Mitsubishi ecodan ASHP no heating

Reed_Richards

UnicornGirl81 said:

They decided it was a fault with both the pumps but clearly it isn’t. 

There's a principle called "Occam's Razor" which basically states that the simplest explanation for a problem is more likely to be correct.  So both pumps going wrong at the same time sounds a bit unlikely, particularly if there a possible explanation where only one thing has gone wrong, like the blockage I suggested.

2131tom

I don't know if it's too late to comment and you've sorted out your heat pump problems, but I've just had a similar issue resolved with my Mitsubishi heat pump-driven system and I'm not sure if my experience might help.  It's a 10-year-old system that I inherited when I bought the house last year and serves a mixture of radiators and underfloor zones, and a hot water tank as well.  Last year everything worked as expected and through the summer the hot water was fine.

When I came to turn the heating on a few weeks ago, the radiators heated up OK but none of the underfloor loops worked.  The pumps (there are two) hummed as though they were working and the inlet manifold got warm(ish), though the outlet stayed cold.  I'm no expert but I felt, as it was something in common to the 5 underfloor circuits, the pump serving those, or motorised valves (aka port zone valves) in that part of the system were the most likely culprits.      

The people who service the system came out earlier this week and found one of the motorised valves was the cause - it had stuck closed, as the motor had stopped working - and a quick and (relatively) cheap replacement cured the problem.  The circulating pump was fine.

For what it's worth, I asked the engineer about underfloor leaks.  In his experience, he said the underfloor pipes weren't jointed and were very tough, with leaks very rare - and almost invariably the result of mechanical damage (e.g. a nail or drill being unthinkingly driven into the floor and accidentally through a pipe).

UnicornGirl81

Just a quick update

today it finally got resolved and I have it working although not warm yet as it takes an age to get up to temperature. But still it’s progress!

It was the 3 point valve stopping the water going to the radiators/underfloor heating 

thank you all for taking the time to comment and help where you could 😊