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Old 08-30-15, 09:53 AM   #11
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I went through all the settings when I installed my ecobee thermostat, I looked at everything to do with the desuperheat and it was set how the manual says it should be

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Old 08-30-15, 01:42 PM   #12
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It's a geothermal heat pump. With a low ground temperature, it's entirely possible that the discharge temperature could sometimes be too low for thermal recovery to work. A temperature datalogger can tell a lot.
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Old 08-30-15, 05:39 PM   #13
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NiHao,

The compressor by definition superheats in the AC mode. Even with low inlet temps. I have worked with my cousin in northern Vermont that have very low inlet ground water temps (44 F, open loop "pump and dump" geothermal) and the desuperheater provides LOTS of hot water in the summer on those days when AC is being used.

Something is amiss . . . .


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Old 08-30-15, 07:36 PM   #14
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Quote:
Originally Posted by mechanic View Post
Well that's how it thought they were supposed to work, use the waste heat when in cooling mode.... Mine does nothing in cooling mode though, only works in heating mode. It's a climate master tranquility series.
A desuperheater is plumbed into the refrigerant circuit immediately following the compressor. If it is a reversing unit, the dsh is between the compressor discharge and the reversing valve. It does its job whether heating or cooling. As long as the compressor is running, the thing will heat water.

The main difference between heating and cooling mode is system pressure. Most hydronic units do not heat the indoor loop up to dhw temperature. Since longer run times at lower loop temps are more energy efficient, that's how they are set up. At this lower loop temp, the high side pressure can only provide "warm bath" temp. The desuperheater runs somewhat hotter than the main hx, but it won't scald you.

Last edited by jeff5may; 08-31-15 at 08:35 AM.. Reason: soelling spell check
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Old 08-30-15, 08:04 PM   #15
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Mine is a water to air, there are no in floor loops... When in cooling mode you cannot tell a difference in hot water line temp from air temp...
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Old 08-31-15, 12:46 AM   #16
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Aha! In that case, I agree with Steve: something is not right. With a refrigerant to air heat exchanger as the condenser(heating mode), the discharge temp and pressure are much higher than a hydronic loop(cooling mode). This gives the dsh a higher ceiling to leech heat from in heating mode. If the unit blows good, warm air, the compressor discharge line gets hot enough to produce hot water.

The fact that you get less hot water in cooling mode is due to your latitude and the fact that you heat more than you cool. Your lower ground and loop temperatures outdoors are reducing your compressor head pressure. Also, the reduction in run time reduces your potential dsh output.

If your entering water temp is very low, the dsh may not see the water long enough to heat it up hot. For example, 45 degF water heated to 80 degF will have absorbed lots of btu's, but still not feel hot. If the dsh is recirculating through a large preheat tank, the heat gained will slowly raise the tank temperature while the heat pump is running. When incoming fresh water enters the preheat tank, its effects are pretty immediate unless you have the tank set up to stratify.

The entering and leaving water temp spread of the hx should remain fairly constant after the heat pump has run long enough to find its balance point. This would be the first parameter I would verify. As others have said, it doesn't take millions of btu's to heat up a single family home-sized tank of water. This can be easily calculated with the dT parameter of the dsh and a reasonable estimate of your water flow through the hx.

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Old 09-19-15, 02:49 PM   #17
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Cooling mode hasn't been running much lately but we've finally had some hot weather and I did some checking so:
-the compressor discharge is almost too hot to touch
-if there is a temp difference in the hot water lines it's very slight
-there is power to the circulating pump, it's very hot, as hot as the discharge line, but the water line is room temperature
-the water line is hot for about 10" from the heat exchanger, then goes to room temp

So everything basically points to a seized circulating pump I would say, right? But I know this is not the case because it has never worked in cooling mode and it always works in heating mode. But like stevehull said the heat exchanger is the first thing after the discharge, before the reversing valve, I followed all the lines, it's pretty drop dead simple...

I guess I could depressurize my water system, cut the pex lines and put some temporary lines into a bucket, turn it on and see what happens... Maybe the pump is air locking somehow? Not sure how cause it should pump just the same as in heat mode...
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Old 09-19-15, 08:18 PM   #18
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The list of possible defects is short with this one. Either your pump is shot, or not being activated properly, or there is a restriction in the plumbing or desuperheater. Obviously the refrigerant circuit is ok.
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Old 09-19-15, 08:54 PM   #19
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Well the pump is being activated, only way to be sure it is pumping is to unhook the lines I guess though... It feels the same plugged in or not but the compressor shakes everything so hard you'd never feel the pump...
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Old 11-03-15, 12:05 PM   #20
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Any updates?

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