You’re planning to refurbish your bathroom. Why not replace the heating system while you’re at it? You can also install the modular floor heating in individual rooms. So, out with your old radiators and in with floor heating!
The VarioPump distributor station or Pump microstation with pump connects the new low-temperature floor heating with the existing high-temperature heating system.
Drywall construction floor heating reacts very quickly. Thanks to their low construction height of 20 mm, the heating pipes are close to the floor covering. This means that the floor heats up quickly. This makes the VarioComp floor heating system excellently suited to rapidly changing room air temperatures, such as large glass surfaces, or many people in a single room, wood burning stoves, kitchens, etc.
The room stays cosy and warm – even at lower flow temperatures.
Due to the quick response time of the VarioComp the room air temperature is easier to regulate using a room thermostat than with screed floor heating.
You can lay whichever floor covering you like, whether it’s stone, laminate and multi-layer parquet, ceramic tiles, linoleum or carpet. It’s important that the floor covering is suitable according to the manufacturer’s specifications.
In general, the thicker the covering, the slower the heat transfer, since the floor has to be heated up for longer. For example, tiles and natural stone have a high thermal conductivity and quickly radiate heat into the room.
Floor heating is a low-temperature system. In other words, the heating pipes are laid over the entire floor area. The system can operate with low flow temperatures. Depending on the outside temperature, it is sufficient when water is heated to between 26 and 38 °C. By comparison, conventional radiators require a flow temperature of up to 60 °C. The reason for this is that due to their small surface area, they only radiate heat into the room at certain points.
The radiant heat also lowers heating costs: the room air temperature can be reduced by up to 2 °C compared to convection heating systems. And we still feel comfortably warm. Every degree less saves around 6% heating costs per year.
I'm really happy with my system - Cool Energy ASHP, UFH in a liquid screed, 300L hot water tank, Salus auto-balancing actuators and Wunda controls.
All works as it should, running at about 35 degrees on the UFH.
My only issue is the Wunda controls. I have the control units (x10 - it's a big house) in my plant room and temp sensors in the walls with a mesh type wall mounted panel. I've calibrated the Wunda controllers so they are pretty accurate to room temp. BUT, the control units have a min temp trigger 0.5 degrees above / below target temp. So this means if target is 22 degrees, the actuator(s) will be opened/pumps triggered at 21.5 degrees and stay this way until 22.5 - this doesn't sound bad but the reality is that the temp will then carry on increasing for at least another 0.5-1 degree due to the continuing heat coming from the screed.
What are the best options? Things I can think of:
1) Replace all (or some) controllers with more sensitive ones. Ideally just cutting out at the target temp would be a big improvement
2) Use a lower UFH temp, the Wunda provided manifold I don't think goes much below 35 degrees
3) Anyway to get my Wunda controllers to stop heating at the target temp and not go on for another 0.5 degrees
Nothing sounds cheap or easy apart from 3 but that may not be possible
HI thanks for comments @joth @dpmiller
I should have maybe said the ASHP feeds a buffer. We have 4 manifolds, 1 per floor (we're on a hill), flooring is all porcelain laid on 55mm liquid screed with insulation beneath (pretty standard)
ASHP set temp is 40 and it starts to heat (from memory) when buffer temp drops to 36 and stops at something like 43 - it was a bit arbitrary choosing the range
The manifold for the largest floor was at 35 but I put down to the lowest on the blender which looks like 30 but is not marked - I guess as they lose accuracy maybe that low
Increasing the temp slightly on the thermostat doesn't really help I think as the issue with the thermostat is that it triggers a call for heat when 0.5 below target temp and only stops when 0.5 above target temp which doesn't sound like it should be an issue but to fine tune things I'd rather have it stop sooner. By lowering the temp at the manifold
May experiment next week with the ASHP temp being set to 30 (with something like a range of 26 to 34) - I suppose an issue then may be that by the time a thermostat calls for heat it will then take somewhat longer for the eventual temp change but maybe that won't be noticable.
We run ours differently as well. And our system is slightly different - a larger buffer tank and no auto-balancing actuators (there's a recent thread on whether these are actually useful for ASHPs with UFH).
