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HEAT PUMPS & Geothermal Energy => Heat Pumps => Topic started by: eabadger on July 02, 2017, 04:34:13 PM



Title: air to water ashp
Post by: eabadger on July 02, 2017, 04:34:13 PM
done it got all the solar in and now fitted the cheepo heat pump.
few issues, first was the victron 3000 multiplus could not start the 1.8kw heat pump so i have had to parallel up the two victrons, not to big an issue because we now seem to have excess power every day, we were using a 3kw immersion to heat the dhw until yesterday.
configuring the multis took some time as instruction book seems to be out of date, no longer works on the dip switches, you now have to use quick ve bus configure, could i find this info anywhere?
so unit now starts and runs off grid, but kept giving me a high pressure error ee01, after playing around i found that the unit needs water pump on full power, but then had an issue that the water pump when heat pump was off kept cycling the water and dhw did not go above 44* played around with setting, one was pump control, normal or special, default was normal, nothing in manual but found with special selected it runs water pump for 30secs before and after heat mode, hot water now at 51*.
will build up control to heat second cylinder in series when first is at temp, also plan to automate run immersion at least once a week to kill the dreaded bug, may get the morningstar rd1 to automate this when been in absorption for xx time.

on the whole very happy with how it is going.



Title: Re: air to water ashp
Post by: eabadger on July 03, 2017, 10:30:16 AM
so far so good.
worked on timer, on at 8 off at 21:00 not sure if this is ideal yet, may be better less or more?
have plumbed in to whole house system so towel radiators can be on, got to sort the zone valves and may fit a threeway valve to ufh so i can select which heat source.
changing between winter use and summer automated and wood boiler overrules heat pump, valve for back boiler fail safe as in normally open, back boiler still fully open to heat sink radiators directly on the two floors above it.

steve


Title: Re: air to water ashp
Post by: eabadger on July 03, 2017, 11:00:10 AM
leaves the house here, gate valves to allow me to shut down when very cold and drain, fitted auto air vent and drain on machine itself.
this area due to be boxed in with an access door.
system failed a few times on start up due to air but after a while all ok, this is on an open vented system, not sure if this is normal or they are normally pressurized? manual (joke) that came with it only shows presurised.

steve


Title: Re: air to water ashp
Post by: phoooby on July 04, 2017, 03:13:17 PM
Is this one of those dream heat pumps from the well known auction site ?. I would be interested to see how you get on with it as I have seen mixed reviews on the net about them. I was thinking of getting an air to water heat pump to run the ufh in our house using overnight E7 and they seemed to crop up quite a bit and are cheap. Was thinking of using over night and use the screed as a big storage heater during the day as it takes a good 24 hours to cool down noticeably. 


Title: Re: air to water ashp
Post by: eabadger on July 04, 2017, 04:06:48 PM
it is indeed, only 800 when i collected, seems fine so far, we have over depth slab and do the same.
i notice bimble solar also sell them on their website.
other than terrible manual all seems fine, today out side air is 31* and 250lt of water at 52* so well chuffed but time will tell, if it turns out to be a pile of poo i will know whether to invest in a proper one, but for our dhw seems fine, plan is to put a three way valve on ufh and in autumn/spring heat floor with ashp and water with wood boiler, as we all like the fire in when the nights are longer.

i will keep updating on how it works out, good bad or ugly.
google searching on web parts of the manual shows many different brands worldwide made to same design many as swimming pool heaters, from dubai to holland and many in-between.

steve


Title: Re: air to water ashp
Post by: Tinbum on July 04, 2017, 05:00:49 PM
i will keep updating on how it works out, good bad or ugly.
google searching on web parts of the manual shows many different brands worldwide made to same design many as swimming pool heaters, from dubai to holland and many in-between.
steve
I bought a used one, 3 years ago, and use it to heat a swimming pool and it's been great.


Title: Re: air to water ashp
Post by: phoooby on July 04, 2017, 10:45:53 PM
Thanks, all sounds encouraging, I will look out for any updates in the future.


