Home  5  Books  5  GBEzine  5  News  5  HelpDesk  5  Register  5  GreenBuilding.co.uk
Not signed in (Sign In)

Categories



Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

Buy individually or both books together. Delivery is free!


powered by Surfing Waves




Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.

Welcome to new Forum Visitors
Join the forum now and benefit from discussions with thousands of other green building fans and discounts on Green Building Press publications: Apply now.




    • CommentAuthorEd Davies
    • CommentTimeDec 15th 2020
     
    Oops, must have trimmed too much off the end of the URL. Here's one like it found by searching “thermostat hysteresis timer”:

    https://www.ebay.co.uk/itm/Electric-Thermostat-Controller-Regulator-Digital-Temperature-Outlet-Timer-Socket/393010011979?hash=item5b8138df4b:g:4aoAAOSwpVxfqi8S
    • CommentAuthorGreenPaddy
    • CommentTimeDec 15th 2020
     
    I often use a Honeywell L6188 2002. I like Honeywell stuff, and this gives up to a 10oC hysteresis. This one goes in a thermowell, but there are variations on this.

    Set it to say 35oC, close on fall, so it shuts off the call signal at 35oC, and re sets at 25oC. My slight concern, as others have mentioned above, is that you may well be interfering with the HP's preferred operational mode, and create short cycling.

    Think through the various scenarious, eg,

    Hot DHW top section, and no call for UFH
    Hot Dhw top section, with UFH drawing
    DHW drawing but no UFH draw
    etc, etc, and determine if there are times when the HP will tend to short cycle

    10oC is a decent thermal gap, though only with half the TS's volume (bottom half). Weather compensation to assist the HP to back off whilst still running would help too, though maybe not in the way you mentioned earlier, by using it to blend down the UFH flow, since that will still be using warmer water than necessary generated by the HP. Better to get the HP to generate that cooler water in the first place.

    Does your HP not allow you to set the UFH flow temp, and adjust the heat curves. It's a wee while since I set up an AHSP, but I recall setting curves for external temp verus HP output temp, which would allow you to drive down the HP output temp for UFH.

    Give it a go, change one thing at a time, and monitor it.
  1.  
    Posted By: Ed DaviesOops, must have trimmed too much off the end of the URL. Here's one like it found by searching “thermostat hysteresis timer”:

    https://www.ebay.co.uk/itm/Electric-Thermostat-Controller-Regulator-Digital-Temperature-Outlet-Timer-Socket/393010011979?hash=item5b8138df4b:g:4aoAAOSwpVxfqi8S" rel="nofollow" >https://www.ebay.co.uk/itm/Electric-Thermostat-Controller-Regulator-Digital-Temperature-Outlet-Timer-Socket/393010011979?hash=item5b8138df4b:g:4aoAAOSwpVxfqi8S


    Yes, that looks like what I'm looking for!
  2.  
    Posted By: GreenPaddySet it to say 35oC, close on fall, so it shuts off the call signal at 35oC, and re sets at 25oC. My slight concern, as others have mentioned above, is that you may well be interfering with the HP's preferred operational mode, and create short cycling.

    Yes, that sounds like a good idea. I also agree that it may not be what the ASHP controls are 'expecting'. I expect (!) it expects a direct connection to the UFH where the return is say 25-30 and it can provide a consistent 30-35. With a buffer tank, the temperature in the buffer keeps increasing, which seems to make it modulate down considerably, and this seems not to be very efficient.

    It's a difficult balance between using the buffer to get cheap electricity (3p per kWh this morning on the flexible tariff) and efficiency of the ASHP performance.
  3.  
    You can put a timer in series with the stat so it doesn't call for heat more often than say every 15mins, search for run on timers. We looked into this because every short cycle started off with a defrost.

    Though it is better to eliminate short cycling at source by having the HP modulate down as GP suggested. Our heat pump controller came with a lot of options for control schemes based on differential pricing times, load compensation, weather compensation etc, all obscurely documented on a website restricted to 'approved installers'. Once we found the right one it ran nicely.
  4.  
    For whatever reason, the ASHP doesn't like being connected to the UFH directly. Efficiency is really low, and it runs at quite low power. My suspicion is that the the fact that parts of the UFH are covered in wood is reducing the heat transfer. So far it's been more efficient to heat the TS in one blast a couple of times a day (3-4 hours) and then run the UFH off the TS from there constantly. The heat transfer may become more effective if I bring some radiators upstairs online.
Add your comments

    Username Password
  • Format comments as
 
   
The Ecobuilding Buzz
Site Map    |   Home    |   View Cart    |   Pressroom   |   Business   |   Links   
Logout    

© Green Building Press