Need help/advice on new house with MVHR & no heat

[mccltd]

I have recently purchased a new build that's 3 years old as builder went bust.

It has an MVHR vent axia system with an inline 2.4kw duct heater, other than that the house house a small plinth heater and 3 towel rails.

As you can imagine the house is currently freezing, I'm having to run some electric oil rads and electric heaters and sit under a heated blanket.

Not ideal.

Their is no gas to the property and the hot water tank sits right in the middle of the house so running pipes etc would be a nightmare.

Can anyone offer any advise as to a cost effective heating system(s) I can put in but wont require destroying the inside.

I am looking at having a couple of daikin aircon units installed in the lounge and the master bedroom that's located n the roof as they can run the pipe work up one side of house. This was primely for aircon in summer but hoping the heating side maybe good.

Any helps most appreciated.

 

 

 

 

 

 

[ProDave]

One or 2 of the split aircon units would do the job, and give you the advantage of being a heat pump so roughly for every 1kWh of electricity you use, you will get about 3kWh of heat.

 

If they are all on the same side of the house, you can buy ones that have just one outside unit that feeds to a number of inside units making it both cheaper and neater.

 

If the house was built with the 2.4kW duct heater as the only heating source, one would hope that means it has been built very well insulated so it only needs a small heat input.

[Wumpus]

If the house is correctly designed to have great insulation and air tightness it’s perfectly feasible to heat with a post-heater in the MVHR with a small top up when it’s very cold. Running that type of system would need high confidence in the insulation and air tightness of the building.

 

Is there anything from the builder that shows heat loss calculations or air tightness test results?

it can take a while (possibly days) for a passive type build to warm up and find its balance, but it sounds like you have been in for a while now?

[mccltd]

38 minutes ago, Wumpus said:

If the house is correctly designed to have great insulation and air tightness it’s perfectly feasible to heat with a post-heater in the MVHR with a small top up when it’s very cold. Running that type of system would need high confidence in the insulation and air tightness of the building.

 

Is there anything from the builder that shows heat loss calculations or air tightness test results?

it can take a while (possibly days) for a passive type build to warm up and find its balance, but it sounds like you have been in for a while now?

We have been in for about 5 months now. But I think I let the house get to cold.

I'm wondering if the duct heater is in the wrong place as its actually a Post heater, its inline with the duct that comes from the MVHR to the distribution unit for the pipes to the rooms.

 

Also If I set the thermistor to 24 degrees and leave the heater on I presume depending on the temperature of the heating element depending on the incoming air temperature, or will it just sit at 24?

[ProDave]

6 minutes ago, mccltd said:

We have been in for about 5 months now. But I think I let the house get to cold.

I'm wondering if the duct heater is in the wrong place as its actually a Post heater, its inline with the duct that comes from the MVHR to the distribution unit for the pipes to the rooms.

 

Also If I set the thermistor to 24 degrees and leave the heater on I presume depending on the temperature of the heating element depending on the incoming air temperature, or will it just sit at 24?

A low energy house (assuming that is what this is) will not need much heat input to maintain the temperature. But it will need a lot more heat to raise the temperature to a comfortable level if it has been allowed to get cold.

 

I think you are confusing what the sensor and thermostat does.  It does not set the temperature of the air blowing out of the vents, it is a room temperature sensor.  The air will blow out of the vents at whatever temperature the heater can manage, until the room reaches the required temperature, then the heater will switch off.  Thereafter it will cycle on and off from time to time to maintain the room temperature.

 

So set it to 20 degrees and leave it alone for a while.

 

EDIT: post a picture of the thermostat you are talking about in case it is me that has misunderstood it?

[mccltd]

12 minutes ago, ProDave said:

A low energy house (assuming that is what this is) will not need much heat input to maintain the temperature. But it will need a lot more heat to raise the temperature to a comfortable level if it has been allowed to get cold.

 

I think you are confusing what the sensor and thermostat does.  It does not set the temperature of the air blowing out of the vents, it is a room temperature sensor.  The air will blow out of the vents at whatever temperature the heater can manage, until the room reaches the required temperature, then the heater will switch off.  Thereafter it will cycle on and off from time to time to maintain the room temperature.

 

So set it to 20 degrees and leave it alone for a while.

 

EDIT: post a picture of the thermostat you are talking about in case it is me that has misunderstood it?

 

Hi,

The heating element has been set to power on / off by a nest thermostat. They have wired it so that it literally supplies the power to power on or off the ventmatika. bit crude.

The thermistor is like a thermostat mounted next to the ventmatika ( in the loft ) which I understand sets the temperature of the heating element.

Link to video below.

 

Also had the heating element been put in the intake to the MCHR would it not have then heated up the heat exchanger helping the air temperature?

 

link : https://share.icloud.com/photos/0aeAfwbJh98Oe5IfVNoBRU-0A

 

[Radian]

2 hours ago, mccltd said:

This was primely for aircon in summer but hoping the heating side maybe good.

What's the model number of the A/C units? Did the installer size them up for the property in which case there should be a comprehensive heat loss calculation involved. Unless huge corners were cut leading to a big discrepancy between as-designed and as-built performance of your house the A2A's should more than solve your problem. I have a couple of 3.5kW Daikin A/C heating a large outbuilding and I'm a total convert. If the gas boiler packs up in the house I'll be very tempted to try and figure out how to switch over to A2A but my house is a 90's nightmare.

[ProDave]

5 minutes ago, mccltd said:

 

Hi,

The heating element has been set to power on / off by a nest thermostat. They have wired it so that it literally supplies the power to power on or off the ventmatika. bit crude.

The thermistor is like a thermostat mounted next to the ventmatika ( in the loft ) which I understand sets the temperature of the heating element.

Link to video below.

 

Also had the heating element been put in the intake to the MCHR would it not have then heated up the heat exchanger helping the air temperature?

 

link : https://share.icloud.com/photos/0aeAfwbJh98Oe5IfVNoBRU-0A

 

So I assume the flashing green light means it is burst firing the heater.

 

I would set the thermostat in the loft to maximum so the heater runs at full power, and leave the nest room thermostat to turn it on and off as needed.

 

I think the heater is in the right place.  Putting it on the exhaust before the heat exchanger would probably just result in a percentage of the new heat being expelled as the heat exchanger is not 100% efficient. 

[JohnMo]

I would agree with Dave when installed pre heat exchanger it's there for frost protection of the HE, not for heating the house. Post heat is for heating the house.

[mccltd]

48 minutes ago, ProDave said:

So I assume the flashing green light means it is burst firing the heater.

 

I would set the thermostat in the loft to maximum so the heater runs at full power, and leave the nest room thermostat to turn it on and off as needed.

 

I think the heater is in the right place.  Putting it on the exhaust before the heat exchanger would probably just result in a percentage of the new heat being expelled as the heat exchanger is not 100% efficient. 

The green light means the systems booted up and working, the red light means it heating the element.

[Gone West]

2 hours ago, mccltd said:

But I think I let the house get to cold.

There is nothing wrong with your heating system, in fact it's very similar to the system I designed for my Passivhaus. I had three electric towel rails and an EASHP built into the MVHR which provided warm air through the MVHR ducting. We also had a solar gain area to add to the heating when suitable. Once the house was warm, the heating was never turned off during the cold months. We kept the house at 23C 24/7 with very low electricity bills. The house had very good airtightness 0.47 ACH and the U factor for the walls and roof was 0.095 W/m2K. Without the high insulation levels and airtightness there would be no chance of keeping the house warm.