Chriss Posted January 7 Share Posted January 7 I have underfloor heating running off a 15kw heat pump. The heat pump runs fine when the 6 lines are all fully open but the flow is obviously running too fast for the floor to heat properly. The problem is when I adjust the flow valves to reduce the flow the heat pump sstops straight away and says flow fault. I have a circulation pump on the manifold and have added an extra circulation pump. Would adding another circulation pump at the heat pump itself help solve this issue or could it be another problem. Any help would be greatly appreciated. cheers Link to comment Share on other sites More sharing options...
Conor Posted January 7 Share Posted January 7 How many zones, what's your flow temp, how are they controlled, do you have a buffer tank? It sounds like pump is oversized. Link to comment Share on other sites More sharing options...
Chriss Posted January 7 Author Share Posted January 7 I have 7 zones, no buffer tank yet I hope to sort one out next year I just don’t have the time this year. Temperature on heat pump set at 40. I don’t think it is over sized as I worked out the cubic metre of the house before I bought it and if anything it’s slightly undersized. Link to comment Share on other sites More sharing options...
JohnMo Posted January 7 Share Posted January 7 Basics are Heat pump will have a defined minimum flow rate. That sized heat pump could be around 25L/min or more. If you are trying to operate without a buffer and you have loops closed, or part closed - then no chance. UFH basics Heat output is linked to the mean flow temperature, the higher the flow rate, the smaller the dT so higher the output. You are stating the opposite? 6 loops will only output only part of the load your heat pump is putting out. Something sounds odd. Can you explain your full system? It is more likely your heat pump is cycling, so not transfering the heat needed. Too big for the duty it's being asked to do. 1 Link to comment Share on other sites More sharing options...
Conor Posted January 8 Share Posted January 8 12 hours ago, Chriss said: I have 7 zones, no buffer tank yet I hope to sort one out next year I just don’t have the time this year. Temperature on heat pump set at 40. I don’t think it is over sized as I worked out the cubic metre of the house before I bought it and if anything it’s slightly undersized. The constraining factor will be the water volume and flow rate. A 15kW heatpump will require a large volume and flow rate. 7 zones/loops (assuming max 100m each) is too small. Your pump can't modulate down enough when you reduce the flow rate. We've 15+ loops for our 9kW heat pump and a buffer. Link to comment Share on other sites More sharing options...
Chriss Posted January 8 Author Share Posted January 8 Thank you for the replies I really appreciate it. I sized the heat pump to the cubic metre of the house as I was told to by a couple of people. The house is 125 sqm but with huge ceilings. I didn’t know the amount of zones would be a factor also. If I was to add a buffer tank, how big of a tank would I need to buy and would I then be able to regulate the flow at the manifold. cheers Link to comment Share on other sites More sharing options...
JohnMo Posted January 8 Share Posted January 8 You size heat pumps based on heat demand, those that say you size based on your house size, are not people to listen too, for any sort of advice. You need to calculate heat loss first. You need to find out your heat pump minimum output. You then size based on the min modulation output and system minimum capacity and heating requirements. The min capacity is the smallest zone capacity. Would help if you share as much information as you can about heating system, ASHP and house. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 9 Share Posted January 9 House volume is often used as a proxy for heat loss, and I have known a salesman that just counted the number of windows and used that (500W per window I seem to remember). Take two houses with the same volume, one terraced over 3 floors and the other a detached over 2 floors. The thermal losses will be very different. Link to comment Share on other sites More sharing options...
Chriss Posted January 9 Author Share Posted January 9 I have been renovating an old barn in France, 125sqm. The kitchen sitting room and 1 of the bedrooms have large ceilings. The walls in sitting room and bedroom have been pointed, so no insulation on them. My sons bedroom is really well insulated everywhere as is the bathroom and en-suite. We have large window doors throughout the house. I will attach some pictures. I bought my heat heat pump from a website in the uk Dream heat pumps, as it was reasonably priced. Unfortunately I don’t have a never ending pit of money and couldn’t afford an expensive heat pump. I will also add a picture of the specs of the heat pump taken from the website. cheers Link to comment Share on other sites More sharing options...
