Brian Herbert Posted July 6, 2020 Share Posted July 6, 2020 Hello - I have a self build / designed home, and we have a free standing Heat Pump ( air to water) with a vertical Fan on top. I recently replaced the fan & fan motor as one of the blades had broken. ( This site helped me clarify the fan type I required). I had an electrician wire it in with the new capacitor. It heats a small swimming pool. It worked fine for a few days, then suddenly decided to Ice up badly at the weekend. The frost stat kicked in and cut it off. It was a warm day so I would not have expected that to happen. After it had thawed out, I checked everything still worked ok - and it does. It has never iced up before, and I am wondering if the new fan is too powerful and has caused the problem? I did in fact get a slightly smaller fan blade diameter than the original, as there were none at the diameter I required, so I would be surprised if it is? It draws air in through the sides, over the refrigerant coils, and then eventually blows the cold air vertically out of the top after the heat extraction . It is housed with ample free air space around it, but it is clearly condensation badly for some reason. Last year I had new refrigerant put in when a small leak was repaired. I am wondering if possibly that leak has returned, however the operating pressure meter seems to read ok? It seems too coincidental that this has occurred only a few days after changing the fan. The fan sucks and blows in the same direction as the old one. The HP is now 10 years old and we are fed up spending money repairing it when perhaps we should have a new one installed. The company that repaired it last year has now dissolved and so before I engage another professional engineer, I just wondered if anyone had any thoughts, suggestions or advice in case I am missing something obvious. If I get a professional engineer , should they be able to test that the compressor & condenser are working correctly? Any ideas welcomed. Thanks. Link to comment Share on other sites More sharing options...
SteamyTea Posted July 6, 2020 Share Posted July 6, 2020 Smaller fan diameter will cause less airflow though the element. So more time for frosting up to happen. Have a look at where it starts to freeze up first. Probably where there is little airflow. Link to comment Share on other sites More sharing options...
ProDave Posted July 6, 2020 Share Posted July 6, 2020 Yes definitely, not enough airflow now so the heat pump's evaporator is getting too cold. Link to comment Share on other sites More sharing options...
dpmiller Posted July 6, 2020 Share Posted July 6, 2020 fans need to be a close fit in their housing otherwise efficiency is reduced, the air basically recirculates. Link to comment Share on other sites More sharing options...
Brian Herbert Posted July 6, 2020 Author Share Posted July 6, 2020 Thank you for your advice. My new fan is 450mm Dia the old one was 480mm so I didn't think that would be such a problem. The engineer didn't mention anything to me either when I told him my plan. Sounds like there is nothing I can do as I can't find anyone who can supply a 480mm diameter fan sadly. Link to comment Share on other sites More sharing options...
dpmiller Posted July 6, 2020 Share Posted July 6, 2020 can you fabricate a ring of something to fill the gap? Link to comment Share on other sites More sharing options...
Brian Herbert Posted July 6, 2020 Author Share Posted July 6, 2020 No - I don't think I can given it's construction. I now see ( belatedly) that the RPM of the original fan was 675RPM whereas the new one is 1360 rpm which I would have thought would have increased the airflow - but clearly not. The Spanish company that supplied the original has long since gone bust and no spares are available sadly. I think I may have to accept the end has arrived and I will have to bit the bullet - it will have to wait till next year though. Link to comment Share on other sites More sharing options...
SteamyTea Posted July 7, 2020 Share Posted July 7, 2020 9 hours ago, Brian Herbert said: My new fan is 450mm Dia the old one was 480mm so I didn't think that would be such a problem 12% smaller, so assuming that all things are equal (they are not as the centre of the fan will be a similar diameter), you have lost an 1/8th of the airflow, just when you need it most. Link to comment Share on other sites More sharing options...
Brian Herbert Posted July 7, 2020 Author Share Posted July 7, 2020 Thanks for all your help and advice - much appreciated. Link to comment Share on other sites More sharing options...
Miek Posted July 7, 2020 Share Posted July 7, 2020 (edited) 9 hours ago, Brian Herbert said: Thank you for your advice. My new fan is 450mm Dia the old one was 480mm so I didn't think that would be such a problem. The engineer didn't mention anything to me either when I told him my plan. Sounds like there is nothing I can do as I can't find anyone who can supply a 480mm diameter fan sadly. You would be surprised. The vast majority of the power comes from the fan blade tip so it can make a big difference reducing diameter. You would need to increase the RPM to get the same flow rate. Edited July 7, 2020 by Miek Spelling Link to comment Share on other sites More sharing options...
ProDave Posted July 7, 2020 Share Posted July 7, 2020 Presume it was just the motor gone? Can you not get a new motor of the right spec and use it with the original fan blade? Link to comment Share on other sites More sharing options...
dpmiller Posted July 7, 2020 Share Posted July 7, 2020 @ProDave broken blade sadly Link to comment Share on other sites More sharing options...
Brian Herbert Posted July 7, 2020 Author Share Posted July 7, 2020 I have now found a replacement fan and motor ( they will not split) for this heat pump for £410 inc Vat - so I am going to buy this and fit it. Expensive but cheaper than a new HP! It superseded the original but is guaranteed to work with the HP - so here's hoping. A fan blade would have been cheaper!! Thanks again - I have learnt a lot. Link to comment Share on other sites More sharing options...
SteamyTea Posted July 7, 2020 Share Posted July 7, 2020 Just hope it works. Have you thought about adding some solar thermal for the pool? Quite simple to DIY it. Did it for my parents pool back in 1984. Worked well. Link to comment Share on other sites More sharing options...
Brian Herbert Posted July 7, 2020 Author Share Posted July 7, 2020 I really should look at that - to be honest I am having to prioritise things a bit at the moment as I've got too many projects on the go. But duly noted - good idea. Link to comment Share on other sites More sharing options...
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