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Author Topic: Seem to be over the main problems, but still not right..........  (Read 11710 times)
rogermunns
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« on: December 29, 2010, 04:00:14 PM »

Me again.

The situation is now that I can get things going but after about 10 minutes the compressor turns off on Eo04.

I cannot understand what I need to do - I can see from the pdf that its related to          'how long in seconds the HP switch of the compressor stays open (Ec06)'

Can I change this setting and, if so, how, and is that wise?

Just to refresh, I have shorted wires 31 and 32 to wire 30, but in addition I have a flow valve in the well line which cuts all power if well pump fails.

I don't know what the water flowrate is from the well pump. But in steady running (during the 10 minutes or so that the compressor is on) the water inlettemp from well is 12.2deg.C and the return is 6.9deg. C.

I have serious concerns about flow from the circulating pump to the UFH loops. I have 7 loops, each about 110metres long, 'standard' dia 16mm. I have a flowmeter on each loop and only loop 2 shows any flow  (about 4litres/minute). I realise I need all loops flowing, I'm sure the Grundfos would like to flow 40litres/minute or so. I have had endless trouble with, presumably, air.  I have tried closing loop 2 to try to get any other loop purged, but failed. Naturally I was reluctant to dead-head the Grundfos, but it was only for a few seconds.

Could anyone please help with advice? I will look for another forum that might concentrate on UFH technicals........................
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dhaslam
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« Reply #1 on: December 29, 2010, 04:18:54 PM »

What valves do you have on the  separate UFH circuits, are you sure they are opening properly?   The wax type  valves can be checked by running your finger  over the valve top  and you can tell  if it is open slightly.     Is it normal to run a heat pump without any kind of buffer tank?   Surely there will always be a problem  if circulation is just cut off rather than controlling  the heat pump by water temperature.     
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Countrypaul
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« Reply #2 on: December 29, 2010, 04:30:15 PM »

Just an observation since I do not yet have a heat pump. But you indicate that the source water temperature is dropping by oslightly more than 5 degrees and I would assume that you well pump will deliver roughly the same as the UFH pump so about 40l/min (this may be entirely wrong though). If your UFH pump is only managing 10% of what you hope then that may be 10 time hotter than expected. So if you expected it to rise by 5 degrees it may be rising by 50 and as such causing an over temeperature problem.  Could you use a large bucket/barrel  of water for the output and see if circulating the water freely solves the problem of the HP stopping?

You may have solved the original problem completely, but the UFH blockages may be causing a second issue that appears to be the HP.

I have no experience on these things, this is just an suggestion from someone who maybe in a similar position in teh future.

Paul
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ecogeorge
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« Reply #3 on: December 29, 2010, 05:33:34 PM »

Compressor overload is usually because it can't disapate the heat (poor flow into house) or can't disapate the cold (poor flow into well in your case).
Can you confirm 110% your flows??

Check the well is easy, - see the speed at which it returns to the well.Your return dropping by 5 degrees suggests that this flow is good.-- but still check it!
The house circuit is a bit harder, as if the flow rate is poor the return temp will not display a high figure and therefore not turn off the compressor.
It sounds as if the heat cannot be removed quickly enough from the heat exchanger. I echo countrypaul and suggest temporary inlet and outlet into a 40 gal drum to check correct operation. Use 32mm mdpe pipe from heat pump.
What size are the pipes to & from the heatpump on the house side ?  should be 28mm cooper or 32mm mdpe IMHO.
As various zones get to temp will the flow slow?
Have you got a buffer tank? if not why not? 
I would use a buffer tank to reduce compressor cycling (when you finally get it running continuously)  and use a "normal" central heating pump to circulate in the house. The WR09 pump is a bit overkill (energy sapping) for domestic heating circulation- use it only for the buffer tank supply.
I expect Welshboy or Alan will be along soon with more learned suggestions.
rgds George.
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welshboy
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« Reply #4 on: December 29, 2010, 07:07:04 PM »

As Ecogeorge says it is likely that the heat is not leaving the heat pump heatx fast enough.
Firstly I would check the pump speed - set it to max
If that fails purge each loop with a hosepipe to ensure you have flow through the ufh pipes and this would then confirm they did not kink when they were laid.
You are then left with the valves to check and bleeding.

7 loops @110m each should keep it running for quite a while - Ours will run ok with 5 loops @100m each even if I turn off the upstairs rads.

Good luck
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rogermunns
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« Reply #5 on: December 29, 2010, 07:48:07 PM »

Thanks, all, for (again) valuable help.

I do not really understand the role of a buffer tank but I'll google it and learn up.

I will try the excellent idea of mocking the UFH up with a large tank of water.

I think this is the right answer - the UFH is not efficient enough to get rid of the heat.

Over the next few days I hope that I will be able to report success, I sense the finish post is near.

