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Author Topic: Seem to be over the main problems, but still not right..........  (Read 11708 times)
rogermunns
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« Reply #45 on: January 02, 2011, 03:17:57 PM »

Just had a thought.

Turned off today after 3 hours, problem being ice on both canisters and temp dropping on UFH circuit.

The thought is that maybe the machine had gone into 'cooling mode' which I guess would be it's way of not getting too cold. In the panic to turn off I didn't look to see if the display had gone to 'cooling'.

Could anyone confirm whether that's how it operates, please?
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welshboy
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« Reply #46 on: January 02, 2011, 04:28:11 PM »

Just had a thought.

Turned off today after 3 hours, problem being ice on both canisters and temp dropping on UFH circuit.

The thought is that maybe the machine had gone into 'cooling mode' which I guess would be it's way of not getting too cold. In the panic to turn off I didn't look to see if the display had gone to 'cooling'.

Could anyone confirm whether that's how it operates, please?
I don't think so.
As the temperature of your well is falling the HP is working harder to lift the temperature of your UFH.
You may find the well does not have enough capacity to run the HP for long periods.
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rogermunns
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« Reply #47 on: January 02, 2011, 04:56:43 PM »

Welshboy, HNY and thanks again. You've been a real brick.

After a couple of hours I ran again, but closed after an hour for the same reason.

But I looked at the display first - it hadn't changed.

What I did notice, however, was that well return temperature was now up to water temperature from the well.  i.e. the HP was no longer taking heat out of the well water.

Now the well will contain 'cold' water underneath 'warm' water. I have the pump near the surface, with the return pipe delivering lower down. I believe there are 4m of water height at about  1.2m diameter. Water surface is 4m below ground level so, the bottom of the well is about 8m down.

The well is hewn out of limestone which, however, is fissured and ground water level is up to the well water surface. So I suppose the water will gain heat again in time. 
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ecogeorge
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« Reply #48 on: January 02, 2011, 06:08:52 PM »

How about fitting a tee in the well return and ocasionally dumping some return water down the drain ?

This would alow the well to refill - with warmer water Huh  wouldn't it ?

rgds George.
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rogermunns
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« Reply #49 on: January 02, 2011, 07:04:02 PM »

George

I'll try that, got everything I need. Also, it will allow me to measure flowrate.
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welshboy
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« Reply #50 on: January 02, 2011, 08:03:11 PM »

Good Idea George.
Roger
The heat pump needs a flow rate of 1800 litres an hour. If you measure the drop in the well ( and its corresponding Volume) compared with your discharge to a soakaway you have an idea of the speed of the well  being refilled by groundwater and yo could adjust your spillage accordingly.

Just a thought
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rogermunns
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« Reply #51 on: January 02, 2011, 08:16:32 PM »

I thought you might like to see the replies I have had from the American A/C forum when I posted my system information and my concerns about the ice on the compressor canister.

1.     I don't like the look of the frost on the compressor (bigger black pot) but would need to know evaporating pressure/temperature and compressor inlet temp to be sure.
If you run the system with a frozen evaporator you risk splitting it, this will likely write off the system.
I wouldn't expect to see frost anywhere on a chiller system, i wonder if your well water flow rates are correct?
The temperature drop in the supply water after only 9 hours is cause for concern too.....

2.    The water return temp to the well should really only be about 3C below the supply temp. So either your water supply is too slow (pump or piping too small) or you have a blockage, either at a filter or from debris from the bore getting to and clogging up the heat exchanger.
You also need to check the gas charge in the unit. An overcharged unit can frost up at the compressor similar to what you have there due to liquid feedback. However this may be contributed to by the poor water flow through the evaporator so fix that first.
Once the water drops to 4C you're in icing territory and run the risk of bursting the HX.

3.    Note that water to water systems don't defrost, they have no need to

4.    I agree. There is insufficient water flow... but no reason to believe the system is overcharged. We really can't tell if there are other problems until the water flow is right.

5.    Actually, reading your post again, you have 2 problems.
The flow is too slow,
Secondly your dump well is either dumping too close to the supply well or is upstream from the supply well and the water is short cycling i.e the same water you just extracted energy from is cooling the water that is being extracted from the supply well and dragging down your supply temp and efficiency of the unit.
The first is an easy fix, the second may require you to drill a new dump well or switch the pump from bore 1 to bore 2

And my reply to those comments;

Thank you all for speedy and informative replies.
I have to work within serious constraints. One is that, for this winter, the single well is my only possible source. By next winter I will have got my ground loop installed as well. There is no way that I can afford to have another well dug - space and expense and difficulty (rock from 1 foot down).
(For the ground loop I am going to lay the pipe on the rock and then build a raised bed 1.5 metres deep on top).
I don't really have enough ground available to supply all the heat I need.
Also, if the two methods of collection (well and ground) are not enough I intend to use swimming pool heat (through a heat exchanger) as well. My pool will have solar assistance, so hopefully the 55 cubic metres volume will help the complete overall requirement.
Hope that makes sense. The well supply was the easiest to get ready and the hope was that the groundwater surrounding the well would top up the water temperature within a few hours. I do have a second pump which I could use in addition
and also I could dump some return water to waste, thus encouraging the groundwater supply to replenish the well with warmer water.

