debate: storage or not

looking at efficiency curves for the GEO 036 climate master it seems the less storage the more efficient?

i have 1000 sq ft. 5 ton design of pipe in a lake.
1200 feet of staple up
500 sq of cement with 400 feet of pex
up to 120 gallons of storage

it is working

Could you post or link to efficiency curves you cite?

Large storage tank in an unconditioned space would increase standing loss and decrease system;s efficiency. On the other hand, a good sized storage tank should allow system to cycle less often but for longer times. That would increase equipment efficiency and improve durability by reducing number of starts.

i am going to attempt to attach the operating data for the climate master GEo036 water to water unit that i have.
from the data it seems the lower the incoming temperature to the unit the higher the COP.

here is my theory
if i want 105 degree water as my set point
the dead band or differetial set at 5
it turns on at 100 and heats 120 gallons to 105 and shuts off
the average temperature over this time frame is about 103
the machine is trying to add heat to the 103 degree water for over 1/2 this time
the unit runs at a duty cycle of about 60 %

same scenario as above but with 40 gallons
105 set point
delta of 10
turns on at 95

i think the unit will cycle more as youi mention.
but, since a good chunk of that heat tranfer time is into cooler water the machine should run less

the average water temperature is the same as above

does the unit suffer for multiple starts? (efficiency)
i am having an issue getting the charts pasted here
http://www.climatemaster.com/downloads/RP812(3).pdf (page 7 036 heating)

If you have 120 gallon tank and it is working I don't see a good reason to swap it out. A good investment might be an extra layer of insulation for the tank if it lacks decent insulation already. Also insulate all water lines.

If the tank and lines are in conditioned space, this is less important.

As for setpoints, yes, the cooler the average water temperature sees, the more efficient it will run. You want the coolest water temperature that'll meet your heating load. If you can tolerate 95 degree water some of the time, then reduce the lower limit on the 120 gallon tank to 95.

Is this a DIY or did your installer set it up a certain way?

I'm not clear on how your second floor is heated, is it radiant as well...fan coil....? Does this unit provide DHW? What is the radiant loop circulator GPM flow vs storage tank circulator GPM?
Short cycling is not advantageous to compressors/motors. Before you reduce storage, let's make sure we don't reduce life of compressor.
Radiant floors are less common geo applications and good installers are even less common than water to air guys so we want to be careful about fine tuning their work.
Good luck,
Joe

What am I missing
wouldnt simply lowering the temp of the larger tank have the same effect
I dont see how the volume of water being heated has anything to do with eff
water temp yes , volume no . right?
forgetting for now the heat lost by the tank

first off thanks for replies, where to start....

i am in Northern Ontario on a lake. heated with wood. wanted out from wood chores. had no heating infrastructure in main living 800 sq ft hrdwd 16" center joist with crawl space single level. had added 600 sq ft two storey addition couple years ago and put two 200 ft loops in the pad but had done nothing with it. ( this area was cold)Also, 1200 sq ft garage that needs heat.

GEO grant for 7,000...so hired appropriate contractor, put lake loop in 5 X 300 ft 3/4" loops. ( supposed design for 5 ton). Not enough electricity (currently) for the 5 ton so installed the 3 ton 036. Yes, DHW loop with pump and pre heat tank installed. (currently only allowing this pump to run in evenings when water will be used).

ran double 1/2 pex 4 250 foot loops under hardwood floors. first mistake i used light weight plates then r20 bats. am going to replace with heavy plates to get water temp down.

need to use flow meters to work on effeciency of system as you said. i am elect engineer and have access to the required equipment. just starting to work on system efficiency. contractor hasn't got a clue but not his fault i was his first project

Oh no - another electrical engineer! (I'm one as well - all this thermodynamics wasn't covered in my EE classes)

Any carpets on top of radiant floors? Those can really drive up needed water temps

Not sure you gain much by limiting desuper pump to operation only at night - they are most effective (since you have a preheat tank) when allowed to recover and store heat all day. However, if your system is undersized, any diversion of heat to domestic water cuts into heat needed for house. Desuper diverts about 10% of heat to domestic water.

when they were comisioning the unit i did not have the temperature interlock sensor on the desuper pump that would stop flow in the pre heat tank when it reached 135 degress as per desgn. When i did hook it up i was able to measue a distinct length of time increase in operation to bring load storage up to set point. i realize there could be other factors but it made sense to me that it would take longer. hense the running it only in evening. during this run it has enough time to warm it up but i think as you mention more experimentation will be required to determie the maximum operational time. we do not use the hot water from bed time till after supper the next day so......
as for carpets no there are none anymore. it is quite noticable how they reduce BTU transfer.

i still am installing loops etc. my wife was very cold till i got it going. the house is almost warm. one more loop in main living area to go

amazing the different opinions on staple up efficiency
plates or not....
radiant barrier or not....
r value under the pipes....
gaps......


your thoughts?

i did double runs per joist / light weight plates / R20 no air gap

seems the latest best thing to do???????????

o ya and holly humidity!!!!!!!!!!!!!!!!!!!!!!!!
went from adding water on top of wood stove to having it dripping from all the windows!!!!!!!
dehumidifier running 24/7
wife says it is getting better

Ummmm GPM?

Where did all the humidity come from? Operating a dehu 24/7 in winter way up north seems very odd to me.

i hope from the 30 year old crawl space. it is damp ground in a couple spots. live on a lake, humidity naturally hi in summer????????? just turned on hydronic in joists and pad?????

i is seaerching for answers

I asked about GPM as your radiation may have one requirement and the heat pump another. undersizing the heat pump may be mitigated in part by a large storage tank (reduction of which could diminish comfort). How do you get ventilation air into the home? If it is not designed in and you stopped drafting for the woodburner, stale air could be part of the problem or leaking radiation. How do you add make up water to your loops?
J

i think the humidity problem is due to what is currently going on. When we had our grant inspection (before starting) one of the tests indicated a huge air gap between the addition and the old section. this allows crawl space air into the house. With the system running and poor to no insulation in the crawl space with wet areas it is drying up. this humidity is causing the grief. it is getting much better. the system has only been running for two weeks.
as for GPM the lake loop pump flow is a mystery. if i had all the pipe info and pump info including elevations could it be calculated? 5 300 foot 3/4 poly runs off of 1 1/4 poly feed / return. the 1 1/4 is 100 foot run. the pump is ten feet above lake level. sorry will have to look at pump it is grunsos 220 v

make up water is a cool thing: i have a spilral vent thingy on the main loop. it has a 1/2 port on bottom, i purchased a expansion tank with a pre set regulated input that maintains 12 psi
neatest setup. seems to work very well. got it all at pex supply.com but duty killed any savings


the heat loop pump also was set up by the installer. it has a variable speed option (prop adjustment). i have not played with it but when the unit turns on it takes quite a while before i see a increase in storage temperature.