Replies

1. GBA Editor
   Martin Holladay|Jul 06, 2017 11:03am|#1

   Jabk,
   There are lots of issues here.

   To summarize: You live in a hot country, and not in the U.S. (Care to tell us where?)

   Your house has an air-to-water heat pump that creates warm water in the winter and cool water in the summer. This water is circulated through tubing in your floors -- so you have a hydronic heating system and hydronic cooling system.

   You have just discovered why people don't install hydronic cooling systems very often: You end up with puddles on your floor. Now you need whole-house dehumidification.

   If you lived in the U.S., your house would probably have forced-air ducts. But since you probably live in Europe or Asia, you only have ventilation ducts.

   My advice: Experiment with basement dehumidifiers and see if they work.

   If they don't, your three options are: (1) Install a dehumidifier on each floor, with the condensate piped to the basement drain, or (2) Install a whole house dehumidifier, along with the necessary ductwork; or (3) abandon the hydronic cooling system, and cool your house with ductless minisplits instead.

2. 
   JaBK|Jul 06, 2017 11:47am|#2

   I live in Slovenia, Europe. I am aware and was warned beforehand. But since I only need dehumidifiers when cooling and I only need coling 3-4 weeks a year I didn't want convectors to deal with moisture, because they always give me grief healthwise. So your number 3 is a no-go as well. I dread A/C.

   Am doing number 1 right now without the automatic drainage, which I would probably not do. We are done with the house for now and have been liiving in it for 3 years. I see no construction work in near future. So, with that in mind I started googling how people deal with humidity. I was surprised I could only find american discussion sites, Europe obviously does not recognise humidity as an issue. Whole house dehumidifiers do not exist here or at least I was unable to find any. There are standalone dehumidifiers but no disscussion whatsoever about putting one large dehumidifier to deal with the whole house. Hence, I could find noone with any experience on the subject. This is completely new for me.

   What baffles me now is my experiment and how relevant it may prove. As of tommorow when we are expecting high temperatures again I will plug in 3 dehumidifiers. A couple of 10L/day with air flow of 100m3/h and one 20L/day with unknown air flow volume 200m3. My question remains (if it can be answered): Is this the same as one latge dehumidifier with capacity 40L/day and air flow volume of 260m3/h. Can I simply sum the litres or is it not that simple? How about air flow volume? Can those be summed and 3 humidifiers are better?

3. 
   Steve Knapp CZ 3A Georgia|Jul 06, 2017 02:04pm|#3

   I have a whole house ventilator dehumidifier. It is rated at max blower of 320 CFM and will remove 98 pints of water a day at 80 degrees (F) and 60 percent relative humidity. It is not a ducted install, so I depend on a combination of stack effect and an HVAC air handler for air mixing. This works for the most part but is not ideal during the shoulder seasons.

   At the moment, outside it is 88 degree (F) with 62 percent humidity. Inside it is 76 degrees with 40 percent humidity. Indoor humidity normally stays between 38 and 41 percent at this time of year.

   I don't know how standalone dehumification would work in your home without mechanical ventilation. As Martin suggested, you should experiment.

4. Expert Member
   Dana Dorsett|Jul 06, 2017 06:27pm|#4

   Slovenia doesn't have nearly the outdoor humidity issues found in the south eastern US. Compare the humidity graph (a bit more than half way down the page) of Ljubljana to that of say, Mobile Alabama:

   https://weatherspark.com/y/77419/Average-Weather-in-Ljubljana-Slovenia

   https://weatherspark.com/y/13102/Average-Weather-in-Mobile-Alabama-United-States

   只要至少有一些开放的对流or mechanically driven air flow between floors a small dehumidifier in the basement of a tight house that size will keep up with the humidity in the rest of the house, as long as you don't have excessive ventilation rates during periods when the outdoor dew points are high (say 16C or higher.) In fact, just one would do it for most homes. For most houses that size, a whole-house dehumidifier would be like using a cricket bat to swat mosquitoes- way more capacity than would ever be needed.

   The key is to reduce the ventilation rate on the ERV on days when outdoor humidity is high (dew point of 16C or higher)to avoid taking on humidity from outdoors, increase the ventilation rates when outdoor humidity is low (dew point of 15C or lower) to purge humidity from the house. That will use a lot less electricity than relying solely on the dehumidifier.

   For most houses that size a whole-house dehumidifier would be like using a cricket bat to swat mosquitoes- way more capacity than would ever be needed unless high ventilation rates are desired.

   Dehumidifiers convert latent heat (moisture) in to sensible heat (hot air), raising the cooling load on the house. Modifying the cooling system to allow for a chilled water air coil for dehumidification may be the best solution, but it would require a bit of design and rework. It's probably not going to be worth it in your climate.

5. 
   JaBK|Jul 07, 2017 08:46am|#5

   The ERV is set to cca 150m3/h, this is as low as possible before I start complaining about stale air. That is about a quarter of the whole net volume of the house. Usually it is set to 300m3/h.

   I want to use only one dehumidifier, but before I buy, I want to know if these two options are comaprable:
   1.) 3 dehumidifiers: 10L + 10L + 20L
   2.) 1 dehumidifier: 40 L

   I am trying out the first option right now. and if it works, can I assume one 40L would worka as well? tahe same, better or worse? That is my main concern, I cannot borrow a 40L anywhere right now.

6. 
   JaBK|Jul 10, 2017 05:29am|#6

   So, I have been running my 3 dehunidifiers in my basement throughout the latest "heat peak" which will hopefully end in a couple of days (outside dew point above 18C) and been able to keep the RH in the house below 60%.

   Now I am waiting for the postman to bring me my brand new 50L dehumidifier. perhaps it will be strong enough to work nights only - that is when the electricity is cheaper, outside dew point is as low as it gets as well as temperature, so my ERV will go on bypass and exctract some of the heat produced by the dehumidifier. There is an exhaust duct in that room. Will see how that experiment goes. But mostly I am happy I will not have to hear or see that thing till the rest of the summer when I will unplug it.

7. 
   leonardwulf|Jul 21, 2020 09:23am|#7

   Ifs someone wants u can read an article about How to Choose the Right Size Dehumidifier:https://www.bestadvisor.com/how-to/how-to-choose-the-right-size-dehumidifier
   I hope it'll help somebody