Replies

1. 
   TooManyTools | Aug 25, 2002 06:09am | #1

   Here is a link to an explanation of what a dprv is supposed to do.  I did not find any information on a  Thrush valve.  

   http://www.honeywell.ca/braukmann/ans-tank/tips06.htm

   Since you did not mention any problem before your remodel and I assume you did not make any other changes to the heating system it is probably due to the undercounter heate.  Perhaps, as mentioned in the honeywell link  you used a valve that closes to rapidly, probably one not designed for heating service, perhaps a solenoid valve.  If you can give me a schematic sketch of the piping perhaps I can spot another problem.

1. 
   Tomasaur | Aug 25, 2002 06:52am | #2

   Hi,

   I can do better than a schematic, I can give you a couple of photos of the various valves involved. I put up a little web site documenting the process of remodelling the kitchen, and they're on this page, : http://www.execpc.com/~tdaniels/construc.htm

   It's about halfway down the page.

   Thanks!

   Tom

1. 
   TooManyTools | Aug 26, 2002 02:39am | #3

   I really can't see from the pictures all of the interconnections.  It appears that the DPRV is functioning only as a relief valve since I cannot see but two connections to it, one of which you say is where the water is discharging from.  Normally a DPRV is connected between the pump outlet and the inlet so that when the pressure rises as various zones shut off it will open and bypass flow back to the inlet of the pump.

   One thought:  What kind of valve was on the radiator you removed.  If it was a three way valve and you installed a two way on the new fancoil that might explain the problem.  The three way may of been there to establish a minimum pump flow to prevent excessive pressure rise.  If occasionally the new circulator is the only zone calling for heat and shuts off it may essentially "dead head' the pump causing the system to ride up the pump curve to where the DPRV discharges.  In any case I would get someone to look at the current pump sizing.   In a residence it should not be necessary to have a pump with that steep a curve.  I would also check all the wiring.  Is the circulator pump controlled by end switchs in each zone valve?  If so is the new fan coil valve properly connected so that the pump (and boiler) will shut off as soon as no zone calls for heating including the demand from the new coil.

1. 
   Tomasaur | Aug 26, 2002 05:42am | #4

   Hi there,

   Complex questions for a pretty simple system I think.

   The whole house is essentially one zone. No feedback mechanisms to the boiler other than the thermostat. The kickspace radiator allows the water to pass through its coils passively, and only has a fan that blows air across them when the water is circulating and reaches a certain temperature.

   One thing that may be a factor that I hadn't considered though is that there's a pipe diameter change here. The radiators hook up using... what... 2.25" iron pipe? Something big like that. I stepped it down to I think 1" or 3/4" copper pipe for the radiator. Would that cause a problem? There's a ball valve in the line, but that's always wide open.

   Thanks for the considered reply.

   Tom

1. 
   TooManyTools | Aug 26, 2002 07:07am | #5

   2.25 inch pipes!! That is probably a converted steam system.  Yes necking down to 3/4 will introduce significant additional pressure drop.  It may of been enough to make a marginal problem worse.

   One other thing I'd check is the system pressure regulator (that little silver valve) that maintains the boiler pressure at a nominal 12 psig for most systems (By the way is there pressure and temperature gauge on the system?)  These will sometimes stick and fail to close resulting in full domestic water pressure being applied to the heating system.  This will cause the PT valve on the boiler (you do have a PT valve don't you? It's a little valve with a lever on top with a relief opening hopefully piped to the drain) to open.  The one in your picture looks fairly new.  By the way when replacing these it is a good idea to spring for a reduced pressure backflow valve as well.  It is required in new installations and in some jurisdictions whenever the valve is replaced.

   Another thing: After reading your web site again you said you turned off Valve A to shut down the system.  This indicates that Valve A was open bypassing the pressure regulator which will apply full domestic water pressure to the system.  Domestic water pressure often varies significantly and could definitely be your problem together with the increased head pressure from the pump due to the reduced pipe diameter. 

   The pressure regulator is piped wrong!  There should be a service valve on both sides of it so you can open the bypass A and close the service valves and replace the PR without draining the system.

