Geothermal problem that no one can solve

mrhappy42

We had plumbers and people who deal with Geothermal systems in and we still have a problem that the HPS goes off after a day or two, I'm close to ripping it out - really upset with this.

We replaced the pump taking the hot water out as people said it caused over heating within the system.

We put temp sensors on all the pipes and nothing out of the ordinary (I'll attach them).

About a year ago we had a hot water tank over heat due to a bad heating element and the HPS blew (we think its the reason), the HPS switch was replaced and gas was put back in. Up to then it had been running for about 7 years without any issues.

- could the gas have been put in at the wrong pressure?
- could the heat from the broken element have damaged the temp sensor that switches on/off the system to avoid over heating? (i.e make it work intermittently).
- could the HPS be faulty?

Anyone around the Kenmare/Sneem that could help - happy to pay for results :-).

mrhappy42

An example (I have more) of what the temp sensors are showing - i.e the system working from what I can see.

Aaarrgghh..frustrated.

mrhappy42

temperature showing, temp of input and output pipes as well as the temp of the pump taking the water out of the geothermal system. Also temp were the water is mixed with the return. I've attached the spreadsheet that generated the graph (the first 300k). I think this was every 5 seconds.

sawdoubters

http://blog.heatspring.com/the-third-most-common-mistake-made-designing-geothermal-heat-pump-systems/

mrhappy42

sawdoubters, Agreed, it has "one-heat pump, one-loop, one-pump GSHP" and its been running for years - it still runs but switches on the HPS. The HPS switches when the internal gas gets to high in pressure (P = T) to save the pump - its like a fuse. The HPS switch used in this system does not have a gauge so can't tell what the pressure actually is. I also do not know it should be.

thatssound

Hi mr happy.
Am interested to know what type of heat mapping you used to get temp of pipework.
Very useful info.
Tks

Froststop

I wouldn't be an expert in Geo, but from a plumbing point of view, have you checked how accurate the temp stat is? some of these can be out by a good bit. I came across one lately which was out by 38 degrees.

If you had a similar problem it might be upsetting your system by allowing it reach the high limit set point due to the temps your system is working at.

Your question regarding the gas in the system, if the incorrect gas load was put into the compressor then it would effect it's operation. It would also need to have been pressure tested and a vac put on it to take out any moisture.

Another thought: in the pic below you have four high points on the pipe work on the left which could be air locked and restricting circulation. There should be vents fitted on the high points or the pipe work should rise to the connection.
https://us.v-cdn.net/6034073/uploads/attachments/28442/293853.jpg

Dtp1979

Have a chat with condenser on here. He knows geothermal very well

Condenser

Dtp1979 wrote: »

Have a chat with condenser on here. He knows geothermal very well

I wouldn't be able to make head nor tail of anything from the way the info was presented so far.
I can't even figure out what the main problem seems to be.

Whats the HPS (High pressure switch???)

mrhappy42

thank you all.

thatsound - I coded an mbed with a set of temp sensors, something like this example (https://mbed.org/users/4180_1/notebook/lm61-analog-temperature-sensor/)

rest -

we have a bleading valve on the top of the system and its bled to death.

I have found someone that with a pressure meature and going out tomorrow - however as I had nothing to loose I left some gas out and got the following results, the spike is coming from inside the system were the gas filter is beside the HPS (High Pressure Switch). The gas is reading 'dry' (I can show picture of the little window showing this).

The spike in the graph is a sensor next to the HPS. The spike is a lot lower than it was before I removed some gas and its been running 24 hours so far.

Condenser

mrhappy42 wrote: »

thank you all.

thatsound - I coded an mbed with a set of temp sensors, something like this example (https://mbed.org/users/4180_1/notebook/lm61-analog-temperature-sensor/)

rest -

we have a bleading valve on the top of the system and its bled to death.

I have found someone that with a pressure meature and going out tomorrow - however as I had nothing to loose I left some gas out and got the following results, the spike is coming from inside the system were the gas filter is beside the HPS (High Pressure Switch). The gas is reading 'dry' (I can show picture of the little window showing this).

The spike in the graph is a sensor next to the HPS. The spike is a lot lower than it was before I removed some gas and its been running 24 hours so far.

Stop, stop, stop. You're fiddling with stuff and you haven't a clue what your doing. Releasing gas is illegal (you could be fined up to 5k) and of little to no use when you don't have any idea whats going on in the system.
You're supposed to have a "spike" next to the high pressure switch its called your discharge temperature and is the hot gas exiting the compressor directly before it enters the condenser to exchange its heat to the water.
Your readings make no sense as they apply to nothing.
You've taken readings, added your own interpretation of what they might be called and posted them. No one can work out anything from that. I suggest you go away and take pictures of where you have placed these sensors and try and post as concise an explanation of the problem as you see it on here and I can try and help you out.

The "little window" you described is the sight glass and is an indicator, not always a very good one, of how well the system is charged with gas. Whether the litmus paper reads dry or wet I would not put much meas in. Its a poor indicator but supposed to read dry

Froststop

mrhappy42 wrote: »

we have a bleading valve on the top of the system and its bled to death.

If your referring to a vent on top of the manifold in the pic, then it only vents that manifold! You still have a high point on the four connections on the left hand side. You can vent the manifold for days on end and still have air trapped in the high points. As the saying goes, "**** doesn't flow up hill" just like "air doesn't flow down hill!!"

mrhappy42

Condenser, agreed with your points.

