want that to come on as a worst-case because it is so expensive to run.

Our unit is sized to heat and cool our house without the backup heat to the coldest weather expected here in MO. We have a variable everything unit (compressor, pump, fan), and our heat strips are actually disabled and have to be turned on as 'emergency' heat. Now, when it gets cold, our unit runs a lot, A LOT! Our thermostat tells us how much it runs and we've had days where it has run for 22 hours in a day. Now, most of that is running on a low power setting, which is where the GSHP really shines. Basically, we are heating our entire 2500 sq. ft. main level plus finished basement with WAY too many windows for about what it takes to run a 1500 watt ceramic heater (based on the reading on our thermostat), even in the coldest weather. To me, that's pretty impressive. Our electric bill runs about $30/month more in the coldest months than when we have no heat or air on at all. Our bill doesn't change much when the A/C is on because it saves money not having to pay to heat our water.

 

[Redneck in training]

Variable everything is great and way to go. But it is hard to retrofit. It needs a control system that integrates all parts together.

 

[davesl708]

If you are talking about the resistance heat as backup, for a ground-source unit, you only want that to come on as a worst-case because it is so expensive to run.

Our unit is sized to heat and cool our house without the backup heat to the coldest weather expected here in MO. We have a variable everything unit (compressor, pump, fan), and our heat strips are actually disabled and have to be turned on as 'emergency' heat. Now, when it gets cold, our unit runs a lot, A LOT! Our thermostat tells us how much it runs and we've had days where it has run for 22 hours in a day. Now, most of that is running on a low power setting, which is where the GSHP really shines. Basically, we are heating our entire 2500 sq. ft. main level plus finished basement with WAY too many windows for about what it takes to run a 1500 watt ceramic heater (based on the reading on our thermostat), even in the coldest weather. To me, that's pretty impressive. Our electric bill runs about $30/month more in the coldest months than when we have no heat or air on at all. Our bill doesn't change much when the A/C is on because it saves money not having to pay to heat our water.

The frequency in which a unit runs is determined by the heat load on the structure, i.e. insulation and air exchange. The less air exchange and greater the insulation reduces the frequency the unit runs. The duration of the run is determined by the btu's produce by the unit. The greater the btu's the less time the unit runs.
My unit comes on about every hour and runs for 10 minutes. Less during the summer.

Definitely the benefit of the geo producing hot water is a big savings.