Opinions, advice vmc df preheating system

[xxx74]

Hello,

Having acquired a VMC DF Aldes Dee Fly Cube 300 Microwatts via my former boss at a more than reasonable price, I would like to have your opinions on the preheating systems of the incoming air for the winter.

Living in Haute Savoie at an altitude of 940m, the winters are not hot, but when I see the electrical consumption of the preheating systems, it is a little scary concerning the electric bill.

Knowing that the operating temperatures given are from -7 ° to 40 °, with automatic flow reduction around 0 ° I believe, are there people in the same configuration as me who could give me feedback experience?

- Do you have a preheating system on your DF?

- Have you calculated the cost per winter / fall?

- What system are you using?

- Which one is advisable?

- Is it necessary?

Regarding the Canadian well, even if I'm for 100%, the cost is not possible at the moment ...

- Having a Stiebel Eltron WPL 25AS air / water heat pump with buffer tank and domestic hot water tank, would it be possible to use it for a system for preheating the incoming air for the winter?

Thank you in advance for your answers.

[chatelot16]

the purpose of the double flow exchanger is to recover the heat from the air that leaves! if we preheat the air that comes in before the exchanger, it will reduce the heat recovered ... the stale air will come out hotter ... the heat from the preheating source will therefore be wasted

preheating can be useful in cases where the double flow exchanger does not work properly, for example below zero degrees: the humidity of the viscous air makes ice and clogs the exchanger: a preheating by ground heat avoids electrical defrost

if the heating of the house is electric an electric preheating just to avoid icing will not be worse than the electric heating

if there is better heating than electricity, the same means should provide anti-icing preheating

[xxx74]

Thank you for the answer. However, at home, I only have one electric heater, the one in the bathroom.

What I would like to know is if there is a way to use automatic hot water production from my air water heat pump, knowing that I have a hot water cold water supply just the place where the Vmc will be, to simply prevent the icing of the exchanger by negative temperature in winter, that's all !!

Otherwise, I already know the operating principle of an exchanger ...

And I do not seek to permanently preheat the incoming air, only on an ad hoc basis and simply do without an electrical resistance.

Thank you beforehand.

[chatelot16]

I think of 2 theoretically equivalent solution to avoid icing

1) pass the outside air through an air-water heat exchanger thermostatically controlled at 0 ° before entering the double flow exchanger: the exchanger will only recover the heat above 0 ° and will not freeze ... with this thermostat at zero degrees this system will not waste heat when the outside temperature is above 0 °, but that poses the problem of freezing this exchanger in case of system shutdown

2) thermostat which measures the exhaust air outlet temperature and reduces the proportion of outside air passing through the exchanger: as long as the outlet temperature the entire flow passes through the exchanger and the output is maximum: when the outlet temperature goes below 0 ° the thermostat degrades the output just enough so as not to frost: the energy loss is the same as with preheating at 0 ° but it is simpler: not need of heat source at the level of the VMC, therefore no risk of frost: the loss of energy in the form of ventilation air a little colder: the heating of the house will have to heat it

[xxx74]

Thank you for these two solutions, it already corresponds more to what I am looking for.

For your solution no. 2, this is in principle what the vmc already does automatically? Reduced flow to prevent icing.

As for solution no. 1, I imagined, without knowing if it would work, like a hot water pipe that I would wrap around the air intake duct, with a boiler circulator that I already have, and it would trigger via thermostat.

Where I get stuck is how to return the hot water, should it be sent where? In the PAC buffer tank? Or in the chess ball?

And apart from the circulator and the thermostat, what kind of equipment would this require?

[chatelot16]

if your vmc already does what it takes there is nothing to invent!

preheating has no energy advantage compared to reducing the flow rate if the price of heat for preheating is the same as heating the house

the only advantage of preheating would be to use a cheaper or even free energy like the Canadian well

but the Canadian well is not the only solution: it can also be a buried water pipe long enough to take the heat from the ground

be it water at ground temperature or water from the heat pump the solution is not to wrap a water hose around the air hose: you need a real air water heat exchanger

[xxx74]

I'm not necessarily looking for free, I'm just looking for a cheaper alternative than electrical resistance ...

The Canadian well would be ideal, I know it, but I do not have the financial means for the moment ...

I just said to myself that since my heat pump will produce hot water for my two heated floors + my DHW, why not make a bypass on the arrival of the heated floor which would go rolled up as I already said previously around the air intake duct or why not create a coil inside the duct to gain in exchange (theory) for VMC with a valve controlled by a thermostat which would trigger the arrival of water from 0 °, without seeking to obtain a high temperature, just to prevent the exchanger from freezing, then the water would leave in the return of the heated floor, especially since the water from the heated floor revolves around the 32 or 35 ° in general.

I tell myself that my heat pump will surely preheat for less than an electrical resistance, because the management of the flow rate of my VMC in cold weather surely has these limits in terms of performance, it is not for nothing that he advises their preheating unit electric optional, which still makes 1500 w, which accumulated over a whole winter represents a significant cost!

Is my idea so weird as that?