ST3VE78

I can see one pump for the DHW and another after the buffer for the ufh. Both on the flow side. These are both bigger compared to the ones on the manifolds. I can’t see how this would stop the heat pumps getting out of the 20’s when it’s cold out tho. Above 5 degrees the system works well.

I’ll look at getting 1 bigger modern one I think. I just think these pumps are not designed to handle the cold weather. Even if I only turn 1 room on the flow temp stays low. It’s 8 degrees out now and the floor has warmed to 40 degrees no problem and it’s toasty here with room stats on 20. Heat pump have turned off too. Below 3 deg and I may as well turn them off and plug in electric blow heaters ☹️

No is the answer Dave. They have always struggled when the outside temperature drops. When it’s warm out your feet are toasty on the ufh. Because the company went bust soon after I fitted them and lack of knowledge in my area with ashp’’s I’ve just put up with them. It took me nearly 2 years after fitting to get someone who was MCS accredited to sign them off so I could receive the grant. I have not checked the the heat exchangers steamy tea but I did have a local guy come to look at them 2 years ago as 1 stopped working. It turned out a wire had burned the plastic in the big red on off switch. There are 2 pumps in the drawing. One above the other. I presume they both supply and return as I can have one to go off at say 30 when it’s warm out and the other will take the water to 35+ easy. I think I’ve been sold a duff system by the look of it. As andehh said, these ashp’s have come along way in the last 10+ years so I’d like to think there’s something out there that would work well with the rest of my system.

When my architect completed the SAP he said space heating kWh per year 21,158 and water heating kWh per year 2,578. When it was -8 the other week, the heat pumps wouldn’t put out more the 19 deg 🥶 I’ve been meaning to paint them. Only 2 years ago I put the covers above them. Bit like shutting the stable door after the horse has bolted 😂

More insulation is not possible sadly.

That’s my set up. The temp will go up to 35 easy enough today as it’s about 9 deg. It’s only just came on as it does the DHW 8-10 am.

Hi Dave, have read a lot of your posts over the years of researching my pumps, all good may I add, My DHW has an internal 3kw immersion that I have a timer on that I set through the winter. It is separate from the heat pumps. When it’s really cold I just heat the DHW from the immersion only so the heat pumps can focus on the ufh. Not that that makes much difference tho. The pumps do start to defrost when it gets cold, I’m thinking around 7 deg.

I have 100mm insulation under the ground floor with 70mm liquid screed. Other 2 floors I fitted batten and put the pipes in 25mm of screed. The house was built over 10 years ago and built to a better spec than building regs. When the water comes out of the pump at 35 degrees the house warms well and keeps the heat. In cold weather the 25 deg that comes out of the pump is too low to put any heat into the house. The temps I get from the manifolds in the house are the same as what the heat pump says so there’s not really any heat lost through the buffer. Ashp’s Have come a long way since I the ones I have so I think it’s time for an upgrade. Any recommendations on new ashp or reliable firms that deal with these. I have all the details from the previous install.

I averaged the last 9 years between 18000 and 20000 kw per year, that was with the room stats set to 22 deg. I lowered the room stats to 20 this year because of the rise in electricity prices so hopefully I’ll be closer to 15000 kw this year.. For 10 months of the year the system is great, but the other 2 months when heat is needed, it’s rubbish and costs a fortune.

As peter said, no weather compensation. They do run in tandem and the total floor space is 358 m2. After years and years of researching these pumps, the only I can find is that they are good for heating swimming pools. I would like to think the insulation is really good. I’ve insulated and put 6mm ply on all the stud walls and In Between both floors. The main issue is the heat pumps not putting out over 25 deg when it gets cold out. I have even tried turning most of the room stats off so there is less water to warm but that doesn’t make any difference. When I open the side of the ashp, the only thing I can do is adjust the ufh temp up to a max of 55 deg. I have tried this but it doesn’t make any difference. There is no option for me to turn an internal immersion heater on.

Hi, I’m having a dilemma with my heating system. So over 10 years ago We build our own home and my wife decided she wanted ashp. A firm that went bust not long after we had the system designed a system that consisted of 2 x Calorex aw9002 ashp’s, a 240l buffer tank, a 300l DHW cylinder and ufh over 3 floors with 100mm centres. The flow temp for the ufh is set to 35 and when outside temperature is above 5 degrees the house will warm to 22 deg no problem. When the outside temperature goes to 3 deg or lower, the flow temp struggles to get over 25 deg and so the room temps struggle to get over 19 deg. This is confusing to me as the pumps will warm the DHW up to 60 deg no problem but struggle to get the ufh temp over 25. So, I’m debating getting a new ashp that will warm the water to a min of 35 deg when outside temp is below 0 deg or just get gas.