Temporary heat supply for ufh?

[ProDave]

28 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.

Yep I had a customer like that, running a washing machine AND a tumble dryer from a wound up extension lead.  I think she said she was on the third one "they keep melting" before she called me to fit a new permanent socket to plug them into.

 

The extension lead in the picture in this thread does appear to be fully unwound.

 

My own "3kW" immersion heater appears to draw more like 2.8kW in real life.

[TonyT]

15 hours ago, Nickfromwales said:

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

For some reason didn’t read that it was a temp set up!

 

seen a few lash ups that have been temporary for 10 years plus?

[Radian]

9 hours ago, Barryscotland said:

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?

The PRV could open if the thermostat contacts weld shut causing the water to boil. Granted it's very unlikely but at the very least I would have it pointed at the wall and not at face level ?

Another reason might be if the expansion vessel lost pressure on the dry side without you knowing about it when filling, then the natural expansion from heating the water might open the PRV. Again unlikely if only heating to 25C but it would bother me all the same.

 

I do understand that you're making it uber-simple as a highly temporary fix but those NI pipe-bombs give me the willies ?

(says the man seriously considering one to get another UFH loop going while waiting for the current price of ASHPs to de-orbit)

[Barryscotland]

1 hour ago, Radian said:

says the man seriously considering one to get another UFH loop going while waiting for the current price of ASHPs to de-orbit)

I was sceptical that the wee heater tube would make any difference to the heat of the house as was the joiner, builder n sparky however it’s currently -3 outside but inside the house is now 13 degrees and now that I’ve turned the flow valves down it has raised the input temperature to 35 degrees  so I expect the temp to raise further in the house. So for the sake of £40 buy one.

 

remains to be seen if I still recommend them after I’ve had my leccy bill tho.

 

 

[ProDave]

26 minutes ago, Barryscotland said:

I was sceptical that the wee heater tube would make any difference to the heat of the house as was the joiner, builder n sparky however it’s currently -3 outside but inside the house is now 13 degrees and now that I’ve turned the flow valves down it has raised the input temperature to 35 degrees  so I expect the temp to raise further in the house. So for the sake of £40 buy one.

 

remains to be seen if I still recommend them after I’ve had my leccy bill tho.

 

 

Has anyone done a heat loss calculation on your house yet?  Ours needs just a little over 2kW when it's -10 outside and +20 inside.  Based on last weeks heat pump consumption we are running at about 1kW heat input at the moment (averaged over the whole day, that does not mean it is on 24/7)

[Barryscotland]

48 minutes ago, ProDave said:

Has anyone done a heat loss calculation on your house yet?  Ours needs just a little over 2kW when it's -10 outside and +20 inside.  Based on last weeks heat pump consumption we are running at about 1kW heat input at the moment (averaged over the whole day, that does not mean it is on 24/7)

No heat loss calcs done unless that’s part of the sap calcs done for the building warrant? I’d say our insulation levels are average for a new build.

[Radian]

1 hour ago, ProDave said:

Has anyone done a heat loss calculation on your house yet?  Ours needs just a little over 2kW when it's -10 outside and +20 inside.  Based on last weeks heat pump consumption we are running at about 1kW heat input at the moment (averaged over the whole day, that does not mean it is on 24/7)

Calculations are one thing but Barryscotland is in the process of gaining real, empirical data. If he logged his indoor/outdoor temperature differential vs. kWh input wouldn't that yield a more accurate Q instead of arriving at it from U*A*ΔT using a long list of assumed U values? Often wondered about this because it sounds a lot easier ?

[joth]

9 hours ago, Radian said:

Calculations are one thing but Barryscotland is in the process of gaining real, empirical data. If he logged his indoor/outdoor temperature differential vs. kWh input wouldn't that yield a more accurate Q instead of arriving at it from U*A*ΔT using a long list of assumed U values? Often wondered about this because it sounds a lot easier ?

Yes and the nice thing about the Willis heater (or any direct resistive heating) is you just have to log the electricity used by it to know how much heat energy has been delivered into the house per day.

Heat pumps complicate matters as you either have to make a guess at the CoP or log the actual heat output from the thing. In the case of ours (ecodan) I know it has the data inside it (it will show periodic graphs of energy consumed vs delivered) but trying to extract this info from its brain is nontrivial.