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Ground Source Heat Pumps

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  • I've just been reading this thread for the first time with great interest! I've got an IVT Greenline HT+ E11 with 300l cylinder and 600m horizontal slinky collector ground loop split across three 50m trenches. This is partnered with a 4kW solar PV installation, both of which were installed in Feb 2012 and which I've been very happy with so far - so much so that I've become a bit of a GSHP evangelist!

    I'm a software engineer by trade and geek at heart so was keen on building a monitoring solution for everything (including the CurrentCost monitor I use for electricity consumption).

    The reason I'm posting to this thread is because of the comments about the H10 and Patrol's interest in a more open solution:
    Patrol wrote: »
    Be interesting to hear the response lovegshp.

    Beardy, your H10 is giving more accurate figures down to minutes of operation. I could buy one but I'm wondering whether a Raspberry Pi with expansion port might be a more open option. I know an electronics engineer and am familiar with software but suspect the stumbling block would be understanding how the port functions. Might see if any light can be shed on the matter.

    I've done exactly this and built my monitoring solution around a Raspberry Pi running open source software, some custom software written by me and some custom hardware interfacing.

    The system currently does the following:
      I monitor the solar PV generation from my SMA inverter via bluetooth (data at 5 minute intervals).
      I monitor electricity consumption using a USB to serial connection to the CurrentCost base unit (data at 6 second intervals).
      I have built an interface to the Rego controller on the heat pump which allows me to connect via USB and gather readings from all the Rego registers (currently capturing data at 1 minute intervals).
      All data is stored in a database and I have written browser based reports and charts to visualise this data.
      I'm also working on an interface to read the IrDA output from an Elster A100C meter which I will put on the heat pump supply to measure HP consumption (this is working in prototype form already)

    Nearly all of the information I needed to put this together is already out there on the internet but it did take a fair amount of effort finding it and getting it all implemented, especially my foray into electrical engineering building the Rego interface and IrDA reader!

    If you are interested in any of this I can point you in the right direction - just let me know.
  • PatrolPatrol Forumite
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    I'd like to hear more. My Pi is lent to a friend at present and I've had a lot of other things to do but am keen on doing something similar when I find time.
  • edited 29 August 2014 at 2:29PM
    howardhthowardht Forumite
    5 posts
    edited 29 August 2014 at 2:29PM
    I'm new to this forum and am very impressed with just how much expertise is out there re GSHPs. I wonder whether anyone can advise me on the following. I have an IVT Greenline C GSHP with 2 sets of vertical panels installed in 2011 by the prevous house owner which has been working well. House temperatures are as set by the thermostats, DHW is always available, and electricity consumption is at the expected level. However I have always needed to top up the expansion bottle with 2-3 pints of glycol/water mix every 3-4 months. Recently, returning from a 3 week break away, I noticed a larger than average drop in the fluid in the expansion bottle. After topping up, it dropped again faster than it had done over the previous 3 years. I estimate the current rate of decrease to be about 2-3 pints per month. Before I contemplate the nightmare of locating a possible leak under the cobbled driveway or the garden path, is there any action I can take to check that it may not be a leak but something else? Could there be a problem with pressure, for example? But if it is a leak, has anyone any experience of detecting a glycol leak underground (there is no evidence of any leak near the pump itself or in the manifold).

    ps I have noticed that other GSHP users have had visible glycol loss in the expansion bottle, but they have not indicated that they have gone on to investigate a glycol leak.
  • lovesgshplovesgshp Forumite
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    howardht wrote: »
    I'm new to this forum and am very impressed with just how much expertise is out there re GSHPs. I wonder whether anyone can advise me on the following. I have an IVT Greenline C GSHP with 2 sets of vertical panels installed in 2011 by the prevous house owner which has been working well.
    Are you talking of a borehole type system, or compact type collectors, as is not clear? Which model C

    House temperatures are as set by the thermostats, DHW is always available, and electricity consumption is at the expected level. However I have always needed to top up the expansion bottle with 2-3 pints of glycol/water mix every 3-4 months. Recently, returning from a 3 week break away, I noticed a larger than average drop in the fluid in the expansion bottle. After topping up, it dropped again faster than it had done over the previous 3 years. I estimate the current rate of decrease to be about 2-3 pints per month. Before I contemplate the nightmare of locating a possible leak under the cobbled driveway or the garden path, is there any action I can take to check that it may not be a leak but something else? Could there be a problem with pressure, for example? But if it is a leak, has anyone any experience of detecting a glycol leak underground (there is no evidence of any leak near the pump itself or in the manifold).
    What is the pressure on the inlet circuit to the pump from the ground circuit. The top -up levels to the system may suggest a leak, but without knowing the setup then it is more difficult. If you have 2 valves from the ground loops, then you could shut one down and make sure the pressure stays at between 0.5-1.0 bar. If that stays for 24hrs, then check the second circuit, to see if that is the same.

    ps I have noticed that other GSHP users have had visible glycol loss in the expansion bottle, but they have not indicated that they have gone on to investigate a glycol leak.

