Temporary heat supply for ufh?

[Barryscotland]

Taping and filling meant to be starting next week and would like to get some heat into the house. Has anybody plumbed anything into there ufh pre boiler install? I’ve seen the portable electric boilers but no hire company near us does them. Would a 3kw hot tub heater do anything? Any other easy options? Have a few electric heaters in there now but not really doing much. Our ceiling plasterboard also sat outside for a month and although it looks dry it’s bound to have a bit of moisture in it so another reason to get heat inside if possible 

[Dudda]

You can connect up an external wills heater. They're very cheap, readily available and easy to fit. A few people here have such low heating requirements we actually use these instead of ASHP's. Depending on the house, airtightness and level of insulation it mightn't bring the house up to 21 degrees throughout but it will definitely help drying out and take the cold out of the house. 

[Conor]

We got three cheapy 2kw fan heaters form B&Q last week and just two of them have raised the house temp to 14-15c. The screeders have just turned them all off as they say the screed will dry too quickly on the warmth. 

 

The taping and joining stuff dries out in just a couple days of you leave the windows open. 

Edited November 29, 2021 by Conor

[PeterW]

38 minutes ago, Barryscotland said:

Would a 3kw hot tub heater do anything?

Yes - and they normally have a pump built in. The downside is that you’ll be looking at about 75p/hr or £18/day to run it … 

[nod]

I’d avoid anything that blows 

I use the infra Speedy hire heaters 

30amp plug 

We've been using two today 

Very frosty and -4 outside 

We will topcoat both houses tomorrow 

Then sand and spray  on Monday 

[Barryscotland]

8 hours ago, Dudda said:

You can connect up an external wills heater. They're very cheap, readily available and easy to fit. A few people here have such low heating requirements we actually use these instead of ASHP's. Depending on the house, airtightness and level of insulation it mightn't bring the house up to 21 degrees throughout but it will definitely help drying out and take the cold out of the house. 

Can you send me a link for a wills heater, had a look but can’t find anything, ta

[joe90]

Before I installed my ASHP i just used the back up immersion heater in the buffer tank, yes expensive to run but did the job.

[Nickfromwales]

22 minutes ago, Barryscotland said:

Can you send me a link for a wills heater, had a look but can’t find anything, ta

https://www.ebay.co.uk/itm/283804621436?epid=1155212630&hash=item421412da7c:g:pGoAAOSwu~ReYAxN

 

[A_L]

24 minutes ago, Barryscotland said:

Can you send me a link for a wills heater, had a look but can’t find anything, ta

 

You need to search for 'Willis Immersion'

[Barryscotland]

On 29/11/2021 at 12:46, Dudda said:

You can connect up an external wills heater. They're very cheap, readily available and easy to fit. A few people here have such low heating requirements we actually use these instead of ASHP's. Depending on the house, airtightness and level of insulation it mightn't bring the house up to 21 degrees throughout but it will definitely help drying out and take the cold out of the house. 

I decided for the sake of £40 it’s got to be worth trying so I’ve ordered a Tesla version of the Willis heater. I have an old expansion vessel with filler, bleed point etc on it and the pump is on the ufh manifold. Once I’ve plumbed it up, bled it any suggestion on pressure? Turn the pump as low as it will go and just leave it and heater on 24 - 7? There’s 160m2 so presuming I won’t need to worry about thermal cut outs? Any idea how long it will need to be on till we see any heat in the floor?

Any advice welcomed

[Dudda]

50 minutes ago, Barryscotland said:

I decided for the sake of £40 it’s got to be worth trying so I’ve ordered a Tesla version of the Willis heater. I have an old expansion vessel with filler, bleed point etc on it and the pump is on the ufh manifold. Once I’ve plumbed it up, bled it any suggestion on pressure? Turn the pump as low as it will go and just leave it and heater on 24 - 7? There’s 160m2 so presuming I won’t need to worry about thermal cut outs? Any idea how long it will need to be on till we see any heat in the floor?

Any advice welcomed

About one bar pressure. You won't need to worry about thermal cut outs but you still want to heat the slab up slowly. What I did was left it on for 3-4 hours, then a break for the same and then on again for the same. I built up the temperature slowly. I did have a polished concrete floor and was paranoid about it cracking. The manifold will have a flow and return temperature and use these to judge. Eg If the flow is 16 degrees flow on Monday, 18-20 on Tuesday and 22-25 on Wednesday. Then by Thursday on full time. 

 

Depending on how well and insulated the house is and how cold it is outside, I don't think you'll need to leave it on full time as after a few days the house should be up to 21 degrees inside. My house is very well insulated and the one wills heater heats all 240sqm

[Barryscotland]

11 hours ago, Dudda said:

My house is very well insulated and the one wills heater heats all 240sqm

 

Wow that’s quite impressive 

[Barryscotland]

Anything obviously wrong other than the dodgy wiring? Should I have the flow valves all fully open? Think I’ve finally got all the air out so how long before it starts to show heat on the return side?

