Underfloor heating issue in newly tiled bathroom

[rangor gubbins]

That loop is the least efficient way to run UFH. Snail shell pattern means a good even spread of heat. This sort of snake pattern means that you are grouping lots of heat together, not spreading it out.

We've used the same loop pattern in the rest of the house and it works fine. For such a short run of pipe i wouldn't have thought the loop pattern would make much difference, the flow and return temp doesn't feel all that different. The pipes are sitting in 70-80 mm of screed, so there is lots of material there for the heat to spread out into. Either way its too late now to change the pattern!

 

[henry hoov3r]

Are the flow and return temperatures different from the others on the circuit? Are they cooler or roughly the same?

 

[rangor gubbins]

flow and return temps feel the same as other loops, and also hard to say whether there is difference on the flow and return. I'm planning on getting a laser temp sensor or thermal camera to take some surface measurements.

 

[jpaul]

. There is 100 mm PIR insulation below that though, rather than only 25 mm in the shower room

is that 4x ratio indicative of relative additional losses shower room would have , so when system has stabilized you'd have to be providing more Watts/m2,
and maybe accept that during warm up you'd have to run shower zone inefficiently with higher return rates.

Is shower room and kitchen on same foundations - not an extension.

I might have a play with a ufh simulator and configure with the layers you have eg. https://www.htflux.com/en/

 

[rangor gubbins]

is that 4x ratio indicative of relative additional losses shower room would have , so when system has stabilized you'd have to be providing more Watts/m2,
and maybe accept that during warm up you'd have to run shower zone inefficiently with higher return rates.

Is shower room and kitchen on same foundations - not an extension.

I might have a play with a ufh simulator and configure with the layers you have eg. https://www.htflux.com/en/

The shower room is in an extension.
I think you're right, the problem is likely to be because there isn't enough insulation below the screed, and also I think the screed is too thick or rather the pipes are too far away from the tiles.
So now it's a case of ripping it all out again or living with it.
There is also an electric towel radiator in the room, so that can be used more to warm the room and I may swap it for a larger radiator.

 

[dirtychinchilla]

We've used the same loop pattern in the rest of the house and it works fine. For such a short run of pipe i wouldn't have thought the loop pattern would make much difference, the flow and return temp doesn't feel all that different. The pipes are sitting in 70-80 mm of screed, so there is lots of material there for the heat to spread out into. Either way its too late now to change the pattern!

flow and return temps feel the same as other loops, and also hard to say whether there is difference on the flow and return. I'm planning on getting a laser temp sensor or thermal camera to take some surface measurements.

For your flow and return temps, you should be maximising the temperature difference. It basically just means you're using the heat properly. There's a natural limit though. If the flow is 45C and the room is 21C, you'll never get your return below 21C and probably wouldn't get it that low anyway.

The reason for the snail loop arrangement is that you end up with a flow and return pipe next to each other, so you get good heat distribution. If you run them as your installer has, you risk the room end closest to the flow being warmer than the end closest to the return. Having said that, it may not matter if your rooms are very small. https://www.multipipe.co.uk/ufh-patterns/

 

[b0rn2sk8]

How is the rest of the UFH set up and are you getting a decent flow rate?

I’m pretty sure with an ASHP you want to be running it entirely open loop with no zoning or hydronic separation for maximum efficiency.

 

[ANDARIAL]

Could there be a part blockage in the ufh pipework?
And could you disconnect the pipework to the shower room only and flush it through with a pump or mains water?

 

[PermaChanged]

I’m pretty sure with an ASHP you want to be running it entirely open loop with no zoning or hydronic separation for maximum efficiency.

This is true!

Another question to add to the mix, how was the rest of the floor which is working as anticipated screeded?

I assume bathroom is a standard sand and cement screed, and the rest of the flooring was a liquid flow screed?

 

[JRJ]

@rangor gubbins are you sure the loop is full, the flow meter is either empty or the flow is set too high

 

[rangor gubbins]

How is the rest of the UFH set up and are you getting a decent flow rate?

I’m pretty sure with an ASHP you want to be running it entirely open loop with no zoning or hydronic separation for maximum efficiency.

In The rest of the house there is either a single or double loop per room, each with its own thermostat and controller (heatmiser). There's a manifold on the ground and first floor. Both fed from the same buffer tank, heated by the ASHP.
Now I think about it, the ground floor rooms do have snail loops, and the first floor have up and down loops on spreader plates with 25 mm PIR insulation underneath with rock wool below that. All of this works great. The rooms are all warmed nicely. Our bathroom on the first floor is set to 22 °C and the UFH manages this fine.
It all seems pretty efficient too as the house in total uses about 7000-8000 kwh per year and is a 4 bed detached house.

@PermaChanged the rest of the house was done 5 years ago but I think it was all sand and cement screed, not liquid.

 

[rangor gubbins]

@rangor gubbins are you sure the loop is full, the flow meter is either empty or the flow is set too high

Well this could be part of the problem. There is definitely air in the flow meter of the new loop. Engineers have been out to bleed the system and got lots of air out. Maybe there is still air in the new loop. The UFH is booked for a service and full system flush in a couple of weeks, so I hope they can get any residual air out.

We've tried with the flow set to max (4.5 l/min) and half that. Still the same result.

 

[rangor gubbins]

Could there be a part blockage in the ufh pipework?
And could you disconnect the pipework to the shower room only and flush it through with a pump or mains water?

