Temperature Constant

[Barney12]

Thought the collective would find this interesting. MBC build, externally finished but nothing but bare plaster walls inside. MVHR operational but no form of heating yet in place. I have a heat battery on the MVHR intake but that’s not commissioned yet either. 

 

The temperature up up here on the moor has been pretty cold of late. Certainly close to freezing for over a week now. However, the temperature in the house seems to sit at a pretty constant 12-15 degrees. Hopefully it bodes well for future heating demand. 

 

 

[TerryE]

Thermal gain?   Our new house is now toastie just heating it overnight with the Willis heater And we haven't moved in yet!

[A_L]

@Barney12- Do you have any thoughts on the outgoing dT of 7°C with an incoming dT  of 13°C? Airflows  not yet balanced? Lots of condensate? Incoming reduced to protect heat exchanger?

Edited December 9, 2017 by A_L
More thinking!

[pdf27]

8 minutes ago, A_L said:

@Barney12- Do you have any thoughts on the outgoing dT of 7°C with an incoming dT  of 13°C? Airflows  not yet balanced? Lots of condensate? Incoming reduced to protect heat exchanger?

Umm... that it probably breaks the laws of physics? I think the indoor temperatures look like they're the wrong way around - that seems to be saying that the heat exchanger is taking indoor air at 11°C and sending fresh, warmed air out again at 15°C. Much more likely is the other way around - that gives outgoing dT of 11°C and incoming of 9°C. If flow rates are equal in and out (as they should be) then that's about 82% efficiency.

[Jeremy Harris]

Solar and incidental gains can make up most of the heating requirement, especially on clear and cold days, we've found.  Our house (same construction as yours, but in a more sheltered location) was boarded out and plastered in January/February, when it was pretty cold.  There was no heating, and the MVHR wasn't commissioned or running, but the heat from two or three people, plus a couple of 400W halogen worklights soon made the temperature indoors unbearably hot.  I had to go and buy some low energy worklights, just to reduce the heat input.

[Barney12]

1 hour ago, A_L said:

@Barney12- Do you have any thoughts on the outgoing dT of 7°C with an incoming dT  of 13°C? Airflows  not yet balanced? Lots of condensate? Incoming reduced to protect heat exchanger?

 

Not even got any covers on the room plenums so definitely not balanced

Plastering only just finished so yes plenty of moisture.

 

[Barney12]

1 hour ago, TerryE said:

Thermal gain?   Our new house is now toastie just heating it overnight with the Willis heater And we haven't moved in yet!

 

Definitely a factor. Plenty of south facing glazing and it’s been sunny. 

Lets hope the brise soleil do their job properly (when I eventually get them installed!)

[Jeremy Harris]

There's loads of heat released as a consequence of condensation in the heat exchanger, so with warm, moist air being drawn out, and the moisture condensing in the heat exchanger and giving up its heat to the incoming fresh air, you can get some pretty high apparent heat exchange efficiencies, especially if the outside air is dry, as it will be in cold weather.

[Barney12]

Insulation is definitely doing it’s job as well as there isn’t any sign of any snow falls melting. This was yesterday mornings dusting later in the day.

 

 

[Barney12]

Going to try and get the MVHR heat battery commissioned this weekend. It’s powered by ground source heat loop and if I run the pump to circulate there’s clearly warmth to be gained down there 1.5m below the soil.  

 

[jack]

As a comparison, we went away for three weeks over Christmas. We've had some problems with our ASHP (hopefully to be fixed in a couple of weeks) and had been using a single column heater to keep the house warm. I didn't want to leave this on, so turned it and the immersion heaters on the UVC off for the whole three weeks.

 

The only incidental gains were the losses from the fridge and freezer motors, and whatever solar gains there were over that period (some very cold temps and gale force winds I believe). Everything else was switched off at the power point.

 

We returned to a very chilly house on Saturday evening the weekend before last. I didn't check the temp at the time, but I guess it was around 13 deg C based on the temperature the next day. Bear in mind we'd had cold temps and gale force winds during much of the period we were away. I switched everything back on and turned the column heater (2kW) on full with a small fan on it to distribute the heat. 

 

The house temp initially rose by around 1.5 degrees a day. Things were pretty unpleasant for a few days (not just because of my grumbling family!), but by around Thursday we were in the very high teens and I switched down to medium power. We're sitting at around 20 C now, with 1kW input from the column heater.

 

As I've said before, we don't have great solar gain, so I was surprised to see the house sitting well into the teens after three weeks away with no incidental energy being supplied.