Maxwell_Montes

So my UFH only gets warm once the thermostat calls and the pump is off. my plumber has tried to convince me that UFH is slow to heat up and that’s what I’m experiencing. This is not the case. When it’s on, the flow pipe is hot and the return pipe is cold. As soon as I stop it calling for hot water, the return pipe gets warm and the floor starts to heat, but if I left it on all day it would stay cold. any ideas what is causing this behaviour? I’ll upload a picture as the manifold isn’t standard, showing how the hot water is flowing. Although it isn’t the usual configuration, supposedly it *should* work but I wonder if the flow valves being on the return arm is the issue(?)

I've moved it from the area pre-flow meters to the area circled in green. That manifold seems to be about the same temperature as the bottom half, so I'm not sure how much impact this has. Would the area circled in pink (return to the boiler), be too far over for it to mix effectively?

Yes, the first response mentioned this. It might be a little while before I can get someone to swap them around. I have moved the sensor to the position just after the pump connects to the top manifold for now. Do you think this will help until they are inverted? Is it a case of taking the manifold off, or could the flow metres and valves just be switched over? From a technical perspective, does having the flow from top to bottom, or bottom to top make any odds? (my guess is yes, as I imagine the flow meters are unidirectional)

Fair enough, I wondered if it was pulling it across the flow meters, rather than forcing it down the correct pipes, creating a reverse flow (if that makes sense)?

I'm not sure, as it was installed by the previous owners. I guess it's not that thick as the temperature on it changes under 10 minutes. I was brought up in a house with UFH, so I understand the principles of it working differently to radiators, and that it will heat up slower BUT I also understand enough to know something is amiss with the way something in the manifold is behaving. Annoyingly, keep getting similar responses from plumbers, assuming I don't know how it works and they don't even want to look at it. I wondered if this forum might be able to give me some suggestions that I can pass on

Is that the Pump Orientation thread? Looking at it, their supply and return pipes are on the same side as the boiler, whereas mine isn't, which is more the question of it affection the fuctionality. I understand this concepts, its more of a case that the heating up of the floor, once it stops, is very sudden. If it was hours later, then sure but its less than 10 minutes and it's up by 5 degrees or more. The sudden change in the return pipe temp also suggests something odd happening

Brilliant news, thank you for shedding light on this - lots of setups have the pump at the start but I also noticed they looked different elsewhere. It's interesting you mention the sensor. I took it off to see if that held any answers and interestingly the return started to heat up, so could it be the sensor overheating and closing off as it's so early in the chain?

Firstly, I'm new to the forum, so hi! I have been battling my UFH for a few years - I think the original owner did it wrong, annoyingly he has a habit of getting it wrong at both ends so sometimes stuff works. After a few months we started on the kitchen, the plumber got the lay of the land and pointed out a few bits he'd like to fix on it - fast forward, it still doesn't work well. the bit with the actuators on gets got first, making me think the flow is reversed the bit with the flow meters on is very cool - I thought this could be a blockage, but I noticed they warm up when the system stops calling and the pump turns off - not sure if this is a pump thing or a thermostatic valve thing whilst the floor isn't cold cold, its just warm enough when the system runs but I'm doing it for hours to get to 24c, but as I said when it turns off, that temp creeps up for a bit. I looked at the data sheet for the valve and sensor, this seems to suggest that the valve should be mounted on the return and the sensor on the flow side, this isn't what's going on in my system but I'm not sure if this would stop anything getting hot as I can feel both sides of the manifold are hot. I've included a diagram of what I almost certain is going on. Any suggestions about the return warming up once it turns off would be ace. TIA