Its possible there is a blockage but I don't think so as the flow and return temps seem fine.
When the system gets serviced I'll ask if they can flush it.

 

[JRJ]

Well this could be part of the problem. There is definitely air in the flow meter of the new loop. Engineers have been out to bleed the system and got lots of air out. Maybe there is still air in the new loop. The UFH is booked for a service and full system flush in a couple of weeks, so I hope they can get any residual air out.

We've tried with the flow set to max (4.5 l/min) and half that. Still the same result.

Try it at 1.2-1.5, did you get flow calculations for each loop? Also check the speed on the pump.
Air in the system is not good and you need to work out where that's coming from, also check if the auto bleed valve is working properly as that should help avoid air locks.

 

[rangor gubbins]

This is true!

How is the rest of the UFH set up and are you getting a decent flow rate?

I’m pretty sure with an ASHP you want to be running it entirely open loop with no zoning or hydronic separation for maximum efficiency.

Why is it better to have the whole system running open without zoning? Why would it be better to heat parts of the house that aren't being used? Or to heat the whole house to the same temp?

 

[rangor gubbins]

Try it at 1.2-1.5, did you get flow calculations for each loop? Also check the speed on the pump.
Air in the system is not good and you need to work out where that's coming from, also check if the auto bleed valve is working properly as that should help avoid air locks.

The air came from when they put the new loop in. I think they connected it to the manifold without filling it.
Will try lower flow rates.

 

[JRJ]

The air came from when they put the new loop in. I think they connected it to the manifold without filling it.
Will try lower flow rates.

Just checked the images and there's no auto bleed valve on the manifold, might be worth asking them to fit one.

 

[jpaul]

in addition to disabling shower thermostat , can just disable all other zones and see/flir how long shower takes to heat, in best of cases

(not sure, too, how running system open loop could be optimal- the zones like radiators have their individual power requirements needing valves (picvc ?) to distribute the heat proportionately to them,
pumps probably got to be powerful enough too to push water through the system and the longest zones,
freeware flow calculation software would be good,
although this thread presents some ideas on calculations https://forum.buildhub.org.uk/topic/17437-heating-design-calcs-and-process-ashpufh/page/3/
)

 

[b0rn2sk8]

In The rest of the house there is either a single or double loop per room, each with its own thermostat and controller (heatmiser). There's a manifold on the ground and first floor. Both fed from the same buffer tank, heated by the ASHP.
Now I think about it, the ground floor rooms do have snail loops, and the first floor have up and down loops on spreader plates with 25 mm PIR insulation underneath with rock wool below that. All of this works great. The rooms are all warmed nicely. Our bathroom on the first floor is set to 22 °C and the UFH manages this fine.
It all seems pretty efficient too as the house in total uses about 7000-8000 kwh per year and is a 4 bed detached house.

The general consensus is building around minimal zoning to get the most out of a heat pump.

Having less zones means to can use lower flow temperatures. This is because if you zone off a room and set it to a lower temperature or off, the adjacent room which you are heating will now have a higher heat loss because they will lead heat into the adjacent rooms. To compensate for this, the flow temperatures need to increase to account for this additional heat loss.

The efficiency curve on a heat pump is fairly brutal and that is before considering the additional cycling that can tank efficiency further.

The summary, 3rd party controls typically reduce efficiency. You'll get better SCOPs out of a heat pump by running it with minimal zoning and controlling the temperature using the weather compensation curve on the heat pump controls.

Have a look at this:

HeatGeek Guide: Why Not to Zone Heat Pumps or Boilers

Get a deep understanding about why you should not zone heat systems from the HeatGeek Experts.

www.heatgeek.com

Why NOT to ZONE your heating!!.. (SHOCKING RESULTS!!)

We take a look at a section from our online heating design training which forces us to question just how efficient zoning heating systems is. Using a heat pu...

www.youtube.com

When Should I Zone A Heating System? | Toolbox Talks

Want to know why we suggest not to zone? Watch this: https://youtu.be/zpTVIeUh04E → More free content: https://www.heatgeek.com/→ COURSES - Become a MASTER o...

www.youtube.com

How To Install an Ultra Efficient Heating System - Heat Pump + UFH.

#heatpump #airsourceheatpump #vaillant In this video, I take you through a full installation of a heating system with an air source heat pump and UFH through...

www.youtube.com

The buffer or low loss header is a more complex calculation, it depends on the heat loss and the size of the pipes in the house, someone needs to do the maths. A buffer or low loss header will reduce the efficiency of the system but it may be required, most people don't need them but its entirely dependent on your property. Manufactures say you should install them but they are effectively a get out of jail free card and protects against a dodgy installation because they will always keep the heat pump happy regardless of whether they need one or not. The issue is that they come at the expense of efficiency, space and installation costs if they are not needed.

 

[jpaul]

(
yes like with smart (hive&co) trv's which is also a type of zoning these produce inefficiencies for gas systems too - unless you have pre-characterised settings
or some wonderful AI/learning system (temperature compensation ...).
When you disable zones the system is no longer in the mode it was balanced during initial setup, you get inefficiencies from wrong flow rate, drops and inefficient non-modulated boiler solicitation,
so you may be better running no zone.
PICV's in the principal distribution zones (like upstairs and downstairs) or ability to override (supposedly) smart trv with a (pre-characterized)valve opening setting, which some of their UI's provide,
seems like best bang for the buck.
)