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Posted By: tonyU-values for walls and ceiling? and duct sizes?
Is the house orientated and designed to make use of solar gain, lots of glazing on the south side, little on the north etc?
Water heating is provided by a "Vanvex", this is an air to water heat exchanger of about 0.8kw integrated with a 185 L water tank.snipThis leads to the strange situation on very cold winter days of the water tank taking 20 hours to recover from 20 to 50c
Posted By: daysleeperStrangely both the vanvex and genvex are located with the air ducting coming in through one side of the house and out through the other. This ductwork runs though the joist void between ground and first floor. So last winter it was sucking in large quantites of -10 air, and putting out similar amounts of -17 air. (cold bridge anyone?)
Posted By: CWattersSomeone check my figures but...(185 x 30 x 4186) / 20 x 60 x 60 = 322 watts
Posted By: daysleeperWell that’s embarrassing, I’d completely forgotten about that thread when I sat down in a grump last night to write this one.
Posted By: davidfreeboroughdaysleeper has already said that the two systems are independently ducted to the outside world, so I don't think the DHW recovery time issue is related to the MVHR. I just want to work out whether the MVHR flow rate is set sufficiently high to manage humidity levels & carry all the available ASHP energy into the house.David
Posted By: davidfreeboroughdaysleeper has already said that the two systems are independently ducted to the outside world, so I don't think the DHW recovery time issue is related to the MVHR. David
I just want to work out whether the MVHR flow rate is set sufficiently high to manage humidity levels & carry all the available ASHP energy into the house.
Hmm, so has anything changed since then?
Posted By: daysleeperThe builder's already accepted that the system can't push/pull enough air through the house to match the spec. Though they are unsure if that is the reason for the condensation. They "think" the volume problem is because of undersized ducting, though in addition the house is right at the top of the volume range for the machine. The question is what's to be done about it. We'd rather not rip all the walls apart to get at the ducting and running the fans on high at night means the noise in the downstairs bedroom is unacceptably high.
How bad is the condensation? Is it running down the windows onto the window sill? Does is evaporate on its own in the morning or does it need to be wiped away? If it's pooling on the window sill then I would say you need to do something about it.
Can you reduce the amount of water vapour being released in the house? Do you cook on gas? Would you consider moving to a halogen or induction hob? Do you dry washing in the house? Could you put washing outside until it is almost dry & then bring it inside to remove the last few percent of water?
If you've done everything you can to reduce water vapour being released in the house then you need to check that the condensation isn't due to cold spots. Do you notice significant variations in temperature around the house? Does the condensation collect in areas which are colder than others? Can anything be done to increase the temperature in these areas?
Once you've been through these options then you're left with increasing the ventilation rate &/or the distribution of heat coming from the MVHR unit. Has the MVHR unit been properly commissioned, i.e. has the flow been checked & adjusted at each extract/inlet vent?
Is the temperature drop along the ducting within specification? Are all of the ducts lagged with at least 50mm mineral wool? Is the pressure drop along the ducting within specification? Is all of the ducting low loss rigid ducting, or do you have some flexible ducting?
If you can get answers to these questions then you can decide whether to reject the MVHR unit as not performing to specification &/or reject the builders installation as not fit for purpose.David
Posted By: daysleeperIt's worse than that, the ASHP input is only 520w !
Posted By: daysleeperIf we use the woodburner in anything other than arctic conditions then the lounge rapidly goes from conditions needing 2 overcoats to wearing shorts. Seriously the woodburner punches the temperature in the lounge up to about 25c very quickly even in cold weather, problem is that heat does not travel.
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