Title: Re: air to water ashp
Post by: eabadger on July 06, 2017, 05:28:32 PM
been very hot here today and the pump has errored and locked out a few times, but having now done the research i seem to have missed the bit that says the water flow in the cylinder coil should be reversed!!
so itt appears the too hot water is letting the heat pump get the gas too hot and shutting down, least the safty works whistle

so tomorrow will need to do a bit of remedial work, so word of warning for others considering it, but i am sure elsewhere on the forum i could have found the info wackoold

steve


Title: Re: air to water ashp
Post by: eabadger on July 19, 2017, 07:22:33 PM
done all the remedial banghead: plumbing work.
working fine, but......

we have had some scorching days here and on those days the heat pump has struggled to get water past 50* if i mess with the max temp or return temp settings the unit goes in to over pressure error?
but on cooler days with default setting no issues and easily 53* at top of cylinder.
i assume the refrigerant gas doesnt like to high temp? is this odd or is my unit over gassed?

steve


Title: Re: air to water ashp
Post by: TT on July 19, 2017, 07:34:18 PM
Do check the parameters on the heat pump, we have one at work and the installers set the max temp to 50deg.
Also worth while adding a power meter onto the ashp circuit to work out consumption.



Title: Re: air to water ashp
Post by: Iain on July 19, 2017, 07:50:55 PM
Hi

Quote
.we have had some scorching days here and on those days the heat pump has struggled to get water past 50* if i mess with the max temp or return temp settings the unit goes in to over pressure error?
but on cooler days with default setting no issues and easily 53* at top of cylinder.
i assume the refrigerant gas doesnt like to high temp? is this odd or is my unit over gassed?

steve

Do yo need it that high?
I have my cylinder set to 42 deg c
My mate has just had an air water heat pump fitted and his is set to 45 deg c, and is plenty hot enough.

Iain


Title: Re: air to water ashp
Post by: eabadger on July 19, 2017, 08:33:05 PM
default max output temp 55* max return temp 45*
wanted to get water temp above 50* as below that it is a breeding ground for legionella?
manually run immersion once a week to 60*

steve


Title: Re: air to water ashp
Post by: phoooby on July 19, 2017, 09:03:20 PM
Perhaps have the immersion set on a timer plug to heat to 60 degrees once per week (just after your normal heating cycle to minimise elec use) to tick the legionnaires box. I'm sure I have read or been told that there have been no cases of legionnaires in a domestic hot water system in the UK but better safe than sorry.


Title: Re: air to water ashp
Post by: TT on July 19, 2017, 09:24:47 PM
Legionella guidance is aimed at business premises generally where people are employed, so with a healthy turnover from hardly any outlets Imimagine a risk assessment as per L8 would see it as low risk.
I certainly don't see the point in a domestic area to heat water to then add lots of cold water to reach the optimum temperature.


Title: Re: air to water ashp
Post by: eabadger on July 20, 2017, 08:38:11 AM
automating in some way is no problem and on the cards.
from what i just re read the cases in uk are on the up, still a small percentage but rising, one ugov report suggests 6% of showers in domestic homes are showing traces!
now i normally take a dim view on health and safety, but on this one i think i will get water hot at least once a week, but we average store at 50* + now, which appears to kill the bug within two hours where as 60* is 2 mins.

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/627888/Monthly_LD_Report_-_June_2017.pdf

but back to original question, why does my new heat pump appear to not like hot weather? fan too slow? it is very quite in operation, too much gas?
dont take this as a downer on the dream pump, just fiddling to get it better.
but remember the pump setting needs to be on special or all your water will keep circulating outside.

steve


Title: Re: air to water ashp
Post by: dhaslam on July 20, 2017, 05:17:17 PM
The compressor can overheat in warm weather so there is normally a sensor to protect it.



Title: Re: air to water ashp
Post by: Fionn on July 20, 2017, 05:39:52 PM
It sounds to me like your cylinder coil is undersized and the HP is running at the upper limit of it's output temperature range.

