UFH flow temps, wood burner and store

Greenfish

What temps do people feed their UFH? I am particularly interested in systems heated by WBS via thermal store (like mine). Still trying to get my head around my UFH unresponsiveness, any experiences others can share would be interesting.

Triassic

Mine is set to control at 45deg C.

Triassic

Posted By: GreenfishStill trying to get my head around my UFH unresponsiveness,

How quick do you expect it to respond?

borpin

It is all about how much heat the rooms needs at a given time. I run mine relatively low normally (about 24deg C) but this winter, as the temp dropped, I have found that I need to increase the temperature to around 28deg C (current) so I have enough heat to keep the room at the right temp (unsurprisingly).

I also tend to run it so the room temp is maintained within a small range 24/7 so only letting the temp drop a degree or so overnight and through the day as at that supply temp the warm up is not responsive. If I run the floor warmer, I find that the controls cannot anticipate the 'over run' i.e. floor hot at point when room air temp reaches the desired level; pump goes off but room continues to heat - over heat in fact, then cannot anticipate the cooling point. I find I then get a big hysteresis that cannot be controlled (too hot or too cold).

I have a Thermomatic EC Home control on my tank which I currently have setup so it provides a constant temp output to the manifold (mixes from different parts of the tank). The UFH manifold itself has a TRV on it which controls the temperature supplied to the floor directly (slightly lower than supply from tank). This tank controller has the ability to control the supply temp from the tank, has some hysteresis learning and could have weather compensation added in (has a timer etc). I think I want to play with this at some point in time and see if I can use that to increase the UFH supply temp when the outside temp demands it.

Greenfish

Posted By: Triassic

Posted By: GreenfishStill trying to get my head around my UFH unresponsiveness,

How quick do you expect it to respond?

Having let the house cool to 16C it has taken 77kg of wood burning 24 hours over a 54 hour period, plus some solar thermal, solar gain, body and cooking warmth etc. less modest DHW use to raise it to 18C. Lounge with WBS much warmer of course. Now waiting to get one room, farthest from the thermal store, to 19C but it sit stubbornly at 18C. Thermal store is supplying UFH at 25 to 30C, any bets how long it will take to get to 19? Outside temps, insulation and thermal mass all contribute of course. Can tie myself in knots doing energy calcs, here I was just wondering how others drive thier UFH.

borpin

Sounds a long time. What is the flow rate of water in the UFH and the pipe spacing may help others comment. Sure there is not an air lock somewhere and the water is flowing? Well insulated and air tight?

Archmoco

I was in the same situation when we first moved into the house, it took a while to get up to temperature.

I found the following helped a lot

Burn only Kiln dried hard wood or well air dried, and check wood regularly with moisture meter. I've temp sensors in the TS so was able to record the Kw output of WBS compared to the advertised figures, amazing the difference
Regular cleaning of the stove including wire brushing the boiler elements
Large interior wood store to keep a good supply of wood

Greenfish

Interesting flow temp range - Triassic at 45, Borpin 24 to 28C. Currently I am running with the blender set at 35 but the supply temp is often lower than that. I have been wondering if the system needed constantly higher flow temps.

Well insulated and air tight?

Yes, and without thermal bypass too AFAICT. Once at a temp the house stays there easily, just slow to rise (or fall).

Sure there is not an air lock somewhere and the water is flowing?

Something I will try to check - actuators behaving as expected, system should be self bleeding, not sure what else I can do?

What is the flow rate of water in the UFH and the pipe spacing may help others comment

Not sure. Pumps set on 2 (3 pumps, one feeder and 2 manifolds), but don't know what flow rate that actually is.

Archmoco - all good advice on wood burning, and we do that. How much heat I am getting from the WBS, and how much is up the flue, is a question. Doing experiments looking at TS temps, wood weights etc., but considering other issues here. I will burn more if I need too, but also wondering about the speed that the system can take that energy out the store.

That room now at 19C and holding happily, but crawled up to that. Morning store temps of around 40C, higher at the very top. Might try for 20C when I burn tonight, but expect it will take a while.

So guys, what UFH flow temp should I be trying to achieve?

Chris P Bacon

Have you got a ir thermometer? I got a cheap one off eBay, it's handy for checking the surface temp of the floor around the house and for measuring the flow and return temps in your underfloor loops. Will quickly show up any problems.

Greenfish

Yes, IR thermometer. Not sure my pipe readings with it are that accurate, but not sure what I should see either. What kind of drop should there be? What temps do you see?

Chris P Bacon

If you put some masking tape on the pipe and aim at that from pretty close then you should get pretty decent readings. My flow temp is normally around 30°C and temp drop on return can be up to 5°C.

Greenfish

Thanks for the temp data Chris. Pipes from manifold are white (Pex?), a metal/plastic composite of some kind. Thought that IR thermometer did better on black, but you are suggesting white tape? Confused!

Sunny day, house nice and toasty. But do I light a fire to heat the TS in case I need to keep feeding warm water to the 19C room. For now all temps are holding stable without any flow.

Chris P Bacon

I think the pex pipes don't need anything added to get a good temp reading. Where I was checking the temp of the copper pipes before the manifold I put a lap of masking tape around the pipes which gave a better reading. Black insulating tape may well do the job, I can't remember who suggested masking tape but I think it was on here.

Gotanewlife

Yes use black tape on anything remotely shinny or white for best reading and consistency for comparisons.