    The level on the glycol expansion tank will go up and down, but not by a major amount as you are saying. Try the tests that I suggested above and get back to me with what is happening.
    As Manuel says in Fawlty Towers: " I Know Nothing"
  • Many thanks lovesgshp for getting back to me.

    The exact name of the GSHP is IVT Greenline HT Plus C and it was supplied and commissioned by Ice Energy. It collects heat from two sets of 2m x 1m panels set vertically in the ground c 1m below the surface (i.e. not a borehole or a slinky loop). There are 7 panels in total, 4 in one line and 3 in another.

    I will carry out your suggestions but can I ask the following:

    1) how can I determine the pressure on the inlet circuit to the pump from the ground circuit?

    2) shutting a valve down on the group loop:
    A week or so ago, with the help of the builder who installed the panels and ground loop, I shut down one loop by turning off one of the valves on the manifold in the inspection chamber in the driveway. (Both the builder and Ice Energy suggested doing this as well). The effect was quite dramatic. The fluid level in the expansion bottle dropped in the space of 3 hours by as much as I would expect in 5-6 weeks. Unfortunately the builder did not tag or identify the loops during the original build so we don't know which set of panels (there are two running at a right angle to each other) was responsible for this fluid decrease. At that point I panicked a bit, opened the valve up again and refilled the bottle. Since then the rate of the loss has slowed down, but it is still at an increased level compared to the previous three years or so.

    I think this is the procedure that you are suggesting. If I do it again, (see my question above) how do I ensure that the pressure is maintained at 0.5-1.0 bar while one valve is off. Is there an adjustment mechanism somewhere on the GSHP?

    Thanks
    howardht
  • lovesgshplovesgshp Forumite
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    Hi howardht.

    Unfortunately, it sounds as if no pressure gauge is fitted, so that will be a problem to check the collectors. I think in an earlier post this subject came up as well. Normally we fit a gauge, plus a mains water inlet valve, so that you visibly see the pressure on the circuit. There is nothing on the pump that controls it.
    Pic of pressure gauge below expansion tank, plus filling hose.

    http://www.geotherm.it/esempi-impianti-geotermici-progetto-23-geotermia.html#0

    Do you know how to get into the installer/service menu, as if so you can manually start the ground circuit pump to run the check.
    On the manifold, there should be 2 valves for each circuit, make sure you close both for the circuit not being tested.

    Have you got flow valves prior to the manifold? See the brass/red units in the pic?

    http://www.geotherm.it/esempi-impianti-geotermici-progetto-27-geotermia.html#4

    Will wait to hear back from you, but it is looking like a full pressure test may be required.
    As Manuel says in Fawlty Towers: " I Know Nothing"
  • beardymarrowbeardymarrow Forumite
    152 posts
    Sixth Anniversary 100 Posts Combo Breaker
    howardht wrote: »
    I'm new to this forum and am very impressed with just how much expertise is out there re GSHPs. I wonder whether anyone can advise me on the following. I have an IVT Greenline C GSHP with 2 sets of vertical panels installed in 2011 by the prevous house owner which has been working well. House temperatures are as set by the thermostats, DHW is always available, and electricity consumption is at the expected level. However I have always needed to top up the expansion bottle with 2-3 pints of glycol/water mix every 3-4 months. Recently, returning from a 3 week break away, I noticed a larger than average drop in the fluid in the expansion bottle. After topping up, it dropped again faster than it had done over the previous 3 years. I estimate the current rate of decrease to be about 2-3 pints per month. Before I contemplate the nightmare of locating a possible leak under the cobbled driveway or the garden path, is there any action I can take to check that it may not be a leak but something else? Could there be a problem with pressure, for example? But if it is a leak, has anyone any experience of detecting a glycol leak underground (there is no evidence of any leak near the pump itself or in the manifold).

    ps I have noticed that other GSHP users have had visible glycol loss in the expansion bottle, but they have not indicated that they have gone on to investigate a glycol leak.

    Hi Howard, Welcome aboard. lovesgshp is "THE MAN" when it comes to GSHP. He's taught so many people on this forum, myself included. The leak I had on my collector loop was at the joint between the collector loops and the top of the GSHP itself. Was easily fixed by just tightening that joint up a bit. Was a !!!!!! to find out where it was, but it was obvious it was within my boiler room, not in the underground bit as there was a small pool of glycol in the bottom of the GSHP. I wasn't getting anywhere near the loss you were though.

