control valves

Could you be a little more forthcoming with your data? What are you trying to do? What are you trying to do it with.

'Need more info.

If you have a system with 2 way control valves could i install crossovers in the mains to keep the mains hot instead of changing the 2 ways to 3 ways.thanks for any input.

I hate guys with post no:1

What question are you asking and what you want to do?

What is the system of operation ? why you have 2 way control valve? what purpose is it doing? Do you have one valve/ two? in series/parallel? what functions is being applied in control & where is it getting the signal from - pressure/flow/level/temperature?

all valves are 2 ways unless you really require a 3 way for diverting or mixing or dumping. what is cross over to keep mains hot?

You want an intellegent answer to help you out - ask an intellegent question.

One has to consider the flow in the cylinder coil and the flow in the radiator loop. It might be better to convert the radiator loop to a series system, with temperature control valves on each radiator, and to install a second circulating pump that energises whenever the thermostat switches the radiator loop valve on.

Temperature of the return water will be determined by the dissipation on each loop which will, in turn, determine the burn/idle time ratio of the boiler.

Does that help?

Assuming that you have a hot water system with a circulating pump, then yes you could install a crossover line between the mains, and yes that would help keep the mains hot, but why? The usual practice of installing a 3-way valve at the end of the main or at the last connected load, is to maintain a minimum flow through the pump. If you do use a crossover line, I would suggest the you install an orifice in the line to minimize the flow, because there will always be a flow through the crossover line whenever the pump is operating. In a domestic (potable) hot water system, it is quite common to install a "return" line at the end of the longest run in order to maintain temperature at the hot water faucet.

First of all, a P&ID or PFD (at least) is required to review the process, controls and fluid mechanics.

Maybe they want something like the AutoCircII instant hot water system.

http://www.lainginc.com/

Good item, something new . Txs. I doubt however if he is looking for this.

Using 2-way valve in place of 3-way reduces installation costs, simplifies balancing the system, and reduces pumping costs. It is a common practice to add a crossover at the end of branches in the piping system with a circuit setter in line to keep some flow in the loop so it does not cool off (for heating) or warm up (for cooling) under light or no load conditions. Alternatively a three-way valve may be the last control element in the loop although I think using circuit setters is a better way to go as you have more control over the minimum flow through the loop.

Usually heating loops have relatively small pumps, relatively small valves and piping so the advantages of a variable flow system is not that great.

If I have the system? You will not be allowed to modify it.