Also I mentioned some time back that I thought my DHW pump was constantly running when there was no call for heat.....this pump has manual speed control and I can confirm that the pump is running as it is evident when adjusting speed.....I don't understand that one either, if anyone has the pre-plumbed ecodan system just wondered if they have noticed similar behaviour.
Have you solved this Dave..... my understanding is that this first pump is always on because it is the Primary Flow pump serving both the DHW and the ongoing central heating, it’s just dependent on the 3way valve calling for hot water or space heating. The second pump then switches on with the primary pump to circulate through the radiators. It would also suggest there should be some hydraulic separation somewhere. .?.?
@Sun&Air...thanks for your comments......a lot of water has passed under the bridge since I posted back on page 5 so things have got a bit disjointed in view of continuity in the forum,
I have attached my system schematic showing the 3 pumps and photo of the cylinder arrangement............As i see it if the system is calling for space heating then the two pumps on the left hand side of the cylinder will be running though the LLHeader.................I would have expected that if DHW was calling for heat then the primary heat pump would run via the 3 way valve to the plate heat exchanger, the DHW pump (on the right of cylinder) would also run.
I cannot see why if there is only space heating demand that the DHW pump needs to run ?.....interested in your thoughts.
It probably does so because your installer wired both water pumps to the same output. If there is only the one output from the controller then you require an interposing relay, such that when one pump is on the other is off.
The unit came all prewired and plumbed from Mitsubishi so it sounds like it has to be as you have said...I think I will give mitsubishi a call on this one as that DHW pump will be running most of the day and must be affecting efficiency and added costs.
Other than the fact that all three pumps are manufactured by Grundfos, I cannot see which models.
Derek....if you zoom in I think the model no's can be seen but I can clarify the auto pump is UPM3 Auto L(think this is the heating circuit pump)......The pump next to it which doesn't seem to have any manual control is UPHGEO 25-85(think this is the primary heat pump in the ashp return)
The pump on its own is the DHW and is a UPS015-60 which has manual speed control.
I cannot see why if there is only space heating demand that the DHW pump needs to run ?.....interested in your thoughts.
I couldn’t begin to understand the complex piping of your pre-plumbed cylinders. It’s beyond me… I think I have been spoiled with a very simple pipe layout I’ve sketched below.
The first pump is on the primary flow before the 3-way valve and is always on when the HP is on. When hot water is called the valve feeds the cylinder. And when room heating is called the headder tank is fed. Then the second pump switches on and feeds the radiator loop. Both pumps run only when the room heating is on. they are both wired in to the FTC6 controller. That’s all I know about our simple plumbing circuit. (oops return piping is all wrong)
I cannot see why if there is only space heating demand that the DHW pump needs to run ?.....interested in your thoughts.
I couldn’t begin to understand the complex piping of your pre-plumbed cylinders. It’s beyond me… I think I have been spoiled with a very simple pipe layout I’ve sketched below.
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The first pump is on the primary flow before the 3-way valve and is always on when the HP is on. When hot water is called the valve feeds the cylinder. And when room heating is called the headder tank is fed. Then the second pump switches on and feeds the radiator loop. Both pumps run only when the room heating is on. they are both wired in to the FTC6 controller. That’s all I know about our simple plumbing circuit.
Agree it looks a bit like a rat's nest!!
I think I differ in that I have an external plate heat exchanger (not the internal coil )and the dedicated DHW pump pumping the cylinder water contents through the heat exchanger.
It probably does so because your installer wired both water pumps to the same output. If there is only the one output from the controller then you require an interposing relay, such that when one pump is on the other is off.
The EcoDan preplumbed cylinder would have been, er, preplumbed and prewired in the Mitsubishi factory. Not that mistakes don't happen of course.
DaveW, do you have a screen shot or two of the tank temperatures? How often do you run the heating cycle?
Mitsubishi EcoDan 8.5 kW ASHP - radiators on a single loop 210l Mitsubishi solar tank Solar thermal 3.94kW of PV
It probably does so because your installer wired both water pumps to the same output. If there is only the one output from the controller then you require an interposing relay, such that when one pump is on the other is off.
The EcoDan preplumbed cylinder would have been, er, preplumbed and prewired in the Mitsubishi factory. Not that mistakes don't happen of course.
DaveW, do you have a screen shot or two of the tank temperatures? How often do you run the heating cycle?
You are probably correct. It had obviously been a long day and the old grey matter was not firing on all cylinders.
I think that all my brain cells should be fully functional today, unless senility is setting in.
It is to be hoped that your pre-plumbed water cylinder was correctly wired to the FTC controller, and that your installer did not make any changes, so when operating in DHW mode it should be expected that only the primary water pump and the DHW water pump are operational, and not the CH water pump. If my understanding is correct this is not the case.
The 'Outputs' table shown on page 22 of the attached manual, clearly shows that the DHW circulation pump should be fed from output OUT14, and should be connected to CNP4. Can you confirm that this is the case?
Managed to peek in the main control panel and look at the dip switches. The bottom 2 switches of SW1 are opposite to the rest so safe to conclude there is no booster heater in my system.
Im quite pleased with my basic understanding and efficiency of HP compared to a week ago, although the weather has been a bit milder perhaps.
Next, I want to try and balance my rads as a bedroom and the lounge struggle to get to temp, although both are at North side of bungalow. They are possibly at the far end of the CH pipe run which would explain why the rads don't feel as warm as those closest to the HP inlet. I've read various balancing guides so will see how we go.
Also have ideas for a battery storage, more solar PV, introducing solar thermal, capping gas project, but will start another thread for that. All from reading this forum!
I think that all my brain cells should be fully functional today, unless senility is setting in.
It is to be hoped that your pre-plumbed water cylinder was correctly wired to the FTC controller, and that your installer did not make any changes, so when operating in DHW mode it should be expected that only the primary water pump and the DHW water pump are operational, and not the CH water pump. If my understanding is correct this is not the case.
The 'Outputs' table shown on page 22 of the attached manual, clearly shows that the DHW circulation pump should be fed from output OUT14, and should be connected to CNP4. Can you confirm that this is the case?
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Hi Derek....no wonder you were not at your peak with the amount of input you contribute to the forums.
Your assumption of my query could be correct and should be but I have got a different issue which is worse.
My DHW pump is running when there is no demand so if the heating is calling for heat the DHW pump runs constantly as well which seems madness.
I noticed last night in my manual that the DHW pump should be on its own output ....I am not looking at the manual at the moment but I found the first output in the table a bit confusing as it mentions the heating pump and Dhw In the same sentence .....I wonder could both pumps be fitted on this one output....at work today so need to check....in your opinion would that be physically possible?
It is quite feasible to connect both pumps to OUT1, since the output is rated a 230v at 1 amp, which equates to 230 Watts of available power. Each pump could possibly draw up to 80 Watts, but normally much less.
It is designated as being for 'Space heating/cooling & DHW' because it is pumping the heated water from the heat pump, so will always be required, when the system is operating.
The DHW circulation pump only needs to operate when the system is in DHW mode, so should therefore be wired to OUT14.
I suggest that you check where the various pumps are actually wired, once you return from work, we can then take it from there as to what is the best course of action.
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