Posted: Thu Sep 09, 2010 10:57am

7 years ago i took out a 2 coil calorifier and replaced it with a 3 coil ,did not put in a non return valve or an expansion bottle and every thing worked fine. then recenty i had a problem with the pressure release valve opening and staying open i replaced the prv and the problem remained ,although the prv was higher than the pump pressure but lower than the calorifier i ended up with a split calorifier ,I have now fitted a new one using an expansion bottle and a non return valve on the cold water feed i have also fitted a shut off tap on the cold water feed so i can use the domastic cold water ,when i opened the hot tap water comes out without the pump coming on for a while ,then when the pump comes on and the hot tap is shut off ,then the pump stays on and the PRV opens,Sureflo pump 30 psi ,expansion bottle set at 2.2 bar, PRV is 3 bar .i have looked at some previous answers to questions and nothing works .When the PRV opens I stop the water going into the calorifier by shutting the tap on the cold water feed the PRV stops after a short while ,but before it stops it seems to let more air out than water ,with the isolation tap open it lets all water out .I am now in dispair ,is it safe to run the fire and engine though the coils while i have still got this problem,could there be air in the calorifier if so could that be the problem in dispair John

Posted: Thu Sep 09, 2010 6:53pm

Dear John, I suspect your pump has a faulty pressure switch and is not turning off at the stated pressure. With an expansion vessel water will come from the hoe tap after an untill warm up of the calorifier because the expanding water has pushed into the expansion vessel and pressurised the air above the diaphragm. I can assure you that if you have a proper inland calorifier you only need the PRV. Although your old one could have had a perished seal or scale on the seal the primary candidate is the water pump pressure switch. If you have one of the expensive pumps that alter their speed according to the demand then I would be triply suspicious of it. Unless you have physically measured the pressure with the PRV venting you have no way of knowing it is 30psi. I suspect it is not. Tony Brooks

Posted: Thu Sep 09, 2010 8:57pm

dear tony thankyou for your reply ,I never thought about the pressure switch ,but when I turn off the cold water tap on the cold water feed going into the calorifier ,( tap is 6 " from calorifier), i can use the bathroom and kitchen cold taps ,when the tap is turned on the pump comes on staight away and when it is turned off the pump goes off sraight away as it should ,would this happen if is was a faulty pressure switch ? regards John

Posted: Fri Sep 10, 2010 7:47am

Well, not quiet straight away if it is a hot tap since you fitted the expansion vessel but the cold tap would work like that. unscrew the plastic cap on top of the pressure vessel to to expose a car type tyre valve. Get a tyre pressure gauge and check the pressure in the expansion vessel with the pump turned off. It should be set at the pump cut off pressure. Then turn the pump on with the taps off whilst monitoring the air pressure in the pressure vessel. It should not rise, but I bet it does. This will indicate a high setting on the pressure switch. Tony Brooks

Posted: Tue Sep 21, 2010 11:35am

Hi Tony Yes you were right about the pressure switch we had a replacement pump,and fitted it and everything fine .The only thing is there is a delay on the hot water side with the pump coming on and off and also every 5 minutes the pump comes on for a second or two we have checked for leaks everything is dry when I isolate the cold water feed from the calorifier we don't have the problem we are monitoring the expansion bottle to see if it is loosing air would it make sense John

Posted: Tue Sep 21, 2010 12:12pm

If you are absolutely sure there are no leaks on the pipework or calorifier then it could be: 1. valves in the pump allowing water to back-feed into the tank. If so fit an ordinary plumbers' non-return valve between tank & pump. Test by getting the system up to pressure and then turning off the isolating valve. If the pump continues to run after 5 minutes the leak is else where. 2. A leaking calorifier PRV but that should affect the hot as well as the cold supply. 3. A leak in the calorifier coil allowing domestic water to get into the engine. Again this should affect both supplies. In fact all of them should affect both supplies. Tony Brooks