Is it normal for ground loop pumps to run constantly?
Last Post 23 Aug 2014 01:34 PM by DrDull. 26 Replies.
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DrDullUser is Offline
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22 Aug 2014 03:44 PM
Thanks, G.O. Joe. I just checked the wiring (to the extent I could without taking things apart). There are three wires (green, black, red) running through a short ~6" run of BX that comes from the wall and goes to the flow controller. I have two Grundfos UP26-99 pumps. The pumps are on the same circuits as the heat pump (threw the breaker first this time). I'm a bit confused by the wiring diagram in the flow controller manual. Figure 8a (Page 8 in my copy) shows the heat pump/circulator pump power wiring - it illustrates something called the "Unit Control Box" that has three wires (two for the loop pump and one ground) going to the "External Loop Pump." So the questions are where is the "Unit Control Box" and is it somehow tied to the compressor. I suppose the wires I see could be coming directly from the house power distribution box and have nothing to do with the heat pump, but the fact that the manual talks about "the wiring required between the heat pump and the Flow Controller" suggests that there should be some connection.
G.O. JoeUser is Offline
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22 Aug 2014 07:12 PM
So the questions are where is the "Unit Control Box"


That is where you were poking around last week (danger lurks within). Time to call a qualified tech? or can you post a pic(s) of the control wiring in the HP? Power off this time.
dave111User is Offline
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23 Aug 2014 08:21 AM
Those two 7 amp breakers inside your heat pump should be the source for the loop pumps, from what you have said it sure seems like your pumps are currently hardwired to the heat pump source. It should be noted however that the voltages involved can be deadly, and that if you make an error wiring it up the price of the damaged parts can get expensive fast. For reference look up the price of that Grundfos pump. I guess what I'm trying to suggest is that if you are not certain of what you are doing that you should consider Joe's suggestion and get a qualified tech to hook it up.
DrDullUser is Offline
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23 Aug 2014 11:40 AM
Thanks, G.O. Joe and dave111. I did call a 'qualified tech' (the company that installed the system) and was told that it was 'normal' for the loop pumps to run all the time. I started this thread because that really didn't make sense to me and was looking for some other opinions. As you suggested I just took some pictures of the control box (after throwing the breakers) and pumps. I'll post them as soon as I can figure out how to do that.
DrDullUser is Offline
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23 Aug 2014 12:05 PM
I'm going to try and post links to the pictures.

Loop pumps photo is here.   This photo shows the pumps and the BX with the wiring.

Left side of control board photo is here.  This photo shows the left side of the control board.  The yellow and orange wires attached to the terminal blocks just left and below the center of the picture come from the box with the two 7A circuit breakers.  The beige block to the left sitting on the bottom of the compartment is the free-floating (not screwed down) transformer(?) that caused the short when I tried moving it around to follow the wiring.  The red tag at the top of the image is attached to wires (not connected) that are for the hot water generator.

Closer view of terminal blocks and transformer is here.   The orange and yellow wires coming from the circuit breakers are the only ones attached to the terminal blocks.
dave111User is Offline
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23 Aug 2014 01:24 PM
The terminal block with the yellow and orange wires is where the pumps would hook up. If you do a search the install manual for your unit is right at the top of the results. I have a CM W2W, and it is very similar. Keep in mind that those are 240V when on, make sure that your pumps are also 240V (check the label on the motor). Based on the wire colors you noted I suspect that it is, those are the correct colors, but don't trust anything, it is amazing what installers will do. If it were my system I'd add a new run of flex conduit from the heat pump to the pumps, cap off the connections in the current box, and be done with it. If you go this route be careful, the cost of errors can be high, but the job is easy. If you don't trust yourself I think the average electrician would have no trouble doing the work.
DrDullUser is Offline
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23 Aug 2014 01:34 PM
Thanks so much, dave111. I think yours is the definitive answer. It seems obvious now that indeed the pumps have been running constantly, that they are wired directly to the 240V circuit, and that new wiring would be needed to control them with the heat pump. I certainly would not try to do the wiring myself. I wish I had paid more attention when the system was being installed; it never occurred to me that the pumps would run all the time. At least now I know that I can just throw the breakers during the transition seasons when the system is idle for weeks at a time. Thanks again- I appreciate it.

Barry
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