nikolay Posted January 8 Share Posted January 8 Hello I bought an apartment with installed UFH and ASHP. The heating system was installed in 2016, and previous owners are happy with it. However, it has no documentation about pipe lengths and needed flow rates. It's around 130 sqm, 8 zones. HP is 11kw heat power, split system, DHW tank and no buffer, feeding directly to one manifold. The issue I had initially was that there were some different temperature zones, and one zone in the kitchen was completely turned off from the flow meter because the previous owners said it was too hot. Anyway, I opened the flow meter, and in order to equalize temperatures in the zones, I rotated most of the flow meters blindly just to equalize return temperature, and because the flow meters are dirty I thought I couldn't see the flows but later I found out I could see the flows by using a light. Anyway, I completely de-balance the flow configuration without knowing the initial flows.😀 This was partially ok - now it's much better, heating is fine however I want to know what is the correct approach to balance the flow meters on unknown pipe lengths.  Here is what I did: 1. Opened all zones and flow meters to the max, noted the flow rates (as much as I can in the dirty flow meters) and they are around 0,75 to 1 L/min per zone, total flow in the manifold is around 6 L/min. The nominal water flow of the water pump is 0,52 L/sec. 2. In the HP manual, it's noted that delta T should be between 4 and 7 deg; however even with all zones opened to the max delta T is about 8 deg according to the HP temp sensors (with 35C output water) They say if delta T is higher than 7C circulation needs to increase by adding a pump eventually. 3. I just balanced the circuits without closing too much the flow rates to keep the flow in the manifold to the max (in order to decrease delta T), however, that's it - It can't go down below 8C on the HP and about 8-10C in each zone. (only bathroom zone is with delta 5-6C).  I was thinking of buying Salus auto balancing actuators, but they won't be able to reach 7C delta, so they will keep the valves open to the max. So what to do in this case? What is your advice?  Apparently, the heating is fine - the heat pump is configured with weather compensation, I turned it off only for testing today with 35C constant T. It has been working like that for 7 years and now it is also comfortable. I suspect the water pump is on the edge with the current pipe lengths, and if I need a lower delta T, I should add a pump. The filter has recently been cleaned, so it's not clogged. I can leave it like that and balance the return temperatures for the best comfort, which I more or less already did. I am only afraid that if it works with delta T more than 7C, the heat pump is not maximum efficient; however, 1C difference from the specs is not so far...  Link to comment Share on other sites More sharing options...
JohnMo Posted January 8 Share Posted January 8 Are you certain of those flow rates, they all sound very low. But if you have a large dT that could be issue.  If you add an additional pump, add it to the return leg on a fixed duty, so it doesn't interfer with original pump modulation. Link to comment Share on other sites More sharing options...
nikolay Posted January 9 Author Share Posted January 9 I summed all flow meters on the manifold, and it ended up with about 6 L/min. The flow meters are dirty, so they are probably not 100% correct. But I don't expect to be so much wrong. Currently flows on the zones are like: 0.5, 0,5, 1, 0.75, 0.75, 0.75, 0.75, 0.4. The heating is ok, but the delta is 8C, even this morning it was 10C, but outside is cold, and the water outlet is 37C.  The setting has no option to change the pump speed (the heat pump is Olimpia Splendid Sherpa 3W). There is only an option if the pump works constantly, which is the case now. I didn't notice any modulation of the speed of the pump to vary the flow. I am also attaching a photo of the pump it seems it has different speeds but it's not noted in the manual, and I don't know how to switch it. Maybe I have to check the pump inside more carefully.  Here are the specs in the manual (the one with 0,52 l/s): Link to comment Share on other sites More sharing options...
jayc89 Posted January 9 Share Posted January 9 I balanced mine by measuring the flow/return temps on each loop. For mine, the flow rates provided by the supplier were out of whack to what made the most sense in reality; some ran too hot, some too cold. Link to comment Share on other sites More sharing options...
nikolay Posted January 9 Author Share Posted January 9 2 hours ago, jayc89 said: I balanced mine by measuring the flow/return temps on each loop. For mine, the flow rates provided by the supplier were out of whack to what made the most sense in reality; some ran too hot, some too cold.  Yes, I was doing it the same for similar reasons. What delta T are you targeting? I was looking at least to equalise the return temperatures in the same rooms or if I feel the floor colder in some room to increase the flow. In that way I would be able in the future to use only weather compensation and no room stats.  For the pump - I found out the specs from the manufacturer and this pump has 3 speeds selectable. I will check when I return home, but I suspect the pump runs at the lowest RPM.  Link to comment Share on other sites More sharing options...
