does running this loop increase or decrease efficiency of unit?
pump running cost not included.

in heating mode it slightly lengthens run cycles and slightly depresses supply air temperature, both effects on the order of 10%. I haven't checked amps in heating, but in cooling mode I noticed no change in compressor amps with dhw pump on or off; I expected a slight decrease in compressor amps with it on since it helps reject heat, but the effect wasn't perceptible.

The DHW current draw is about .3 Amps, although at what power factor I have no idea

I often wondered if DSH can really be touted as "free" by manufacturers. Engineer, do you have data to go with this or is it hypothesis based on the accepted output values?
J

my unit is water to water. no air? got me thinking about air for a minute.....there are no cooling vents on unit......

the information in the manuals do not refer to the DHW option. makes it hard to determine

DSH is essentially free throughout cooling season, except for the power to run its small pump. More precise instrumentation (than mine) might even reveal that compressor power drops by an amount similar to pump use. This is plausible since any heat rejected before condenser reduces its load and therefore compressor head.

I have run time (hourmeter) data for my storage electric water heater, and it drops by 80-100% on very hot and very cold days when DSH recovery is highest.

DSH is cheap in winter - you get it at system's COP, more or less.

what is DSH?
when (in heating mode) i allow the DHW optional pump to run the water through it heats up quite a lot. i can feel the cold and warm pies. the main laod tank water temperature stops rising! this i did last night. when i shut the DHW pump off the load tank temperature began to rise to set point again. the load tank temperature did not fall after the unit turned on but it did not rise. i imagione that if i had let it running eventually it waould have warmed up my dHW until warm enough that it would again transfer more heat into my load loop. as i mentioned the load loop temperature was not falling so some heat was being put into it as my radiant zones were still operational.
this tells me it does hurt load tank heat efficiency but replacing the DHW feed with warmed water saves on the electric hot water tank running so.....??? what is better???

DSH same as DHW. Superheated refrigerant gives up its highest temperature heat to domestic water.

I recommend leaving DHW / DSH on unless radiant heat isn't keeping up.

Thinking a bit deeper - if DSH operation diverts heat from loop / geo such that aux activates or remains on longer than it otherwise would have, then it might not be such a good deal.

Off the top of my head, I'm not sure how to precisely control for that other than via an outdoor reset, and getting that right would involve trial and error.

Presently some systems interlock DSH when aux comes on. That may be too late if DSH caused an otherwise avoidable aux call.

OTOH, interlocking DSH upon a stage 2 call might be premature - denying considerable high efficiency hot water generation.

Actually we need to ask you the question what you mean by DHW. Are you referring to a heat exchanger that makes domestic hot water or suplemental hot water?
J

Good point - I took it as 'Desuperheated Hot Water' but 'Domestic Hot Water' is more common.

Shaedog - please confirm if this is a dedicated, run-on-demand primary domestic hot water setup or a supplemental desuperheater that runs only during calls for space heating / cooling/

thanks for responding. Shae is my dog, my name is Gord but that don't matter

. i have a climatemaster 036 water to water unit. i have a lake loop and 120 gallon inside storage. the DHW option on the unit provides a "pre heat" to my domestic hot water on a seperate pump with seperate connections on the unit. i have a 40 gallon hot water "pre heat" tank installed before my regular electric hot water tank. so, when the unit is running it recirculates this pre heat tank water and warms it up..

i am workjing on determinig operating efficiencies of this unit. i will be installing presure guages on the inside storage loop tonight. my fear is the flow is low on this loop cauising efficiency loss. if i look at the curves provided for this unit the more flow the better

Gord,

What supports your suspicion of low efficiency?

Temperature rise across main heat exchanger allows you to infer approximate flow - I don't know how these are designed but I imagine the intent is moderate flow resulting in 10-20 degree ise across heat exchanger. The DSH should work the same way - might only get 10 degree rise across it.

i am concerned that it is not operating efficiently. my load side pump was supplied by contractor, the load side plumbing and design was by me. i have three 40 gallon hot water tanks in series, about 30 feet of 1 inch pex and a check valve.
acording to the charts avalable on line i need to maximize this flow to obtain maximum efficiency. hense the questions
maybe it is ok i do not know. i need to check ( me being stuborn engineer) presures and temperatures are what is needed to determine this ( i think)