Know about plumbing?

Maybe plumbing is much like electronics: Read the manual :-)

Carefull: this is just my guess: Describe your heating system. Is it a single heater to provide both hot water and heating to your building ? In that case, the circuits are separated. The heating system operates on 1 to 2 bar, with a 3 bar maximum. It's contents gets pumped around, but it is not connected to the water supply (OK, about once a year it is, because you refill the system. But the hose you use keeps the pressure well below 5 bar :-)

The hot water part of your system (boiler) is connected to the 5 bar water supply. But it is also well designed to operate under this pressure.

So, it is quite like electronics. You try to solve a problem that is no problem at all :-)

--
Kind regards,
Gerard Bok

Yes but it's very unsatisfactory. With 3bar of pressure it should be much better. I know it can be because...

There is also a 3bar over pressure relief valve designed to protect the heating if the regulator fails. If I temporarily remove the pressure regulator the 3bar relief valve opens to limit the pressure to 3bar (think

5V power supply with a 3V zenner diode clamp on the output putting it into current limit). In this situation I get 3bar at the shower head, good flow and everything is perfect...except I waste huge quantitiies of water through the relief valve (current through the zenner). This experiment demonstrates that the pipes are still in good order etc.

I guess I'll just have to look for a better quality regulator - one that doesn't restrict the flow so much.

Yes.

All understood.

Yes that's correct. I've no problem with the heating side (A sealed rad loop operating at 1.5 bar)

Your description is correct. It's a mains pressure hot water system but the max mains input pressure rating is 3bar not 5 bar hence the need for a regulator. There is a 3 bar over pressure relief valve on the mains input in case the regulator fails.

I've installed pressure guages at various points now and it's clear the problem is with the pressure regulator - it's just not "ideal" enough. It drops the 5bar down to 3bar ok but it doesn't open enough when the pressure is reduced by turning on a tap (too much internal resistance).

See also my other reply to Ken.

In the common hydronic heating systems in the states the supply to the furnace has an inline pressure regulator to protect the closed heating system. The furnace will also have an over pressure blow off regulator on it and in older system an expansion tank.Hot water for faucets and showers is a separate supply running at house pressure ~ 70PSI or 4.8 BAR. If you're drawing hot water off behind the regulator for a shower I can see how the pressure would be greatly reduced. The regulators I deal with look like the ones on this page:

Except they have an over ride lever on the top. When we refill a system we over ride the inlet pressure regulator othewise the system will take hours to fill.

3 bar would be at the low end of an acceptable home supply. >1 bar would be miserable!

No what I have is...

Mains in -> 3bar pressure regulator -> Safety valve -> Tank -> Hot taps and shower

A closed primary loop (at nominal 1.5bar) circulates water from the Furnace to either the Rad loop or a coil in the tank to heat the water. There is a manual valve (normally closed) between the output of the safety valve and the primary loop. This is used to adjust the pressure in the primary loop. This only needs to be done once a year as it stays around 1.5bar. There probably is another safety pressure relief valve somewhere in the furnace enclosure for the primary loop.

Yes that looks very much like the reducer I'm using.

Humm. Sounds like my tank/furnace has a low rating.

That sounds like a good possibility. There is almost no data on the packaging for the reducers available locally. Will try and find a better supplier.

Strange. I took out the paperwork from my own heater. ('Nefit HR combiketel'). And it accepts 0.9-10 bar input water pressure.

(And 1-3 heating system pressure.)

--
Kind regards,
Gerard Bok

I'm beginning to see the light... The hot water that comes out of the taps never goes near the boiler/furnace. Only the primary circuit goes between the hot water tank and boiler/furnace...so... I need to be looking at the spec for the tank NOT the boiler itself. Unfortunately I don't have that.

Anyway I made some progress today. The main pipe to the hot water tank with the pressure reducer in is 15mm (call it 1/2"). Upto now I had a 1/2" pressure reducer in the line because everyone said to match the size. Today I changed it for a 3/4" regulator of the same 3bar rating. With no water flowing the output pressure is the same as before (adjusted to just under

3bar) but now when you turn on a tap/shower the pressure only falls to around 2 bar instead of 1 bar (ish) - much better.

It looks like the 3/4" regulator has less internal resistance than the 1/2".

Thanks for the ideas.

wrote

So is it like one of these systems:

And what I don't understand is why it isn't set up like this:

Mains in I-> 3bar pressure regulator ->Boiler-> Safety valve ->

I> heat exchanger>I Mains in---cold water inlet--4.8bar-----------------> Tank -> Hot taps and shower

The only time I've seen pressure regulators on taps/shower supply is when the inlet pressure is too high >60-70 psi

and

Furnace

Yes, this one......

