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stevehull · 09-12-16, 06:59 AM

If you are concerned with oversize at 3 tons, then put in a two ton unit. The key is the two speed compressor. Most of the time the GTHP will run on stage 1 (lower compressor setting). This maximizes water extraction and maximizes efficiency.

Remember that minimal human activity, electronics, appliances and cooking can easily add one ton of cooling. And cooling is your 80% issue - not heating. This is on top of the manual J load. So if the house, by manual J, is one ton, then you really need two tons for the most basic cooling issues. Cooking is a major contributor. Second is electronics and appliances in terms of providing vampire heat load. People are significant and significant heat, but a LOT of moisture. Remember that cooling load is just not heat, but also indoor latent humidity in addition to that which is outdoors (and leaks in).

I am just not seeing the longevity with minisplits as compared to GTHPs.

I also REALLY like SIPS for speed of building, envelope tightness and strength

Steve

09-12-16, 06:59 AM	#13
stevehull Steve Hull Join Date: Dec 2012 Location: hilly, tree covered Arcadia, OK USA Posts: 826 Thanks: 241 Thanked 165 Times in 123 Posts	If you are concerned with oversize at 3 tons, then put in a two ton unit. The key is the two speed compressor. Most of the time the GTHP will run on stage 1 (lower compressor setting). This maximizes water extraction and maximizes efficiency. Remember that minimal human activity, electronics, appliances and cooking can easily add one ton of cooling. And cooling is your 80% issue - not heating. This is on top of the manual J load. So if the house, by manual J, is one ton, then you really need two tons for the most basic cooling issues. Cooking is a major contributor. Second is electronics and appliances in terms of providing vampire heat load. People are significant and significant heat, but a LOT of moisture. Remember that cooling load is just not heat, but also indoor latent humidity in addition to that which is outdoors (and leaks in). I am just not seeing the longevity with minisplits as compared to GTHPs. I also REALLY like SIPS for speed of building, envelope tightness and strength Steve __________________ consulting on geothermal heating/cooling & rational energy use since 1990 Last edited by stevehull; 09-12-16 at 07:51 AM..