The delta T between the water in the coil and that in the cylinder is much reduced (vs an oil boiler) due to the low flow temperature from a heat pump.
If you had a larger coil the water would have more of a chance to cool before returning to the HP.
As it stands, the HP is tripping out on over temp as the set point is too high for it to run in high ambient temps without the benefit of cool return water.

This would still occur once the tank fully heated up though, even if you had a bigger coil, so it sounds to me that the HP is at the upper limit of it's ouput temperature range and you'll need to dial back this setpoint.
One would have to assume that the refrigerant level would be set correctly in a new unit with fixed volume, there's no variation here due to refrigerant pipe runs etc.


Title: Re: air to water ashp
Post by: JonG on July 21, 2017, 07:31:40 AM
Flow rates are critical on heat pumps and usually with a design delta of 7 degrees across the plate, pipework ends up being 28mm or above. It looks as if you have plastic at 22mm? Which with its thicker wall and liners may be causing flow rate restrictions.

Is the circulating pump on full speed, is there a 3 way valve passing to heating perhaps and as per Fionn is the cylinder a dedicated heat pump variant and tested with the unit?


Title: Re: air to water ashp
Post by: eabadger on July 21, 2017, 09:06:46 AM
thanks for suggestions, just to confirm it isnt the motor that is tripping out, it is the gas pressure sensor.

since fitting i have considered pipe size having read the samsung manual, but outlet of heat pump is 3/4" and inlet of cylinder is 3/4" which is 19mm, even my speedfit pipe 22mm has a bore of that, isnt flow restricted to smallest piece or would over size pipe make a difference? pump is a modulating one but set to full speed, the motorised valve is a 28mm shared with rest of system.

cylinder is not a dedicated HP one but is a oso solarcyl, and i have seriesed up the two coils, feeding hp in at top of cylinder and out of lower coil at bottom.

what i have noticed is the high pressure max on these pumps is 4.2mpa my split air air heat pump is 4.5mpa, when my air water pump is at rest at 17* temp the pressure seems to be .2mpa greater than manual states as new fill.

look it isnt an issue and the temps we have had recently are not normal, but i was expecting great results with the extra heat not lower results.

i am so far really happy with the system, make unsure of but am now convinced this is the way for off us, am setting up monitoring on it both heat and power so will know for sure, am going to set my morningstar rd1 to trigger the immersion whenever the batteries reach float or on timer if that not reached once per week.

steve


Title: Re: air to water ashp
Post by: JonG on July 21, 2017, 04:34:04 PM
What is the heat pump rated capacity and I can calculate flow rate from that for you? I would pipe the coils in parallel, in series there is likely to be too much resistance, can you use temp clamps to assess flow and return temps to the cyl.


Title: Re: air to water ashp
Post by: eabadger on July 21, 2017, 07:31:56 PM
heat pump is 8kw, the cylinder coils are 11 and 18 i think.
not in to dynamics of flow, but isnt flow reduced by smallest point?
i had just one coild connected, and worked, but error 001 when warm out, two coils does it less.
gauge on side of unit shows error occur spot on 4.2


Title: Re: air to water ashp
Post by: JonG on July 22, 2017, 10:19:32 AM
Ok 8kw at 7 degree delta is 16 LPM, very roughly 22mm plastic will only carry around 6.5kw at that velocity, if you had a bigger pump or higher pump speed it could do it, but might create harmonics on the coil.

This is the maths though, real world can be different.

If it happened on 1 but was better on 2, I would say it is a combination of factors. Not enough surface area for heat transfer, when 1 was plumbed in and too much resistance when 2 are in series.

Options therefore include, bigger pipework, coils in parallel, heat pump cylinder with a suitable coil size, larger pump etc.


Title: Re: air to water ashp
Post by: eabadger on July 22, 2017, 10:36:59 AM
thanks for info, the heat pumps says flow of 1.2m per hour, the pump is set at and showing near 4m per hour.
happy to fit 28mm pipe if that improves things, but no real problems just wondering.
but if the pump is 3/4" will this not be the limit to it all?
again can paralel up the coils, but would this not have adverse effect as at different heights in the water? so different temperatures.

reading the manual for same pump but sold in dubai they have different settings on the eev and superheat temperature.

steve


Title: Re: air to water ashp
Post by: JonG on July 22, 2017, 11:05:19 AM
1.2 m3/h is around 20 litres per minute which would mean a design delta of around 6. 4m3 is around 66 litres per minute which is pretty immense, you would probably hear that in the coil and would be a pretty big pump at that duty.