ProDave Posted January 9 Share Posted January 9 On 07/01/2024 at 18:27, Chriss said: I have underfloor heating running off a 15kw heat pump. The heat pump runs fine when the 6 lines are all fully open but the flow is obviously running too fast for the floor to heat properly. Having the water flowing too fast won't make the floor heat any less well. You need an automatic bypass valve at the far end of the flow / return loop to ensure water always flows even with one or more of the loops shut down. 1 Link to comment Share on other sites More sharing options...
JohnMo Posted January 9 Share Posted January 9 When I made some mods to my heating system and I added a buffer. Pretty easy to do. I used a 50L cylinder across the supply and return, so no additional pumps required. Your heat doesn't modulate, so needs some provision to dump loads to get a decent run time (about 10 mins). Link to comment Share on other sites More sharing options...
Chriss Posted January 10 Author Share Posted January 10 I have been renovating an old barn in France, 125sqm. The kitchen sitting room and 1 of the bedrooms have large ceilings. The walls in sitting room and bedroom have been pointed, so no insulation on them. My sons bedroom is really well insulated everywhere as is the bathroom and en-suite. We have large window doors throughout the house. I will attach some pictures. I bought my heat heat pump from a website in the uk Dream heat pumps, as it was reasonably priced. Unfortunately I don’t have a never ending pit of money and couldn’t afford an expensive heat pump. I will also add a picture of the specs of the heat pump taken from the website. cheers Link to comment Share on other sites More sharing options...
Chriss Posted January 11 Author Share Posted January 11 Thanks for the replies, I really appreciate it. My partner was in touch with an underfloor heating and heat pump specialist yesterday who explained everything. Basically we have had shit advice from the start. He confirmed that our pump is way oversized, he advised on the exact pump to get and where to find it for the best price. Pretty gutted but at least we know now and can get it sorted soon. Looks like the kitchen will have to wait! cheers Link to comment Share on other sites More sharing options...
Andehh Posted January 11 Share Posted January 11 (edited) This building house malarkey is a tough gig, we've all been in your situation in one form or another! For me it was a shyster of an electrician taking us for a ride to the tune of several grand! Edited January 11 by Andehh Link to comment Share on other sites More sharing options...
Nick Laslett Posted January 11 Share Posted January 11 On 10/01/2024 at 01:22, JohnMo said: When I made some mods to my heating system and I added a buffer. Pretty easy to do. I used a 50L cylinder across the supply and return, so no additional pumps required. Your heat doesn't modulate, so needs some provision to dump loads to get a decent run time (about 10 mins). Hello @JohnMo, is the buffer tank a recent change? I really appreciated your ASHP commissioning topic, lots of useful information. How much water volume did you have in your UFH pipes? Link to comment Share on other sites More sharing options...
JohnMo Posted January 11 Share Posted January 11 11 minutes ago, Nick Laslett said: Hello @JohnMo, is the buffer tank a recent change? I really appreciated your ASHP commissioning topic, lots of useful information. How much water volume did you have in your UFH pipes? I have around 50 to 60L in total. Recent change. In an attempt to run the system hotter to get better performance out of the summer house UFH without overheating the house. I made the following changes. Added a thermostatically controlled ESBE mixer and pump to house UFH - this is generally dropping flow temp down to 29 from 34 so spends most its time less than 50% open, it also close fully. This in effect reduces the system capacity. Added a buffer across the supply and return piping, this acts a min flow valve, with 50L capacity. UFH in summer house is still rubbish, so now installing a fan coil, which generally requires around 35 Deg flow temp. Things still a little fluid, but will look to operate, as such 1. Single house thermostat 2. ESBE mixer, if no heat demand, flow temp 29, if house thermostat has heat demand, flow increases to 35. 3. Single flow temp of 35 degs for heat pump (may alter but will see how things go) 4. Fan coil, Salus self balance actuator to give a 7 deg delta across fan coil and shut off flow as required. 1 Link to comment Share on other sites More sharing options...
HughF Posted February 2 Share Posted February 2 Remove all the pumps, remove the mixers. Straight from the heating side of the 3 port diverter (I assume the heat pump also heats a water cylinder, if not then ignore that last bit) to the ufh manifolds. Open up all the actuator heads and get the heat pump set to around 33 degrees flow temp. Open loop, large connected volume is what you want. Buffers/pumps/mixers and all that stuff aren’t required in a full ufh setup. Link to comment Share on other sites More sharing options...
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