Link to Mufeng
The other main difference is that our UFH loops are incorporated in the insulated slab - so probably our system is slower to heat up and cool down than UFH in screed.
We have 12 loops and 3 zones with Tado thermostats - and just like you @Adam2 the thermostats tend to cycle on and off which means the ASHP cycles too much.
We've solved this more by chance than good management. We're on Octopus Go, so we scheduled the thermostats to 22 degs from 00:30 to 04:30 on the 7p tariff. This was fine in the autumn and I could see from some monitoring of the various temperatures that the ASHP runs continuously for 4 hours and the slab is loaded with heat. As things got colder, I added another scheduled period from 15:00 to 19:00 again at 22 deg. This didn't cause cycling most of the time - the exceptions were on sunny days where we get a lot of heat into the house from the large south facing windows. Obviously also, when it's really cold the HP goes through it's defrost cycles, so doesn't run continuously. When the thermostats aren't scheduled for 22 degs, they're in frost protection, so no chance that there will be a call for heat. I should add that we use solar PV and the 7p tariff for DHW, so the ASHP is on Heating only.
So basically, we've almost got round the fact that the thermostats are less than ideal with a HP through scheduling things. I would really like though to have a much wider window between the call for heat and the thermostats saying they are up to heat.
One idea from another forum would be to use the wiring to the thermostats as the wiring for DS18B20 temperature sensors hooked up to a suitable microcontroller and have that switch the call for heat to the wiring centre. It could even be done with wireless temperature sensors like the Sonoff ones (there are plenty of other makes) which are pretty cheap. Obviously this isn't an off the shelf solution but should be quite easy to implement.
Simon
On 01/02/ at 23:45, Adam2 said:What are the best options? Things I can think of:
1) Replace all (or some) controllers with more sensitive ones. Ideally just cutting out at the target temp would be a big improvement
2) Use a lower UFH temp, the Wunda provided manifold I don't think goes much below 35 degrees
3) Anyway to get my Wunda controllers to stop heating at the target temp and not go on for another 0.5 degrees
Nothing sounds cheap or easy apart from 3 but that may not be possible
Another option Adam that I've considered is to add a delay timer into the thermostat circuits. These are the kind of things that keep a bathroom fan running when you've turned off the light.
Although we've mostly overcome the cycling caused by the thermostats turning on and off too much/quickly with the way we're scheduling them if we had a delay time in the circuit, then it would prevent the call for heat being switched off by the thermostat after a few minutes. For your situation, you could maybe lower the target temperature and make sure with the delay that the ASHP runs for at least say 30 minutes. So ensuring the HP runs more efficiently.
Simon
great thanks, so much useful info
Yes I do have the regular manual - only query was the existence of something else that would, for example, have explained that putting the fan mode into Low Speed would have an impact on the temp setpoints as this is not logical (to me at least)
Have changed fan mode to Day and brought down the heating set point and increased the overshoot as suggested. Essentially the blending valves won't be doing much unless there's an issue with the ashp overheating the buffer
With the buffer tank and my smallest zone being 35m then I don't think we have a high probability for any short-cycle issue but not sure how to easily monitor that aside from watching what happens on the app for a while
Ideally you’d ditch the buffer and allow the heat pump to run direct into the ufh circuit, gaining considerable efficiency there. The industry is moving away from the buffer/llh/plate installation scheme and moving towards direct installations, as a drive to increase efficiency. Plenty of articles from Brendon Uys on LinkedIn about this (and the renewable heating forum)
You then wouldn’t have a disconnect between the heat generator and the heat consumer. The issue now present is that unfortunately the Cool Energy unit doesn’t have any idea of room temperature and thus cannot do load compensation.
You could however use the room stats to drive the call-for-heat input on the heat pump, and use them as hi-limit stats. Once the weather comp is set correctly then the internal Temperature should stay consistent. The high limit stats would take care of any solar gain.
Remember, not many heat pumps actually have load compensation, for some reason. LG and Mitsubishi are the only two that I remember.
tl;dr - your weather comp is set too high.
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