The size of the pump inlet/outlet is not hugely relevant, the pressure drop across it will affect flow inevitably but short restrictions provided there are not too many won't cause too much issue.

As an aside if you increase the pressure available from a pump the resulting increase in resistance is something like a factor of 4 from memory.

Using the coils in parallel isn't a perfect solution, but it does increase surface area and decrease resistance, both of which may be causing the undesirable alarm. Whilst the alarm is intermittent and only annoying at this stage, the high temperatures that the compressor experiences and the cycling that occurs will rapidly result in wear and potentially premature failure.

Flow rate and long run times (or adequate run times) are high priorities when we design heat pump installations, hence the use of buffers, big bore pipework, minimal zoning and tank in tank or thermal store type hot water delivery systems.

I think the gauge that you referenced will be pressure of the refrigerant, if you check the pressure on tables pertaining to the refrigerant, it will tell you what temp is equivalent to that pressure, you can then check this against the temp at which the HP stat is tripping to see if the stat is out of calibration, which does happen. Alternatively the stat should have its tripping pressure on it or it should be in the MI.



Title: Re: air to water ashp
Post by: eabadger on July 22, 2017, 01:08:20 PM
so instead of replacing the 22mm speedfit with 28mm copper, what if i double up the 22mm flow and return?


Title: Re: air to water ashp
Post by: Countrypaul on July 22, 2017, 01:31:47 PM
You could look at 28mm plastic, I have just got a length of 28mm polyplumb as a coil - it was recommended as being much more flexible than speedfit which appear to only be available as straight lengths like copper and so much easier to run the polyplumb. This to be used between our thermal store and ASHP when we get one later this year. The cross sectional area of 28mm vs 22mm is asbout 50% more but using a larger diameter pipe should give less resistance though how significant that it I have no idea. Using a flexible pipe with bends rather than a more rigid pipe with elbows should also reduce resistance.


Title: Re: air to water ashp
Post by: JonG on July 22, 2017, 01:44:50 PM
28mm plastic should be fine, 28mm copper better and yes with as few 90 degree bends as possible, 22mm copper will actually carry 8.5kw at 7 degree delta, but the heat pump power is likely to be much higher than this in warmer temps, again the MI should provide a range of power outputs at different ambients to allow you to size correctly and not cut it fine.

You can double up the pipework providing that the length and resistances are kept equal, so same number of fittings etc. It would be good practice to use a flow setter on each leg though to ensure they are balanced, don't take the readings as gospel though (around 10% variance usually unless you spend heavy).



Title: Re: air to water ashp
Post by: eabadger on July 22, 2017, 02:33:09 PM
if i do redo in 28mm i think i will do in copper due to price, i still cant get my head round why the 3/4" 19mm outlets and inlets dont reduce the flow negating the bigger pipe/tube?
i have a straight run after arriving in house, would it make any positive difference to do just the straight run in 28mm? about 6 meters. total run about 8 eachway.

steve


Title: Re: air to water ashp
Post by: djh on July 22, 2017, 05:48:56 PM
You could look at 28mm plastic, I have just got a length of 28mm polyplumb as a coil - it was recommended as being much more flexible than speedfit which appear to only be available as straight lengths like copper and so much easier to run the polyplumb.

My entire house is plumbed using speedfit coils, so it definitely exists!

http://www.johnguest.com/speedfit/product/pipe/jg-layflat-polybutylene-pipe-in-coils-2/


Title: Re: air to water ashp
Post by: Countrypaul on July 22, 2017, 06:02:10 PM
You could look at 28mm plastic, I have just got a length of 28mm polyplumb as a coil - it was recommended as being much more flexible than speedfit which appear to only be available as straight lengths like copper and so much easier to run the polyplumb.

