I have a new 40 gallon water heater. I also replaced the expanion tank. The water heater runs through a FlatPlate to heat my basement with radiant heat. Once every 24 hours my T & P valve opens and releases about 5 - 7 gallons of HOT water. That seems like my/ FlatPlate is heating water and sending it back to the water tank. Is that possible

Please explain "FlatPlate". House PSI? Is there a PRV valve installed? What's the temp of the water discharged from the T&P valve? What's the heater setting? Back to you Tom

Tom I am not sure if the link below will be the correct one or not but it is worth to look into it, Thanks.

John

Solar Water Heating Panels | Solar Flat Plate Collectors | Flat Panel | Residential (http://www.solarpanelsplus.com/residential/water-heating-flat-plates/)

I think he's talking about basically a heat exchanger such as below: http://www.gea-phe.com/fileadmin/user_upload/documents/product_datasheets/NA_GF_Series_March_2013_usa_.pdf

Assuming that is correct, I don't see any way the flatplate could be heating the water in it in any fashion that would build pressure in the water heater. What is used to circulate water through the flatplate? Is some sort of pump used here?

BTW, assuming that the water heater also supplies the rest of the house with hot water. Correct??

OK. Looked a little more. More likely something like this? Basically a glorified radiator? http://www.lytron.com/~/media/Images/Lytron/Heat%20Exchangers/heat_exchanger_AS04-05_img.jpg

Temperature & Pressure relieve valve will activate under two conditions: Pressure too high and/or Temperature is too high. There is an aluminum tag on the valve itself indicating maximum values for pressure and temperature. Make necessary adjustments to keep your pressure and/or temperature under these values.

Hope that helps

Milo

Strange that it happens only once a day, and then releases 5 gallons of water. Strange. Oh well. I think the poster has moved on. I'd like to know how this was resolved.

Yep, but you guys did a nice job in his absence