Hot water reset with cast iron boiler?

Chuck_7

A large house with a hot water system with radiators and a cast iron boiler. If we have TRV's on the radiators, a secondary water system with temperature reset based on outside temperature the comfort level should be pretty good. (the large old house is used for offices) The problem is the boiler at a high temperature full time for the entire season. Is there a better way?

don_92

Not sure

what could be your problem.You have to remember as outdoor temperature decreases the building heating load increases.
So if it running on high water temps most of the time,can only mean your heatloss is high and it very cold outside.

Is there a better way,sure there is and that is you need to reduce your heatloss thru your envelope.

Like better windows,more insulation in the attic and crawl.
If it is on a crawl making sure your vents are closed to keep the air from passing under the house.

It could even be your outdoor sensor not working or you simply need to readjust your heating curve.

Who's reset control are you using?

Ken_8

He's not using O.R.,

At least not on the boiler itself. But is asking if he should or could.

The answer is yes. Simply leaving the boiler at 140 before the circ. pump kicks in will be a simple strategy. There are of course many others, e.g., bypasses, thermostatic 3-way, P/S, to name a few.

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Paul Pollets

Best way

The best way to control a radiators system with TRV's and a cast iron boiler is by using an outdoor reset control, a 4 way mixing valve and motor actuator and a pressure bypass differential valve (PBD) to protect the pump when the TRV's are modulated. The 4 way will protect the boiler from thermal shock and condensation issues. It will accurately control the setpoints in the radiator zones, while reducing energy costs and run time on the boiler.

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Chuck_7

I don't think I stated the question correctly.
The secondary system will be reset based on outside air. The primary system (the boiler and loop through the boiler) will not be reset. Does it have to stay at temperature all the time even when it is not so cold out (say 45 deg), or will the controller turn it on and bring it up to temp when the demand is there (Tekmar controller).
Side question - what can a four way valve do that a threeway can't besides add pressure drop to the secondary pump?

BTW this work is not done yet. Right now it is just a Weil-Mclain boiler, one pump, and one thermostat. We are doing a renovation with an addition with radiant panels on a new loop (I did not want to complicate the question). Since the first question I have gone to the weil-Mclain web site which will help. I may have time to read their info this weekend.

don_94

I

can only assume that you're using a condensing boiler if you
are going with a three port valve.

As mention above the four port valve will protect your boiler by maintaining relaitively high return water temps.

Maybe a pic of the piping diagram will help us to answer your question much better and what type of boiler is being used.

I'll shutup now because,I'm now more confuse then I was before.

Ted_9

New products

Be careful, not all 3 ways are like this. The Taco I Series 3 way mixing valve has out door reset, and boiler protection.

PATRIOT HEATING & COOLING, INC.

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don_96

Thanks Ted

for the heads up..it sadden me to say,dont get to see much new product when it come to the wetstuff.

I'm kindda in a part of the country that is more forceair then hydronic..thats why I drop by every now and again to see what I'm missing.

STEVE N

I think...

I think I know what you are up against. This WM boiler is it an older 88 with an aquastat that is set very high and is not really adjustable? It maintains like 150 all the time? Am I on the same page with you? I don't want to give you an opinion unless I understand what you have.

Steve

John Cockerill

even heat


There sure is. Adjust your boiler temp with thermostat demand activity over time. You will smooth it all out with 60% circulation at lower temps. Exact BTU replacement and even comfort throughout the house garunteed.

John Cockerill Exquisite Heat
www.Exqheat.com

Chuck_7

I can come up with a diagram. I have the technology. It will take a bit though, I think my current idea is flawed and I have a couple ideas on how to work it so bear with me.
There are two issues; 1. I want to use outdoor temp. reset and need to protect the boiler (Weil McLain p-FG-5). The design temp is 180 by the way. 2. The owner wants thermostatic control valves so there is no space temperature feed back.

Boilerpro_3

Usually with rads

the max you need to run the boiler is about 150 to 160F supply on the coldest day of the year. I would just turn the operating limit down and see how you do next year. Offices usually have very high internal gains, so you probably don't need much water temp.

Boilerpro

Chuck_7

Ok here you go (if I can get this attached0. Obviously I had nothing better to do while watching the games.
A is my original concept. B is right out of the Tekmar catalog and would use a universal control to reset both the boiler water (with a low limit) and reset the secondary loop. C is sort of a Weil-McLain suggestion with a bypass pump which would come on for boiler shock protection during mild temperatures.