My entire house is plumbed using speedfit coils, so it definitely exists!

http://www.johnguest.com/speedfit/product/pipe/jg-layflat-polybutylene-pipe-in-coils-2/

The web site says available in June, so maybe it had not yet got through to my supplier when I ordered the polyplumb - plus I needed slightly less than 25m, so a 50m coil might have been serious overkill, pity as all the rest of the house exept the WCs are done in JG speedfit.


Title: Re: air to water ashp
Post by: JonG on July 22, 2017, 06:21:45 PM
It comes down to the pressure drop which has to be considered and can be calculated, but in most scenarios using a rule of thumb for the heat carrying capacity of the pipe is sufficient. This gives you the required flow rate (lpm/lps/m3h), the velocity also has to be considered (m/s) and this is generally kept as close to 0.9 m/s as possible to avoid noise and erosion.

If you need multiple pumps or hydraulic separation then the velocity needs to be reduced in a header or buffer but that is probably out of scope of the OP. In order to achieve what you want you want the correct flow rate, and a pressure drop low enough to work with the duty of the pump at the required flow rate.

It can all be calculated out but generally copper is a better choice than plastic, due to the lack of inserts which increase pressure drop and smaller internal diameter, which increases linear friction.

We are starting to see more issues with plastic too, in terms of water quality. This is thought to be because the fittings have no barrier against oxygen entrainment, and where a plastic fitting joints copper to plastic the dissimilar coefficients of expansion and contraction may result in ingress at the o-ring. These are just hypotheses at the moment.

We now wont use it on heating circs and only use copper or MLCP.




Title: Re: air to water ashp
Post by: eabadger on July 23, 2017, 09:18:08 AM
i have always used the specific barrier type pipe for heating, which i understand has an oxygen barrier, i tend to use hep20 either blue stripe no barrier for fresh water and red stripe for heating, with tails in speedfit as white, all inserts superseal and have had no issue.
all backboiler pipe in 28mm copper with hard brazed joints (rules here).
more than happy to pipe it all in copper and will to test out, our saying is "its all a big experiment", my logic tells me that the exit of heat pump an entry of cylinder will be the limiter, but happy to be wrong.

what is MI? manufactures instructions? if yes i will post on here.
yes the gauge i was referring to was the refrigerant pressure, hence comment that it appears to have slightly too much at rest .2mpa more than instructions state.
also what i have read, the initial gas should be (on high end units) be set onsite and calculated for local weather.
i dont understand why max mpa on my air to air pump is higher on the same gas? assume manufacturing differences.


what i have done last night is to open the manifold to the 5 x towel radiators, could not do last week as was so hot, yesterday afternoon was pretty miserable weather, so not a conclusive test as outside temperature was cooler, water in cylinder topped out at 51*

again dont get me wrong, so far very happy with the heat pump, only time will tell as to how long it will last, but looks ok and is far quieter than i thought it would be, the dogs loved it in the hot weather, they lay down with the cold air blowing over them!
on that point why not duct the cold air back in to the house to cool it? possible?

steve



Title: Re: air to water ashp
Post by: JonG on July 23, 2017, 04:20:38 PM
How are you avoiding an HP trip when the wood burning stove is lit and contributing?


Title: Re: air to water ashp
Post by: eabadger on July 23, 2017, 05:20:20 PM
one of the sensor on wood burner closes zone valve and locks out the heat pump, why?
28mm two port valve n/o is powered shut when heat pump is on.

steve


Title: Re: air to water ashp
Post by: JonG on July 23, 2017, 06:11:24 PM
Same principle really if the heat pump circulates water at WBS temps through its plate while the compressor is running the fridge temps can rise and trip the HP stat. If the signal is simply 230 v off the 2-port without some form of hysteresis this may be an issue.

If you upload a schematic happy to have a look for you.

We had a GSHP with a PV array also heating the cyl, and periodically the high temps in the cyl would result in a hot slug which tripped the HP stat, so ended up capping the PV immersion temps. With a WBS unless you are feeding out of a buffer through a mixer more of a potential issue.