jayc89 Posted January 9 Share Posted January 9 27 minutes ago, nikolay said:  Yes, I was doing it the same for similar reasons. What delta T are you targeting? I was looking at least to equalise the return temperatures in the same rooms or if I feel the floor colder in some room to increase the flow. In that way I would be able in the future to use only weather compensation and no room stats.  For the pump - I found out the specs from the manufacturer and this pump has 3 speeds selectable. I will check when I return home, but I suspect the pump runs at the lowest RPM.   I have a Grundfos UPM3 and it's just running on the lowest setting. Aiming for a delta of 7c. Link to comment Share on other sites More sharing options...
nikolay Posted January 9 Author Share Posted January 9 It turned out the pump works at the fastest speed. I am surprised and am no longer confident in the flow meter values. I closed all zones and left only the short bathroom and it was doing something like 4.5 L/min. I don't know what flow values to expect; the pump does not have modulation; it is working at a constant speed as selected by the switch. If I want to run with higher flows, I need an additional pump, or my system is clogged. I noticed when the heat pump produced DHW, it could reach 6C delta T even with higher water temperature but not when the water went to the floors. So, I am confused and do not have the experience to estimate if these flows are low for this pump... Everyone is speaking about 1-2L/min but I can't reach even 1L/min for these 8 zones. Or it might be the flow meters are totally wrong and need cleaning. Also another thing - Can be that the system is clogged somehow, for example clogged plate heat exchanger? I found another surprise - the flow switch for protecting the pump was bypassed by someone, and when measured with a multimeter, it is not working. It has a setpoint of 420L/h, which is about 7L/min, and if I can't reach 7 L/min, why is that? The filter on the return flow was cleaned 1 month ago and it was pretty dirty... Link to comment Share on other sites More sharing options...
nikolay Posted January 12 Author Share Posted January 12 Ok, I found the reason for the low flows. Mesh filter was completely clogged with some black dirt, although it was cleaned 40 days ago. We moved on a month ago, and the filter cleaned before that, but it was not so dirty. For the last 2 years, this apartment was not inhabited permanently, so I suspect the corrosion particles come from DHW tank serpentine... Â Â Link to comment Share on other sites More sharing options...
marshian Posted January 12 Share Posted January 12 is it magnetic?  I wonder if it had rads before UFH and that's a hangover from magnetite that had built up previously in the system  https://vexoint.com/what-is-magnetite-and-how-to-stop-it/  I have a magnetic filter in my CH/HW Circuit but the circuit is pretty clean and in the 6 months between cleaning it picks up very little  Link to comment Share on other sites More sharing options...
nikolay Posted January 12 Author Share Posted January 12 I guess it's magnetite, but the filter is a mesh one and not magnetic. It's UFH and no radiators before except towel radiator in the bathroom. Also water is diverted to DHW tank serpentine for DHW production. The tank is this one, 300L: https://burnit.bg/en/project/solar-water-heaters-sn/ . My biggest suspect is the serpentine in the tank, but it might also be the towel radiator corrosion. I have to consult with a plumber... Link to comment Share on other sites More sharing options...
JohnMo Posted January 12 Share Posted January 12 34 minutes ago, nikolay said: DHW tank serpentine Very unlikely to carbon steel, will be copper or stainless. Towel rad strong suspect 1 Link to comment Share on other sites More sharing options...
nikolay Posted January 13 Author Share Posted January 13 DHW tank is low-carbon steel with titanium enamel. Not sure how fast this one corrodes. The whole system was installed approximately 7 years ago, and the apartment was almost uninhabited for the last 2 years. If the problem is the bath radiator then it will be cheaper to replace it. Link to comment Share on other sites More sharing options...
JohnMo Posted January 13 Share Posted January 13 Normally they have an anode to stop corrosion, when there is carbon steel in a cylinder. These are replaced every couple of years. Maybe the anode has depleted and you have plenty of corrosion going on. Link to comment Share on other sites More sharing options...
nikolay Posted January 14 Author Share Posted January 14 Isn't the anode protection protecting only the DHW water side, as the inside of the serpentine is another water circuit? Link to comment Share on other sites More sharing options...
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