This is a follow-up to my earlier post titled Trane XL19i sizing question. We have narrowed our heat pump decision to the new Trane XL20i (thanks for the estimate on the release date of this new model, Jimj). We are also considering the XL15i based on the tip from gary g and performance data that we downloaded from the ARI website.
To answer a question from gary g, the reason we are considering a 2-stage heat pump in Pittsburgh is because I truly have no idea what energy costs are going to be over the next 15 years, which is the expected life span we are hoping to get from the unit. I do think that heating with a heat pump will eventually become cheaper than heating with fossil fuels like propane and natural gas because McCain plans to subsidize electricity with nuclear power and Obama plans to subsidize electricity with renewables.
Right or wrong, we have decided to go with a 100% electric system and our goal is to set up the most efficient size unit and model for our combined heating and cooling needs over the entire year. I'm thinking this may mean compromising the cooling efficiency a little bit in favor of heating capacity, which will hopefully give us the lowest overall annual operating cost for our area.
We have also looked at geothermal, but we do not have enough room for a drilling rig to get into our back yard to install a system. So, we have decided to go with an air source heat pump and auxiliary electric heat strips in a variable speed air handler. My wife has been “Tranewashed” by one of her friends, so going with Trane will cause me less friction with the Mrs. Trane makes a decent unit and if something happens to it, I won’t have to hear her say I told you so.
Anyway, our heating requirement in Pittsburgh is much greater than our air conditioning needs. I think a 2.5 ton heat pump would be perfect for our cooling needs (we have a 1500 square foot brick home), but I’m thinking that size heat pump will require the auxiliary heat strips to support much of our heating needs during December, January, and February. I’m thinking that we might have the most efficient all-around system if we purchase a two-stage 5 ton XL20i heat pump. The COP would be above 1, even in the coldest weather, and I think the unit would not be short cycling during the air conditioning season because it could run on low stage at 50%. However, I realize this is just based on my simple math and it may not be that easy. I’m sure there is something I may be overlooking or a reason why this cannot be done.
We are going to contact the Trane rep that we have been dealing with over the phone and schedule an appointment with him to come to our house for sizing and pricing. We would like to know as much as possible prior to meeting with him though. We don’t want to waste his time or look stupid, if possible. His service so far on our current Goodman furnace has been excellent, and we will probably not even shop his price if his estimate is in the ballpark.
Yes, I do know about Goodman’s reputation, and the furnace was in the house when we bought it. We also have three carbon monoxide detectors that I installed after we replaced the heat exchanger. I hate that furnace. I plan to donate the carbon monoxide detectors to Goodwill after we get a Trane. I found out the hard way that some things are just worth researching and paying a little bit more for at the beginning to avoid problems down the road. So what do you think? Can we “oversize” our system with a 3, 4, or even 5 ton XL20i two stage heat pump, or should we just go with a single stage 2.5 ton XL15i?
Thanks again for all your advice. We really appreciate it.
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seriously just get a heat gain calculation from your trane dealer and he will let you know what size you need. too much cooling capacity is not a good option in most cases.
Originally Posted by smittyii