Title: Re: air to water ashp
Post by: eabadger on July 24, 2017, 08:07:34 AM
hello, it is the pressure causing the error and not a stat at high temp, admittedly the temp does change the pressure.
we dont intend to use both at the same time, our wood boiler is a 25kw to water and does all our dhw and heating good hardwood ranges from cheap to free here, collecting a corde of dry oak for 100 this week :), the heat pump is for water heating when not wood burning season, i have added the automation to stop a mistake, so if temp of the gravity up pipe of the back boiler is above 40* the heat pump is shutdown and locked out at which time the normally closed zone valve shuts isolating it.
same sort of principal with wood boiler, when heat pump is on it drives a normally open valve shut on the pumped side of the wood burner, to stop the wood burner being a radiator in the summer, the back boiler is a 4 port type, two cross linked on pumped side and others for unobstructed no matter what gravity feed to two 3kw rads.


back to the heat pump, i tried something different yesterday, parameter for max water temp is 55* default parameter for water return is 45* but on a dutch website of a very similar looking unit both theses temps are 50*, so tried it that seemed to make a positive difference, only time will tell as weather not the best currently, but water topped out last night at 53* with no trip outs.

i can do a pipe layout schematic in as far as a fag packet sketch?

steve


Title: Re: air to water ashp
Post by: eabadger on July 29, 2017, 11:19:47 AM
bit of an update, changed the modulating pump for a grudfoss standard 3 speed one, made a slight difference, but having taken some advice i checked the eev setting which is the expansion valve, on these pumps it appears the eev times down to create more pressure, it seems the default 35 setting was increasing pressure too soon, changing this setting to 40 has stopped the problem, i am going to re pipe as suggested in 28mm copper and set eev back to 35 to see.

any advice from those in the hvac trade on the setup of initial eev setting appreciated, i read the hitachi manual for a similar hp that suggested the setting was based on environment and charge of gas, wet and dry bulb measuring which went over my head, simple explanation?




Title: Re: air to water ashp
Post by: eabadger on September 12, 2017, 05:19:47 PM
ok, another update, re-piped in 28mm copper, sloping bends, no difference.
however biggest difference was changing pump from return as shown in the manual to the flow, works a treat now, just in time for wood burning season. :(
but hope to use the ashp for floor heating, tried yesterday and very happy with results, so new plan is if generator needed in the autum winter months we can pre charge floor at same time as charging batteries.
also got my second battery bank set up with a manual changeover switch to the ashp supply, i can heat the dhw for 3 days if need be, then switch back and leave the spare battery to re-charge.

steve


Title: Re: air to water ashp
Post by: noah on March 19, 2019, 09:07:29 PM
Hi I`m thinking of buying a few of these heat pumps (on the basis that they are cheap enough that I could buy an extra one as a spare). Is it still holding up OK?
(actually I`d be going for ground source but same people)


Title: Re: air to water ashp
Post by: knighty on March 19, 2019, 11:53:36 PM
bit late to this thread

refrigeration systems are pretty rubbish outside their design temperatures, they have a surprisingly accurate amount of refrigerant in them, if it's very cold the gas does not expand enough if it's very warm it expands too much


what's the pressure switch set to?  it could be it's just set a bit low, with more safety margin that you need?


or... you mentioned pluming in an extra cylinder... if the return water diverted through that cylinder it should lower the water temp enough to sort it for you?  - could always use a pipe thermostat and a 3 way valve, so once return temps are high enough water diverts through second cylinder?


but first... I'd check the pressure setting and see if there's room to bump it up a bit


Title: Re: air to water ashp
Post by: noah on March 20, 2019, 11:10:50 AM
`bit late for this thread` er, yes thats sort of the point: pump has now been in use for some time so an evaluation has some weight.


Title: Re: air to water ashp
Post by: knighty on March 20, 2019, 02:41:20 PM
I meant a bit late to offer help/advice

I've been fixing fridge systems since I was a kid  (used to pass tools and go up/down ladders getting things for refrigeration engineers at my dads work)