You all have been really kind and generous in giving your help.
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knighty
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« Reply #6 on: December 29, 2010, 11:24:58 PM »

if your 16mm pipe is 12mm internal (at a guess) and you have 700m or pipe total.... that will only hold about 80litres of water

and your heat pump can heat up that 80litres of water quicker than the heat can be transferred out of the pipe and into your floor/house - especially when some rooms are turned off, or are up to temperature so shut off / reduce flow automatically

if only 2 rooms are being heated then there is only 24(ish) litres of water to heat, 2 would be 36(ish) etc. etc....


once you're heating less water/rooms, the heat pump will have to turn on and off a lot to maintain the temperature of the water, as the temperature falls slightly the heat pump will come on, run for a shot time then shuts off, a short time later the water temperature has fallen again so it comes on again etc. etc.

all the on/off/on/off running doesn't do your heat pump any good and is the most inefficient way to run it
(start up can use up to ten times run current, and is also when most component failures happen)


so... it's best to add a buffer tank....  hot you connect it up depends on your system.... but it does what it says on the tin, it's a buffer tank on the output of the heat pump, the idea being that if you heat up more water it will stay hotter for longer.... so the heat pump doesn't need to turn on and off so much :-)

heat pump heats the tank of water which is circulated around your house... if the tank temperature falls the heat pump comes on and heats it all up again... then shuts off.... the tank water keeps heating your house without the heat pump running.

do you have E7 power ? (cheap rate at night)


what size tank you go for depends on a couple of factors but mostly... how much space do you have for a tank ?

do you have E7 power (cheap night time rate) ?

if so, because you're heat is coming from the well water, which should be the same temperature day or night, you could save yourself a lot of money by fitting a bigger buffer tank / thermal store (same thing really) and running the heat pump overnight on cheap power... once your big tank is hot/warm it should be able to heat your house all day (or most of the day)


iirc that is how StBarnabas runs his system ?
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Mostie
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« Reply #7 on: December 30, 2010, 12:31:09 AM »

Roger, Please dont try to tamper with the high pressure cut out, its telling you as the others have said that your not getting a good flow through the heat exchanger. Perhaps as a tester, you can get a hold of a direct DHW cylinder and pipe it into that, take the UFH right off the top. You will need another pump though.
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rogermunns
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« Reply #8 on: December 30, 2010, 06:01:09 PM »

I've had a lot more luck today with bleeding.

Our incoming mains water pressure is quite high (7+bar) so a couple of years ago, when we started to install washing machine  / dishwasher I put in a pressure reducer and lowered incoming to 3,5bar.

I have had to temporarily increase this reducer to 5 bar and have now manage to get 4 loops flowing properly. But not all seven, I'll have to continue tomorrow.

I can see the wisdom of a buffer volume. I have ample room to do this - I'll have a look around at how best to proceed.

Thanks again for the practical advice. 
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rogermunns
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« Reply #9 on: December 30, 2010, 07:50:14 PM »

Thought I would try again, now that I had much more underfloor flow potential, after bleeding.

But no.

The UFH pump in the WRB09 doesn't seem to be man enough -if all loops are open then there is not enough umph to flow up any of them.

I tried twice this evening. No go - compressor cuts after 2 mins. with console display showing 43 deg. C. and rising fast.

More bleeding.....................

Any idea how much pressure is generated by the Grundfos?  I really can see that I need at least 5 bar.
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rogeriko
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« Reply #10 on: December 30, 2010, 08:36:18 PM »

When the grundfoss hits an air bubble it stops pumping regardless of pressure.  I would disconect the return from the ufh and let the water flow, using the pressure from the mains, from the 7 pipes until all the air is gone and then reconnect it while the water is still flowing out that way no air can get in.
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welshboy
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« Reply #11 on: December 30, 2010, 08:52:57 PM »

The pump in ours has plenty of punch.
For the benefit of everyone trying to help can you tell us something about your system.
Wrb09 in basement- how much head are you trying to lift the heat ?
Any chance of a pic/sketch of the manifold pipework - Is there a lazy way for it to pump ?
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Iain
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« Reply #12 on: December 30, 2010, 08:56:50 PM »

Hi
Would an automatic air vent on the discharge of the pump help?
Iain
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knighty
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« Reply #13 on: December 30, 2010, 09:17:39 PM »

-if all loops are open then there is not enough umph to flow up any of them.

that bit doesn't make seance to me (even if that is what is happening)

have you tried running with 1 loop then turning the extras on one at a time ?

at a guess... I'd say that with them all open the flow must drop too low for your flow meter to pick up ?

if it's not that.... then that points to the possibility of there being another problem Shocked
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Countrypaul
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« Reply #14 on: December 30, 2010, 11:14:25 PM »

I hope this is so obvious that you've already checked it but - Have you checked the pump and made sure it does work properly, or tried substituting another pump in to test things?

Paul
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