1) > Mains in I-> 3bar pressure regulator ->Boiler-> Safety valve -> 2) > Mains in---cold water inlet--4.8bar-----------------> Tank -> Hot taps

Well it's very similar except the regulator on the secondary circuit (2) is

3 bar not 4.8 bar and there is a 3 bar safety valve in case the tank boils. I think I need to find data on the tank to see if I can replace these two with 5 bar parts. That's going to be the best solution.

The primary is sealed and topped up by a tap rather than a regulator. This tap is normally closed and almost never needs to be used. Perhaps once in the last five years?

1) > Mains in I-> 3bar pressure regulator ->Boiler-> Safety valve -> 2) > Mains in---cold water inlet--4.8bar-----------------> Tank -> Hot taps

I don't understand why there needs to be a pressure regulator on that side of the circuit. This would be the case only if your supply pressure exceeds 120 psi or so ~ 8.5 bar! Check this out:

html and:

(talking about inlet pressure reducing valves) "Factory settings are usually between 50 and 60 PSI. I happen to prefer a setting of 70 PSI. Settings at or near 70 PSI allow you to take vigorous showers." That would be 4.8 bar

Well that is the job of the TPR valve which usually vents out the top of the tank into a drain. These are both thermostatic 210=BAF and pressure 150 psi (10.32 bar!!) all US figures. See:

and these not only prevent boiling but conditions were a hot water heater can become superheated and explode. Think of a 50 gal superheated steam rocket!

I think we're talking about separate issues here with the 2 valves. Make sure that second valve is a TPR valve and blows off to the outside. These will have a manual overide so they can be checked regularly

This primary would also have a TRP valve and that's good that's good there's a valve because as it seems the way your system is hooked up there is the chance of backflow from the boiler into the hot water side of your system. So if this valve is closed the inlet pressure regulator is out of the circuit? I think the inlet water pressure of your hot water supply tank could be at city pressure unless that exceeds 8.5 bar or so. I just looked at this indirect system and they also recommend the use of a cold water inlet pressure releaf valve set at 150 psi.

df This would also blow off into a drain.

It's not got a temperature sensitive valve unless hidden inside the tank enclosure somewhere. It's just got a the 3bar relief valve. Perhaps locals codes (Belgium) don't require anything more than a regular relief valve.

I think the only way that could happen is if there was a hole in the heat exchanger in the tank. Otherwise the primary and secondary are seperate once the filler is closed..

Yes with the primary fill valve closed the primary loop is sealed. The regulator continues to feed the secondary side, heat exchanger and onto the hot taps.

Yes it looks like that. I just need to find out the data on the tank to conform that it's rated for that. There must have been a reason why the reflief valve installed is only 3 bar.

Meanwhile it's performing a bit better now that I changed the regulator from a 1/2" 3bar to a 3/4" 3 bar unit. The drop accross it when the taps are turned on is less.

Thanks for the info.

Colin

Well if that valve were open and someone used the hot water the pressure drop in the boiler would cause a backflow into the cold side supply line.

This is where I think it's hooked up wrong. I think the best thing to do is to find a local plumbing Guru and run it by him. I have a few like that here in Chicago and they have really been a font of info for me on stuff I run into in the old houses I work on. The last time it's went like this: "When was it made?" - "In '93"-" Does it look like a white jell?" -"Yup" "It's the dip tube they were all made by the same ....then he sold the company....That will be $1.50" Good luck. Richard, who loves a vigorous shower

Colin,

That doesn't sound right to me. The relief is not there to limit the inlet pressure it's to prevent the pressure in the tank from going too hign re: 150 psi ^. If was installed like a normal pressure relief valve it would be constantly open at 3 bar and if it wasn't it wouldn't prevent the tank going over pressure. I would run this by some local plumbing guru. I have many I rely on here in Chicago. Usually I just describe the problem and often they have the solution before I can even finish. Last year I had one like that there was a gel like goop .......before I could finish he said. " Oh yah those water heaters made around '93 have defective dip tubes.....see one company made all of those...then they sold the company .....gel in the bottom of the tank....little white flecks in all the tap screens..." Good luck Richard who enjoys good water pressure.

Yes, perhaps I wasn't clear. The input to the tank is like this

(Switch to fixed font)

Mains in at 5bar---> Regulator (set at 2.8) ----> Relief valve (3bar) tank | V Waste

If the tank boils the relief valve will open and water will flow back from the tank and out through the relief valve to the waste. What I meant before is that it's only got this overpressure relief there doesn't seem to be a seperate over temperature relief (unless there is a thermal fuse or something elsewhere).

Colin

Thats a very interesting idea. I've now got enough pressure gauges in the system to see what's going on at various points. I'm 100% convinced it's the regulator because I can see the pressure drop across it when water is flowing. That plus changing the size from 1/2" to 3/4" (both set 3bar) did make a difference. I never thought of using two in parallel though.