So I am shutting down for a few days to see how the well water temperature recovers. I have a second pump I could easily drop into the well and run in tandem with the current one. Sadly the well level takes hours to replenish if I dump the  return, but just maybe I could return some of the water and dump the rest and find a balance.
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welshboy
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« Reply #52 on: January 02, 2011, 09:20:28 PM »

Try Googling Rock saw trenching- there is some amazing kit to be had
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Mostie
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« Reply #53 on: January 02, 2011, 10:19:04 PM »

Right, here goes, the replies you got were about as I expected,
1. he's right it could damage it but it should have an anti ice thermostat or temperature probe on the ground side heat exchanger, if its a stat its probably a manual reset if it trips.
2. roughly 3deg difference, if your well water is 9deg then the return from the ground side heat exchanger should be 5 or 6deg not 3deg as I think you posted a couple of days ago, have you got a filter on the water inlet to the ground side heat exchanger? I still think the flow through it is too low as well as the guy suggests. Overcharging can cause other problems not necessary icing of the evaporator side.
reply 3,4 and 5 pointing to lack of flow again.

I'm pretty sure your heat pump is using R407c refrigerant.

So basically, lack of flow through the ground side heat exchanger, would cause a low suction pressure at the compressor, the resulting evaporating temperature of the refrigerant is below 0deg causing icing on the suction accumulator and the compressor, a low suction temp will give you a lower discharge pressure and temperature at the compressor outlet, therefor a lower undefloor temp flow.

Another question, does it have a refrigerant sight glass? Although its probably charged correctly anyway.
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2x Solis PV = 1.875 kW, Mitsubishi inverter heat pump. Yorkshire Boiler Stove.
knighty
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« Reply #54 on: January 02, 2011, 10:23:28 PM »

what kind of pump do you have in the well ?

what size of hose ?

and does the hose for the return water go right down into the well, or is it just sticking in the top of the well hole ?
(it should go down at least as far as the pump)
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rogermunns
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« Reply #55 on: January 02, 2011, 11:28:04 PM »

Yes it is 407c.
No sight glass.
It is a cheap submersible with 8,5m head capability. I have 4,5m head to get out of well, then down about 1,5m to the heatpump. I have pump about half-a-metre below water surface.
I am using 25mm MDPE pipe (used normally as underground water supply pipe) and the overall length from well pump to Heatpump about 28metres. And 30metres back, 'cos return pipe does go tobottom of well.

I will measure flowrate over the nextday or so. I should have done it before. But I can't believe it's anything like 1,8cubic m. / hour. And I will monitor if / how the temperature of the well water is recovering.
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ecogeorge
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« Reply #56 on: January 02, 2011, 11:30:51 PM »

My moneys on 25mm pipe being too small !!!!!  go for 32mm it's not much more expensive.
rgds George.
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rogermunns
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« Reply #57 on: January 03, 2011, 04:49:36 PM »

George, thanks. But impractical 'cos I have placed the 25mm pipes inside a 'gaine' (an 80mm dia. flexible plastic pipe) and buried the lot.  And I haven't the energy to dig up and replace.  Maybe in the Spring, when I will have a digger on site.

I do have a second identical pump and I could use this, again running 25mm pipe to / from HP, joining the other just as it reaches the HP. i.e. two identical runs in parallel. But this second set of pipes would be laying over the garden, maybe risky if we get big frost (which can happen here).

The well water temperature is slowly recovering but it will take 3 or 4 days before I can have the system running again.

I haven't been able to measure flowrate of the well pump yet. Maybe tomorrow.

Could someone please  answer a couple of Q's for me?

1.   what is the ideal inlet temperature into the WRB09 for the (in my case) well water? Or  inlet temperature from a Ground Loop?
2.   what would be the ideal length of underground pipe (25mm MDPE) and in what area of ground? My house has a heated floor area 170 sq. m.

Later this year I will be installing a ground loop as the main supply to the HP.

The well experiment was worthwhile to prove the HP after it had laid in the garage, sitting in ambient temperatures between -15 and +45 deg. C over a period of 5 years since it was purchased.


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rogeriko
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« Reply #58 on: January 03, 2011, 05:37:50 PM »

Just pull the return pipe out of the well while its running to see the flow rate if not enough replace the pump with a stronger model that will pump 2 tons of water an hour through the existing pipe. Pipe size dosn't matter if you have a stronger pump. 8.5 meter head means the pump is not even capable of pumping 1 bar thats really weak. A good pump goes at least 40 meters of head (about 4 bar) that can push the water fast through all sorts of pipes and heat exchangers etc. could well be the problem, no pun intended.
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knighty
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« Reply #59 on: January 03, 2011, 05:54:05 PM »

you could always just add an extra pump in-line higher up the system where it's easier to get to ?

with well water / ground source heat pump you really want as much flow as possible, the only thing holding you back is how much power the pump uses vs how much benefit the extra flow is


unless the pump is easy enough to get at.... in which case a proper well pump might be the best option - they're very expensive but you might get lucky on ebay ?
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