   Let me recommend a couple of books from Dan Holohan who writes a column for professional plumbing magazines. 

   Hydronic Radiant Heating

   How Come? Hydronic heating questions we've been asking for 100 years (with straight answers!)

   Also Pumping Away

   Dan's site is

   http://www.heatinghelp.com/

   You could also ask the question there.

   Edited 8/26/2002 12:33:35 AM ET by JANATION

2. 
   Tomasaur | Aug 26, 2002 05:56pm | #6

   Wow, thanks for the wealth of info. Of course, after writing that last note, I decided to get off my duff and actually measure the pipes so I wasn't just talking from memory. The old iron radiator pipes are 1.25" OD and the new copper pipe was 5/8" OD... Not quite as huge as I'd thought before.

   The boiler is a Valliant GA92-100. It does have a pressure and temp gauge on it. The pressure currently shows about 12 psi, but it could be a tad over... I did find the PT valve, but it's just piped to the floor. Far as I know it's never released (fingers crossed).

   And actually I turned off another valve other than A that's just out of the picture and connects to the inflow pipe leading to A. That's what I meant by shutting off the water to the system... I can see how that was confusing. So, the little silver regulator actually can be isolated from the rest of the system.

   Thanks again for the referral to Dan and for your help. You've been very thorough!

   Tom

3. 
   Wet_Head | Aug 28, 2002 06:41pm | #7

   Be prepared for expensive repairs on that boiler.  Company no longer in US and very trouble prone crap in my opinion.

   I find it hard to diagnose one of these without seeing the whole system.  But you got one very good answer here so good luck.

2. 
   ahneedhelp | Sep 03, 2002 05:51am | #8

   My quick guess is you haven't fiddled with the steel expansion tank while filling the system - water level may be too high with not enough air.

   Devices such as the Airtrol Tank Fitting (by Bell and Gossett) helps you set the proper level of air/water in the tank as you fill the system to reach proper pressure level (usually around 12 lbs).

   Many folks make the mistake of simply draining the expansion tank - it has to be a bit more precise that that.

   Running around and venting the air while water is being refilled is sortof an art in itself and it helps if you are certain that the automatic fill valve/pressure regulator is functioning properly.

   This is especially so if your system is not equipped with air separator and automatic air vent.

   It took me two heating seasons to fully understand the intricacies of our boiler plumbing with much head scratching and replacement of components and correcting some improper installations.

1. 
   Tomasaur | Sep 03, 2002 11:02pm | #9

   You got it exactly right about how I dealt with the air tank; I just emptied it out and figured if I bled the air from the system starting at the lower floors first and then finishing at the top floor I'd be good to go. Apparently it's more of an art than this. I guess I've reached my limit of what I can do now, and should get a pro to come in and get the air/water levels right so that the system hangs out at the correct pressure. Sheesh, it seemed so simple...

   Tom

1. 
   ahneedhelp | Sep 03, 2002 11:44pm | #10

   Hi, Tom -

   Let me see if I can explain the best way I can - you may be able to use this technique once you study your particular setup, such as first locating ALL bleeder valves.

   In a system without automatic air vents, folks try to bleed the air without making up the bled air with fill water.

   Air should be bled while it is being pushed out as water is introduced to the system while you keep an eye on the boiler pressure gauge to make sure it hovers around 12-lbs. This involves leaving open a properly functioning fill valve. (Do this while the system is cold)

   There is final tweaking at the expansion tank - an Airtrol Tank Fitting can be used to drain out excess water and air will start sputtering when the correct water level is reached.

   Then take a look at the pressure gauge to make sure it is still at 12-lbs....introduce more water and raise the pressure to the correct level, then open the Airtrol and drain the excess water.

   All of this I just mentioned is after you're done running around bleeding the air out of all the upper level bleeders, some of which can be hidden behind access panels in the ceiling.

   Do find out if you have an Airtrol Tank Fitting, which is commonly installed on many steel expansion tanks. This gizmo does help you set the proper air/water ratio.

   Good luck,

   Alan

1. 
   Tomasaur | Sep 04, 2002 01:14am | #11

   Cool. I'll head home and take a look and get back to you. Thanks for the detailed explanation!

   Tom