    If I was you I'd firstly take all of lovesgshp's advice. Secondly go through the whole of the ground loop circuit that is accessible (both within the GSHP itself and the pipe work as it leaves the GSHP but before it goes underground) with a fine toothed comb (or more accurately a bit of kitchen paper), to try to detect any leaks there. Will obviously be a whole hell of a lot easier to fix them there, than underground :-(

    I've also learnt something new today on GSHP, as I had never heard of the vertical panels you're talking about. Only ever borehole or slinky. Every day is a school day, as they say.

    Beardy
  • lovesgshplovesgshp Forumite
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    Thanks Beardy for your confidence in me, as always good to get a solution to a problem. Let's hope we can resolve this one easily!!!
    As Manuel says in Fawlty Towers: " I Know Nothing"
  • edited 31 August 2014 at 8:20PM
    howardhthowardht Forumite
    5 posts
    edited 31 August 2014 at 8:20PM
    Hi Lovesgshp and Beardy

    I very much appreciate both your support on this one as it's causing me sleepless nights!!

    Action so far:

    1. I have checked the GSHP with the front off and can see no sign of any leakage and likewise on the floor of the utility room, there is no evidence of glycol. (I can't see where the loops enter the GSHP - all I can see is the pipe leading to the expansion bottle.)

    2. Now re your first suggestions, lovesgshp. You are correct that there is no pressure gauge beneath the expansion bottle as in your photo. There are also no flow valves before the manifold.

    Q.1 Assuming I can get into the installer's menu to activate the pump manually, don't I need a pressure gauge to check what is happening?

    Q.2 Re testing each circuit, and to make sure that I have understood you correctly, if I were to test each circuit at the manifold, I presume that both inflow and outflow valves on the circuit to be tested are switched off. (When I tested before, I only switched one of these off).

    Q.3 What is involved in a pressure test? I take it the builder who did the groundwork or the GSHP installer could do this. Who would you advise?

    Q.4 If we are dealing with a leak underground, does the following make any sense? A nationally available leak testing company said that they could pump compressed air into the system, which (in their words) would clear the glycol from the top of each panel and allow air to escape at any point where a leak may be. They said they could do this without draining the groundloop. Their detectors would then pinpoint where the leak or leaks could be, thus cutting down the amount of repair groundwork needed. Assuming a leak was found, could it be repaired without draining the loop. (Seems dubious to me).

    Sorry if these questions are a bit basic.

    Thanks
    howardht
  • lovesgshplovesgshp Forumite
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    howardht wrote: »
    Hi Lovesgshp and Beardy

    I very much appreciate both your support on this one as it's causing me sleepless nights!!

    Action so far:

    1. I have checked the GSHP with the front off and can see no sign of any leakage and likewise on the floor of the utility room, there is no evidence of glycol. (I can't see where the loops enter the GSHP - all I can see is the pipe leading to the expansion bottle.)
    The inlet/outlets are on the top of the pump unit, fairly close together. If no leak is showing internally then we have to move on.

    2. Now re your first suggestions, lovesgshp. You are correct that there is no pressure gauge beneath the expansion bottle as in your photo. There are also no flow valves before the manifold.
    With those missing then it is harder to identify the loss, as we do not know what pressure the system is operating at on each circuit.

    Q.1 Assuming I can get into the installer's menu to activate the pump manually, don't I need a pressure gauge to check what is happening?
    Yes, as you can repressurise that circuit at the same time. To get into the I/S menu, you need to hold down the Menu button for about 10 secs, then it is menu 5.

    Q.2 Re testing each circuit, and to make sure that I have understood you correctly, if I were to test each circuit at the manifold, I presume that both inflow and outflow valves on the circuit to be tested are switched off. (When I tested before, I only switched one of these off).
    As you have no flow valves that you can shut down, then you cannot close one circuit completely, so just makes the process more complicated, as there will still be some feed into the 2nd circuit.

    Q.3 What is involved in a pressure test? I take it the builder who did the groundwork or the GSHP installer could do this. Who would you advise?
    The installer should do the pressure test, as the builder would not have been involved in that under a normal install. The collectors would normally be covered under a long warranty. Here it is 10 years, but not sure in the UK.

    Q.4 If we are dealing with a leak underground, does the following make any sense? A nationally available leak testing company said that they could pump compressed air into the system, which (in their words) would clear the glycol from the top of each panel and allow air to escape at any point where a leak may be. They said they could do this without draining the groundloop. Their detectors would then pinpoint where the leak or leaks could be, thus cutting down the amount of repair groundwork needed. Assuming a leak was found, could it be repaired without draining the loop. (Seems dubious to me).
    Use IE to do the checks, not a independent company, if you have the guarantee on the ground circuit.

    Sorry if these questions are a bit basic.

    Thanks
    howardht

    Don't get stressed about it. You need to take it step by step.
    As Manuel says in Fawlty Towers: " I Know Nothing"
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