Nibe Fighter 1240 Heat Pump Problems

Notoldorwise wrote: »

I have a 7 year old Nibe 1240 Ground Source Heat Pump. About 5 weeks ago, a "High Hotgas " alarm put it in fault. A Heat Pump Technician came and diagnosed that the Evaporator was clogged with oil. He flushed it and refilled the refrigerant. He also tested if the compressor was ok. I had noticed that I was also venting a lot of air via the "Double Jacket Vent Valve". The technician suggested that I may have an underfloor leak & that it was a job for a plumber. There is no obvious sign of a leak anywhere. The heat pump has been working fine over Christmas except that I was venting it every day.
A plumber came out to have a look this week. He is stumped as to how air is getting in to a system that is operating @ 1.5 bar approx. The council water supply (feeding it) is always strong pressure. Now, tonight, the HIGH HOTGAS alarm is back. Any opinions as to what is going on? Thanks.

With regards to the leak on the underfloor side of the system. This would be a sealed system, so the council mains water pressure shouldnt be a factor. Can you answer the following
1. Do you ever need to top up the pressure in the underfloor or heating system by opening a valve connected to the water mains.
2. Do you have a pressure guage on the heating system & does it drop it pressure.

If there was a small leak and the pressure dropped, the circulating pump could draw air in on the supply side of the pump. There should be automatic vents on the manifold, anyway.

I have a NIBE 1240 that has the following totals to date;
64,727 starts, 11,077 hours.

It has been running badly for a few days (water/house not reaching expected temps) and I got the following numbers from the menu yesterday;
2.3 Flow temp 23.5 deg
5.11 Hot gas 21 deg
5.12 Liquid line 21 deg
5.13 Hot bulb 15.4 deg
These are all alot diferent that the expected values

I turned it off last night and when I turned it ob this morning I got a Phase fault alarm message. I've phoned the service engineer and am waiting for him to get back.

I'm wondering if the compressor could be part of the problem - are nearly 65,000 starts and 11,00 hours typical for the compressor lifetime?

MikeKaiserBud wrote:

I turned it off last night and when I turned it ob this morning I got a Phase fault alarm message. I've phoned the service engineer and am waiting for him to get back.

There is a chance it's a soft starter or capacitor gone either. I had similar error few years back on the 1245.

MikeKaiserBud wrote: »

I'm wondering if the compressor could be part of the problem - are nearly 65,000 starts and 11,00 hours typical for the compressor lifetime?

I'm pretty sure 65k start/stop cycles over 11k hours is not anywhere close to normal for GSHP. Your heat pump does on average 6.5 on/off's per hour.



Either you have faulty or extremely oversized unit or near 0 heat loss with extremely tight hysteresis setting. My money is on the former.


I have air source system. It counted 0 on/offs over past 7 days.


Is your heat pump inverter or full stop/on type?

Latro wrote: »

I'm pretty sure 65k start/stop cycles over 11k hours is not anywhere close to normal for GSHP. Your heat pump does on average 6.5 on/off's per hour.



Either you have faulty or extremely oversized unit or near 0 heat loss with extremely tight hysteresis setting. My money is on the former.


I have air source system. It counted 0 on/offs over past 7 days.


Is your heat pump inverter or full stop/on type?

Thanks everybody for comments.
I don't know if system is inverter or full stop/on type - first time I've come across those terms. As I understand it, I have a standard ground source HP, a NIBE 1240. I played around with it for a year or two when I first had it, trying to get everything right, and those two years could have caused quite a few of the excess starts etc. For example, I had six thermostats on, now I have at most two on. In recent years I have relied on the service engineer to get the settings right. Since the last service in May 2018 there have been 6400 starts for 1500 hours run time - over 4 starts per hour. I think there's a setting in the menu where it sets a minimum 20 minutes between starts so that seems to be contradictory. It's looking like I should get an expert in to sort out how it is set up.
How can you get 7 days with zero starts? Is that house heating only, no hot water heating included? (by the way, I have hot water in addition to house heating). That sounds like zero heat loss over 7 days, or the outside temp was as high as indoors? Or are there other heat sources involved, eg fire, cooker etc? Sounds amazing anyway.

An update for Hatchman and Latro in particular: You both were in the right areas with your comments. The service engineer had to replace both the softstart and the capacitor. So far so good. After it got going again I noticed tha tthe water heater was coming on very regularly for only about 5 mins, then off for about 15 mins, then back on again even though nobody was using hot water. I decided to sit and watch it for a couple of hours to see what was happening. The service guy set the hot water start temp to 46 and stop temp to 54. Once it reached 54 the compressor cut off as expected. I tracked the hot water temp and it fell at about one degree per minute average over period of 15 mins which took it below the start temp. The delay between comp starts was set at 20 mins so onc e the 20 mins were over it came on again. That explained the 5 mins on followed by 15 mins wait to next start. I changed the delay between starts to 55 mins to reduce the number of starts. I wonder why they don't use the temp of the hot water tank for the start temp? One other thing I noticed was that thd flow temperature exceeded the max temp setting during the water heating period so does the hot water temp value take precedence over the flow temp while water heating is going on? Last question: some people seem to use only the extra hot water at night time for heating the water using the immersion heater directly(I think). Is the setback/timer setup the way to do that? Thanks again for your help