Questionable content?

It seems that someone has been flagging a few of my blogs to contain questionable content. How about this, to whom it may concern. Instead of flagging my blog leave a comment citing what you believe to be questionable. To the best of my knowledge i represent all figures accurately. 

Just in case someone thinks they are going to pull a fast one, i have paper evidence to back up all my claims. That being simple strait forward energy bills from my electric supplier and previous years oil bills for base line determination.

I have another blog which was flagged for no known reason. That blog deals with the thermal gradient of ground (which has huge potential in terms of heat pump modification to save energy).

If you don't like this information you are part of the problem. In that case leave a comment and have a good day.

Basic Modification

I have a 10 seer 2.5 ton air to air heat pump. This unit has a 3 ton air handler. There is also 15KW of electric strip heat installed in the air handler.

I bought the unit two years ago (used) and installed it last year just before the heating season. I disabled the electric strip heat in defrost mode to save energy. I never liked the idea of turning on strip heat, compressor and blower to defrost the evaporator coil. My first modification was to eliminate the strip heat in defrost mode. 

I'll give a little background on air to air heat pumps and their operation.

When in heating mode the heat pump simple moves heat from the external system (outside) to the internal system (my home). The heat pump moves heat by phase change(refrigerant changin from gas to liqiode, and liquid to gas) in addition to spatial displacement; that is an internal coil rejects heat while the external coil accepts heat. To accept heat the coil must be cooler than the system in which it is working. This is almost a catch 22. We are heating our home because it is cold outside. The external coil is picking heat up from that cold system by getting even colder than the outside temperature. Moisture condenses and freezes on the evaporator while accepting heat energy. This creates a blanket of frost. The frost eventually becomes ice as the system cycles (ie, heating up in the off cycle which begins to melt the frost).  When the system enters the next heating cycle the partially melted frost turns into ice.

As frost and ice accumulate the COP drops. When the COP drops below 1.0 the system operates in a deficient manor(wasting energy). Frost and ice have very good insulating properties this is the affective mechanism which dampens the heat exchanger throughput, and ultimately the heating system. Obviously a means of control is needed to avoid this adverse operating condition. This means is the defrost cycle. Normally the defrost cycle operates by simply switching the system into air conditioning mode while activating the resistive strip heat(electric heat).  That is, it accepts heat from the internal system and rejects that heat to the external system. This effectively heats the coils which are frozen or frosted. At the same time the air handler is activated along with resistive strip heat

This in itself is a very disturbing operating mode. The system takes all the precious heat in our home and it ejects it outside. If that is not bad enough the system is turning on electric heat to make up the heat which is being dumped outside!. The final blow comes in that the system consumes just as much energy to move our precious heat to the outside as it does to heat out home. In fact the typical defrost cycle costs many times more than a heating cycle since it activates resistive strip heating(electric heat).

If have found that that a typical winter day (20 degrees) an air to air heat pump will spend 4 hours in defrost mode for every 20 hours in heat mode. That is 1/5 of the time! Remember that this mode costs more than heating mode and is completely deficient!

This may be the number one reason that air to air heat pumps are regarded as the low end heat pump. Given that operation, i have no arguments with that assertion. However a little thought can correct a-lot of these short comings.

While analyzing the system i determined that the electric heat was not need in defrost. I heated my home for a few weeks with the electric heat disabled. When the system entered the defrost cycle(which it did quite often) A cool breeze blew around my home but not enough to circumvent the heating cycle. This in itself saved a great deal of electrical energy. However at a cost of discomfort. After thinking about the newly created problem i came to the conclusion that the air handler need not be activated for the entire defrost cycle. After all - all we need to accomplish in this cycle is to melt the frost and ice from the coils. I bought a delay timer that was designed to break the cycle after x amount of time.

I had to tinker with the timer for a few days until i found the ideal setting. For my setup it just so happened to be 2 mins. The defrost cycle typically runs for 15 mins. Now i only have to put up with 2 mins of cool air with a substantial saving in electricity. Once again, i became unhappy with the 2 mins of cold air causing discomfort. Thinking a little i discovered that i only need to run the blower if it is very cold outside(the heat within the refrigerant line set and coil will suffice for melting the frost and ice). To solve this problem i bought a temperature controller which allows me to adjust the point of which the air handler will be activated. At the moment that point is 15 degrees F.

While tinkering with the defrost cycle i discovered that the defrost controller has no intelligence what so ever. It simply works off of an external thermal switch. When the outside temperature falls below a given point the switch closes. That point is likely to be 32 degrees F. The controller then begins to monitor the amount of time the system has operated while at this temperature. After a programmed amount of time has expired it enters the defrost cycle. This works, but it is not efficient. After watching my heat pump in operation i discovered that it will enter a defrost cycle when there is no need for a defrost cycle. I must explain this point a little further. Even though it is below freezing there is enough heat energy in the air to defrost the coils if the external fan would be activated. This fan only consumes a few hundred watts where as the defrost cycle consumes a few thousand. I admit that this condition only exists a fraction of the time, none the less it can save energy.

I firmly believe that an air to air heat pump can be much more economical to install and operate than the geothermal counterpart. That is, if the air to air heat pump is modified appropriately