[Radian]

Pressure release valve needs a safe route someplace? I assume you put a 13A plug on the end of the cable -- keep an eye on how hot that gets as they're not rated for continuous use at maximum current. Interested in how this goes ?

[joe90]

9 minutes ago, Radian said:

I assume you put a 13A plug on the end of the cable

I would rather see it wired into a fused spur outlet if it were me.

[TonyT]

Shortage of pipe clips..

 

willis heater seems a bit low, to allow you to change a thermostat.

[Nickfromwales]

2 hours ago, joe90 said:

I would rather see it wired into a fused spur outlet if it were me.

I got dragged over the coals here for doing that, so this needs connecting to a 16a supply via a 20amp DP switch with immediate effect. DO NOT leave it running on a 13a plug and an extension lead!!! That's a recipe for an electrical fire. Switch this off until you can rectify this.

Have you adjusted the Willis heater stat to minimum? 

[Nickfromwales]

2 hours ago, TonyT said:

Shortage of pipe clips..

 

willis heater seems a bit low, to allow you to change a thermostat.

It's a temporary rig!! It's fine.

[joth]

 

If you want simple flow temperature control something like this can work.

https://www.amazon.co.uk/Temperature-Controller-All-purpose-Thermostat-Calibration/dp/B00KYL3W32/ref=asc_df_B00KYL3W32/

The relay is too small for the immersion but you could use it for the pump (and rely on the immersion thermal cutout, set to minimum, when the pump is off) or use an additional contactor breaker on it.

Put the probe on the return water pipe as a proxy for measuring the slab temperature.

 

 

Agree with @Nickfromwales that running the Willis from an extension lead is very risky. Our contractor had a couple leads burn out their plug during our build, including one that had been left on overnight. We got lucky but could have easily been a disaster.

 

 

[Barryscotland]

10 hours ago, Radian said:

Pressure release valve needs a safe route someplace? I assume you put a 13A plug on the end of the cable -- keep an eye on how hot that gets as they're not rated for continuous use at maximum current. Interested in how this goes ?

I was going to pipe the prv to a bucket but it’s set at 3bar and I’ve got it running just under 1 so what’s the chances of it blowing? It’s 13amp fuse, no power in house yet so extension lead is all we’ve got but been on all night and only a little heat in plug so sure it’ll be fine…. Hopefully it is only very temporary. The plan was to wire it into an imersion  timer, on a few hours n off a few once there’s warmth in house

 

 

 

anyway point to doing this is house is getting taped n filled starting next week and we need warmth. I’ve had it on all night and the flow temp is only up to 24 degrees and the return is 12 degrees. Should I be turning the flow valves down to get the flow temp up or will it eventually warm up? I have the pump on its slowest setting.  It’s warming up 70mm of cemfloor and it’s frosty outside

[SteamyTea]

5 minutes ago, Barryscotland said:

It’s 13amp fuse

Fuses do not blow at the rated current (well quick blow fuses might).

Just like all things mechanical, it is a combination of temperature and time.  A 13A fuse will eventually fail even if it has only has a small load, say 7A after enough time. This is why normal 13A outlets are only rated at 10A continuous load.

Adding in an extension lead increases the overall resistance and the current drawn goes up.  Why we don't run the whole house of a extension leads and have to put up with fixed position outlets.

[Barryscotland]

6 minutes ago, SteamyTea said:

Fuses do not blow at the rated current (well quick blow fuses might).

Just like all things mechanical, it is a combination of temperature and time.  A 13A fuse will eventually fail even if it has only has a small load, say 7A after enough time. This is why normal 13A outlets are only rated at 10A continuous load.

Adding in an extension lead increases the overall resistance and the current drawn goes up.  Why we don't run the whole house of a extension leads and have to put up with fixed position outlets.

I get that it’s a bit risky but in this instance I’ve got to go with what I’ve got for the time being, if it works an house gets warmer I will run another larger cable into house 

[joe90]

Also extension leads should be fully extended before running anything with high current, when still in a coil it will heat up. I ran an extension lead for something many years ago(I can’t remember what) and found the plastic cable had melted into a lump and was very hot.

[SteamyTea]

13 minutes ago, Barryscotland said:

I get that it’s a bit risky but in this instance

What is the power rating of the element, they are often under the nominal 3 kW.

Just don't leave it unattended to be on the safe side.

[Radian]

22 minutes ago, SteamyTea said:

Adding in an extension lead increases the overall resistance and the current drawn goes up.  Why we don't run the whole house of a extension leads and have to put up with fixed position outlets.

 

Increased resistance makes the current draw go down. The resistance of the long cable run will drop some voltage and reduce the current. It will however dissipate power as heat so the heater element will not reach its design temperature and the cable (from the reel) may exceed its.

 

13 minutes ago, joe90 said:

Also extension leads should be fully extended before running anything with high current, when still in a coil it will heat up. I ran an extension lead for something many years ago(I can’t remember what) and found the plastic cable had melted into a lump and was very hot.

 

A coil of cable has self-inductance from which the magnetic field opposes current flow (inductors are sometimes called chokes). This is similar (in effect only) to resistance and therefore also dissipates heat.