The Gas was just a small amount when I tried to measure with inappropriated equipement. Got proper guages this morning.

Also drew some diagrams and took a pic of the whole system and put some markings on it.

Also attaching the temp measurement from last night as well the pressure readings this morning before and after the timers kicked in (the pump has a 16.7 bar rating on it)

The HPS had not tripped last night, so two days running.

Appreciate you all spending time in this, I'm learning loads bit still losts.

Condenser

The pressures don't mean much without having the corresponding water temps to go along with them. Did the provider of the guages not shed any light for you.
The pressures seem pretty normal but its hard to tell without tracking them for a while and comparing them to the evaporating temp and condensing temp at the time.
Do you still have the guages?
If so run the heat pump and get the following info
Flow temp to heating
Return temp from heating
Condensing pressure red guage
Flow temp to collector
Return temp to collector
Evaporating pressure blue guage
Discharge temp, hot pipe leaving compressor

With that info I can try and give you a diagnosis of what's happening

mrhappy42

Thank you.

I still have them, the gentleman is retired so was limited in his information. To be sure I measure the right things.

I dont have enough temp sensors to continuious monitoring but can move them around while its running - use an old fashioned notebook :-).

The guages did not seem to move while it was running they seemed fairly steady.

To be sure of doing the right thing,
Regards,
Marko


* Flow temp to heating
- I assume you mean the underfloor system. i.e The pipe leaving the geothermal unit to provide hot water to the underfloor. I'm measuring that as T4 above.

* Return temp from heating
- I assume you mean were the underfloor comes back into the geothermal unit, I'm measuring that as T2 above.

* Condensing pressure red guage
- Can connect this to the same pipe as were the high pressure switch is, its not on the actual compressor. Its on a pipe running between the two exchangers? The little guage with the 'dry' is also on this pipe.

* Flow temp to collector
- ??

* Return temp to collector
- ??

* Evaporating pressure blue guage
- I connect that to the valve on the heatpump itself, its on the same pipe as a switch called LPS.

* Discharge temp, hot pipe leaving compressor
- on the compressor I have two pipes, see pic above. One goes to the place were the water returning from the underfloor comes in and the water going to the underfloor comes out. Heatexchanger?. I assume thats the discharge pipe. I'm tracking that as 'T1' in the diagrams above already).

Condenser

Did the big drop off in condensing temp T3 happen while the machine was running or did it switch off at that time?

mrhappy42

Model: Solterra 200
Year of Manufacture 2001
Refrigerant: R407C - 1.7kG

Problem. HPS switching intermittent. (too hot)

Step 1

The HPS switch going seems to cause most folks to think pumps are not taking the heat away quickly enough. This means replacing capacitors in pumps or the pumps themselves or changing the pumps or checking for blockages. This makes perfect sense except when you see this happening.

- The temperature of the outflow pipe (or the place that has the temperature sensor) is higher than the temperature sensor. Something is not switching off when it should, heat keeps building and then the HPS goes.

Step 2

If the pump is heating past the point that the temperature switch is set. Then check the switch is working. Remove it and use hot water for example and see does it switch. Spend some time on this as though it might have an intermittent issue, i.e not something obvious. In the end to remove doubt just replaced it. When replacing it look for a more up to date model that will switch in a range, i.e does not constantly go on/off. For us the problem continued to exist. So we ruled out pumps, ruled out temperature switch.

Step 3

Timer. The timer is the green item in the photos below. It has 3 settings. The bottom is 'E' that means it is working as a delayed timer. This is done to avoid damage to the heatpump. So when you want heating the trigger comes in, via the temperature sensor and into the timer. It counts down, whatever is on the middle setting. in this case 10 minutes (10 m), with an offset of the top in %ages. So in this case 0.6x10min. The actual duration is not 6 min but about 3 for me (well outside of the specs but ignore for now).

Ut will flash for 6 min and then the relay will kickin. The R led. You need to check two things here, (a) is the voltage available on the input (top left of the green item behind A1) on the schematic this is 15. Then while the time is counting check the voltage on 18, the lower left contact way in the back. For us this was a yellow wire. It should go from 0 to 250V when the R light comes on.

All this worked for us.

Step 4.

Contactor. The yellow wire out of the timer from step 3 goes into the black thing with the Omega symbol and the letter K on it. This takes the main voltage to the heatingpump motor. The second the yellow wire has voltage on it, it charges the magnet in the contactor, pulling down the connections and providing power to the heatingpump. You can check this, you should see the front of the relay pull in with the power of the magnet. Also voltage should now exist on contact number 2.

Switch of the heating, stop calling for water or lower the temperature setting. The trigger into the timer drops, the timer switches off (immediately, no timer on off) and the yellow wire bringing power to the contactors magnet then looses power, the magnet without power is pushed back to off with a spring.

The trick here is the watch the time it takes for the magnet to switch off when the yellow wire looses power. Took a while for us to spot this, but sometimes for us this was not immediate, and sometimes it would not let go and kept the connection open. Meaning that even if the temperature sensor said 'stop' it would just keep going. For us this was the fault.

For this model of contactor, I opened it, cleaned the contact, stretched the springs (and in the meantime ordered a newer model).

In essence you could replace the temp sensor, timer and contactor for 200 Euro, a lot less than a plumber to replace your pumps. It might be worth it if you have one of these to do this as a first step.

I'm not an electrician, heating expert, plumber so advice here is at your own risk etc. but hope it helps.